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• How to transfer data between two netowks efficiently

  - by Tono Nam

  I will like to transfer files between two places over the internet. Right now I have a VPN and I am able to browse, download and transfer files. So my question is not really how to transfer the files; Instead, I will like to use the most efficient approach because the two places constantly share a lot of data. The reason why I want to get rid of the vpn is because it is two slow. Having high upload speed is very expensive/impossible on residential places so I will like to use a different approach. I was thinking about using programs such as http://www.dropbox.com . The problem with dropbox is it only enables 2 GB of storage in order for it to be free. I think the deals they offer are ok and I might be willing to pay to get that increase in speed. But I am concerned with the speed of transferring data. Dropbox will upload the file to their server then send it from the server to the other location. I will like it even faster lol. Anyways I was thinking why not create a program my self. This is the algorithm that I was thinking let me know if it sounds to crazy. (remember my goal is to transfer files as fastest as possible) Things that I will use in this algorithm: Server on the internet called S ( has fast download and upload speed. I pay to host a website and some services in there. I want to take advantage of it) Client A on location 1 Client B on location 2 So lets say on location 1 20 large files are created and need to be transferred to location 2. Client A compresses the files with the highest compression ratio possible. Client A starts sending data via UDP to client B. Because I am using UDP I will include the sequence number on each package. Have server S help speed up things. For example every time a package is lost we can use Server S to inform client A that it needs to resend a package. Anyways I think this approach will increase the transfer rate. I do not know if it is possible to start sending data meanwhile it is being compressed. Also if it is possible to start decompressing data even if we are not done receiving all the info. Maybe it will be faster to start sending the files right away without compressing. If I knew that I will always be sending large text files then I will obviously use the compression. I need this as a general algorithm. So i guess my question is should using UDP over TCP could increase performance by using an extra server to keep track of lost packages? and How should I compress files before sending? compressing a 1 GB file with the highest compression ration takes about 1 hour! I will like to take advantage of that time by sending it meanwhile it is compressed.

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• Linux not buffering block I/O when the device is not "in use" (i.e. mounted)

  - by Radek Hladík

  I am installing new server and I've found an interesting issue. The server is running Fedora 19 (3.11.7-200.fc19.x86_64 kernel) and is supposed to host a few KVM/Qemu virtual servers (mail server, file server, etc..). The HW is Intel(R) Xeon(R) CPU 5160 @ 3.00GHz with 16GB RAM. One of the most important features will be Samba server and we have decided to make it as virtual machine with almost direct access to the disks. So the real HDD is cached on SSD (via bcache) then raided with md and the final device is exported into the virtual machine via virtio. The virtual machine is again Fedora 19 with the same kernel. One important topic to find out is whether the virtualization layer will not introduce high overload into disk I/Os. So far I've been able to get up to 180MB/s in VM and up to 220MB/s on real HW (on the SSD disk). I am still not sure why the overhead is so big but it is more than the network can handle so I do not care so much. The interesting thing is that I've found that the disk reads are not buffered in the VM unless I create and mount FS on the disk or I use the disks somehow. Simply put: Lets do dd to read disk for the first time (the /dev/vdd is an old Raptor disk 70MB/s is its real speed): [root@localhost ~]# dd if=/dev/vdd of=/dev/null bs=256k count=10000 ; cat /proc/meminfo | grep Buffers 2621440000 bytes (2.6 GB) copied, 36.8038 s, 71.2 MB/s Buffers: 14444 kB Rereading the data shows that they are cached somewhere but not in buffers of the VM. Also the speed increased to "only" 500MB/s. The VM has 4GB of RAM (more that the test file) [root@localhost ~]# dd if=/dev/vdd of=/dev/null bs=256k count=10000 ; cat /proc/meminfo | grep Buffers 2621440000 bytes (2.6 GB) copied, 5.16016 s, 508 MB/s Buffers: 14444 kB [root@localhost ~]# dd if=/dev/vdd of=/dev/null bs=256k count=10000 ; cat /proc/meminfo | grep Buffers 2621440000 bytes (2.6 GB) copied, 5.05727 s, 518 MB/s Buffers: 14444 kB Now lets mount the FS on /dev/vdd and try the dd again: [root@localhost ~]# mount /dev/vdd /mnt/tmp [root@localhost ~]# dd if=/dev/vdd of=/dev/null bs=256k count=10000 ; cat /proc/meminfo | grep Buffers 2621440000 bytes (2.6 GB) copied, 4.68578 s, 559 MB/s Buffers: 2574592 kB [root@localhost ~]# dd if=/dev/vdd of=/dev/null bs=256k count=10000 ; cat /proc/meminfo | grep Buffers 2621440000 bytes (2.6 GB) copied, 1.50504 s, 1.7 GB/s Buffers: 2574592 kB While the first read was the same, all 2.6GB got buffered and the next read was at 1.7GB/s. And when I unmount the device: [root@localhost ~]# umount /mnt/tmp [root@localhost ~]# cat /proc/meminfo | grep Buffers Buffers: 14452 kB [root@localhost ~]# dd if=/dev/vdd of=/dev/null bs=256k count=10000 ; cat /proc/meminfo | grep Buffers 2621440000 bytes (2.6 GB) copied, 5.10499 s, 514 MB/s Buffers: 14468 kB The bcache was disabled while testing and the results are same on faster (newer) HDDs and on SSD (except for the initial read speed of course). To sum it up. When I read from the device via dd first time, it gets read from the disk. Next time I reread it gets cached in the host but not in the guest (thats actually the same issue, more on that later). When I mount the filesystem but try to read the device directly it gets cached in VM (via buffers). As soon as I stop "using" it, buffers are discarded and the device is not cached anymore in the VM. When I looked into buffers value on the host I realized that the situation is the same. The block I/O gets buffered only when the disk is in use, in this case it means "exported to a VM". On host, after all the measurement done: 3165552 buffers On the host, after the VM shutdown: 119176 buffers I know it is not important as the disks will be mounted all the time but I am curious and I would like to know why it is working like this.

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• Intermittent 404 on select assets, LAMP stack

  - by Tom Lagier

  We have a LAMP stack WordPress server that is serving most assets correctly. However, one plugin's CSS file and several images are returning soft 404s roughly 20% of the time. I can't find any reference to the 404 in the access logs, but the browser is definitely receiving a 404 response from somewhere (WordPress, I would assume). When I use an alias URL that does not match the site URL but does resolve to the asset path, the resource loads correctly 100% of the time. However, using the site url only resolves for the select, problematic assets 20% of the time. You can test one of the problematic assets here: http://www.mreco.org/wp-content/uploads/2014/05/zero-cost.jpg However the alias link always resolves correctly: http://mr-eco.wordpress.promocampaigns.com/wp-content/uploads/2014/05/zero-cost.jpg Stranger, if I attempt to access outdated content that definitely does not exist on the server, at the live URL it returns the content roughly 50% of the time. Using the alias link, it 404s 100% of the time - the correct behavior. Error log and PHP error log are clean. A sample access log (pulled from grep 'zero-cost.jpg' /var/log/httpd/mr-eco-access_log) from several refreshes of the live direct link (where I am not seeing any 404's): 10.166.202.202 - - [28/May/2014:20:27:41 +0000] "GET /wp-content/uploads/2014/05/zero-cost.jpg HTTP/1.1" 304 - 10.166.202.202 - - [28/May/2014:20:27:42 +0000] "GET /wp-content/uploads/2014/05/zero-cost.jpg HTTP/1.1" 304 - 10.166.202.202 - - [28/May/2014:20:27:43 +0000] "GET /wp-content/uploads/2014/05/zero-cost.jpg HTTP/1.1" 304 - 10.166.202.202 - - [28/May/2014:20:27:43 +0000] "GET /wp-content/uploads/2014/05/zero-cost.jpg HTTP/1.1" 304 - 10.176.201.37 - - [28/May/2014:20:27:56 +0000] "GET /wp-content/uploads/2014/05/zero-cost.jpg HTTP/1.1" 200 57027 Chrome's dev tools list the following network activity before displaying 404 page content: zero-cost.jpg /wp-content/uploads/2014/05 GET 404 Not Found text/html Other 15.9?KB 73.2?KB 953?ms 947?ms My Apache configuration is standard, I've listed the virtual host entry and .htaccess file below. I can provide other parts of Apache config if necessary. Virtual host: <VirtualHost *:80> DocumentRoot /var/www/public_html/mr-eco.wordpress.promocampaigns.com ServerName www.mreco.org ServerAlias mreco.org mr-eco.wordpress.promocampaigns.com ErrorLog logs/mr-eco-error_log CustomLog logs/mr-eco-access_log common <Directory /var/www/public_html/mr-eco.wordpress.promocampaigns.com> AllowOverride All SetOutputFilter DEFLATE </Directory> </VirtualHost> .htaccess: # BEGIN WordPress <IfModule mod_rewrite.c> RewriteEngine On RewriteBase / RewriteRule ^index\.php$ - [L] RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{REQUEST_FILENAME} !-d RewriteRule . /index.php [L] </IfModule> # END WordPress I have checked for multiple A records and can confirm that there is a single A record pointing at the domain: ;; ANSWER SECTION: mreco.org. 60 IN A 50.18.58.174 I'm fairly new to systems administration, and at a complete loss as to what could cause this. In the past, inconsistently 404ing assets have been because of out-of-sync instances behind a load balancer. In this case, it is a single instance behind the load balancer. Because of the inconsistency, it feels like a caching issue. We don't make use of Apache caching, and as far as I know WordPress should not be caching either. What I've done so far: Reset WordPress permalinks Disabled WordPress plugins Re-generated WordPress .htaccess file Swapped ServerName and ServerAlias directives Cleared browser cache Confirmed disk location of resources Checked PHP, access, and error logs Confirmed correct DNS setup (can post if necessary) I'm at a total loss. Thanks for helping me out!

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• Is the Cloud ready for an Enterprise Java web application? Seeking a JEE hosting advice.

