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• Xen kernel can't see 2 disks of 6 of 1TB, does it have a limitation?

  - by PartySoft

  Linux gentoo-xen 2.6.18-xen-r12 #3 SMP Tue Oct 5 09:28:53 PDT 2010 x86_64 Intel(R) Xeon(R) CPU E5506 @ 2.13GHz GenuineIntel GNU/Linux I have 6 disks of 1 TB and i can't see all of them only 4, can anyone give me an ideea what can i do ? Filesystem Size Used Avail Use% Mounted on rootfs 886G 4.4G 836G 1% / /dev/sda3 886G 4.4G 836G 1% / rc-svcdir 1.0M 44K 980K 5% /lib64/rc/init.d shm 7.9G 0 7.9G 0% /dev/shm /dev/sdb1 917G 200M 871G 1% /home2 /dev/sdc1 917G 200M 871G 1% /home3 /dev/sdd1 917G 200M 871G 1% /home4 The hardware is Dual xeon E5506 processors on a supermicro X8DTL mobo 4.346585] ata3.00: ATA-8, max UDMA/133, 1953525168 sectors: LBA48 NCQ (depth 0/32) [ 4.346588] ata3.00: ata3: dev 0 multi count 16 [ 4.352861] ata3.00: configured for UDMA/133 [ 4.352867] scsi3 : ata_piix [ 4.352875] PM: Adding info for No Bus:host3 [ 4.510584] ata4.00: ATA-8, max UDMA/133, 1953525168 sectors: LBA48 NCQ (depth 0/32) [ 4.510587] ata4.00: ata4: dev 0 multi count 16 [ 4.516848] ata4.00: configured for UDMA/133 [ 4.516861] PM: Adding info for No Bus:target2:0:0 [ 4.516905] Vendor: ATA Model: SAMSUNG HD103SJ Rev: 1AJ1 [ 4.516910] Type: Direct-Access ANSI SCSI revision: 05 [ 4.516920] PM: Adding info for scsi:2:0:0:0 [ 4.517452] SCSI device sde: 1953525168 512-byte hdwr sectors (1000205 MB) [ 4.517460] sde: Write Protect is off [ 4.517461] sde: Mode Sense: 00 3a 00 00 [ 4.517478] SCSI device sde: drive cache: write back [ 4.517514] SCSI device sde: 1953525168 512-byte hdwr sectors (1000205 MB) [ 4.517521] sde: Write Protect is off [ 4.517522] sde: Mode Sense: 00 3a 00 00 [ 4.517532] SCSI device sde: drive cache: write back [ 4.517534] sde: sde1 [ 4.524551] sd 2:0:0:0: Attached scsi disk sde [ 4.524855] sd 2:0:0:0: Attached scsi generic sg4 type 0 [ 4.524874] PM: Adding info for No Bus:target3:0:0 [ 4.524928] Vendor: ATA Model: SAMSUNG HD103SJ Rev: 1AJ1 [ 4.524933] Type: Direct-Access ANSI SCSI revision: 05 [ 4.524946] PM: Adding info for scsi:3:0:0:0 [ 4.525216] SCSI device sdf: 1953525168 512-byte hdwr sectors (1000205 MB) [ 4.525227] sdf: Write Protect is off [ 4.525228] sdf: Mode Sense: 00 3a 00 00 [ 4.525242] SCSI device sdf: drive cache: write back [ 4.525280] SCSI device sdf: 1953525168 512-byte hdwr sectors (1000205 MB) [ 4.525286] sdf: Write Protect is off [ 4.525289] sdf: Mode Sense: 00 3a 00 00 [ 4.525301] SCSI device sdf: drive cache: write back [ 4.525302] sdf: sdf1 [ 4.532691] sd 3:0:0:0: Attached scsi disk sdf [ 4.533010] sd 3:0:0:0: Attached scsi generic sg5 type 0 [ 4.977669] scsi: <fdomain> Detection failed (no card) [ 5.030479] GDT-HA: Storage RAID Controller Driver. Version: 3.05 [ 5.030635] GDT-HA: Found 0 PCI Storage RAID Controllers [ 5.372350] Fusion MPT base driver 3.04.01 [ 5.372358] Copyright (c) 1999-2005 LSI Logic Corporation [ 5.579176] Fusion MPT SPI Host driver 3.04.01 [ 5.881777] ieee1394: Initialized config rom entry `ip1394' [ 6.166745] ieee1394: sbp2: Driver forced to serialize I/O (serialize_io=1) [ 6.166748] ieee1394: sbp2: Try serialize_io=0 for better performance [ 6.428866] md: md driver 0.90.3 MAX_MD_DEVS=256, MD_SB_DISKS=27 [ 6.428872] md: bitmap version 4.39 [ 6.431518] md: raid0 personality registered for level 0 [ 6.495979] md: raid1 personality registered for level 1 [ 6.570270] raid5: automatically using best checksumming function: generic_sse [ 6.575523] generic_sse: 6608.000 MB/sec [ 6.575526] raid5: using function: generic_sse (6608.000 MB/sec) [ 6.596226] raid6: int64x1 1835 MB/s [ 6.613231] raid6: int64x2 1773 MB/s [ 6.630256] raid6: int64x4 1675 MB/s [ 6.647296] raid6: int64x8 1027 MB/s [ 6.664267] raid6: sse2x1 3578 MB/s [ 6.681268] raid6: sse2x2 4207 MB/s [ 6.698280] raid6: sse2x4 4625 MB/s [ 6.698281] raid6: using algorithm sse2x4 (4625 MB/s) [ 6.698285] md: raid6 personality registered for level 6 [ 6.698286] md: raid5 personality registered for level 5 [ 6.698288] md: raid4 personality registered for level 4 [ 6.781090] md: raid10 personality registered for level 10 [ 7.007043] Intel(R) PRO/1000 Network Driver - version 7.1.9-k4 [ 7.007046] Copyright (c) 1999-2006 Intel Corporation. [ 9.229465] kjournald starting. Commit interval 5 seconds [ 9.229476] EXT3-fs: mounted filesystem with ordered data mode.

