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• how to back up data from a machine that keeps hanging

  - by Amit Phatarphekar

  Hello - I have a storage server running opensolaris. But lately its been acting up - it hangs at random times due to some SCSI/ATA related error messages. I've tried to fix it without any progress, so I'm giving up now. The machine keeps hanging every 30 minutes or 1 hr ...sometimes after 4 hrs. Its very unpredictable. So I've decided to just reformat the storage server and start from scratch...maybe I'll just not use solaris and install something else, since the errors are related to solaris running on ATA HDD or something. Question - Before I reformat it, I want to back up some of the important data on it. Like it has a VM with 200 GB disk files, it has a whole bunch of ISOs stored on it etc etc. I'm using a simple scp to copy the files over to a different machine. My issue is that, because the machine hangs....sometimes my file copy is incomplete and I have to start all over again. Lets say I'm trying to copy a 200GB file which takes like 4 hrs....IF the machine hangs before the whole file i copied over...I have to recopy the file from scratch. Is there a solution to copy the files over such that if the machine hangs or network goes down..the copying can resume from where it left off? - like if 50 GB of a 200GB file was copied and machine hung....next time, it'll just continue to copy rest of the amount, instead of starting all over again. Thanks Amit

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• Website has become slower on a VPS, was much fast on a shared host. What's wrong?

  - by Arpit Tambi

  My shared host suspended my website stating system overload, so I moved my website to a VPS which has 4GB RAM. But for some reason the website has become very slow. This is the vmstat output - procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------ r b swpd free buff cache si so bi bo in cs us sy id wa st 1 0 0 3050500 0 0 0 0 0 1 0 0 0 0 100 0 0 Here's the Apache Benchmark output for a STATIC html page I ran on the server itself - Benchmarking www.ask-oracle.com (be patient)...apr_poll: The timeout specified has expired (70007) Total of 20 requests completed Update: Server Config: List item Centos 5.6 4 cores cpu 4 GB RAM LAMP stack with APC Wordpress Only one website It takes almost double time to load now, same website was much fast on shared hosting. I know I need to tweak some settings but have no clue where to start from? I have already tried to optimize apache, mysql etc. Update 2: CPU usage is low, see uptime output: 11:09:02 up 7 days, 21:26, 1 user, load average: 0.09, 0.11, 0.09 Update 3: When I load any webpage, browser shows "Waiting" for a long time and then page loads quickly. So I suspect server can accept only limited connections and holds extra connections in a waiting state. How to check this? Update 4: Following is the output on executing netperf TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to localhost.localdomain (127.0.0.1) port 0 AF_INET Recv Send Send Socket Socket Message Elapsed Size Size Size Time Throughput bytes bytes bytes secs. 10^6bits/sec 87380 16384 16384 10.00 9615.40 [root@ip-118-139-177-244 j3ngn5ri6r01t3]# Here are the Apache MPM settings from httpd.conf, do they look okay? <IfModule worker.c> StartServers 5 MaxClients 100 MinSpareThreads 50 MaxSpareThreads 250 ThreadsPerChild 125 MaxRequestsPerChild 10000 ServerLimit 100 </IfModule>

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• My linux server "Number of processes created" and "Context switches" are growing incredibly fast

  - by Jorge Fuentes González

  I have a strange behaviour in my server :-/. Is a OpenVZ VPS (I think is OpenVZ, because /proc/user_beancounters exists and df -h returns /dev/simfs drive. Also ifconfig returns venet0). When I do cat /proc/stat, I can see how each second about 50-100 processes are created and happens about 800k-1200k context switches! All that info is with the server completely idle, no traffic nor programs running. Top shows 0 load average and 100% idle CPU. I've closed all non-needed services (httpd, mysqld, sendmail, nagios, named...) and the problem still happens. I do ps -ALf each second too and I don't see any changes, only a new ps process is created each time and the PID is just the same as before + 1, so new processes are not created, so I thought that process growing in cat /proc/stat must be threads (Yes, seems that processes in /proc/stat counts threads creation too as this states: http://webcache.googleusercontent.com/search?q=cache:8NLgzKEzHQQJ:www.linuxhowtos.org/System/procstat.htm&hl=es&tbo=d&gl=es&strip=1). I've changed to /proc dir and done cat [PID]\status with all PIDs listed with ls (Including kernel ones) and in any process voluntary_ctxt_switches nor nonvoluntary_ctxt_switches are growing at the same speed as cat /proc/stat does (just a few tens/second), Threads keeps the same also. I've done strace -p PID to all process too so I can see if any process is crating threads or something but the only process that has a bit of movement is ssh and that movement is read/write operations because of the data is sending to my terminal. After that, I've done vmstat -s and saw that forks is growing at the same speed processes in /proc/stat does. As http://linux.die.net/man/2/fork says, each fork() creates a new PID but my server PID is not growing! The last thing I can think of is that all process data that proc/stat and vmstat -s show is shared with all the other VPS stored in the same machine, but I don't know if that is correct... If someone can throw some light on this I would be really grateful.

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• Unable to PPTP through NAT on Cisco 881