  - by Jakub Holý

  Greetings to all the smart people around here! I'd like to ask whether it is feasible or a good idea at all to deploy a Java enterprise web application to a Cloud such as Amazon EC2. More exactly, I'm looking for infrastructure options for an application that shall handle few hundred users with long but neither CPU nor memory intensive sessions. I'm considering dedicated servers, virtual private servers (VPSs) and EC2. I've noticed that there is a project called JBoss Cloud so people are working on enabling such a deployment, on the other hand it doesn't seem to be mature yet and I'm not sure that the cloud is ready for this kind of applications, which differs from the typical cloud-based applications like Twitter. Would you recommend to deploy it to the cloud? What are the pros and cons? The application is a Java EE 5 web application whose main function is to enable users to compose their own customized Product by combining the available Parts. It uses stateless and stateful session beans and JPA for persistence of entities to a RDBMS and fetches information about Parts from the company's inventory system via a web service. Aside of external users it's used also by few internal ones, who are authenticated against the company's LDAP. The application should handle around 300-400 concurrent users building their product and should be reasonably scalable and available though these qualities are only of a medium importance at this stage. I've proposed an architecture consisting of a firewall (FW) and load balancer supporting sticky sessions and https (in the Cloud this would be replaced with EC2's Elastic Load Balancing service and FW on the app. servers, in a physical architecture the load-balancer would be a HW), then two physical clustered application servers combined with web servers (so that if one fails, a user doesn't loose his/her long built product) and finally a database server. The DB server would need a slave backup instance that can replace the master instance if it fails. This should provide reasonable availability and fault tolerance and provide good scalability as long as a single RDBMS can keep with the load, which should be OK for quite a while because most of the operations are done in the memory using a stateful bean and only occasionally stored or retrieved from the DB and the amount of data is low too. A problematic part could be the dependency on the remote inventory system webservice but with good caching of its outputs in the application it should be OK too. Unfortunately I've only vague idea of the system resources (memory size, number and speed of CPUs/cores) that such an "average Java EE application" for few hundred users needs. My rough and mostly unfounded estimate based on actual Amazon offerings is that 1.7GB and a single, 2-core "modern CPU" with speed around 2.5GHz (the High-CPU Medium Instance) should be sufficient for any of the two application servers (since we can handle higher load by provisioning more of them). Alternatively I would consider using the Large instance (64b, 7.5GB RAM, 2 cores at 1GHz) So my question is whether such a deployment to the cloud is technically and financially feasible or whether dedicated/VPS servers would be a better option and whether there are some real-world experiences with something similar. Thank you very much! /Jakub Holy PS: I've found the JBoss EAP in a Cloud Case Study that shows that it is possible to deploy a real-world Java EE application to the EC2 cloud but unfortunately there're no details regarding topology, instance types, or anything :-(

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• Why the server is not responding?

  - by par

  Hello! Our server occasionally refuses to serve a simple HTML page. This is happening during a relatively high number of requests. However, the processor is not heavy loaded and there are a lot of free memory. The error seems to occure 1 out of 50 requests in average, depending on the server load. I need to find the source of the problem and take the appropriate actions to eliminate it. I have a suspicion that the problem source is a huge number of incoming network packets. There are 5000 packets per second on average. Traffic - 2 MBits/sec Can this be the cause of the error? There is an interesting thing, in case the server fails to respond, the request string is not logged to access.log by Apache. The error is repeatable from several client computers. DNS is not involved, since I have accessed the server by the IP. I have profiled the problem case with tcpdump utility. These are the good and bad sessions traced by tcpdump. The request is the same in both experiments. Good - server returns response. Bad - no response, time-out error. ---- Bad ---- 12:23:36.366292 IP 123.45.67.890.61749 > myserver.superbservers.com.www: S 2125316338:2125316338(0) win 8192 <mss 1460,nop,wscale 2,nop,nop,sackOK> 12:23:39.362394 IP 123.45.67.890.61749 > myserver.superbservers.com.www: S 2125316338:2125316338(0) win 8192 <mss 1460,nop,wscale 2,nop,nop,sackOK> 12:23:45.365567 IP 123.45.67.890.61749 > myserver.superbservers.com.www: S 2125316338:2125316338(0) win 8192 <mss 1460,nop,nop,sackOK> -------- ---- Good ---- 12:27:07.632229 IP 123.45.67.890.63914 > myserver.superbservers.com.www: S 3581365570:3581365570(0) win 8192 <mss 1460,nop,wscale 2,nop,nop,sackOK> 12:27:10.620946 IP 123.45.67.890.63914 > myserver.superbservers.com.www: S 3581365570:3581365570(0) win 8192 <mss 1460,nop,wscale 2,nop,nop,sackOK> 12:27:10.620969 IP myserver.superbservers.com.www > 123.45.67.890.63914: S 2654770980:2654770980(0) ack 3581365571 win 5840 <mss 1460,nop,nop,sackOK,nop,wscale 6> 12:27:10.838747 IP 123.45.67.890.63914 > myserver.superbservers.com.www: . ack 1 win 4380 12:27:10.957143 IP 123.45.67.890.63914 > myserver.superbservers.com.www: P 1:213(212) ack 1 win 4380 12:27:10.957152 IP myserver.superbservers.com.www > 123.45.67.890.63914: . ack 213 win 108 12:27:10.965543 IP myserver.superbservers.com.www > 123.45.67.890.63914: P 1:630(629) ack 213 win 108 12:27:10.965621 IP myserver.superbservers.com.www > 123.45.67.890.63914: F 630:630(0) ack 213 win 108 12:27:11.183540 IP 123.45.67.890.63914 > myserver.superbservers.com.www: . ack 631 win 4222 12:27:11.185657 IP 123.45.67.890.63914 > myserver.superbservers.com.www: F 213:213(0) ack 631 win 4222 12:27:11.185663 IP myserver.superbservers.com.www > 123.45.67.890.63914: . ack 214 win 108 -------- Hoster: SuperbHosting OS: Ubuntu Server parameters: E6300 CONROE 1.86GHZ 2 X 1MB CACHE 1066 1GB DDR2 667MHZ This is a link to apache configuration file we use http://repkin5.snow.prohosting.com/apache.txt This is server-status report taken right after time-out error. http://repkin5.snow.prohosting.com/server-status.htm There are only 10 Child Servers running out of 120, so enough space for new requests. VMSTAT procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu---- r b swpd free buff cache si so bi bo in cs us sy id wa 0 0 8900 725900 8468 65684 0 0 5 18 11 33 4 3 92 1

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• UFW as an active service on Ubuntu

  - by lamcro

  Every time I restart my computer, and check the status of the UFW firewall (sudo ufw status), it is disabled, even if I then enable and restart it. I tried putting sudo ufw enable as one of the startup applications but it asks for the sudo password every time I log on, and I'm guessing it does not protect anyone else who logs on my computer. How can I setup ufw so it is activated when I turn on my computer, and protects all accounts? Update I just tried /etc/init.d/ufw start, and it activated the firewall. Then I restarted the computer, and again it was disabled. content of /etc/ufw/ufw.conf # /etc/ufw/ufw.conf # # set to yes to start on boot ENABLED=yes # set to one of 'off', 'low', 'medium', 'high' LOGLEVEL=full content of /etc/default/ufw # /etc/default/ufw # # Set to yes to apply rules to support IPv6 (no means only IPv6 on loopback # accepted). You will need to 'disable' and then 'enable' the firewall for # the changes to take affect. IPV6=no # Set the default input policy to ACCEPT, ACCEPT_NO_TRACK, DROP, or REJECT. # ACCEPT enables connection tracking for NEW inbound packets on the INPUT # chain, whereas ACCEPT_NO_TRACK does not use connection tracking. Please note # that if you change this you will most likely want to adjust your rules. DEFAULT_INPUT_POLICY="DROP" # Set the default output policy to ACCEPT, ACCEPT_NO_TRACK, DROP, or REJECT. # ACCEPT enables connection tracking for NEW outbound packets on the OUTPUT # chain, whereas ACCEPT_NO_TRACK does not use connection tracking. Please note # that if you change this you will most likely want to adjust your rules. DEFAULT_OUTPUT_POLICY="ACCEPT" # Set the default forward policy to ACCEPT, DROP or REJECT. Please note that # if you change this you will most likely want to adjust your rules DEFAULT_FORWARD_POLICY="DROP" # Set the default application policy to ACCEPT, DROP, REJECT or SKIP. Please # note that setting this to ACCEPT may be a security risk. See 'man ufw' for # details DEFAULT_APPLICATION_POLICY="SKIP" # By default, ufw only touches its own chains. Set this to 'yes' to have ufw # manage the built-in chains too. Warning: setting this to 'yes' will break # non-ufw managed firewall rules MANAGE_BUILTINS=no # # IPT backend # # only enable if using iptables backend IPT_SYSCTL=/etc/ufw/sysctl.conf # extra connection tracking modules to load IPT_MODULES="nf_conntrack_ftp nf_nat_ftp nf_conntrack_irc nf_nat_irc" Update Followed your advise and ran update-rc.d with no luck. lester@mcgrath-pc:~$ sudo update-rc.d ufw defaults update-rc.d: warning: /etc/init.d/ufw missing LSB information update-rc.d: see <http://wiki.debian.org/LSBInitScripts> Adding system startup for /etc/init.d/ufw ... /etc/rc0.d/K20ufw -> ../init.d/ufw /etc/rc1.d/K20ufw -> ../init.d/ufw /etc/rc6.d/K20ufw -> ../init.d/ufw /etc/rc2.d/S20ufw -> ../init.d/ufw /etc/rc3.d/S20ufw -> ../init.d/ufw /etc/rc4.d/S20ufw -> ../init.d/ufw /etc/rc5.d/S20ufw -> ../init.d/ufw lester@mcgrath-pc:~$ ls -l /etc/rc?.d/*ufw lrwxrwxrwx 1 root root 13 2009-12-20 20:34 /etc/rc0.d/K20ufw -> ../init.d/ufw lrwxrwxrwx 1 root root 13 2009-12-20 20:34 /etc/rc1.d/K20ufw -> ../init.d/ufw lrwxrwxrwx 1 root root 13 2009-12-20 20:34 /etc/rc2.d/S20ufw -> ../init.d/ufw lrwxrwxrwx 1 root root 13 2009-12-20 20:34 /etc/rc3.d/S20ufw -> ../init.d/ufw lrwxrwxrwx 1 root root 13 2009-12-20 20:34 /etc/rc4.d/S20ufw -> ../init.d/ufw lrwxrwxrwx 1 root root 13 2009-12-20 20:34 /etc/rc5.d/S20ufw -> ../init.d/ufw lrwxrwxrwx 1 root root 13 2009-12-20 20:34 /etc/rc6.d/K20ufw -> ../init.d/ufw

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• nginx - 403 Forbidden

  - by michell90

  I've trouble to get aliases working correctly on nginx. When i try to access the aliases, /pma and /mba (see secure.example.com.conf), i get a 403 Forbidden but the base url works correctly. I read a lot of posts but nothing helped, so here i am. Nginx and php-fpm are running as www-data:www-data and the permissions for the directories are set to: drwxrwsr-x+ 5 www-data www-data 4.0K Dec 5 22:48 ./ drwxr-xr-x. 3 root root 4.0K Dec 4 22:50 ../ drwxrwsr-x+ 2 www-data www-data 4.0K Dec 5 13:10 mda.example.com/ drwxrwsr-x+ 11 www-data www-data 4.0K Dec 5 10:34 pma.example.com/ drwxrwsr-x+ 3 www-data www-data 4.0K Dec 5 11:49 www.example.com/ lrwxrwxrwx. 1 www-data www-data 18 Dec 5 09:56 secure.example.com -> www.example.com/ Im sorry for the bulk, but i thought better too much than too little. Here are the configuration files: /etc/nginx/nginx.conf user www-data www-data; worker_processes 1; error_log /var/log/nginx/error.log; #error_log /var/log/nginx/error.log notice; #error_log /var/log/nginx/error.log info; pid /var/run/nginx.pid; events { worker_connections 1024; } http { include /etc/nginx/mime.types; default_type application/octet-stream; log_format main '$remote_addr - $remote_user [$time_local] "$request" ' '$status $body_bytes_sent "$http_referer" ' '"$http_user_agent" "$http_x_forwarded_for"'; access_log /var/log/nginx/access.log main; sendfile on; keepalive_timeout 65; include /etc/nginx/sites-enabled/*; } /etc/nginx/sites-enabled/secure.example.com server { listen 80; server_name secure.example.com; return 301 https://$host$request_uri; } server { listen 443; server_name secure.example.com; access_log /var/log/nginx/secure.example.com.access.log; error_log /var/log/nginx/secure.example.com.error.log; root /srv/http/secure.example.com; include /etc/nginx/ssl/secure.example.com.conf; include /etc/nginx/conf.d/index.conf; include /etc/nginx/conf.d/php-ssl.conf; autoindex off; location /pma/ { alias /srv/http/pma.example.com; } location /mda/ { alias /srv/http/mda.example.com; } } /etc/nginx/ssl/secure.example.com.conf ssl on; ssl_certificate /etc/nginx/ssl/secure.example.com.crt; ssl_certificate_key /etc/nginx/ssl/secure.example.com.key; ssl_protocols SSLv3 TLSv1 TLSv1.1 TLSv1.2; ssl_ciphers HIGH:!aNULL:!MD5; /etc/nginx/conf.d/index.conf index index.php index.html index.htm; /etc/nginx/conf.d/php-ssl.conf location ~ \.php$ { try_files $uri =404; fastcgi_pass unix:/var/run/php-fpm/php-fpm.sock; fastcgi_index index.php; fastcgi_param HTTPS on; fastcgi_param SCRIPT_FILENAME $request_filename; include fastcgi_params; } /var/log/nginx/secure.example.com.error.log 2013/12/05 22:49:04 [error] 29291#0: *2 directory index of "/srv/http/pma.example.com" is forbidden, client: 176.199.78.88, server: secure.example.com, request: "GET /pma/ HTTP/1.1", host: "secure.example.com" EDIT: forgot to mention, i'm running CentOS 6.4 x86_64 and nginx 1.0.15 Thanks in advance!