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• Weird Network Behavior of Home Router

  - by Stilgar

  First of all I would like to apologize because what you are going to read will be long and confusing but I am fighting this issue for 3 days now and am out of ideas. At home I have the following setup 50Mbps Internet connects into a home router A 2 desktop computers connect to router A via standard FTP LAN cables including one where the cable is ~20m long. a second router B connects to router A via standard FTP LAN cable X (~20m long). several devices connect to the wireless network of router B and there are a couple of desktop computers connected to it through FTP LAN cables. For some reason computers connected to router B when it is connected via cable X have very slow Internet connection. It is like 5 times slower than what is expected. This is the actual problem I am trying to solve. Interesting facts If a computer is connected to cable X directly instead of through router B the Internet speed is just fine (up to the 50Mbps I get from the ISP). Tested with two computers. I have tried replacing router B with another router C and the problem persists. If I connect router B via another cable to the same ports with the same settings everything seems to work fine and computers connected to router B have quite fast Internet I have tested mainly via Speedtest.net but I have also achieved similar speeds when downloading a file The upload speed is quite higher than the download speed in all cases. Note that my ISP usually has higher upload speed (unless it manages to hit the 50Mbps cap) It seems like the speed when connecting through router B with cable X is reduced 4-5 times no matter what the original speed is. For example via router B I get 10Mbps speed to local servers where I get 50Mbps when connected on router A. If I use a distant server where the ISP is only able to provide 25Mbps I get 4-5Mbps on router B. WiFi is slower than LAN on both routers (which is normal) but the reduced speed is reduced proportionally for WiFi. In addition the upload speed is normally higher from the ISP and it is also reduced proportionally. I have tried two different network configurations. One where I have NAT behind NAT where router B connects to router A via the WAN port and has its own DHCP. Second where router B connects to router A via standard LAN port and has DHCP disabled. In this configuration router B serves as a switch and the Network Gateway for computers connected to router B is the internal IP address of router A. Both configurations work just fine but both manifest the reduced speed issue. pings seem to work just fine As far as I can tell none of the cables is crossed The RJ45 setup for cable X orange orange-white brown brow-white blue blue-white green green-white This is a big problem for me since cable X passes through walls and floors and is very hard to replace. I also may have gotten some of the facts wrong because I am almost going crazy with this issue and testing includes going several floors up and down the staircase. One hypothesis I came up with is that the cable is defective in such a way that the voltage from the router affects its performance. When it is connected to a computer it performs just fine but the router has less power. Related hypothesis includes the cable being affected by electricity cables in the walls when the voltage is low. (I know nothing about electricity) So any ideas what to do, what to test or what the issue may be?

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• Have I pushed the limits of my current VPS or is there room for optimization?