  - by MasterRoot24

  I'm trying to connect to a PPTP server which is sat behind a Cisco 881 NAT router. The server is running Ubuntu Server 12.04 and is running Poptop pptpd as the PPTP daemon listening for connections. As discussed in my other question, I'm trying to setup a Cisco 881 router to replace my old Linksys WAG320N. This same server and WAN connection worked fine with the WAG320N with no special configuration, other than allowing 1723 in through the firewall. On the Cisco 881, I'm using the newer ip nat enable or NAT NVI to setup static routes in through the firewall for the services running behind the router. My reason being that I can't run another copy of my live DNS domains internally with local IP addresses in. For the purposes of this question, though, I have rebuilt the router with ip nat inside/outside style NAT'ing, but this issue is still apparent. HTTP/SMTP/IMAP etc. all work ok from both the WAN and LAN interfaces of the router. I'm only having issues with SIP (see other question) and PPTP. My issue is that the GRE doesn't appear to be passing through NAT correctly and one end of the connection is not receiving GRE traffic when it should be, so the server hangs up the connection. Here's an example of /var/log/syslog with debug enabled in /etc/pptpd.conf: Dec 11 21:06:30 <HOSTNAME> pptpd[22626]: MGR: Launching /usr/sbin/pptpctrl to handle client Dec 11 21:06:30 <HOSTNAME> pptpd[22626]: CTRL: local address = 192.168.1.50 Dec 11 21:06:30 <HOSTNAME> pptpd[22626]: CTRL: remote address = 192.168.1.51 Dec 11 21:06:30 <HOSTNAME> pptpd[22626]: CTRL: pppd options file = /etc/ppp/pptpd-options Dec 11 21:06:30 <HOSTNAME> pptpd[22626]: CTRL: Client 82.132.248.216 control connection started Dec 11 21:06:30 <HOSTNAME> pptpd[22626]: CTRL: Received PPTP Control Message (type: 1) Dec 11 21:06:30 <HOSTNAME> pptpd[22626]: CTRL: Made a START CTRL CONN RPLY packet Dec 11 21:06:30 <HOSTNAME> pptpd[22626]: CTRL: I wrote 156 bytes to the client. Dec 11 21:06:30 <HOSTNAME> pptpd[22626]: CTRL: Sent packet to client Dec 11 21:06:30 <HOSTNAME> pptpd[22626]: CTRL: Received PPTP Control Message (type: 7) Dec 11 21:06:30 <HOSTNAME> pptpd[22626]: CTRL: Set parameters to 100000000 maxbps, 64 window size Dec 11 21:06:30 <HOSTNAME> pptpd[22626]: CTRL: Made a OUT CALL RPLY packet Dec 11 21:06:30 <HOSTNAME> pptpd[22626]: CTRL: Starting call (launching pppd, opening GRE) Dec 11 21:06:30 <HOSTNAME> pptpd[22626]: CTRL: pty_fd = 6 Dec 11 21:06:30 <HOSTNAME> pptpd[22626]: CTRL: tty_fd = 7 Dec 11 21:06:30 <HOSTNAME> pptpd[22626]: CTRL: I wrote 32 bytes to the client. Dec 11 21:06:30 <HOSTNAME> pptpd[22626]: CTRL: Sent packet to client Dec 11 21:06:30 <HOSTNAME> pptpd[22627]: CTRL (PPPD Launcher): program binary = /usr/sbin/pppd Dec 11 21:06:30 <HOSTNAME> pptpd[22627]: CTRL (PPPD Launcher): local address = 192.168.1.50 Dec 11 21:06:30 <HOSTNAME> pptpd[22627]: CTRL (PPPD Launcher): remote address = 192.168.1.51 Dec 11 21:06:30 <HOSTNAME> pppd[22627]: Plugin /usr/lib/pptpd/pptpd-logwtmp.so loaded. Dec 11 21:06:30 <HOSTNAME> pppd[22627]: pppd 2.4.5 started by root, uid 0 Dec 11 21:06:30 <HOSTNAME> pppd[22627]: Using interface ppp0 Dec 11 21:06:30 <HOSTNAME> pppd[22627]: Connect: ppp0 <--> /dev/pts/3 Dec 11 21:06:30 <HOSTNAME> pptpd[22626]: GRE: Bad checksum from pppd. Dec 11 21:06:31 <HOSTNAME> pptpd[22626]: CTRL: Received PPTP Control Message (type: 15) Dec 11 21:06:31 <HOSTNAME> pptpd[22626]: CTRL: Got a SET LINK INFO packet with standard ACCMs Dec 11 21:07:00 <HOSTNAME> pppd[22627]: LCP: timeout sending Config-Requests Dec 11 21:07:00 <HOSTNAME> pppd[22627]: Connection terminated. Dec 11 21:07:00 <HOSTNAME> avahi-daemon[1042]: Withdrawing workstation service for ppp0. Dec 11 21:07:00 <HOSTNAME> pppd[22627]: Modem hangup Dec 11 21:07:00 <HOSTNAME> pppd[22627]: Exit. Dec 11 21:07:00 <HOSTNAME> pptpd[22626]: GRE: read(fd=6,buffer=6075a0,len=8196) from PTY failed: status = -1 error = Input/output error, usually caused by unexpected termination of pppd, check option syntax and pppd logs Dec 11 21:07:00 <HOSTNAME> pptpd[22626]: CTRL: PTY read or GRE write failed (pty,gre)=(6,7) Dec 11 21:07:00 <HOSTNAME> pptpd[22626]: CTRL: Reaping child PPP[22627] Dec 11 21:07:00 <HOSTNAME> pptpd[22626]: CTRL: Client 82.132.248.216 control connection finished Dec 11 21:07:00 <HOSTNAME> pptpd[22626]: CTRL: Exiting now Dec 11 21:07:00 <HOSTNAME> pptpd[5803]: MGR: Reaped child 22626 As far as Cisco are concerned, all I need is ip nat source static tcp <SERVER LAN IP> 1723 interface FastEthernet4 1723 but of course this doesn't seem to the be helping the GRE traffic through as it should. Trying the connection to the LAN IP of the server from the same LAN as the server (behind the router), the PPTP connection works fine, so I'm confident that the server's config is ok. Furthermore, all I needed on my WAG320N was to open 1723 in the firewall. Here's my current router config: ! ! Last configuration change at 20:20:15 UTC Tue Dec 11 2012 by xxx version 15.2 no service pad service timestamps debug datetime msec service timestamps log datetime msec service password-encryption ! hostname xxx ! boot-start-marker boot-end-marker ! ! enable secret 4 xxxx ! aaa new-model ! ! aaa authentication login local_auth local ! ! ! ! ! aaa session-id common ! memory-size iomem 10 ! crypto pki trustpoint TP-self-signed-xxx enrollment selfsigned subject-name cn=IOS-Self-Signed-Certificate-xxx revocation-check none rsakeypair TP-self-signed-xxx ! ! crypto pki certificate chain TP-self-signed-xxx certificate self-signed 01 xxx quit ip gratuitous-arps ip auth-proxy max-login-attempts 5 ip admission max-login-attempts 5 ! ! ! ! ! ip domain list dmz.xxx.local ip domain list xxx.local ip domain name dmz.xxx.local ip name-server 192.168.1.x ip cef login block-for 3 attempts 3 within 3 no ipv6 cef ! ! multilink bundle-name authenticated license udi pid CISCO881-SEC-K9 sn xxx ! ! username admin privilege 15 secret 4 xxx username joe secret 4 xxx ! ! ! ! ! ip ssh time-out 60 ! ! ! ! ! ! ! ! ! interface FastEthernet0 no ip address ! interface FastEthernet1 no ip address ! interface FastEthernet2 no ip address ! interface FastEthernet3 switchport access vlan 2 no ip address ! interface FastEthernet4 ip address dhcp ip nat enable duplex auto speed auto ! interface Vlan1 ip address 192.168.1.x 255.255.255.0 no ip redirects no ip unreachables no ip proxy-arp ip nat enable ! interface Vlan2 ip address 192.168.0.x 255.255.255.0 ! ip forward-protocol nd ip http server ip http access-class 1 ip http authentication local ip http secure-server ! ! ip nat source list 1 interface FastEthernet4 overload ip nat source list 2 interface FastEthernet4 overload ip nat source static tcp 192.168.1.x 1723 interface FastEthernet4 1723 ! ! access-list 1 permit 192.168.0.0 0.0.0.255 access-list 2 permit 192.168.1.0 0.0.0.255 ! ! ! ! control-plane ! ! banner motd Authorized Access only ! line con 0 exec-timeout 15 0 login authentication local_auth line aux 0 exec-timeout 15 0 login authentication local_auth line vty 0 4 access-class 2 in login authentication local_auth length 0 transport input all ! ! end UPDATE 16/12/2012: The only progress that I have been able to make on this issue is that I'm confident that the issue is caused by the GRE tunnels (which are required for the PPTP connection to complete) are being blocked. When attempting a connection, I can see in show ip nat nvi translations that both a TCP translation on 1723 is setup and also a GRE translation is setup also. I appear to be able to see GRE related packets on the LAN that the server is on, so I am lead to believe that the server is sending(?) GRE packets, however running Wireshark on a client PC when attempting a connection shows absolutely no GRE packets. Whilst there are no configuration directives in my config posted above (that I can pin point) which would specifically block them, it would appear that the GRE packets are not being allowed in/out of the router's firewall, even though a NAT translation entry is setup to the server's LAN address. Would anyone be able to provide me with some help to ensure that GRE packets are not blocked by the router's firewall, so that this can be ruled out as a possible issue please?