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• simple and reliable centralized logging inside Amazon VPC

  - by Nakedible

  I need to set up centralized logging for a set of servers (10-20) in an Amazon VPC. The logging should be as to not lose any log messages in case any single server goes offline - or in the case that an entire availability zone goes offline. It should also tolerate packet loss and other normal network conditions without losing or duplicating messages. It should store the messages durably, at the minimum on two different EBS volumes in two availability zones, but S3 is a good place as well. It should also be realtime so that the messages arrive within seconds of their generation to two different availability zones. I also need to sync logfiles not generated via syslog, so a syslog-only centralized logging solution would not fulfill all the needs, although I guess that limitation could be worked around. I have already reviewed a few solutions, and I will list them here: Flume to Flume to S3: I could set up two logservers as Flume hosts which would store log messages either locally or in S3, and configure all the servers with Flume to send all messages to both servers, using the end-to-end reliability options. That way the loss of a single server shouldn't cause lost messages and all messages would arrive in two availability zones in realtime. However, there would need to be some way to join the logs of the two servers, deduplicating all the messages delivered to both. This could be done by adding a unique id on the sending side to each message and then write some manual deduplication runs on the logfiles. I haven't found an easy solution to the duplication problem. Logstash to Logstash to ElasticSearch: I could install Logstash on the servers and have them deliver to a central server via AMQP, with the durability options turned on. However, for this to work I would need to use some of the clustering capable AMQP implementations, or fan out the deliver just as in the Flume case. AMQP seems to be a yet another moving part with several implementations and no real guidance on what works best this sort of setup. And I'm not entirely convinced that I could get actual end-to-end durability from logstash to elasticsearch, assuming crashing servers in between. The fan-out solutions run in to the deduplication problem again. The best solution that would seem to handle all the cases, would be Beetle, which seems to provide high availability and deduplication via a redis store. However, I haven't seen any guidance on how to set this up with Logstash and Redis is one more moving part again for something that shouldn't be terribly difficult. Logstash to ElasticSearch: I could run Logstash on all the servers, have all the filtering and processing rules in the servers themselves and just have them log directly to a removet ElasticSearch server. I think this should bring me reliable logging and I can use the ElasticSearch clustering features to share the database transparently. However, I am not sure if the setup actually survives Logstash restarts and intermittent network problems without duplicating messages in a failover case or similar. But this approach sounds pretty promising. rsync: I could just rsync all the relevant log files to two different servers. The reliability aspect should be perfect here, as the files should be identical to the source files after a sync is done. However, doing an rsync several times per second doesn't sound fun. Also, I need the logs to be untamperable after they have been sent, so the rsyncs would need to be in append-only mode. And log rotations mess things up unless I'm careful. rsyslog with RELP: I could set up rsyslog to send messages to two remote hosts via RELP and have a local queue to store the messages. There is the deduplication problem again, and RELP itself might also duplicate some messages. However, this would only handle the things that log via syslog. None of these solutions seem terribly good, and they have many unknowns still, so I am asking for more information here from people who have set up centralized reliable logging as to what are the best tools to achieve that goal.

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• Strange enduser experience with Liferay, Glassfish and Apache on RedHat

  - by Pete Helgren

  Tried multiple forums to get to the bottom of this. I hope I can get some direction here: Here is the stack I am working with: Red Hat Enterprise Linux Server release 5.6 (Tikanga) Liferay 6.0.6 on Glassfish 3.0.1 MySQL 5.0.77 Apache 2.2.3 The Liferay portal provides a variety of portlets to end users. Static content (web pages), static resources (primarily pdf and mp3 files 1mb - 80mb in size), File upload and download capabilities (primarily 40-60mb mp3 files) and online streaming of those MP3 files. Here is the strange end user experiences: Under normal load: (20-30) users uploading, downloading or streaming files and 20-30 accessing static content (some of it downloads), we see the following: 1) Clicking a link triggers the download of a portion of an MP3 (the portion is a few seconds long). 2) Clicking on a link tiggers the download of the page content rather than rendering. 3) Clicking a link causes the page to dump binary data to the end user rather than the expected content. 4) Clicking a link returns the text of a javascript file rather than rendering the page. Each occurrence is totally random (or appears so). Sometimes it works, sometimes it doesn't. It seems to have no relation to browser or client OS. The strange events seem to occur much more frequently when using an SSL connection rather than regular http. Apache serves as a proxy server only (reverse). It basically passes all the requests through to Glassfish. There isn't any static content proxy served by Apache. We rebuilt the entire stack from scratch and redeployed the portlet wars and still have the same issues. Liferay is running as a single server (not clustered). We disabled mod_cache in Apache. The problems are more frequent as the server load grows. This morning the load is pretty light and we are seeing few problems but the use of the site will grow, particularly tonight around 9pm CST through Wednesday morning. You could try the site (http://preview.bsfinternational.org) during those times and I would expect that you might experience one of the weirdnesses as you randomly click links on the site (https is invoked only when signed in). Again, https seems to exacerbate the issue. This seems very much like a caching issue but I don't know where in the stack to start peeling the onion. Apache? Liferay? Glassfish? MySQL? Maybe even Redhat? We are stumped and most forums we have posted to (LifeRay and Glassfish) have returned very few suggestions. I just need an idea of where to start looking. I understand that we could have a portlet EDIT: Opening the files in a Hex editor that appear to be pages that download rather than render, we see that the first 4000 characters are "junk" and then the "HTTP/1.1 ...." 'normal' header is seen. So something is dumping a jumble of characters up to offset 4000 (when viewing it in a Hex editor). Perhaps a clue? Ideas?

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• Performance issues when using SSD for a developer notebook (WAMP/LAMP stack)?

  - by András Szepesházi

  I'm a web application developer using my notebook as a standalone development environment (WAMP stack). I just switched from a Core2-duo Vista 32 bit notebook with 2Gb RAM and SATA HDD, to an i5-2520M Win7 64 bit with 4Gb RAM and 128 GB SDD (Corsair P3 128). My initial experience was what I expected, fast boot, quick load of all the applications (Eclipse takes now 5 seconds as opposed to 30s on my old notebook), overall great experience. Then I started to build up my development stack, both as LAMP (using VirtualBox with a debian guest) and WAMP (windows native apache + mysql + php). I wanted to compare those two. This still all worked great out, then I started to pull in my projects to these stacks. And here came the nasty surprise, one of those projects produced a lot worse response times than on my old notebook (that was true for both the VirtualBox and WAMP stack). Apache, php and mysql configurations were practically identical in all environments. I started to do a lot of benchmarking and profiling, and here is what I've found: All general benchmarks (Performance Test 7.0, HDTune Pro, wPrime2 and some more) gave a big advantage to the new notebook. Nothing surprising here. Disc specific tests showed that read/write operations peaked around 380M/160M for the SSD, and all the different sized block operations also performed very well. Started apache performance benchmarking with Apache Benchmark for a small static html file (10 concurrent threads, 500 iterations). Old notebook: min 47ms, median 111ms, max 156ms New WAMP stack: min 71ms, median 135ms, max 296ms New LAMP stack (in VirtualBox): min 6ms, median 46ms, max 175ms Right here I don't get why the native WAMP stack performed so bad, but at least the LAMP environment brought the expected speed. Apache performance measurement for non-cached php content. The php runs a loop of 1000 and generates sha1(uniqid()) inisde. Again, 10 concurrent threads, 500 iterations were used for the benchmark. Old notebook: min 0ms, median 39ms, max 218ms New WAMP stack: min 20ms, median 61ms, max 186ms New LAMP stack (in VirtualBox): min 124ms, median 704ms, max 2463ms What the hell? The new LAMP performed miserably, and even the new native WAMP was outperformed by the old notebook. php + mysql test. The test consists of connecting to a database and reading a single record form a table using INNER JOIN on 3 more (indexed) tables, repeated 100 times within a loop. Databases were identical. 10 concurrent threads, 100 iterations were used for the benchmark. Old notebook: min 1201ms, median 1734ms, max 3728ms New WAMP stack: min 367ms, median 675ms, max 1893ms New LAMP stack (in VirtualBox): min 1410ms, median 3659ms, max 5045ms And the same test with concurrency set to 1 (instead of 10): Old notebook: min 1201ms, median 1261ms, max 1357ms New WAMP stack: min 399ms, median 483ms, max 539ms New LAMP stack (in VirtualBox): min 285ms, median 348ms, max 444ms Strictly for my purposes, as I'm using a self contained development environment (= low concurrency) I could be satisfied with the second test's result. Though I have no idea why the VirtualBox environment performed so bad with higher concurrency. Finally I performed a test of including many php files. The application that I mentioned at the beginning, the one that was performing so bad, has a heavy bootstrap, loads hundreds of small library and configuration files while initializing. So this test does nothing else just includes about 100 files. Concurrency set to 1, 100 iterations: Old notebook: min 140ms, median 168ms, max 406ms New WAMP stack: min 434ms, median 488ms, max 604ms New LAMP stack (in VirtualBox): min 413ms, median 1040ms, max 1921ms Even if I consider that VirtualBox reached those files via shared folders, and that slows things down a bit, I still don't see how could the old notebook outperform so heavily both new configurations. And I think this is the real root of the slow performance, as the application uses even more includes, and the whole bootstrap will occur several times within a page request (for each ajax call, for example). To sum it up, here I am with a brand new high-performance notebook that loads the same page in 20 seconds, that my old notebook can do in 5-7 seconds. Needless to say, I'm not a very happy person right now. Why do you think I experience these poor performance values? What are my options to remedy this situation?