  - by JRameau

  I am currently on a mediatemple DV server (basic) 512mb dedicated ram, this is a CentOS based VPS with Plesk and Virtuozzo. My experience with it from day 1 has been bad and I only could sooth my server issues with several caching "Band-aids," but my sites are not as small as they were a year ago either so the issues have worsen. I have 3 Drupal installs running on separate (plesk) domains, 1 of those drupal installs is a multisite, that consists of 5-6 sites 2 of those sites are bringing in actual traffic. Those caching "Band-aids" I mentioned are APC, which seemed to help alot initially, and Drupal's Boost, which is considered a poorman's Varnish, it makes all my pages static for anonymous users. Last 30day combined estimate on Google Ananlytics: 90k visitors 260k pageviews. Issue: alot of downtime, I am continually checking if my sites are up, and lately I have been finding it down more than 3 times daily. Restarting Apache will bring it back up, for some time. I have google search every error message and looked up ways to optimize my DV server, and I am beyond stump what is my next move. Is this server bad, have I hit a impossibly low restriction such as the 12mb kernel memory barrier (kmemsize), is it on my end, do I need to optimize some more? *I have provided as much information as I can below, any help or suggestions given will be appreciated Common Error messages I see in the log: [error] (12)Cannot allocate memory: fork: Unable to fork new process [error] make_obcallback: could not import mod_python.apache.\n Traceback (most recent call last): File "/usr/lib/python2.4/site-packages/mod_python/apache.py", line 21, in ? import traceback File "/usr/lib/python2.4/traceback.py", line 3, in ? import linecache ImportError: No module named linecache [error] python_handler: no interpreter callback found. [warn-phpd] mmap cache can't open /var/www/vhosts/***/httpdocs/*** - Too many open files in system (pid ***) [alert] Child 8125 returned a Fatal error... Apache is exiting! [emerg] (43)Identifier removed: couldn't grab the accept mutex [emerg] (22)Invalid argument: couldn't release the accept mutex cat /proc/user_beancounters: Version: 2.5 uid resource held maxheld barrier limit failcnt 41548: kmemsize 4582652 5306699 12288832 13517715 21105036 lockedpages 0 0 600 600 0 privvmpages 38151 42676 229036 249036 0 shmpages 16274 16274 17237 17237 2 dummy 0 0 0 0 0 numproc 43 46 300 300 0 physpages 27260 29528 0 2147483647 0 vmguarpages 0 0 131072 2147483647 0 oomguarpages 27270 29538 131072 2147483647 0 numtcpsock 21 29 300 300 0 numflock 8 8 480 528 0 numpty 1 1 30 30 0 numsiginfo 0 1 1024 1024 0 tcpsndbuf 648440 675272 2867477 4096277 1711499 tcprcvbuf 301620 359716 2867477 4096277 0 othersockbuf 4472 4472 1433738 2662538 0 dgramrcvbuf 0 0 1433738 1433738 0 numothersock 12 12 300 300 0 dcachesize 0 0 2684271 2764800 0 numfile 3447 3496 6300 6300 3872 dummy 0 0 0 0 0 dummy 0 0 0 0 0 dummy 0 0 0 0 0 numiptent 14 14 200 200 0 TOP: (In January the load avg was really high 3-10, I was able to bring it down where it is currently is by giving APC more memory play around with) top - 16:46:07 up 2:13, 1 user, load average: 0.34, 0.20, 0.20 Tasks: 40 total, 2 running, 37 sleeping, 0 stopped, 1 zombie Cpu(s): 0.3% us, 0.1% sy, 0.0% ni, 99.7% id, 0.0% wa, 0.0% hi, 0.0% si Mem: 916144k total, 156668k used, 759476k free, 0k buffers Swap: 0k total, 0k used, 0k free, 0k cached MySQLTuner: (after optimizing every table and repairing any table with overage I got the fragmented count down to 86) [--] Data in MyISAM tables: 285M (Tables: 1105) [!!] Total fragmented tables: 86 [--] Up for: 2h 44m 38s (409K q [41.421 qps], 6K conn, TX: 1B, RX: 174M) [--] Reads / Writes: 79% / 21% [--] Total buffers: 58.0M global + 2.7M per thread (100 max threads) [!!] Query cache prunes per day: 675307 [!!] Temporary tables created on disk: 35% (7K on disk / 20K total)

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• Tomcat dying silently on regular basis