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• Compressing and copying large files on Windows Server?

  - by Aaron

  I've been having a hard time copying large database backups from the database server to a test box at another site. I'm open to any ideas that would help me get this database moved without having to resort to a USB hard drive and the mail. The database server is running Windows Server 2003 R2 Enterprise, 16 GB of RAM and two quad-core 3.0 GHz Xeon X5450s. Files are SQL Server 2005 backup files between 100 GB and 250 GB. The pipe is not the fastest and SQL Server backup files typically compress down to 10-40% of the original, so it made sense to me to compress the files first. I've tried a number of methods, including: gzip 1.2.4 (UnxUtils) and 1.3.12 (GnuWin) bzip2 1.0.1 (UnxUtils) and 1.0.5 (Cygwin) WinRAR 3.90 7-Zip 4.65 (7za.exe) I've attempted to use WinRAR and 7-Zip options for splitting into multiple segments. 7za.exe has worked well for me for database backups on another server, which has ~50 GB backups. I've also tried splitting the .BAK file first with various utilities and compressing the resulting segments. No joy with that approach either- no matter the tool I've tried, it ends up butting against the size of the file. Especially frustrating is that I've transferred files of similar size on Unix boxes without problems using rsync+ssh. Installing an SSH server is not an option for the situation I'm in, unfortunately. For example, this is how 7-Zip dies: H:\dbatmp>7za.exe a -t7z -v250m -mx3 h:\dbatmp\zip\db-20100419_1228.7z h:\dbatmp\db-20100419_1228.bak 7-Zip (A) 4.65 Copyright (c) 1999-2009 Igor Pavlov 2009-02-03 Scanning Creating archive h:\dbatmp\zip\db-20100419_1228.7z Compressing db-20100419_1228.bak System error: Unspecified error

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• Server nearly unusable when doing disk writes

  - by Wikser

  My question closely relates to my last question here on serverfault. I was copying about 5GB from a 10 year old desktop computer to the server. The copy was done in Windows Explorer. In this situation I would assume the server to be bored by the dataflow. But as usual with this server, it really slowed down. At least I could work with the remote session, even there was some serious latency. The copy took its time (20min?). In this time I went to a colleague and he tried to log in in the same server via remote desktop (for some other reason). It took about a minute to get to the login screen, a minute to open the control panel, a minute to open the performance monitor, ... Icons were loading maybe one per second. We saw the following (from memory): CPU: 2% Avg. Queue Length: 50 Pages/sec: 115 (?) There was no other considerable activity on the server. The server seldom serves some ASP.NET pages, which became also very slow in this time. The relevant configuration is as follows: Windows 2003 SEAGATE ST3500631NS (7200 rpm, 500 GB) LSI MegaRAID based RAID 5 4 disks, 1 hot spare Write Through No read-ahead Direct Cache Mode Harddisk-Cache-Mode: off Is this normal behaviour for such a configuration? What measurements could give further clues? Is it reasonable to reduce the priority of such copy I/O and favour other processes like the remote desktop? How would you do that? Many thanks!