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• Bizarre and very specific Internet connection loss

  - by Synetech

  Yesterday (Friday, September 21, 2012), my Internet connection started acting up. After some testing, I confirmed a very specific and baffling set of symptoms: Internet connection goes away every 25-35 minutes (I did not confirm the exact interval, but it seems to be about 30 mins.) Only some protocols are affected; HTTP*, P2P, etc. stop working; FTP, etc. continue to work When it’s stopped, cannot even ping router or cable-modem IPs or view their firmware pages Domain-names and IPs are irrelevant (for protocols that stop working, neither work, for those that still work, both work) Resetting router fixes it for another 30 minutes Keeping the connection idle or active doesn’t seem to make a difference (nor the bandwidth usage in that period) Connecting directly to cable-modem allows it to work indefinitely Disconnecting the router from the cable-modem works indefinitely (no Internet connection obviously, but can still access router IP and firmware page) Connecting the router to the cable-modem, but putting the modem on standby also works indefinitely Same problem with both a wireless laptop and wired (on any port) desktop (both Windows 7; will try to test Windows XP when possible) Nothing had changed in the days leading up to the issue. No modifications to the networking configuration or the router; there were not even any Windows updates except for an MSSE definition update. Waiting does not fix it, nor does any amount of fiddling with anything; only resetting the router fixes it for 30 minutes (resetting the cable-modem doesn't work either) I tried cleaning the pins in the router’s plugs, but that didn’t help, which was not really a surprise since I was not getting a lost connection error. Obviously my first thought was that the router was having a problem, and this is borne out by some tests. The problem is that when it drops, it is not a full drop since I can still do things like ftp ftp.mcafee.com and such which means that the connection and DNS are still working. Moreover, if it were the router, then why does it stay alive indefinitely when not connected to the cable-modem (i.e., no outside influence)? The problem doesn't seem to be either the cable-modem nor the router, but rather an interaction between the two, like something from the outside (port scan? hacker? ISP?) that is triggering a problem in the router. I see that there have been a couple of vulnerabilities for the DI-524, but those were a while back and should be fixed since I have the last firmware for it. I don’t think it’s my ISP (Rogers) since I have been using the router for several years without problem and can connect indefinitely when bypassing it. But I can’t rule them out since that is one of the only possible things that could have suddenly changed. Does anybody have any ideas of explanations, fixed, or tests? (I note that when I opened the router, I heard a very high-pitched noise from somewhere near the capacitors/ferrite ring which I don’t think I heard the last time I opened it a few years ago, but then if it were that, then why would it affect only a very small, specific set of functions?)

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• Samba with remote LDAP authentication doesn`t see users properly

  - by LucasBr

  I'm trying to setup a samba server authenticated by a remote LDAP server, and I'm having some problems that I can't figure how to solve. I was able to make an getent passwd at samba server and I could see all users at ldapserver, but when I tried to access \\SAMBASERVER at my windows box I had this at the /var/log/samba/log.mywindowsbox: <...snip...> [2012/10/19 13:05:22.449684, 2] smbd/sesssetup.c:1413(setup_new_vc_session) setup_new_vc_session: New VC == 0, if NT4.x compatible we would close all old resources. [2012/10/19 13:05:22.449692, 3] smbd/sesssetup.c:1212(reply_sesssetup_and_X_spnego) Doing spnego session setup [2012/10/19 13:05:22.449701, 3] smbd/sesssetup.c:1254(reply_sesssetup_and_X_spnego) NativeOS=[] NativeLanMan=[] PrimaryDomain=[] [2012/10/19 13:05:22.449717, 3] libsmb/ntlmssp.c:747(ntlmssp_server_auth) Got user=[lucas] domain=[BUSINESS] workstation=[MYWINDOWSBOX] len1=24 len2=24 [2012/10/19 13:05:22.449747, 3] auth/auth.c:216(check_ntlm_password) check_ntlm_password: Checking password for unmapped user [BUSINESS]\[lucas]@[MYWINDOWSBOX] with the new password interface [2012/10/19 13:05:22.449759, 3] auth/auth.c:219(check_ntlm_password) check_ntlm_password: mapped user is: [SAMBASERVER]\[lucas]@[MYWINDOWSBOX] [2012/10/19 13:05:22.449773, 3] smbd/sec_ctx.c:210(push_sec_ctx) push_sec_ctx(0, 0) : sec_ctx_stack_ndx = 1 [2012/10/19 13:05:22.449783, 3] smbd/uid.c:429(push_conn_ctx) push_conn_ctx(0) : conn_ctx_stack_ndx = 0 [2012/10/19 13:05:22.449791, 3] smbd/sec_ctx.c:310(set_sec_ctx) setting sec ctx (0, 0) - sec_ctx_stack_ndx = 1 [2012/10/19 13:05:22.449922, 2] lib/smbldap.c:950(smbldap_open_connection) smbldap_open_connection: connection opened [2012/10/19 13:05:23.001517, 3] lib/smbldap.c:1166(smbldap_connect_system) ldap_connect_system: successful connection to the LDAP server [2012/10/19 13:05:23.007713, 3] smbd/sec_ctx.c:418(pop_sec_ctx) pop_sec_ctx (0, 0) - sec_ctx_stack_ndx = 0 [2012/10/19 13:05:23.007733, 3] auth/auth_sam.c:399(check_sam_security) check_sam_security: Couldn't find user 'lucas' in passdb. [2012/10/19 13:05:23.007743, 2] auth/auth.c:314(check_ntlm_password) check_ntlm_password: Authentication for user [lucas] -> [lucas] FAILED with error NT_STATUS_NO_SUCH_USER [2012/10/19 13:05:23.007760, 3] smbd/error.c:80(error_packet_set) error packet at smbd/sesssetup.c(111) cmd=115 (SMBsesssetupX) NT_STATUS_LOGON_FAILURE [2012/10/19 13:05:23.010469, 3] smbd/process.c:1489(process_smb) Transaction 3 of length 142 (0 toread) <...snip...> /etc/samba/smb.conf file follows: [global] dos charset = 850 unix charset = LOCALE workgroup = BUSINESS netbios name = SAMBASERVER bind interfaces only = true interfaces = lo eth0 eth1 smb ports = 139 hosts deny = All hosts allow = 192.168.78. 192.168.255. 127.0.0.1 10.149.122. 192.168.0. name resolve order = wins bcast hosts log level = 3 syslog = 0 log file = /var/log/samba/log.%m max log size = 100000 domain logons = No wins support = Yes wins proxy = No client ntlmv2 auth = Yes lanman auth = Yes ntlm auth = Yes dns proxy = Yes time server = Yes security = user encrypt passwords = Yes obey pam restrictions = Yes ldap password sync = Yes unix password sync = Yes passdb backend = ldapsam:"ldap://192.168.78.206" ldap ssl = off ldap admin dn = uid=root,ou=Users,dc=business,dc=intranet ldap suffix = ldap group suffix = ou=Groups ldap user suffix = ou=Users ldap machine suffix = ou=Computers ldap idmap suffix = ou=Idmap ldap delete dn = Yes add user script = /usr/sbin/smbldap-useradd -m "%u" delete user script = /usr/sbin/smbldap-userdel "%u" add group script = /usr/sbin/smbldap-groupadd -p "%g" delete group script = /usr/sbin/smbldap-groupdel "%g" add user to group script = /usr/sbin/smbldap-groupmod -m "%u" "%g" delete user from group script = /usr/sbin/smbldap-groupmod -x "%u" "%g" set primary group script = /usr/sbin/smbldap-usermod -g "%g" "%u" add machine script = /usr/sbin/smbldap-useradd -W -t5 "%u" idmap backend = ldap:"ldap://192.168.78.206" idmap uid = 16777216-33554431 idmap gid = 16777216-33554431 load printers = No printcap name = /dev/null map acl inherit = Yes map untrusted to domain = Yes enable privileges = Yes veto files = /lost+found/ /publicftp/ So, \\SAMBASERVER says he couldn't find my user, but I can see it by getent passwd . What I can do in order to SAMBASERVER see and authenticate my user? Thanks in advance!

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• How to set up a centralized backup server with lots of offsite workstations, intermittent internet connectivity, and stubborn users?

  - by Zac B

  This might be an impossible question. Context: We have a bunch of computers across around 1000 users. We have a centralized office where 900 of the users work, most of the time. Most of the computers are laptops. They are very frequently coming on and off the network for hours at a time. Users often take their computers home and do lots of work from home. In addition, there are a handful of users who work elsewhere in the country, who are offline (no internet connection whatsoever) for more than half of the time they use their machines. All of the machines are Windows 7/XP. Problem: People are always losing data. One day someone accidentally deletes a bunch of files. The next day someone else installs a bad driver or tries to mess with something in system32 and needs a personal data backup/reinstall of Windows. Because of how many of our business operations are done without an internet connection, and how frequently computers come on- and offline, it's unfeasible to make users use network storage for all of their data. We tried giving them Dropboxes, and they stored their files elsewhere. We bought and deployed Altiris, and they uninstalled it and blamed us when they couldn't get files back that they accidentally deleted while they were offline and hadn't taken a backup in months. We tried teaching them backup best-practices, and using scheduled sync tools to upload things to the network drives, and they turned them off because they "looked like viruses". It doesn't help that many of these users are pretty high up in the business and are not amicable to any sort of "you need to do something regularly because we say so" solution. Question: Other than finding another job where IT is treated differently and users are willing to follow best practices, how would people recommend I implement a file backup solution that supports the following: Backs up to a centralized server over LAN or WAN whenever a network link becomes available, or on a schedule. Supports interrupted/resumed backups (and hopefully file-delta only backups), since connections to the network (WAN or LAN) are often slow and only open for half an hour or so. Supports relatively rapid, "I accidentally deleted the TPS reports! Oh no!" single-file recovery, ideally administered from the central backup server rather than the client PC. Supports local-to-local file delta backup on a schedule, so that users without a network connection for a few days can still retrieve accidental deletions or whatnot. Ideally, the local stored backups would be pushed up to the server whenever network link is available. Isn't configurable on the clients without certain credentials. Because the CFOs (who won't give up their admin rights on the domain) will disable it if they can. Backs up the entire hard drive. There are people who are self-righteous about storing things in C:\, or in the recycle bin, or in the C:\Windows dir (yes, I know). I'm fine integrating multiple products/solutions, or scripting different programs together myself (I'm a somewhat competent programmer), but I've been drawing a blank on where to start. Dropbox is folder-specific, Altiris doesn't cope with LAN outages or interrupted/resumed backups, Volume Shadow Copy is awesome for a local-to-local solution, but I don't know how to push days of stored shadow copies up to a server in a 2 hour window of network access. The company is fine with spending decent money on this, thousands (USD) on a server, and hundreds on clients, if necessary. I want to emphasize that this isn't a shopping list request. While I wish there was a program out there that did what I want, I've looked pretty hard, and not found anything that fits the bill. Instead, I'm hoping for ideas on where to start hacking things together from scratch/from different technologies to make something stable that works. Cheers!