  - by Hendrik

  My tomcat (6.0.32, Java Sun 1.6.0_22-b04 on Ubuntu 10.04) keeps crashing multiple times daily without any specific output in catalina.out. This usually happens on high load (see top output). Update: The pid-file is properly removed when this happens. Update 2: No CATALINA_OPTS set, _JAVA_OPTS are: export _JAVA_OPTIONS="-Xms128m -Xmx1024m -XX:MaxPermSize=512m \ -XX:MinHeapFreeRatio=20 \ -XX:MaxHeapFreeRatio=40 \ -XX:NewSize=10m \ -XX:MaxNewSize=10m \ -XX:SurvivorRatio=6 \ -XX:TargetSurvivorRatio=80 \ -XX:+CMSClassUnloadingEnabled \ -Djava.awt.headless=true \ -Dcom.sun.management.jmxremote \ -Dcom.sun.management.jmxremote.port=37331 \ -Dcom.sun.management.jmxremote.ssl=false \ -Dcom.sun.management.jmxremote.authenticate=true \ -Djava.rmi.server.hostname=(myhostname) \ -Dcom.sun.management.jmxremote.password.file=/etc/java-6-sun/management/jmxremote.password \ -Dcom.sun.management.jmxremote.access.file=/etc/java-6-sun/management/jmxremote.access" Top: top - 12:40:03 up 9 days, 12:15, 3 users, load average: 30.00, 22.39, 21.91 Tasks: 89 total, 4 running, 85 sleeping, 0 stopped, 0 zombie Cpu(s): 53.2%us, 9.7%sy, 0.0%ni, 34.7%id, 1.5%wa, 0.0%hi, 0.8%si, 0.0%st Mem: 4194304k total, 3311304k used, 883000k free, 0k buffers Swap: 4194304k total, 0k used, 4194304k free, 0k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 25850 tomcat6 20 0 1981m 1.2g 11m S 161 29.6 11:41.56 java 12632 mysql 20 0 393m 97m 4452 S 141 2.4 1690:05 mysqld 14932 nobody 20 0 253m 44m 9152 R 56 1.1 3:26.57 php-cgi 7011 nobody 20 0 241m 31m 9124 S 30 0.8 1:35.96 php-cgi 10093 nobody 20 0 228m 18m 8520 S 25 0.5 2:29.97 php-cgi 27071 nobody 20 0 237m 28m 8640 S 11 0.7 3:13.72 php-cgi 3306 nobody 20 0 227m 16m 6736 R 7 0.4 2:29.83 php-cgi 7756 nobody 20 0 261m 58m 15m R 5 1.4 2:22.33 php-cgi 7129 www-data 20 0 3646m 7228 1896 S 2 0.2 0:36.65 nginx 2657 nobody 20 0 228m 18m 8540 S 1 0.5 1:59.51 php-cgi 7131 www-data 20 0 3645m 6464 1960 S 1 0.2 0:34.13 nginx 7140 www-data 20 0 3652m 12m 1896 S 1 0.3 0:35.80 nginx 619 nobody 20 0 231m 29m 15m S 0 0.7 2:33.46 php-cgi 16552 nobody 20 0 250m 41m 8784 S 0 1.0 2:48.12 php-cgi 17134 nobody 20 0 239m 37m 16m S 0 0.9 2:32.86 php-cgi 21004 nobody 20 0 243m 34m 8700 S 0 0.8 1:19.85 php-cgi 26105 root 20 0 19220 1392 1060 R 0 0.0 0:00.82 top 32430 nobody 20 0 256m 47m 9196 S 0 1.2 2:19.01 php-cgi 314 nobody 20 0 256m 47m 8804 S 0 1.1 1:46.00 php-cgi 2111 nobody 20 0 253m 44m 9196 S 0 1.1 3:01.14 php-cgi 2142 root 20 0 26452 2564 868 S 0 0.1 0:00.56 screen 2144 root 20 0 19484 2012 1368 S 0 0.0 0:00.00 bash 2333 nobody 20 0 249m 41m 9160 S 0 1.0 1:10.33 php-cgi 2552 root 20 0 19484 2260 1620 S 0 0.1 0:00.01 bash 2587 nobody 20 0 258m 49m 9192 S 0 1.2 2:04.50 php-cgi 2684 root 20 0 4092 652 540 S 0 0.0 0:00.00 xvfb-run 2696 root 20 0 60720 13m 2352 S 0 0.3 0:09.12 Xvfb 2759 root 20 0 617m 12m 4676 S 0 0.3 0:00.66 node 3514 nobody 20 0 270m 61m 9216 S 0 1.5 3:13.69 php-cgi 5270 root 20 0 25164 1324 1036 S 0 0.0 0:00.01 screen 5402 nobody 20 0 227m 16m 8032 S 0 0.4 1:33.61 php-cgi 5765 root 20 0 81180 3820 3028 S 0 0.1 0:00.31 sshd 5798 nobody 20 0 242m 32m 9124 S 0 0.8 1:52.08 php-cgi 5856 root 20 0 19496 2292 1636 S 0 0.1 0:00.03 bash 6442 root 20 0 62332 20m 1960 S 0 0.5 0:30.58 mrtg 7082 root 20 0 88992 1916 1636 S 0 0.0 0:00.00 PassengerWatchd I can't find any concrete reason for it, no Exceptions or messages of a shutdown in catalina.out (and no other logs in tomcat's log dir). I can start up the service and it will run for a few days or just minutes before dying again. Is there somewhere else i could look for output? Could the kernel start killing threads due to a lack of ressources and by that bring the VM down?

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• How to transfer data between two networks efficiently

  - by Tono Nam

  I would 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 would 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 in residential places so I would like to use a different approach. I was thinking about using programs such as http://www.dropbox.com . The problem with Dropbox is that the free version comes with only 2 GB of storage. 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 would like it to be even faster. Anyway I was thinking why not create a program myself. This is the algorithm that I was thinking of. Let me know if it sounds too crazy. (Remember my goal is to transfer files as fast 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 at location 1 Client B at location 2 So lets say at 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 packet. Have server S help speed up things. For example every time a packet is lost we can use Server S to inform client A that it needs to resend a packet. Anyways I think this approach will increase the transfer rate. I do not know if it is possible to start sending data while it is being compressed. Or if it is possible to start decompressing data even if we are not done receiving the whole file. 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 could I increase performance by using UDP instead of TCP and by using an extra server to keep track of lost packets? And how should I compress files before sending? Compressing a 1 GB file with the highest compression ratio takes about 1 hour! I would like to take advantage of that time by sending it as it is being compressed.