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• Configured Samba to join our domain, but logon fails from Windows machine

  - by jasonh

  I've configured a Fedora 11 installation to join our domain. It seems to join successfully (though it reports a DNS update failure) but when I try to access \\fedoraserver.test.mycompany.com I'm prompted for a password. So I enter adminuser and the password and that fails, so I try test.mycompany.com\adminuser and that too fails. What am I missing? EDIT (Update 9/1/09): I can now connect to the machine and see the shares on it (see my response to djhowell's answer) but when I try to connect, I get an error saying The network path was not found. I checked the log entry on the Fedora computer for the computer I'm connecting from (/var/log/samba/log.ComputerX) and it reads: [2009/09/01 12:02:46, 1] libads/cldap.c:recv_cldap_netlogon(157) no reply received to cldap netlogon [2009/09/01 12:02:46, 1] libads/ldap.c:ads_find_dc(417) ads_find_dc: failed to find a valid DC on our site (Default-First-Site-Name), trying to find another DC Config files as of 9/1/09: smb.conf: [global] Workgroup = TEST realm = TEST.MYCOMPANY.COM password server = DC.TEST.MYCOMPANY.COM security = DOMAIN server string = Test Samba Server log file = /var/log/samba/log.%m max log size = 50 idmap uid = 15000-20000 idmap gid = 15000-20000 windbind use default domain = yes cups options = raw client use spnego = no server signing = auto client signing = auto [share] comment = Test Share path = /mnt/storage1 valid users = adminuser admin users = adminuser read list = adminuser write list = adminuser read only = No I also set the krb5.conf file to look like this: [logging] default = FILE:/var/log/krb5libs.log kdc = FILE:/var/log/krb5kdc.log admin_server = FILE:/var/log/kadmind.log [libdefaults] default_realm = test.mycompany.com dns_lookup_realm = false dns_lookup_kdc = false ticket_lifetime = 24h forwardable = yes [realms] TEST.MYCOMPANY.COM = { kdc = dc.test.mycompany.com admin_server = dc.test.mycompany.com default_domain = test.mycompany.com } [domain_realm] dc.test.mycompany.com = test.mycompany.com .dc.test.mycompany.com = test.mycompany.com [appdefaults] pam = { debug = false ticket_lifetime = 36000 renew_lifetime = 36000 forwardable = true krb4_convert = false } I realize that there might be an issue with EXAMPLE.COM in there, however if I change it to TEST.MYCOMPANY.COM then it fails to join the domain with a preauthentication failure. As of 9/1/09, this is no longer the case.

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• VLAN Through Switch Doesn't Work

  - by vcsjones

  I have the following scenario: I have a Cisco Aironet 1040 access point. I have it configured with two SSIDs, each going to a different VLAN. So: SSID internal : VLAN 90 SSID guest : VLAN 70 On the router side, I have a Cisco RV220W (with the radios now turned off) and have setup VLANs with like VLAN IDs. VLAN 90 : 192.168.90.0/24 VLAN 70 : 192.168.70.0/24 As far as DHCP is concerned, each VLAN has a "DHCP Server" in the router's configuration: So with the access point connected directly to the router, everything works great. I connect to the internal network, and I get a 192.168.90.x address, and the guest network gets a 70.xxx address. Next I introduced a Cisco SG200-50 PoE switch between the router and the access point. The port is configured as a trunk port, so the VLAN tags should go right through the switch back to the router. However, when something is connected to the access point, nothing works. It isn't able to get an IP address, and manually assigning one doesn't seem to let any traffic route. Given that the access point works correctly when connected to the router directly, I believe the switch is misconfigured. What am I missing here? What can I use to better diagnose what the problem might be? It's small business equipment, so CLI access is not available. Below are screenshots of the switch's config. The access point is connected to GE2.

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• Testing for disk write

  - by Montecristo

  I'm writing an application for storing lots of images (size <5MB) on an ext3 filesystem, this is what I have for now. After some searching here on serverfault I have decided for a structure of directories like this: 000/000/000000001.jpg ... 236/519/236519107.jpg This structure will allow me to save up to 1'000'000'000 images as I'll store a max of 1'000 images in each leaf. I've created it, from a theoretical point of view seems ok to me (though I've no experience on this), but I want to find out what will happen when there will be directories full of files in there. A question about creating this structure: is it better to create it all in one go (takes approx 50 minutes on my pc) or should I create directories as they are needed? From a developer point of view I think the first option is better (no extra waiting time for the user), but from a sysadmin point of view, is this ok? I've thought I could do as if the filesystem is already under the running application, I'll make a script that will save images as fast as it can, monitoring things as follows: how much time does it take for an image to be saved when there is no or little space used? how does this change when the space starts to be used up? how much time does it take for an image to be read from a random leaf? Does this change a lot when there are lots of files? Does launching this command sync; echo 3 | sudo tee /proc/sys/vm/drop_caches has any sense at all? Is this the only thing I have to do to have a clean start if I want to start over again with my tests? Do you have any suggestions or corrections?

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• convert decrypted .vobs to .avi with ffmpeg on ubuntu

  - by Arcath

  I have a .vob file that has bee ripped from a dvd, when I watch the .vob its very good quality video and 5.1 english audio but when I use ffmpeg it has rubbish video and mono french audio. That was using this command: ffmpeg -i /samba/ripping/vobs/12161840#2.vob -f avi /samba/ripping/avis/test.avi I've tried a few different variations on that but it never comes back with anything good just bigger files with bad video and incorrect sound. I know the videos good and the correct audio streams exist so how do I select a 5.1 track and get good video? ffmpeg gives the .vob details as: Input #0, mpeg, from '/samba/ripping/vobs/12161840#2.vob': Duration: 00:42:05.56, start: 0.287267, bitrate: 5738 kb/s Stream #0.0[0x1e0]: Video: mpeg2video, yuv420p, 720x576 [PAR 64:45 DAR 16:9], 8436 kb/s, 25 fps, 25 tbr, 90k tbn, 50 tbc Stream #0.1[0x80]: Audio: ac3, 48000 Hz, 5.1, s16, 384 kb/s Stream #0.2[0x81]: Audio: ac3, 48000 Hz, 5.1, s16, 384 kb/s Stream #0.3[0x82]: Audio: ac3, 48000 Hz, mono, s16, 192 kb/s Output #0, avi, to '/samba/ripping/avis/test.avi': Metadata: ISFT : Lavf52.64.2 Stream #0.0: Video: mpeg4, yuv420p, 720x576 [PAR 64:45 DAR 16:9], q=2-31, 200 kb/s, 25 tbn, 25 tbc Stream #0.1: Audio: mp2, 48000 Hz, mono, s16, 64 kb/s Stream mapping: Stream #0.0 -> #0.0 Stream #0.3 -> #0.1

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• What are the frequencies of current in computers' external peripheral cables and internal buses?