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• How to redirect http requests to https (nginx)

  - by spuder

  There appear to be many questions and guides out there that instruct how to setup nginx to redirect http requests to https. Many are outdated, or just flat out wrong. # MANAGED BY PUPPET upstream gitlab { server unix:/home/git/gitlab/tmp/sockets/gitlab.socket; } # setup server with or without https depending on gitlab::gitlab_ssl variable server { listen *:80; server_name gitlab.localdomain; server_tokens off; root /nowhere; rewrite ^ https://$server_name$request_uri permanent; } server { listen *:443 ssl default_server; server_name gitlab.localdomain; server_tokens off; root /home/git/gitlab/public; ssl on; ssl_certificate /etc/ssl/certs/ssl-cert-snakeoil.pem; ssl_certificate_key /etc/ssl/private/ssl-cert-snakeoil.key; ssl_protocols SSLv3 TLSv1 TLSv1.1 TLSv1.2; ssl_ciphers AES:HIGH:!ADH:!MDF; ssl_prefer_server_ciphers on; # individual nginx logs for this gitlab vhost access_log /var/log/nginx/gitlab_access.log; error_log /var/log/nginx/gitlab_error.log; location / { # serve static files from defined root folder;. # @gitlab is a named location for the upstream fallback, see below try_files $uri $uri/index.html $uri.html @gitlab; } # if a file, which is not found in the root folder is requested, # then the proxy pass the request to the upsteam (gitlab puma) location @gitlab { proxy_read_timeout 300; # https://github.com/gitlabhq/gitlabhq/issues/694 proxy_connect_timeout 300; # https://github.com/gitlabhq/gitlabhq/issues/694 proxy_redirect off; proxy_set_header X-Forwarded-Proto $scheme; proxy_set_header X-Forwarded-Ssl on; proxy_set_header Host $http_host; proxy_set_header X-Real-IP $remote_addr; proxy_pass http://gitlab; } } I've restarted after every configuration change, and yet I still only get the 'Welcome to nginx' page when visiting http://192.168.33.10. whereas https://192.168.33.10 works perfectly. Why will nginx still not redirect http requests to https? I've also tried the following configurations listen *:80; server_name <%= @fqdn %>; #root /nowhere; #rewrite ^ https://$server_name$request_uri? permanent; #rewrite ^ https://$server_name$request_uri permanent; #return 301 https://$server_name$request_uri; #return 301 http://$server_name$request_uri; #return 301 http://192.168.33.10$request_uri; return 301 http://$host$request_uri; The logs tailf /var/log/nginx/access.log 192.168.33.1 - - [22/Oct/2013:03:41:39 +0000] "GET / HTTP/1.1" 304 0 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10.8; rv:24.0) Gecko/20100101 Firefox/24.0" 192.168.33.1 - - [22/Oct/2013:03:44:43 +0000] "GET / HTTP/1.1" 200 133 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10.8; rv:24.0) Gecko/20100101 Firefox/24.0" tailf /var/log/nginx/gitlab_error.lob 2013/10/22 02:29:14 [crit] 27226#0: *1 connect() to unix:/home/git/gitlab/tmp/sockets/gitlab.socket failed (2: No such file or directory) while connecting to upstream, client: 192.168.33.1, server: gitlab.localdomain, request: "GET / HTTP/1.1", upstream: "http://unix:/home/git/gitlab/tmp/sockets/gitlab.socket:/", host: "192.168.33.10" Resources http://wiki.nginx.org/Pitfalls How to make nginx redirect How to force or redirect to SSL in nginx? nginx ssl redirect Nginx & Https Redirection https://www.tinywp.in/301-redirect-wordpress/ How to force or redirect to SSL in nginx?

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• Does this prove a network bandwidth bottleneck?

  - by Yuji Tomita

  I've incorrectly assumed that my internal AB testing means my server can handle 1k concurrency @3k hits per second. My theory at at the moment is that the network is the bottleneck. The server can't send enough data fast enough. External testing from blitz.io at 1k concurrency shows my hits/s capping off at 180, with pages taking longer and longer to respond as the server is only able to return 180 per second. I've served a blank file from nginx and benched it: it scales 1:1 with concurrency. Now to rule out IO / memcached bottlenecks (nginx normally pulls from memcached), I serve up a static version of the cached page from the filesystem. The results are very similar to my original test; I'm capped at around 180 RPS. Splitting the HTML page in half gives me double the RPS, so it's definitely limited by the size of the page. If I internally ApacheBench from the local server, I get consistent results of around 4k RPS on both the Full Page and the Half Page, at high transfer rates. Transfer rate: 62586.14 [Kbytes/sec] received If I AB from an external server, I get around 180RPS - same as the blitz.io results. How do I know it's not intentional throttling? If I benchmark from multiple external servers, all results become poor which leads me to believe the problem is in MY servers outbound traffic, not a download speed issue with my benchmarking servers / blitz.io. So I'm back to my conclusion that my server can't send data fast enough. Am I right? Are there other ways to interpret this data? Is the solution/optimization to set up multiple servers + load balancing that can each serve 180 hits per second? I'm quite new to server optimization, so I'd appreciate any confirmation interpreting this data. Outbound traffic Here's more information about the outbound bandwidth: The network graph shows a maximum output of 16 Mb/s: 16 megabits per second. Doesn't sound like much at all. Due to a suggestion about throttling, I looked into this and found that linode has a 50mbps cap (which I'm not even close to hitting, apparently). I had it raised to 100mbps. Since linode caps my traffic, and I'm not even hitting it, does this mean that my server should indeed be capable of outputting up to 100mbps but is limited by some other internal bottleneck? I just don't understand how networks at this large of a scale work; can they literally send data as fast as they can read from the HDD? Is the network pipe that big? In conclusion 1: Based on the above, I'm thinking I can definitely raise my 180RPS by adding an nginx load balancer on top of a multi nginx server setup at exactly 180RPS per server behind the LB. 2: If linode has a 50/100mbit limit that I'm not hitting at all, there must be something I can do to hit that limit with my single server setup. If I can read / transmit data fast enough locally, and linode even bothers to have a 50mbit/100mbit cap, there must be an internal bottleneck that's not allowing me to hit those caps that I'm not sure how to detect. Correct? I realize the question is huge and vague now, but I'm not sure how to condense it. Any input is appreciated on any conclusion I've made.

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• Can't sync filesystem without reboot

  - by Fabio

  I'm having an issue with a linux server. Once a week the running mysql instance hangs and there is no way to fully stop it. If I kill it, it remains in zombie status and init does not reap its pid. The server is used for staging deployments and some internal tools, so it's not under heavy load. The only process constantly used id mysql and for this I think that it's the only process which suffer of this issue. I've searched system logs for errors and the only thing I found is this error (repeated a couple of times) in dmesg output: [706560.640085] INFO: task mysqld:31965 blocked for more than 120 seconds. [706560.640198] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [706560.640312] mysqld D ffff88032fd93f40 0 31965 1 0x00000000 [706560.640317] ffff880242a27d18 0000000000000086 ffff88031a50dd00 ffff880242a27fd8 [706560.640321] ffff880242a27fd8 ffff880242a27fd8 ffff88031e549740 ffff88031a50dd00 [706560.640325] ffff88031a50dd00 ffff88032fd947f8 0000000000000002 ffffffff8112f250 [706560.640328] Call Trace: [706560.640338] [<ffffffff8112f250>] ? __lock_page+0x70/0x70 [706560.640344] [<ffffffff816cb1b9>] schedule+0x29/0x70 [706560.640347] [<ffffffff816cb28f>] io_schedule+0x8f/0xd0 [706560.640350] [<ffffffff8112f25e>] sleep_on_page+0xe/0x20 [706560.640353] [<ffffffff816c9900>] __wait_on_bit+0x60/0x90 [706560.640356] [<ffffffff8112f390>] wait_on_page_bit+0x80/0x90 [706560.640360] [<ffffffff8107dce0>] ? autoremove_wake_function+0x40/0x40 [706560.640363] [<ffffffff8112f891>] filemap_fdatawait_range+0x101/0x190 [706560.640366] [<ffffffff81130975>] filemap_write_and_wait_range+0x65/0x70 [706560.640371] [<ffffffff8122e441>] ext4_sync_file+0x71/0x320 [706560.640376] [<ffffffff811c3e6d>] do_fsync+0x5d/0x90 [706560.640379] [<ffffffff811c40d0>] sys_fsync+0x10/0x20 [706560.640383] [<ffffffff816d495d>] system_call_fastpath+0x1a/0x1f When this happens the only way to make everything working again is a full reboot, but in order to do that I'm forced to use this command after I've manually stopped all running processes echo b > /proc/sysrq-trigger otherwise normal reboot process hangs forever. I've tracked reboots script and I've found out that also the reboot process hangs on a sync call, this one in /etc/init.d/sendsigs (I'm on ubuntu) # Flush the kernel I/O buffer before we start to kill # processes, to make sure the IO of already stopped services to # not slow down the remaining processes to a point where they # are accidentily killed with SIGKILL because they did not # manage to shut down in time. sync I'm almost sure that the cause of this is an hardware issue (the RAID controller???) also because I've other two machines with the same hardware and software configuration and they don't suffer of this, but I can't find any hint in syslog or dmesg. I've also installed smartmontools and mcelog packages but none of them did report any issue. What can I do to track the cause of this issue? Today is happened again, here is the status of system after triggering a reboot init---console-kit-dae---64*[{console-kit-dae}] +-dbus-daemon +-mcelog +-mysqld---{mysqld} +-newrelic-daemon---newrelic-daemon---11*[{newrelic-daemon}] +-ntpd +-polkitd---{polkitd} +-python3 +-rpc.idmapd +-rpc.statd +-rpcbind +-sh---rc---S20sendsigs---sync +-smartd +-snmpd +-sshd---sshd---zsh---sudo---zsh---pstree +-sshd---sshd---zsh---sudo---zsh And here is the status of sync process # ps aux | grep sync root 3637 0.1 0.0 4352 372 ? D 05:53 0:00 sync i.e. Uninterruptible sleep... Hardware specs as reported by lshw I think the raid controller is a fake raid. I usually don't deal with hardware (and for the record I don't have physical access to it) description: Computer product: X7DBP () vendor: Supermicro version: 0123456789 serial: 0123456789 width: 64 bits capabilities: smbios-2.4 dmi-2.4 vsyscall32 configuration: administrator_password=disabled boot=normal frontpanel_password=unknown keyboard_password=unknown power-on_password=disabled uuid=53D19F64-D663-A017-8922-0030487C1FEE *-core description: Motherboard product: X7DBP vendor: Supermicro physical id: 0 version: PCB Version serial: 0123456789 *-firmware description: BIOS vendor: Phoenix Technologies LTD physical id: 0 version: 6.00 date: 05/29/2007 size: 106KiB capacity: 960KiB capabilities: pci pnp upgrade shadowing escd cdboot bootselect edd int13floppy2880 acpi usb ls120boot zipboot biosbootspecification *-storage description: RAID bus controller product: 631xESB/632xESB SATA RAID Controller vendor: Intel Corporation physical id: 1f.2 bus info: pci@0000:00:1f.2 version: 09 width: 32 bits clock: 66MHz capabilities: storage pm bus_master cap_list configuration: driver=ahci latency=0 resources: irq:19 ioport:18a0(size=8) ioport:1874(size=4) ioport:1878(size=8) ioport:1870(size=4) ioport:1880(size=32) memory:d8500400-d85007ff

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• Expert iptables help needed?