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• Unable to make the session state request to the session state server

  - by Angry_IT_Guru

  For about 4-5 months now, I seem to be having this sporadic issue--mainly during our busiest time of the day between 10:30-11:45AM, where all my Windows 2003 web servers in a Microsoft NLB cluster start throwing session state server errors. A sample error is below. System.Web.HttpException: Unable to make the session state request to the session state server. Please ensure that the ASP.NET State service is started and that the client and server ports are the same. If the server is on a remote machine, please ensure that it accepts remote requests by checking the value of HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\aspnet_state\Parameters\AllowRemoteConnection. If the server is on the local machine, and if the before mentioned registry value does not exist or is set to 0, then the state server connection string must use either 'localhost' or '127.0.0.1' as the server name. at System.Web.SessionState.OutOfProcSessionStateStore.MakeRequest(StateProtocolVerb verb, String id, StateProtocolExclusive exclusiveAccess, Int32 extraFlags, Int32 timeout, Int32 lockCookie, Byte[] buf, Int32 cb, Int32 networkTimeout, SessionNDMakeRequestResults& results) at System.Web.SessionState.OutOfProcSessionStateStore.SetAndReleaseItemExclusive(HttpContext context, String id, SessionStateStoreData item, Object lockId, Boolean newItem) at System.Web.SessionState.SessionStateModule.OnReleaseState(Object source, EventArgs eventArgs) at System.Web.HttpApplication.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) Now I'm using ASP.NET State service on a centralized back-end Windows 2003 server that all servers communicate to. I was originally using SQL Server state for a couple years as well prior to having this issue. The problem with SQL wqas that when the issue occurred, it created a blocking situation which essentially impacted all users across all servers. The product company recommended that I use the standard ASP.NET State service as that was what they technically supported. Why this would make a difference is beyond me -- but I had no choice but to try it! I have attempted to create multiple application pools, adding additional servers, chaning TCP/IP timeout from 20 to 30 seconds, and even calling Microsoft ASP.NET product support, with very little success. I even recommended that they review whether they are using read-only session state instead of read/write per page request -- as I understand that this basically causes every page to make round-trips to state server even if state isn't being used on the page. Unfortunately, the application is developed by our product company and they insist that it is something with my environment because other clients do not have these sort of issues. However, I've talked to other clients and they tell me when they've seen issues like they, they've basically had to create another web farm. This issue almost seems like I've simply reached some architectural limit within the application... Microsoft's position on the issue is that the session state needs to be reduced and the returncode being reported back from the state server indicates buffers are full. To better understand the scope of issues (rather than wait for customers to call and complain), I installed ELMAH and configured it to send me e-mails when unhandled exceptions occur. I basically get 500-1000 e-mails during the time period of high activity! If any one has any other ideas I could try or better ways to troubleshoot, I'd appreciate it.

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• virturalmin webmin dose not respond