  - by Tim

  From Wikipedia, three different cases of current frequency are discussed along with the types of cables that are suitable for them: An Extra Ordinary electrical cables suffice to carry low frequency AC, such as mains power, which reverses direction 100 to 120 times per second (cycling 50 to 60 times per second). However, they cannot be used to carry currents in the radio frequency range or higher, which reverse direction millions to billions of times per second, because the energy tends to radiate off the cable as radio waves, causing power losses. Radio frequency currents also tend to reflect from discontinuities in the cable such as connectors, and travel back down the cable toward the source. These reflections act as bottlenecks, preventing the power from reaching the destination. Transmission lines use specialized construction such as precise conductor dimensions and spacing, and impedance matching, to carry electromagnetic signals with minimal reflections and power losses. Types of transmission line include ladder line, coaxial cable, dielectric slabs, stripline, optical fiber, and waveguides. The higher the frequency, the shorter are the waves in a transmission medium. Transmission lines must be used when the frequency is high enough that the wavelength of the waves begins to approach the length of the cable used. To conduct energy at frequencies above the radio range, such as millimeter waves, infrared, and light, the waves become much smaller than the dimensions of the structures used to guide them, so transmission line techniques become inadequate and the methods of optics are used. I wonder what the frequencies are for the currents in computers' external peripheral cables, such as Ethernet cable, USB cable, and in computers' internal buses? Are the cables also made specially for the frequencies? Thanks!

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• APC fragmentation on EC2 Micro for Wordpress + W3TC

  - by Maarten Provo

  I'm trying to optimize APC for my Amazon EC2 Micro server running one Wordpress-site with W3TC. I've started with the settings advised by TechZilla in another topic but I keep getting high fragmentation with 50% of space being free. I've uploaded an image to http://www.maartenprovo.be/downloads/apc.jpg but I can't post it here since I need at least 10 reputation. What values can I optimize to prevent fragmentation? [apc] apc.enabled=1 apc.shm_segments=1 ;32M per WordPress install apc.shm_size=164M ;Leave at 2M or lower. WordPress does't have any file sizes close to 2M apc.max_file_size=2M ;Relative to the number of cached files apc.num_files_hint=1000 ;Relative to the size of WordPress apc.user_entries_hint=4096 ;The number of seconds a cache entry is allowed to idle in a slot before APC dumps the cache apc.ttl=7200 apc.user_ttl=7200 apc.gc_ttl=3600 ;Auto update chache files on change in WP-ADMIN or W3TC apc.stat=1 ;This MUST be 0, WP can have errors otherwise! apc.include_once_override=0 ;Only set to 1 while debugging apc.enable_cli=0 ;Allow 2 seconds after a file is created before it is cached to prevent users from seeing half-written/weird pages apc.file_update_protection=2 ;Ignore files apc.filters apc.slam_defense = 0 apc.write_lock = 1 apc.cache_by_default=1 apc.use_request_time=1 apc.mmap_file_mask=/var/tmp/apc.XXXXXX apc.stat_ctime=0 apc.canonicalize=1 apc.write_lock=1 apc.report_autofilter=0 apc.rfc1867=0 apc.rfc1867_prefix =upload_ apc.rfc1867_name=APC_UPLOAD_PROGRESS apc.rfc1867_freq=0 apc.rfc1867_ttl=3600 apc.lazy_classes=0 apc.lazy_functions=0

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• Can't write to samba share

  - by Tiddo

  I try to setup a samba file server, but whatever I do I can't get write access to work (reading works fine). This is my current situation: I have a local fileserver with 3 harddisks mounted at /mnt/share/disk<nr>. 2 of these use the ext4 filesystem, the third one is ntfs. This file server runs Fedora 18 32-bit. The root folders of these harddisks are owned by superman:superman, and testparm outputs the following: [global] workgroup = WORKGROUP netbios name = FILE_SERVER server string = Samba Server Version %v interfaces = lo, eth0, 192.168.123.191/8 log file = /var/log/samba/log.%m max log size = 50 unix extensions = No load printers = No idmap config * : backend = tdb hosts allow = 192.168.123. cups options = raw wide links = Yes [share] comment = Home Directories path = /home/share/ write list = superman, @users force user = superman read only = No create mask = 0777 directory mask = 0777 inherit permissions = Yes guest ok = Yes I've tried a lot to get this to work: the disk are chmodded to 777, I've tried turning off selinux, I've added the samba_share_t label to the disks and as can be seen in the above output I tried to make the smb config as permissive as I could, but still I cannot write to the share (tried from Windows 7 and another Fedora installation). What can I try to be able to write to the shares? EDIT: The replies I got so far are mostly concerned with the smb.conf. I have however tried a lot of different setup, ready made configs, and solutions to similar problems for the smb.conf file, so I suspect that the real problem is somewhere else.