  - by Asad Moeen

  After a detailed analysis, I collected these details. I am under a UDP Flood which is more of application dependent. I run a Game-Server and an attacker is flooding me with "getstatus" query which makes the GameServer respond by making the replies to the query which cause output to the attacker's IP as high as 30mb/s and server lag. Here are the packet details, Packet starts with 4 bytes 0xff and then getstatus. Theoretically, the packet is like "\xff\xff\xff\xffgetstatus " Now that I've tried a lot of iptables variations like state and rate-limiting along side but those didn't work. Rate Limit works good but only when the Server is not started. As soon as the server starts, no iptables rule seems to block it. Anyone else got more solutions? someone asked me to contact the provider and get it done at the Network/Router but that looks very odd and I believe they might not do it since that would also affect other clients. Responding to all those answers, I'd say: Firstly, its a VPS so they can't do it for me. Secondly, I don't care if something is coming in but since its application generated so there has to be a OS level solution to block the outgoing packets. At least the outgoing ones must be stopped. Secondly, its not Ddos since just 400kb/s input generates 30mb/s output from my GameServer. That never happens in a D-dos. Asking the provider/hardware level solution should be used in that case but this one is different. And Yes, Banning his IP stops the flood of outgoing packets but he has many more IP-Addresses as he spoofs his original so I just need something to block him automatically. Even tried a lot of Firewalls but as you know they are just front-ends to iptables so if something doesn't work on iptables, what would the firewalls do? These were the rules I tried, iptables -A INPUT -p udp -m state --state NEW -m recent --set --name DDOS --rsource iptables -A INPUT -p udp -m state --state NEW -m recent --update --seconds 1 --hitcount 5 --name DDOS --rsource -j DROP It works for the attacks on un-used ports but when the server is listening and responding to the incoming queries by the attacker, it never works. Okay Tom.H, your rules were working when I modified them somehow like this: iptables -A INPUT -p udp -m length --length 1:1024 -m recent --set --name XXXX --rsource iptables -A INPUT -p udp -m string --string "xxxxxxxxxx" --algo bm --to 65535 -m recent --update --seconds 1 --hitcount 15 --name XXXX --rsource -j DROP They worked for about 3 days very good where the string "xxxxxxxxx" would be rate-limited, blocked if someone flooded and also didn't affect the clients. But just today, I tried updating the chain to try to remove a previously blocked IP so for that I had to flush the chain and restore this rule ( iptables -X and iptables -F ), some clients were already connected to servers including me. So restoring the rules now would also block some of the clients string completely while some are not affected. So does this mean I need to restart the server or why else would this happen because the last time the rules were working, there was no one connected?

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• php-fpm + persistent sockets = 502 bad gateway

  - by leeoniya

  Put on your reading glasses - this will be a long-ish one. First, what I'm doing. I'm building a web-app interface for some particularly slow tcp devices. Opening a socket to them takes 200ms and an fwrite/fread cycle takes another 300ms. To reduce the need for both of these actions on each request, I'm opening a persistent tcp socket which reduces the response time by the aforementioned 200ms. I was hoping PHP-FPM would share the persistent connections between requests from different clients (and indeed it does!), but there are some issues which I havent been able to resolve after 2 days of interneting, reading logs and modifying settings. I have somewhat narrowed it down though. Setup: Ubuntu 13.04 x64 Server (fully updated) on Linode PHP 5.5.0-6~raring+1 (fpm-fcgi) nginx/1.5.2 Relevent config: nginx worker_processes 4; php-fpm/pool.d pm = dynamic pm.max_children = 2 pm.start_servers = 2 pm.min_spare_servers = 2 Let's go from coarse to fine detail of what happens. After a fresh start I have 4x nginx processes and 2x php5-fpm processes waiting to handle requests. Then I send requests every couple seconds to the script. The first take a while to open the socket connection and returns with the data in about 500ms, the second returns data in 300ms (yay it's re-using the socket), the third also succeeds in about 300ms, the fourth request = 502 Bad Gateway, same with the 5th. Sixth request once again returns data, except now it took 500ms again. The process repeats for several cycles after which every 4 requests result in 2x 502 Bad Gateways and 2x 500ms Data responses. If I double all the fpm pool values and have 4x php-fpm processes running, the cycles settles in with 4x successful 500ms responses followed by 4x Bad Gateway errors. If I don't use persistent sockets, this issue goes away but then every request is 500ms. What I suspect is happening is the persistent socket keeps each php-fpm process from idling and ties it up, so the next one gets chosen until none are left and as they error out, maybe they are restarted and become available on the next round-robin loop ut the socket dies with the process. I haven't yet checked the 'slowlog', but the nginx error log shows lots of this: *188 recv() failed (104: Connection reset by peer) while reading response header from upstream, client:... All the suggestions on the internet regarding fixing nginx/php-fpm/502 bad gateway relate to high load or fcgi_pass misconfiguration. This is not the case here. Increasing buffers/sizes, changing timeouts, switching from unix socket to tcp socket for fcgi_pass, upping connection limits on the system....none of this stuff applies here. I've had some other success with setting pm = ondemand rather than dynamic, but as soon as the initial fpm-process gets killed off after idling, the persistent socket is gone for all subsequent php-fpm spawns. For the php script, I'm using stream_socket_client() with a STREAM_CLIENT_PERSISTENT flag. A while/stream_select() loop to detect socket data and fread($sock, 4096) to grab the data. I don't call fclose() obviously. If anyone has some additional questions or advice on how to get a persistent socket without tying up the php-fpm processes beyond the request completion, or maybe some other things to try, I'd appreciate it. some useful links: Nginx + php-fpm - recv() error Nginx + php-fpm "504 Gateway Time-out" error with almost zero load (on a test-server) Nginx + PHP-FPM "error 104 Connection reset by peer" causes occasional duplicate posts http://www.linuxquestions.org/questions/programming-9/php-pfsockopen-552084/ http://stackoverflow.com/questions/14268018/concurrent-use-of-a-persistent-php-socket http://devzone.zend.com/303/extension-writing-part-i-introduction-to-php-and-zend/#Heading3 http://stackoverflow.com/questions/242316/how-to-keep-a-php-stream-socket-alive http://php.net/manual/en/install.fpm.configuration.php https://www.google.com/search?q=recv%28%29+failed+%28104:+Connection+reset+by+peer%29+while+reading+response+header+from+upstream+%22502%22&ei=mC1XUrm7F4WQyAHbv4H4AQ&start=10&sa=N&biw=1920&bih=953&dpr=1

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• BluRay audio/video stuttering with PowerDVD 11, WinDVD 11 Pro, etc? Xonar/Auzen HD audio option?

  - by jrista

  I recently upgraded my Windows 7 MediaCenter HTPC due to a motherboard failure (really old motherboard and cpu, it was on its last legs.) I chose to upgrade to an i5 system with everything built into the motherboard. I did my due diligence, researched, and found some hardware that was within my budget. I ended up with: Core i5 2500K (3.3Ghz) Corsair XMS3 2x2Gb DDR3 (4Gb) ASUS P8H 61-M LE/CSM MicroCenter 64Gb SSD (Previous BluRay player, forget the brand) The system is pretty awesome, and plays everything I have perfectly. I almost went with an Atom solution, however there have been numerous notes that they do not play NetFlix Instant Watch well...and I am a heavy Netflix IW user. High definition BluRay rips work well, although they usually contain lower audio quality than the BluRay's they were ripped from. The real problem I am encountering is playing back BluRay video from discs. For some reason, I am encountering rather terrible stuttering problems with both the audio and video. The stuttering is synchronous in both, and occurs at seemingly random intervals. I've used PowerDVD 9, PowerDVD 11 trial, and WinDVD 11 Pro trial. All three have stuttering problems, although PowerDVD 11 seems to have the least. Watching system resource usage, CPU load is never above 20%, and memory usage tends to be a constant 1/3rd the total available system memory. When playback is fine, its superb...the video is crystal clear. The audio quality is ok, certainly not what I would expect from a BluRay disc. I did some research, and it seems that playing BluRay from a PC causes a downsampling of the audio? I am curious if the audio is my primary problem here, the cause of the stuttering I am encountering? When stuttering occurs, the audio gets REALLY bad, while the video just pauses momentarily every second until for whatever reason everything picks up and runs fine (usually after a few seconds to a couple minutes.) The audio chipset is a Realtek HD ALC887 8-channel, supposedly designed to support BluRay playback. Has anyone encountered any issues like this playing back bluray discs on a PC (namely with PowerDVD...WinDVD was FAR worse, and seemed to have real trouble even reading the discs, and I have no interest in fiddling with it further.) Is there any reason to suspect the video decoding as the problem?(Given how bad the audio gets during a stutter, and how clean the video remains, I am inclined to think the issue boils down to audio.) Is it even remotely possible that the motherboard, cpu, or ram are causing the stuttering (all three are pretty blazing fast...faster than the hardware that I replaced, which seemed to play BluRay fine with PowerDVD 9.) I've read a bit about the Asus Xonar HDAV 1.3 and the Auzen X-Fi HomeTheater HD home theater hi-fi audio cards. Seems they are the only way to get true full-quality, uncompressed BluRay audio bitstreaming over HDMI on a PC. None of the usual suspects seem to have these cards in stock, however. Are these cards worth getting? Are they even still available, or have they been discontinued (if so, that would indeed be sad...they sound simply fantastic.)

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• How to troubleshoot a PHP script that causes a Segmenation Fault?

  - by johnlai2004

  I posted this on stackoverflow.com as well because I'm not sure if this is a programming problem or a server problem. I'm using ubuntu 9.10, apache2, mysql5 and php5. I've noticed an unusual problem with some of my php programs. Sometimes when visiting a page like profile.edit.php, the browser throws a dialogue box asking to download profile.edit.php page. When I download it, there's nothing in the file. profile.edit.php is supposed to be a web form that edits user information. I've noticed this on some of my other php pages as well. I look in my apache error logs, and I see a segmentation fault message: [Mon Mar 08 15:40:10 2010] [notice] child pid 480 exit signal Segmentation fault (11) And also, the issue may or may not appear depending on which server I deploy my application too. Additonal Details This doesn't happen all the time though. It only happens sometimes. For example, profile.edit.php will load properly. But as soon as I hit the save button (form action="profile.edit.php?save=true"), then the page asks me to download profile.edit.php. Could it be that sometimes my php scripts consume too much resources? Sample code Upon save action, my profile.edit.php includes a data_access_object.php file. I traced the code in data_access_object.php to this line here if($params[$this->primaryKey]) { $q = "UPDATE $this->tableName SET ".implode(', ', $fields)." WHERE ".$this->primaryKey." = ?$this->primaryKey"; $this->bind($this->primaryKey, $params[$this->primaryKey], $this->tblFields[$this->primaryKey]['mysqlitype']); } else { $q = "INSERT $this->tableName SET ".implode(', ', $fields); } // Code executes perfectly up to this point // echo 'print this'; exit; // if i uncomment this line, profile.edit.php will actually show 'print this'. If I leave it commented, the browser will ask me to download profile.edit.php if(!$this->execute($q)){ $this->errorSave = -3; return false;} // When I jumped into the function execute(), every line executed as expected, right up to the return statement. And if it helps, here's the function execute($sql) in data_access_object.php function execute($sql) { // find all list types and explode them // eg. turn ?listId into ?listId0,?listId1,?listId2 $arrListParam = array_bubble_up('arrayName', $this->arrBind); foreach($arrListParam as $listName) if($listName) { $explodeParam = array(); $arrList = $this->arrBind[$listName]['value']; foreach($arrList as $key=>$val) { $newParamName = $listName.$key; $this->bind($newParamName,$val,$this->arrBind[$listName]['type']); $explodeParam[] = '?'.$newParamName; } $sql = str_replace("?$listName", implode(',',$explodeParam), $sql); } // replace all ?varName with ? for syntax compliance $sqlParsed = preg_replace('/\?[\w\d_\.]+/', '?', $sql); $this->stmt->prepare($sqlParsed); // grab all the parameters from the sql to create bind conditions preg_match_all('/\?[\w\d_\.]+/', $sql, $matches); $matches = $matches[0]; // store bind conditions $types = ''; $params = array(); foreach($matches as $paramName) { $types .= $this->arrBind[str_replace('?', '', $paramName)]['type']; $params[] = $this->arrBind[str_replace('?', '', $paramName)]['value']; } $input = array('types'=>$types) + $params; // bind it if(!empty($types)) call_user_func_array(array($this->stmt, 'bind_param'), $input); $stat = $this->stmt->execute(); if($GLOBALS['DEBUG_SQL']) echo '<p style="font-weight:bold;">SQL error after execution:</p> ' . $this->stmt->error.'<p>&nbsp;</p>'; $this->arrBind = array(); return $stat; }