  - by Miranda

  I have installed Virtualmin on a CentOS remote server, but it dose not seem to work https://115.146.95.118:10000/ at least the Webmin page dose not work. I have opened those ports http ALLOW 80:80 from 0.0.0.0/0 ALLOW 443:443 from 0.0.0.0/0 ssh ALLOW 22:22 from 0.0.0.0/0 virtualmin ALLOW 20000:20000 from 0.0.0.0/0 ALLOW 10000:10009 from 0.0.0.0/0 And restarting Webmin dose not solve it: /etc/rc.d/init.d/webmin restart Stopping Webmin server in /usr/libexec/webmin Starting Webmin server in /usr/libexec/webmin And I have tried to use Amazon EC2 this time, still couldn't get it to work. http://ec2-67-202-21-21.compute-1.amazonaws.com:10000/ [ec2-user@ip-10-118-239-13 ~]$ netstat -an | grep :10000 tcp 0 0 0.0.0.0:10000 0.0.0.0:* LISTEN udp 0 0 0.0.0.0:10000 0.0.0.0:* [ec2-user@ip-10-118-239-13 ~]$ sudo iptables -L -n Chain INPUT (policy ACCEPT) target prot opt source destination ACCEPT udp -- 0.0.0.0/0 0.0.0.0/0 udp dpt:20 ACCEPT udp -- 0.0.0.0/0 0.0.0.0/0 udp dpt:21 ACCEPT udp -- 0.0.0.0/0 0.0.0.0/0 udp dpt:53 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:20000 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:10000 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:443 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:80 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:993 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:143 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:995 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:110 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:20 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:21 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:53 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:587 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:25 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:22 Chain FORWARD (policy ACCEPT) target prot opt source destination Chain OUTPUT (policy ACCEPT) target prot opt source destination Since I need more than 10 reputation to post image, you can find the screenshots of the security group setting at the Webmin Support Forum. I have tried: sudo iptables -A INPUT -p tcp -m tcp --dport 10000 -j ACCEPT It did not change anything. [ec2-user@ip-10-118-239-13 ~]$ sudo yum install openssl perl-Net-SSLeay perl-Crypt-SSLeay Loaded plugins: fastestmirror, priorities, security, update-motd Loading mirror speeds from cached hostfile * amzn-main: packages.us-east-1.amazonaws.com * amzn-updates: packages.us-east-1.amazonaws.com amzn-main | 2.1 kB 00:00 amzn-updates | 2.3 kB 00:00 Setting up Install Process Package openssl-1.0.0j-1.43.amzn1.i686 already installed and latest version Package perl-Net-SSLeay-1.35-9.4.amzn1.i686 already installed and latest version Package perl-Crypt-SSLeay-0.57-16.4.amzn1.i686 already installed and latest version Nothing to do [ec2-user@ip-10-118-239-13 ~]$ nano /etc/webmin/miniserv.conf GNU nano 2.0.9 File: /etc/webmin/miniserv.conf port=10000 root=/usr/libexec/webmin mimetypes=/usr/libexec/webmin/mime.types addtype_cgi=internal/cgi realm=Webmin Server logfile=/var/webmin/miniserv.log errorlog=/var/webmin/miniserv.error pidfile=/var/webmin/miniserv.pid logtime=168 ppath= ssl=1 env_WEBMIN_CONFIG=/etc/webmin env_WEBMIN_VAR=/var/webmin atboot=1 logout=/etc/webmin/logout-flag listen=10000 denyfile=\.pl$ log=1 blockhost_failures=5 blockhost_time=60 syslog=1 session=1 server=MiniServ/1.585 userfile=/etc/webmin/miniserv.users keyfile=/etc/webmin/miniserv.pem passwd_file=/etc/shadow passwd_uindex=0 passwd_pindex=1 passwd_cindex=2 passwd_mindex=4 passwd_mode=0 preroot=virtual-server-theme passdelay=1 sessiononly=/virtual-server/remote.cgi preload= mobile_preroot=virtual-server-mobile mobile_prefixes=m. mobile. anonymous=/virtualmin-mailman/unauthenticated=anonymous ssl_cipher_list=ECDHE-RSA-AES256-SHA384:AES256-SHA256:AES256-SHA256:RC4:HIGH:MEDIUM:+TLSv1:!MD5:!SSLv2:+SSLv3:!ADH:!aNULL:!eNULL:!NULL:!DH:!ADH:!EDH:!AESGCM

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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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• 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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• wireless internet in linux is very very slow... but in windows.... everythnings fine