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• Enabling NAT forwarding using a second WAN interface and a second gateway on ubuntu

  - by nixnotwin

  I have 3 interfaces: eth0 192.168.0.50/24 eth1 10.0.0.200/24 eth2 225.228.123.211 The default gateway is 192.168.0.1 which I want to keep as it is in the changes I want to make. I want to masquerade eth1 10.0.0.200/24 and enable NAT forwarding to eth2. So I have done this: ip route add 225.228.123.208/29 dev eth2 src 225.228.123.211 table t1 ip route add default via 225.228.123.209 dev eth2 table t1 ip rule add from 225.228.123.211 table t1 ip rule add to 225.228.123.211 table t1 Now I can receive ping replies from any internet host if I did: ping -I eth2 8.8.8.8 To enable NAT forwarding I did this: sudo iptables -A FORWARD -o eth2 -i eth1 -s 10.0.0.0/24 -m conntrack --ctstate NEW -j ACCEPT sudo iptables -A FORWARD -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT sudo iptables -t nat -A POSTROUTING -o eth1 -j MASQUERADE But it isn't working. To test I used a client pc and put it on 10.0.0.0/24 network and gateway was set as 10.0.0.200. I want to have 192.168.0.1 as default gateway. And the traffic that comes in via eth1 10.0.0.200/24 should be forwarded to eth2 225.228.123.211. I have enabled forwarding on ubuntua also.

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• CloneZilla Broke My System? Ubunut Installation Lost After Running CloneZilla

  - by nicorellius

  I just read through this post and tried to get my installation back using this answer to no avail. What happened to me is this: I spent an hour or more reading through the CloneZilla docs. I thought I was ready to test it out so I burned the disc with the ISO image on it and ran it. The system I used was Ubuntu 10.04, 32-bit. Everything seemed to go fine. I made a clone of my first partition and copied it to my second partition. I followed the instructions, removed the disc and rebooted my system. At this point, I would expect to have two bootable Linux installations, identical to one another. However, upon booting, I got this error message: error: no such device: 4cf1a6ef-xxxx-xxxx-xxxx-4e3a3ce92bcd error: file not found I booted from a Live Ubuntu disc and was able to see my to partitions: 4cf1(1) and 4cf1(2) (abbreviated, because the volumes have long numbers to identify them). The 50 GB partition, on which the original Ubuntu installation sits is the number and the second partition (175 GB) is the same number with an "_" at the end. I could browse the disc partitions and see the files, but I'm not sure what to do next. I know there is a way to restore my grub loader and actually boot either of these installations, but my Linux know-how is limited. Can I edit the boot loader file to fix this problem? The only clue I have is CloneZilla said something about making a new GRUB but I thought it was going to basically modify it so I could boot either installation. Not sure what happened. I am going to look through this post for the time being to see if I can learn anything to help my problem. But I thought that, since this happened as a result of using CloneZilla, it may be a unique question for this board.

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• How To Replace Laptop HDD Without Losing Data?

  - by Ishan

  Hello, I recently went to Dell Service center and they tell that HDD is faulty and needs to be replaced. I have a Studio 1457 laptop with 500 GB HDD and don't want to lose the data(purchased in May 2010, still under warranty). I have searched a bit and I think it may be best to use a disk imaging software for this task. However, I don't know about a good software. I have following steps in mind: Get a 1 TB External HDD. Make an image of existing 500 GB HDD and store data on external disk. Install new HDD and install a brand new Windows copy and then install the software on it. Using the same software I used to make image, restore the old HDD image on new one. However, I have some questions in mind. First, is this possible? Second, I live in a country where piracy is a big issue and I am sure the support executive who will come to change HDD will have a pirated copy. But I have genuine Windows 7 Pro and don't want to lose it. Now, Dell does not supply and OS disks, so I can't install it on new HDD! If I follow above steps, which version of Windows 7 will be retained? One in the image(authentic) or one in the new HDD(pirated). I am ready to purchase a good software for this task and my budget is $50-60. Since laptop is under warranty, new HDD will be free. One last thing, I have created a Windows Migration file whose size is 70 GB. Can it be used to move from Windows 7 Pro to Windows 7 Pro?(In case I get a genuine copy of Windows 7!) Any other method to save all the data? Thanks in advance.

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• Apache 2: Mod_Rewrite Help - If/else for directory exists

  - by BHare

  This is my current and sloppy Apache 2 mod_rewrite. Keep in mine the part with site1 site2..etc has about 50 sites. RewriteEngine on RewriteCond %{HTTP_HOST} ^([^.]+)\.mainsite\.org$ RewriteCond /home/%1/ -d RewriteRule ^(.+) %{HTTP_HOST}$1 RewriteRule ^([^.]+)\.mainsite\.org/media/(.*) /home/$1/special/media/$2 RewriteRule ^([^.]+)\.mainsite\.org/(.*) /home/$1/www/$2 RewriteCond %{HTTP_HOST} ^mainsite\.org$ [NC] RewriteRule ^(.*)$ http://www.mainsite.org$1 [R=302] RewriteCond %{HTTP_HOST} (site1|site2|site3|site4)\.(com|net|biz|org|us)$ [NC] RewriteCond %{REQUEST_URI} !^/media/ RewriteRule ^/(.*)$ /home/%1/www/$1 RewriteCond %{HTTP_HOST} (site1|site2|site3|site4)\.(com|biz|net|org|us)$ [NC] RewriteRule ^/media/(.*)$ /home/%1/special/media/$1 RewriteCond %{REQUEST_URI} favicon.ico$ RewriteRule ^(.*)$ /misc/favicon.ico So if someone tries to go to theirusername.mainsite.org it will check if /home/theirusername/ exists, and if it does use their www (/home/theirusername/www/) as the file location for web files. If they try they try to access theirusername.mainsite.org/media/ it will make a special file location to look for the file(s) at /home/theirusername/special/media/ I would like it if the username did NOT have /home/username that it would automatically default to www.mainsite.org. I am having a hard time understanding how to do skips and such. so: If someone went to notrealusername.mainsite.org/forum/ it would auto direct to www.mainsite.org/forum/ Extra: I am using repetitive code for other site for example lets say foobar has a website foobar.com, it goes through the same process as mainsite.org so figured maybe having something like: RewriteCond %{HTTP_HOST} ^([^.]+).(mainsite.org|com|net|biz|org)$ where I could have one major rule for all existing domains who have a /home/

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• IP Phone over VPN - one way calls unless default route?