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• apache webserver unresponsible with server-status showing all child processes waiting for connection

  - by Jeff

  My setup: i have 3 nearly identical webserver machines serving the same high loaded dynamic website with simple load balancing over dns. The service has been working for over two ears with the same apache config. apache2, php5, ubuntu 8.04 linux 2.6.24-29-server My problem: since about two weeks i'm experiencing problems with this config. Nearly every day i have one small moment about 5 minutes, in which the website is unreachable. I'm still able to login to the servers over ssh. If i run htop, i see the machine simply doing nothing. i have about 1000 apache processes running, but no cpu activity. i've used the apache mod_status to debug this situation. the process scoreboard looks like this: _C.___K_______________________R._______.__K_K____K___C_______.__ _______C__________.___________________________________.________C _.____K__________K___K_WK_____._K_____________________________._ W______K__________K________.____________________._______C_______ _C_.__K__K____.._.._____________________________________C_______ _R___________K___.______C________.C_________.______._____C______ ____________KKC____K_____K__WC_________________C_____.__.____.__ _____________________C_________K______.____C______._____________ _.___C____.___.___________________________.K______.____K________ W__.___________________C.__.____K________K_______R_._.__._______ __C__C_.__________C__C_______._____W______________C_.___C_______ ____.______C_____________C________.____C____________.________._K __.__________.K_____________K_________._____C____.K__________KW_ __K.W________R_________._______.___W___________.____.__K_____W__ W___.___..________W____K Scoreboard Key: "_" Waiting for Connection, "S" Starting up, "R" Reading Request, "W" Sending Reply, "K" Keepalive (read), "D" DNS Lookup, "C" Closing connection, "L" Logging, "G" Gracefully finishing, "I" Idle cleanup of worker, "." Open slot with no current process So the most of the processes are just waiting for connection. after about 5 minutes the situation will return to normal: i have lot least processes on every machine, the most workers have the "."-status (meaing they are open to process a request) and of course the website is reachable! so i'm trying to find something in the logs, but there is simply nothing... the apache access log is silent for about 4 minutes, the same is for the error log. i also can not figure out anything wrong in other system logs. the situation is the same on all 3 webservers (all of them have this load peak and unresposibility at the same time), so i do not thing this is hardware related. but i think, this might be related to some network (tcp) issue. any ideas? EDIT: some more information, that i have just discovered: it has just happened again. and i was able to verify that i'm also not able to connect locally when this problem occurs. i have made some connection statistics with the following command after it happend netstat -an|awk '/tcp/ {print $6}'|sort|uniq -c 109 CLOSE_WAIT 2652 ESTABLISHED 2 FIN_WAIT1 11 LAST_ACK 12 LISTEN 91 SYN_RECV 1 SYN_SENT 16 TIME_WAIT If i execute the same command some time later, i have something like this: 4 CLOSING 108 ESTABLISHED 18 FIN_WAIT1 182 FIN_WAIT2 37 LAST_ACK 12 LISTEN 50 SYN_RECV 11276 TIME_WAIT So in the normal situation i have only 100-200 open connections by clients beeing handled by apache in this moment. when i have this "crash", i have a lot more connections. what is the best way to analyse this? EDIT2: the important lines in apache2.conf are: KeepAlive On MaxKeepAliveRequests 20 KeepAliveTimeout 1 <IfModule mpm_prefork_module> ServerLimit 920 StartServers 30 MinSpareServers 80 MaxSpareServers 120 MaxClients 920 MaxRequestsPerChild 700 </IfModule> it is an apache2 prefork with php_mod. the server has 8GB ram and a 4gb swap partition.

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• All client browsers repeatedly asking for NTLM authentication when running through local proxy server

  - by Marko

  All client browsers repeatedly asking for NTLM authentication when running through local proxy server. When pointing browsers through the local proxy to the internet, some but not all clients are being repeatedley prompted to authenticate to the proxy server. I have inspected the headers using firefox live headers as well as fiddler, and in all cases the authentication prompts happen when requesting SSL resources. an example of this would be as follows: GET http://gmail.google.com/mail/ HTTP/1.1 Accept: image/gif, image/jpeg, image/pjpeg, image/pjpeg, application/x-shockwave- flash, application/x-ms-application, application/x-ms-xbap, application/vnd.ms- xpsdocument, application/xaml+xml, */* Accept-Language: en-gb User-Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729) Accept-Encoding: gzip, deflate Proxy-Connection: Keep-Alive Host: gmail.google.com GET http://gmail.google.com/mail/ HTTP/1.1 Accept: image/gif, image/jpeg, image/pjpeg, image/pjpeg, application/x-shockwave- flash, application/x-ms-application, application/x-ms-xbap, application/vnd.ms- xpsdocument, application/xaml+xml, */* Accept-Language: en-gb User-Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729) Accept-Encoding: gzip, deflate Proxy-Connection: Keep-Alive Host: gmail.google.com Proxy-Authorization: NTLM TlRMTVNTUAABAAAAB7IIogkACQAvAAAABwAHACgAAAAFASgKAAAAD1dJTlhQMUdGTEFHU0hJUDc= GET http://gmail.google.com/mail/ HTTP/1.1 Accept: image/gif, image/jpeg, image/pjpeg, image/pjpeg, application/x-shockwave- flash, application/x-ms-application, application/x-ms-xbap, application/vnd.ms- xpsdocument, application/xaml+xml, */* Accept-Language: en-gb User-Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729) Accept-Encoding: gzip, deflate Proxy-Connection: Keep-Alive Proxy-Authorization: NTLM TlRMTVNTUAADA (more stuff goes here I cut it short) Host: gmail.google.com At this point the username and password prompt has appeared in the browser, it does not matter what is typed into this box, correct credentials, random nonsense the browser does not accept anything in this box it will continue to popup. If I press cancel, I sometimes get a http 407 error, but on other occasions I click cancel the website proceeds to download and show normally. This is repeatable with some clients running through my proxy server, but in other cases it does not happen at all. In the cases where a client computer works normally, the only difference I can see is that the 3rd request for SSL resource comes back with a 200 response, see below: CONNECT gmail.google.com:443 HTTP/1.0 User-Agent: Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0; MALC) Proxy-Connection: Keep-Alive Content-Length: 0 Host: gmail.google.com Pragma: no-cache Proxy-Authorization: NTLM TlRMTVNTUAADAAAAGAAYAIAAAA A SSLv3-compatible ClientHello handshake was found. I have tried resetting user accounts as well as computer accounts in Active Directory. User accounts and passwords that are being used are correct and the passwords have been reset so they are not out of sync. I have removed the clients and even the proxy server from the domain, and rejoined them. I have installed a complete separate proxy server and get exactly the same problem when I point clients to a different proxy server on a different IP address.

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• Cheapest way to connect 20-24 Sata II HDDs in a budget storage server?

  - by Joe Hopfgartner

  I need to assemble a high density storage server for as cheap as possible. It's been a while for me and the last systems I integrated didn't even have Sata yet... During my Research I of course stumbled about Nexsan SATA Beast, the BackBlaze storage Pods as well as some ridiculously overpriced HP Proliant or Dell storage solutions. Finally I choose Norco cases as the way to go. My eye is set on the RPC-4020, which is a 4U 19" Rackmount case with 20 Hot Swap 3.5" SATA/SAS Hdd trays (Backplanes included) and room for two 2.5" OS drives as well as a Slim Line CD-Rom. The backplanes connect with a single SATA port for each drive, so there are 20 internal SATA ports to to be connected. They also have redundant power ports which I think is quite nice. The cheapest price I have found is 290$ + 40$ shipping. In europe the cheapest unfortunately is 370€ (500$) + 40 € shipping... A nice alternative would be the RPC-4224 which has SFF-8087 Mini SAS connectors that bundle 4 SATA trays each. But it doesn't seem to be available in Europe (where i am) anywhere. So here comes my problem: What Mainboard/Controller to choose to connect them for as cheap as possible while still having nice data rates? I have to say that the server is intended as a Storage server with 1gps connectivity and the data transfer will be distributed very evenly across all drives. I also don't require any raid functionality. This is all done at application level, I just need JBOD. So for example if I go for the RPC 4020 Model I need to connect 20 Storage + 1 OS + 1 CDROM Sata ports. I searched a bit and stumbled across this very low priced controller: http://www.intel.com/products/server/raid-controllers/SASWT4I/SASWT4I-overview.htm They sell it for 115 € here and the specs say it can control up to 122 hard discs and has 4 Mini SAS connectors. So I would use 4 Mini SAS 36pin - 4 SATA 7pin cables to connect 4 SATA drives to each port and choose a Mainboard taht has 6 SATA on board (for example this one) and hurray, I can connect my 22 SATA devices for as low as about ~ 220 EUR (cpu, ram, psu, case not counted) Question: WOULD THAT WORK? And if not, why? 2nd Question: If I go for the 4220 or 4224 Model, I have internal Mini SAS connectors. Am I right in assuming that the backplane than acts as a "SAS Expander"? And can I just plug these SAS connectors into any SAS port I can find on my controller / mainboard or are there certain requirements? I know that SATA port multipliers only work with controllers that are ready for that. But isn't this expansion already implemented in the SAS standard? I am sorry that this is a very broad question, but I really spent the last week reading up and it seems to be not so clear! Especially all the controlling hardware specifications! 3rd Question: A lot of hardware specs feature "internal channels" and "internal connectors". The connecors are the physical numbers of places where I can plug a cable in. I got that. But are the "internal channels" always the maximum numbers of physical drives that can be used in the end? Or can I enhance this further by Expanders/Fanouts? 4th and last question: What do you think about the setup so far? Do you know any good alternatives? Maby I am completely going the wrong way and some DAS would be way better? Are there any comparable chassis available in europe? Please feel free to say whatever you think is relevant to the subject!

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• bash: per-command history. How does it work?