  - by Cody Acer

  yesterday when i was connecting to our neighbors wifi connection which is the signal strength is below 50%, i cant browse anything... even ping to gateway. 100% packet loss, and sometimes.. i can connect awesomely i can open my facebook account for 15 minutes but after 15min.. connection is extremely slow. but not windows i can surf even the signal str is very poor weird ey??.. root@Emely:~# lspci -knn 00:00.0 Host bridge [0600]: Intel Corporation Atom Processor D4xx/D5xx/N4xx/N5xx DMI Bridge [8086:a010] Subsystem: Samsung Electronics Co Ltd Notebook N150P [144d:c072] Kernel driver in use: agpgart-intel 00:02.0 VGA compatible controller [0300]: Intel Corporation Atom Processor D4xx/D5xx/N4xx/N5xx Integrated Graphics Controller [8086:a011] Subsystem: Samsung Electronics Co Ltd Notebook N150P [144d:c072] Kernel driver in use: i915 Kernel modules: i915 00:02.1 Display controller [0380]: Intel Corporation Atom Processor D4xx/D5xx/N4xx/N5xx Integrated Graphics Controller [8086:a012] Subsystem: Samsung Electronics Co Ltd Notebook N150P [144d:c072] 00:1b.0 Audio device [0403]: Intel Corporation NM10/ICH7 Family High Definition Audio Controller [8086:27d8] (rev 02) Subsystem: Samsung Electronics Co Ltd Notebook N150P [144d:c072] Kernel driver in use: snd_hda_intel Kernel modules: snd-hda-intel 00:1c.0 PCI bridge [0604]: Intel Corporation NM10/ICH7 Family PCI Express Port 1 [8086:27d0] (rev 02) Kernel driver in use: pcieport Kernel modules: shpchp 00:1c.1 PCI bridge [0604]: Intel Corporation NM10/ICH7 Family PCI Express Port 2 [8086:27d2] (rev 02) Kernel driver in use: pcieport Kernel modules: shpchp 00:1c.2 PCI bridge [0604]: Intel Corporation NM10/ICH7 Family PCI Express Port 3 [8086:27d4] (rev 02) Kernel driver in use: pcieport Kernel modules: shpchp 00:1c.3 PCI bridge [0604]: Intel Corporation NM10/ICH7 Family PCI Express Port 4 [8086:27d6] (rev 02) Kernel driver in use: pcieport Kernel modules: shpchp 00:1d.0 USB controller [0c03]: Intel Corporation NM10/ICH7 Family USB UHCI Controller #1 [8086:27c8] (rev 02) Subsystem: Samsung Electronics Co Ltd Notebook N150P [144d:c072] Kernel driver in use: uhci_hcd 00:1d.1 USB controller [0c03]: Intel Corporation NM10/ICH7 Family USB UHCI Controller #2 [8086:27c9] (rev 02) Subsystem: Samsung Electronics Co Ltd Notebook N150P [144d:c072] Kernel driver in use: uhci_hcd 00:1d.2 USB controller [0c03]: Intel Corporation NM10/ICH7 Family USB UHCI Controller #3 [8086:27ca] (rev 02) Subsystem: Samsung Electronics Co Ltd Notebook N150P [144d:c072] Kernel driver in use: uhci_hcd 00:1d.3 USB controller [0c03]: Intel Corporation NM10/ICH7 Family USB UHCI Controller #4 [8086:27cb] (rev 02) Subsystem: Samsung Electronics Co Ltd Notebook N150P [144d:c072] Kernel driver in use: uhci_hcd 00:1d.7 USB controller [0c03]: Intel Corporation NM10/ICH7 Family USB2 EHCI Controller [8086:27cc] (rev 02) Subsystem: Samsung Electronics Co Ltd Notebook N150P [144d:c072] Kernel driver in use: ehci-pci 00:1e.0 PCI bridge [0604]: Intel Corporation 82801 Mobile PCI Bridge [8086:2448] (rev e2) 00:1f.0 ISA bridge [0601]: Intel Corporation NM10 Family LPC Controller [8086:27bc] (rev 02) Subsystem: Samsung Electronics Co Ltd Notebook N150P [144d:c072] Kernel driver in use: lpc_ich Kernel modules: lpc_ich 00:1f.2 SATA controller [0106]: Intel Corporation NM10/ICH7 Family SATA Controller [AHCI mode] [8086:27c1] (rev 02) Subsystem: Samsung Electronics Co Ltd Notebook N150P [144d:c072] Kernel driver in use: ahci Kernel modules: ahci 00:1f.3 SMBus [0c05]: Intel Corporation NM10/ICH7 Family SMBus Controller [8086:27da] (rev 02) Subsystem: Samsung Electronics Co Ltd Notebook N150P [144d:c072] Kernel modules: i2c-i801 05:00.0 Network controller [0280]: Broadcom Corporation BCM4313 802.11bgn Wireless Network Adapter [14e4:4727] (rev 01) Subsystem: Wistron NeWeb Corp. Device [185f:051a] Kernel driver in use: bcma-pci-bridge Kernel modules: bcma 09:00.0 Ethernet controller [0200]: Marvell Technology Group Ltd. 88E8040 PCI-E Fast Ethernet Controller [11ab:4354] Subsystem: Samsung Electronics Co Ltd Notebook N150P [144d:c072] Kernel driver in use: sky2 Kernel modules: sky2 root@Emely:~# ip addr show 1: lo: mtu 65536 qdisc noqueue state UNKNOWN link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: eth0: mtu 1500 qdisc pfifo_fast state DOWN qlen 1000 link/ether e8:11:32:2e:a6:fd brd ff:ff:ff:ff:ff:ff 3: wlan0: mtu 1500 qdisc mq state UP qlen 1000 link/ether 00:1b:b1:a9:ac:e0 brd ff:ff:ff:ff:ff:ff inet 192.168.1.108/24 brd 192.168.1.255 scope global wlan0 inet6 fe80::21b:b1ff:fea9:ace0/64 scope link valid_lft forever preferred_lft forever root@Emely:~# ip link show 1: lo: mtu 65536 qdisc noqueue state UNKNOWN link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 2: eth0: mtu 1500 qdisc pfifo_fast state DOWN qlen 1000 link/ether e8:11:32:2e:a6:fd brd ff:ff:ff:ff:ff:ff 3: wlan0: mtu 1500 qdisc mq state UP qlen 1000 link/ether 00:1b:b1:a9:ac:e0 brd ff:ff:ff:ff:ff:ff root@Emely:~# rfkill list all 0: samsung-wlan: Wireless LAN Soft blocked: no Hard blocked: no 1: samsung-bluetooth: Bluetooth Soft blocked: no Hard blocked: no 2: hci0: Bluetooth Soft blocked: no Hard blocked: no 3: phy0: Wireless LAN Soft blocked: no Hard blocked: no is this a wireless driver issue?