  - by dannymcc

  I have come across a strange problem with our VPN and BCM 50 (Nortel/Avaya) phone system. As you can tell by my other questions I have been doing some work on setting a VPN up from one location to another and it's all working well. With one exception. We have an IP phone that is connected at the remote location, straight to a router which has a VPN tunnel to our main practice. The phone works mostly, but every few calls it turns into a one way call. As in, the caller (from the remote phone) can't hear the receiver- but the receiver can hear the caller. This is fixed by setting the VPN tunnel to be the default route for all traffic. The problem with fixing it that way is that all traffic then goes through the tunnel which slows internet access etc. down considerably. The router is set to send the following over the VPN: 192.168.1.0/24 192.168.2.0/24 192.168.4.0/24 The IP of the remote location is: 192.168.3.0/24 The remote router (where the phone is) is a Draytek 2830n, and the local router (at the main practice) is a Draytek 2820. We are using an IPSec tunnel with AES encryption <- as a result of a previous answer pointing to the incompatibility in the hardware encryption. Any advice would be appreciated!

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• Can a pool of memcache daemons be used to share sessions more efficiently?

  - by Tom

  We are moving from a 1 webserver setup to a two webserver setup and I need to start sharing PHP sessions between the two load balanced machines. We already have memcached installed (and started) and so I was pleasantly surprized that I could accomplish sharing sessions between the new servers by changing only 3 lines in the php.ini file (the session.save_handler and session.save_path): I replaced: session.save_handler = files with: session.save_handler = memcache Then on the master webserver I set the session.save_path to point to localhost: session.save_path="tcp://localhost:11211" and on the slave webserver I set the session.save_path to point to the master: session.save_path="tcp://192.168.0.1:11211" Job done, I tested it and it works. But... Obviously using memcache means the sessions are in RAM and will be lost if a machine is rebooted or the memcache daemon crashes - I'm a little concerned by this but I am a bit more worried about the network traffic between the two webservers (especially as we scale up) because whenever someone is load balanced to the slave webserver their sessions will be fetched across the network from the master webserver. I was wondering if I could define two save_paths so the machines look in their own session storage before using the network. For example: Master: session.save_path="tcp://localhost:11211, tcp://192.168.0.2:11211" Slave: session.save_path="tcp://localhost:11211, tcp://192.168.0.1:11211" Would this successfully share sessions across the servers AND help performance? i.e save network traffic 50% of the time. Or is this technique only for failovers (e.g. when one memcache daemon is unreachable)? Note: I'm not really asking specifically about memcache replication - more about whether the PHP memcache client can peak inside each memcache daemon in a pool, return a session if it finds one and only create a new session if it doesn't find one in all the stores. As I'm writing this I'm thinking I'm asking a bit much from PHP, lol... Assume: no sticky-sessions, round-robin load balancing, LAMP servers.

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• PS3 controller -> PC -> emulators -> TV

  - by abrereton

  I'm researching a media PC for the living room. Playing videos, audio and streaming Internet is straightforward enough. I would also like to run a gaming console system. I was wondering if anyone has any thoughts on this. So far I've discovered that a PS3 controller (thankfully it uses USB and Bluetooth) can be connected to a PC. I've also found that MAME, MESS and PCSX2 are all the emulators I need (I can even emulate a TI-83 calculator with MESS). These emulators can re-map keys, so for example I can make the Nintendo's A button to the PS3 X button, or the SNES key pad could be the PS3 keypad or the analog stick. There are also front-ends to these emulators which can do fancy things like image scaling, anti-aliasing and double-buffering to improve the image quality of an 8-bit Mario on a 50 inch plasma. My set up would be this: PS3 controller connecting over Bluetooth to the PC, PC with Windows, PS3 controller drivers, all my emulators, Network drive with all my ROMs, PC connected to TV via HDMI TV playing Super Mario Kart Does this sound feasible? Does anyone have experience of doing anything like this? Is this a good idea or should I grow up and stop living in the past?

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• Using NFS for scalable PHP/MySQL web application

  - by Jeroen Moons

  Here's the situation: I have a PHP/MySQL web application that accepts user uploads (pdf files). From these pdf files' pages a preview image is made on the fly and presented to the web app's users. Some pdfs might be on the large side, most will be under 50 MB but some extreme cases could be as large as a few hundred MB. A little waiting for the preview image for large pdf files is acceptable but no more than a minute let's say. Everything is running on one server for now, but soon the app will hit the server's limit on both storage and processing power. My idea to solve the problem: To deal with this situation I had the idea of having one or more pdf processing servers as needed, and one or more file storage servers. These two types of servers are mounted to the server on which the actual app runs using NFS. The app could then use GearMan to delegate pdf processing tasks to these processing servers. The processing server can mount the storage server and read the file stored there, process it and write its output to that server. The servers I'm talking about will be amazon ec2 instances. The web app returns a link to the resulting pdf preview image on the storage server that was used which can then be used on the front end to show the image to the user. My question: I have zero experience with apps that use multiple servers, is this idea viable or is there a better way to do it? Is an NFS setup fast and reliable enough for this situation?

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• Detecting login credentials abuse

  Greetings. I am the webmaster for a small, growing industrial association. Soon, I will have to implement a restricted, members-only section for the website. The problem is that our organization membership both includes big companies as well as amateur “clubs” (it's a relatively new industry…). It is clear that those clubs will share the login ID they will use to log onto our website. The problem is to detect whether one of their members will share the login credentials with people who would not normally supposed to be accessing the website (there is no objection for such a club to have all it’s members get on the website). I have thought about logging along with each sign-on the IP address as well as the OS and the browser used; if the OS/Browser stays constant and there are no more than, say, 10 different IP addresses, the account is clearly used by very few different computers. But if there are 50 OS/Browser combination and 150 different IPs, the credentials have obviously been disseminated far, and there would be then cause for action, such as modifying the password. Of course, it is extremely annoying when your password is being unilaterally changed. So, for this problem, I thought about allowing the “clubs” to manage their own list of sub-accounts, and therefore if abuse is suspected, the user responsible would be easily pinned-down, and this “sub-member” alone would face the annoyance of a password change. Question: What potential problems would anyone see with such an approach?