  - by romainl

  OK. I have an old G5 running Leopard and a Dell running Ubuntu 10.04 at home and a MacPro also running Leopard at work. I use Terminal.app/bash a lot. On my home G5 it exhibits a nice feature: using ? to navigate history I get the last command starting with the few letters that I've typed. This is what I mean (| represents the caret): $ ssh user@server $ vim /some/file/just/to/populate/history $ ss| So, I've typed the two first letters of "ssh", hitting ? results in this: $ ssh user@server instead of this, which is the behaviour I get everywhere else : $ vim /some/file/just/to/populate/history If I keep on hitting ? or ?, I can navigate through the history of ssh like this: $ ssh otheruser@otherserver $ ssh user@server $ ssh yetanotheruser@yetanotherserver It works the same for any command like cat, vim or whatever. That's really cool. Except that I have no idea how to mimic this behaviour on my other machines. Here is my .profile: export PATH=/Developer/SDKs/flex_sdk_3.4/bin:/opt/local/bin:/opt/local/sbin:/usr/local/bin:/sw/bin:/sw/sbin:/bin:/sbin:/bin:/sbin:/usr/bin:/usr/sbin:$HOME/Applications/bin:/usr/X11R6/bin export MANPATH=/usr/local/share/man:/usr/local/man:opt/local/man:sw/share/man export INFO=/usr/local/share/info export PERL5LIB=/opt/local/lib/perl5 export PYTHONPATH=/opt/local/bin/python2.7 export EDITOR=/opt/local/bin/vim export VISUAL=/opt/local/bin/vim export JAVA_HOME=/System/Library/Frameworks/JavaVM.framework/Versions/1.6.0/Home export TERM=xterm-color export GREP_OPTIONS='--color=auto' GREP_COLOR='1;32' export CLICOLOR=1 export LS_COLORS='no=00:fi=00:di=01;34:ln=target:pi=40;33:so=01;35:do=01;35:bd=40;33;01:cd=40;33;01:or=40;31;01:*.tar=00;31:*.tgz=00;31:*.arj=00;31:*.taz=00;31:*.lzh=00;31:*.zip=00;31:*.z=00;31:*.Z=00;31:*.gz=00;31:*.bz2=00;31:*.deb=00;31:*.rpm=00;31:*.TAR=00;31:*.TGZ=00;31:*.ARJ=00;31:*.TAZ=00;31:*.LZH=00;31:*.ZIP=00;31:*.Z=00;31:*.Z=00;31:*.GZ=00;31:*.BZ2=00;31:*.DEB=00;31:*.RPM=00;31:*.jpg=00;35:*.png=00;35:*.gif=00;35:*.bmp=00;35:*.ppm=00;35:*.tga=00;35:*.xbm=00;35:*.xpm=00;35:*.tif=00;35:*.png=00;35:*.fli=00;35:*.gl=00;35:*.dl=00;35:*.psd=00;35:*.JPG=00;35:*.PNG=00;35:*.GIF=00;35:*.BMP=00;35:*.PPM=00;35:*.TGA=00;35:*.XBM=00;35:*.XPM=00;35:*.TIF=00;35:*.PNG=00;35:*.FLI=00;35:*.GL=00;35:*.DL=00;35:*.PSD=00;35:*.mpg=00;36:*.avi=00;36:*.mov=00;36:*.flv=00;36:*.divx=00;36:*.qt=00;36:*.mp4=00;36:*.m4v=00;36:*.MPG=00;36:*.AVI=00;36:*.MOV=00;36:*.FLV=00;36:*.DIVX=00;36:*.QT=00;36:*.MP4=00;36:*.M4V=00;36:*.txt=00;32:*.rtf=00;32:*.doc=00;32:*.odf=00;32:*.rtfd=00;32:*.html=00;32:*.css=00;32:*.js=00;32:*.php=00;32:*.xhtml=00;32:*.TXT=00;32:*.RTF=00;32:*.DOC=00;32:*.ODF=00;32:*.RTFD=00;32:*.HTML=00;32:*.CSS=00;32:*.JS=00;32:*.PHP=00;32:*.XHTML=00;32:' export LC_ALL=C export LANG=C stty cs8 -istrip -parenb bind 'set convert-meta off' bind 'set meta-flag on' bind 'set output-meta on' alias ip='curl http://www.whatismyip.org | pbcopy' alias ls='ls -FhLlGp' alias la='ls -AFhLlGp' alias couleurs='$HOME/Applications/bin/colors2.sh' alias td='$HOME/Applications/bin/todo.sh' alias scale='$HOME/Applications/bin/scale.sh' alias stree='$HOME/Applications/bin/tree' alias envoi='$HOME/Applications/bin/envoi.sh' alias unfoo='$HOME/Applications/bin/unfoo' alias up='cd ..' alias size='du -sh' alias lsvn='svn list -vR' alias jsc='/System/Library/Frameworks/JavaScriptCore.framework/Versions/A/Resources/jsc' alias asl='sudo rm -f /private/var/log/asl/*.asl' alias trace='tail -f $HOME/Library/Preferences/Macromedia/Flash\ Player/Logs/flashlog.txt' alias redis='redis-server /opt/local/etc/redis.conf' source /Users/johncoltrane/Applications/bin/git-completion.sh export GIT_PS1_SHOWUNTRACKEDFILES=1 export GIT_PS1_SHOWUPSTREAM="verbose git" export GIT_PS1_SHOWDIRTYSTATE=1 export PS1='\n\[\033[32m\]\w\[\033[0m\] $(__git_ps1 "[%s]")\n\[\033[1;31m\]\[\033[31m\]\u\[\033[0m\] $ \[\033[0m\]' mkcd () { mkdir -p "$*" cd "$*" } function cdl { cd $1 la } n() { $EDITOR ~/Dropbox/nv/"$*".txt } nls () { ls -c ~/Dropbox/nv/ | grep "$*" } copy(){ curl -s -F 'sprunge=<-' http://sprunge.us | pbcopy } if [ -f /opt/local/etc/profile.d/cdargs-bash.sh ]; then source /opt/local/etc/profile.d/cdargs-bash.sh fi if [ -f /opt/local/etc/bash_completion ]; then . /opt/local/etc/bash_completion fi Any idea?

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• iptables - quick safety eval & limit max conns over time

  - by Peter Hanneman

  Working on locking down a *nix server box with some fancy iptable(v1.4.4) rules. I'm approaching the matter with a "paranoid, everyone's out to get me" style, not necessarily because I expect the box to be a hacker magnet but rather just for the sake of learning iptables and *nix security more throughly. Everything is well commented - so if anyone sees something I missed please let me know! The *nat table's "--to-ports" point to the only ports with actively listening services. (aside from pings) Layer 2 apps listen exclusively on chmod'ed sockets bridged by one of the layer 1 daemons. Layers 3+ inherit from layer 2 in a similar fashion. The two lines giving me grief are commented out at the very bottom of the *filter rules. The first line runs fine but it's all or nothing. :) Many thanks, Peter H. *nat #Flush previous rules, chains and counters for the 'nat' table -F -X -Z #Redirect traffic to alternate internal ports -I PREROUTING --src 0/0 -p tcp --dport 80 -j REDIRECT --to-ports 8080 -I PREROUTING --src 0/0 -p tcp --dport 443 -j REDIRECT --to-ports 8443 -I PREROUTING --src 0/0 -p udp --dport 53 -j REDIRECT --to-ports 8053 -I PREROUTING --src 0/0 -p tcp --dport 9022 -j REDIRECT --to-ports 8022 COMMIT *filter #Flush previous settings, chains and counters for the 'filter' table -F -X -Z #Set default behavior for all connections and protocols -P INPUT DROP -P OUTPUT DROP -A FORWARD -j DROP #Only accept loopback traffic originating from the local NIC -A INPUT -i lo -j ACCEPT -A INPUT ! -i lo -d 127.0.0.0/8 -j DROP #Accept all outgoing non-fragmented traffic having a valid state -A OUTPUT ! -f -m state --state NEW,RELATED,ESTABLISHED -j ACCEPT #Drop fragmented incoming packets (Not always malicious - acceptable for use now) -A INPUT -f -j DROP #Allow ping requests rate limited to one per second (burst ensures reliable results for high latency connections) -A INPUT -p icmp --icmp-type 8 -m limit --limit 1/sec --limit-burst 2 -j ACCEPT #Declaration of custom chains -N INSPECT_TCP_FLAGS -N INSPECT_STATE -N INSPECT #Drop incoming tcp connections with invalid tcp-flags -A INSPECT_TCP_FLAGS -p tcp --tcp-flags ALL ALL -j DROP -A INSPECT_TCP_FLAGS -p tcp --tcp-flags ALL NONE -j DROP -A INSPECT_TCP_FLAGS -p tcp --tcp-flags ACK,FIN FIN -j DROP -A INSPECT_TCP_FLAGS -p tcp --tcp-flags ACK,PSH PSH -j DROP -A INSPECT_TCP_FLAGS -p tcp --tcp-flags ACK,URG URG -j DROP -A INSPECT_TCP_FLAGS -p tcp --tcp-flags SYN,FIN SYN,FIN -j DROP -A INSPECT_TCP_FLAGS -p tcp --tcp-flags ALL FIN,PSH,URG -j DROP -A INSPECT_TCP_FLAGS -p tcp --tcp-flags FIN,RST FIN,RST -j DROP -A INSPECT_TCP_FLAGS -p tcp --tcp-flags SYN,RST SYN,RST -j DROP -A INSPECT_TCP_FLAGS -p tcp --tcp-flags ALL SYN,FIN,PSH,URG -j DROP -A INSPECT_TCP_FLAGS -p tcp --tcp-flags ALL SYN,RST,ACK,FIN,URG -j DROP #Accept incoming traffic having either an established or related state -A INSPECT_STATE -m state --state ESTABLISHED,RELATED -j ACCEPT #Drop new incoming tcp connections if they aren't SYN packets -A INSPECT_STATE -m state --state NEW -p tcp ! --syn -j DROP #Drop incoming traffic with invalid states -A INSPECT_STATE -m state --state INVALID -j DROP #INSPECT chain definition -A INSPECT -p tcp -j INSPECT_TCP_FLAGS -A INSPECT -j INSPECT_STATE #Route incoming traffic through the INSPECT chain -A INPUT -j INSPECT #Accept redirected HTTP traffic via HA reverse proxy -A INPUT -p tcp --dport 8080 -j ACCEPT #Accept redirected HTTPS traffic via STUNNEL SSH gateway (As well as tunneled HTTPS traffic destine for other services) -A INPUT -p tcp --dport 8443 -j ACCEPT #Accept redirected DNS traffic for NSD authoritative nameserver -A INPUT -p udp --dport 8053 -j ACCEPT #Accept redirected SSH traffic for OpenSSH server #Temp solution: -A INPUT -p tcp --dport 8022 -j ACCEPT #Ideal solution: #Limit new ssh connections to max 10 per 10 minutes while allowing an "unlimited" (or better reasonably limited?) number of established connections. #-A INPUT -p tcp --dport 8022 --state NEW,ESTABLISHED -m recent --set -j ACCEPT #-A INPUT -p tcp --dport 8022 --state NEW -m recent --update --seconds 600 --hitcount 11 -j DROP COMMIT *mangle #Flush previous rules, chains and counters in the 'mangle' table -F -X -Z COMMIT

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