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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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• 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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• Magento hosting on a budget

  - by spa

  I have to do a setup for Magento. My constraint is primarily ease of setup and fault tolerance/fail over. Furthermore costs are an issue. I have three identical physical servers to get the job done. Each server node has an i7 quad core, 16GB RAM, and 2x3TB HD in a software RAID 1 configuration. Each node runs Ubuntu 12.04. right now. I have an additional IP address which can be routed to any of these nodes. The Magento shop has max. 1000 products, 50% of it are bundle products. I would estimate that max. 100 users are active at once. This leads me to the conclusion, that performance is not top priority here. My first setup idea One node (lb) runs nginx as a load balancer. The additional IP is used with domain name and routed to this node by default. Nginx distributes the load equally to the other two nodes (shop1, shop2). Shop1 and shop2 are configured equally: each server runs Apache2 and MySQL. The Mysqls are configured with master/slave replication. My failover strategy: Lb fails = Route IP to shop1 (MySQL master), continue. Shop1 fails = Lb will handle that automatically, promote MySQL slave on shop2 to master, reconfigure Magento to use shop2 for writes, continue. Shop2 fails = Lb will handle that automatically, continue. Is this a sane strategy? Has anyone done a similar setup with Magento? My second setup idea Another way to do it would be to use drbd for storing the MySQL data files on shop1 and shop2. I understand that in this scenario only one node/MySQL instance can be active and the other is used as hot standby. So in case shop1 fails, I would start up MySQL on shop2, route the IP to shop2, and continue. I like that as the MySQL setup is easier and the nodes can be configured 99% identical. So in this case the load balancer becomes useless and I have a spare server. My third setup idea The third way might be master-master replication of MySQL databases. However, in my optinion this might be tricky, as Magento isn't build for this scenario (e.g. conflicting ids for new rows). I would not do that until I have heard of a working example. Could you give me an advice which route to follow? There seems not one "good" way to do it. E.g. I read blog posts which describe a MySQL master/slave setup for Magento, but elsewhere I read, that data might get duplicated when the slave lags behind the master (e.g. when an order is placed, a customer might get created twice). I'm kind of lost here.

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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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• 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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• 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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• 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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• 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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• 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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• 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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• 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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• 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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• How to stop Apache from crashing my entire server?

  - by CyberShadow

  I maintain a Gentoo server with a few services, including Apache. It's fairly low-end (2GB of RAM and a low-end CPU with 2 cores). My problem is that, despite my best efforts, an over-loaded Apache crashes the entire server. In fact, at this point I'm close to being convinced that Linux is a horrible operating system that isn't worth anyone's time looking for stability under load. Things I tried: Adjusting oom_adj for the root Apache process (and thus all its children). That had close to no effect. When Apache was overloaded it would bring the system to a grind, as the system paged out everything else before it got to kill anything. Turning off swap. Didn't help, it would unload memory paged to binaries of processes and other files on /, thus causing the same effect. Putting it in a memory-limited cgroup (limited to 512 MB of RAM, 1/4th of the total). This "worked", at least in my own stress tests - except the server keeps crashing under load (basically stalling all other processes, inaccessible via SSH, etc.) Running it with idle I/O priority. This wasn't a very good idea in the end, because it just caused the system load to climb indefinitely (into the thousands) with almost no visible effect - until you tried to access an unbuffered part of the disk. This caused the task to freeze. (So much for good I/O scheduling, eh?) Limiting the number of concurrent connections to Apache. Setting the number too low caused web sites to become unresponsive due to most slots being occupied with long requests (file downloads). I tried various Apache MPMs without much success (prefork, event, itk). Switching from prefork/event+php-cgi+suphp to itk+mod_php. This improved performance, but didn't solve the actual problem. Switching I/O schedulers (cfq to deadline). Just to stress this out: I don't care if Apache itself goes down under load, I just want the rest of my system to remain stable. Of course, having Apache recover quickly after a brief period of intensive load would be great to have, but one step at a time. Right now I am mostly dumbfounded by how can humanity, in this day and age, design an operating system where such a seemingly simple task (don't allow one system component to crash the entire system) seems practically impossible - or at least, very hard to do. Please don't suggest things like VMs or "BUY MORE RAM". Some more information gathered with a friend's help: The processes hang when the cgroup oom killer is invoked. Here's the call trace: [<ffffffff8104b94b>] ? prepare_to_wait+0x70/0x7b [<ffffffff810a9c73>] mem_cgroup_handle_oom+0xdf/0x180 [<ffffffff810a9559>] ? memcg_oom_wake_function+0x0/0x6d [<ffffffff810aa041>] __mem_cgroup_try_charge+0x32d/0x478 [<ffffffff810aac67>] mem_cgroup_charge_common+0x48/0x73 [<ffffffff81081c98>] ? __lru_cache_add+0x60/0x62 [<ffffffff810aadc3>] mem_cgroup_newpage_charge+0x3b/0x4a [<ffffffff8108ec38>] handle_mm_fault+0x305/0x8cf [<ffffffff813c6276>] ? schedule+0x6ae/0x6fb [<ffffffff8101f568>] do_page_fault+0x214/0x22b [<ffffffff813c7e1f>] page_fault+0x1f/0x30 At this point, the apache memory cgroup is practically deadlocked, and burning CPU in syscalls (all with the above call trace). This seems like a problem in the cgroup implementation...

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