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• Use of backreferences in fail2ban filters possible?

  - by Izzy

  From time to time, I see collections of suspect "File not found" errors in my Apache logs, basically using the pattern File does not exist: /var/www/file, referer: http://my.server.com/file In human terms: The file was not found, though it referenced here itself. A clear hacking attempt, as that's hardly possible (and the REQUEST_URIs often enough suggest the same). In my eyes a clear case for fail2ban – if I could get backreferences to work here: failregex = ^%(_apache_error_client)s File does not exist: /var/www(.+), referer: http://.+\1$ (Justin Case: above examples assume the DIRECTORY_ROOT of that webserver being /var/www) I googled for hours, searched the fail2ban wiki up and down – but nowhere I could find a statement concerning backreferences in its filters. Are they not supported, or did I do it the wrong way? Any hints how to make it work (except from "dirty hacks" like first sending the request to another fake url using mod-rewrite, and then catching on that (if anyone is interested, I can elaborate on that approach in an answer), or doing something similar using mod-security)? as an entire log line was requested: [Fri Nov 08 14:57:28 2013] [error] [client 50.67.234.213] File does not exist: /var/www/text/files.htm++++++++++++++++++++++++++Result:+using+proxy+27.34.142.47:9090;+no+post+sending+forms+are+found;, referer: http://www.myserver.com/text/files.htm++++++++++++++++++++++++++Result:+using+proxy+27.34.142.47:9090;+no+post+sending+forms+are+found; (sorry, logs were just switched, so this long candidate was the only one left currently; minor adjustments were made for privacy reasons)

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• Shorewall log question.

  - by Shikoru

  I have been getting various attempts to connect to ports on my shorewall firewall. The ports that I keep seeing connection attempts at are tcp 44444, tcp 44446, udp 55555 and every now and then some slight variation. I ran "netstat -a" and did not see anything listening on those ports. Is this something that I should be worried about or is it just some rouge computers out there? I have noticed alot of the ip addresses are from Spain and Mexico. May 25 18:39:35 Takkun kernel: [62516.626514] Shorewall:net2fw:DROP:IN=eth0 OUT= MAC=00:d0:b7:65:d4:13:34:ef:xx:xx:xx:81:08:00 SRC=200.124.9.113 DST=72.xxx.xxx.xxx LEN=48 TOS=0x00 PREC=0x00 TTL=112 ID=51796 DF PROTO=TCP SPT=2071 DPT=44446 WINDOW=16384 RES=0x00 SYN URGP=0 May 25 18:39:52 Takkun kernel: [62535.433285] Shorewall:net2fw:DROP:IN=eth0 OUT= MAC=00:d0:b7:65:d4:13:34:ef:xx:xx:xx:81:08:00 SRC=72.50.95.174 DST=72.xxx.xxx.xxx LEN=90 TOS=0x00 PREC=0x00 TTL=105 ID=31130 PROTO=UDP SPT=59505 DPT=55555 LEN=70 May 25 18:40:05 Takkun kernel: [62548.963413] Shorewall:net2fw:DROP:IN=eth0 OUT= MAC=00:d0:b7:65:d4:13:34:ef:xx:xx:xx:81:08:00 SRC=77.12.37.1 DST=72.xxx.xxx.xxx LEN=90 TOS=0x00 PREC=0x00 TTL=108 ID=9585 PROTO=UDP SPT=20401 DPT=55555 LEN=70 That is the jist of what im seeing.

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• issue in installing postgresql 9.3.4 on Windows server 2003 x64

  - by randydom

  Hello i really did all what i know to install the PostgreSQL 9.3.4 on my windows 2003 server x64, but i'm always stopped with this error : please see the error : http://oi57.tinypic.com/s4tb8i.jpg I really don't know what to do , if i click OK then when i go to the windows services list i don't find the PostgreSQL service so i can't Start the service . can any one please help me to install it correctly . PS: i've followed all steps in the : wiki.postgresql.org/wiki/Troubleshooting_Installation many thanks . here's the installer log * where i get " Failed to initialise the database cluster with initdb " : Called IsVistaOrNewer()... 'winmgmts' object initialized... Version:5.2 MajorVersion:5 Ensuring we can write to the data directory (using cacls): Executing batch file 'rad22ADE.bat'... processed dir: C:\Program Files\PostgreSQL\9.2\data Executing batch file 'rad22ADE.bat'... The files belonging to this database system will be owned by user "Administrator". This user must also own the server process. The database cluster will be initialized with locale "English_United States.1252". The default text search configuration will be set to "english". fixing permissions on existing directory C:/Program Files/PostgreSQL/9.2/data ... initdb: could not change permissions of directory "C:/Program Files/PostgreSQL/9.2/data": Permission denied Called Die(Failed to initialise the database cluster with initdb)... Failed to initialise the database cluster with initdb Script stderr: Program ended with an error exit code Error running cscript //NoLogo "C:\Program Files\PostgreSQL\9.2/installer/server/initcluster.vbs" "NT AUTHORITY\NetworkService" "postgres" "****" "C:\Program Files\PostgreSQL\9.2" "C:\Program Files\PostgreSQL\9.2\data" 5432 "DEFAULT" 0 : Program ended with an error exit code Problem running post-install step. Installation may not complete correctly The database cluster initialisation failed. Creating Uninstaller Creating uninstaller 25% Creating uninstaller 50% Creating uninstaller 75% Creating uninstaller 100% Installation completed Log finished 05/02/2014 at 04:04:04

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