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• APC PHP cache size does not exceed 32MB, even though settings allow for more

  - by hardy101

  I am setting up APC (v 3.1.9) on a high-traffic WordPress installation on CentOS 6.0 64 bit. I have figured out many of the quirks with APC, but something is still not quite right. No matter what settings I change, APC never actually caches more than 32MB. I'm trying to bump it up to 256 MB. 32MB is a default amount for apc.shm_size, so I am wondering if it's stuck there somehow. I have run the following echo '2147483648' > /proc/sys/kernel/shmmax to increase my system's shared memory to 2G (half of my 4G box). Then ran ipcs -lm which returns ------ Shared Memory Limits -------- max number of segments = 4096 max seg size (kbytes) = 2097152 max total shared memory (kbytes) = 8388608 min seg size (bytes) = 1 Also made a change in /etc/sysctl.conf then ran sysctl -p to make the settings stick on the server. Rebooted, too, for good measure. In my APC settings, I have mmap enabled (which happens by default in recent versions of APC). php.ini looks like: apc.stat=0 apc.shm_size="256M" apc.max_file_size="10M" apc.mmap_file_mask="/tmp/apc.XXXXXX" apc.ttl="7200" I am aware that mmap mode will ignore references to apc.shm_segments, so I have left it out with default 1. phpinfo() indicates the following about APC: Version 3.1.9 APC Debugging Disabled MMAP Support Enabled MMAP File Mask /tmp/apc.bPS7rB Locking type pthread mutex Locks Serialization Support php Revision $Revision: 308812 $ Build Date Oct 11 2011 22:55:02 Directive Local Value apc.cache_by_default On apc.canonicalize O apc.coredump_unmap Off apc.enable_cli Off apc.enabled On On apc.file_md5 Off apc.file_update_protection 2 apc.filters no value apc.gc_ttl 3600 apc.include_once_override Off apc.lazy_classes Off apc.lazy_functions Off apc.max_file_size 10M apc.mmap_file_mask /tmp/apc.bPS7rB apc.num_files_hint 1000 apc.preload_path no value apc.report_autofilter Off apc.rfc1867 Off apc.rfc1867_freq 0 apc.rfc1867_name APC_UPLOAD_PROGRESS apc.rfc1867_prefix upload_ apc.rfc1867_ttl 3600 apc.serializer default apc.shm_segments 1 apc.shm_size 256M apc.slam_defense On apc.stat Off apc.stat_ctime Off apc.ttl 7200 apc.use_request_time On apc.user_entries_hint 4096 apc.user_ttl 0 apc.write_lock On apc.php reveals the following graph, no matter how long the server runs (cache size fluctuates and hovers at just under 32MB. See image http://i.stack.imgur.com/2bwMa.png You can see that the cache is trying to allocate 256MB, but the brown piece of the pie keeps getting recycled at 32MB. This is confirmed as refreshing the apc.php page shows cached file counts that move up and down (implying that the cache is not holding onto all of its files). Does anyone have an idea of how to get APC to use more than 32 MB for its cache size?? **Note that the identical behavior occurs for eaccelerator, xcache, and APC. I read here: http://www.litespeedtech.com/support/forum/archive/index.php/t-5072.html that suEXEC could cause this problem.

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• A gigabit network interface is CPU-limited to 25MB/s. How can I maximize the throughput?

  - by netvope

  I have a Acer Aspire R1600-U910H with a nForce gigabit network adapter. The maximum TCP throughput of it is about 25MB/s, and apparently it is limited by the single core Intel Atom 230; when the maximum throughput is reached, the CPU usage is about 50%-60%, which corresponds to full utilization considering this is a Hyper-threading enabled CPU. The same problem occurs on both Windows XP and on Ubuntu 8.04. On Windows, I have installed the latest nForce chipset driver, disabled power saving features, and enabled checksum offload. On Linux, the default driver has checksum offload enabled. There is no Linux driver available on Nvidia's website. ethtool -k eth0 shows that checksum offload is enabled: Offload parameters for eth0: rx-checksumming: on tx-checksumming: on scatter-gather: on tcp segmentation offload: on udp fragmentation offload: off generic segmentation offload: off The following is the output of powertop when the network is idle: Wakeups-from-idle per second : 61.9 interval: 10.0s no ACPI power usage estimate available Top causes for wakeups: 90.9% (101.3) <interrupt> : eth0 4.5% ( 5.0) iftop : schedule_timeout (process_timeout) 1.8% ( 2.0) <kernel core> : clocksource_register (clocksource_watchdog) 0.9% ( 1.0) dhcdbd : schedule_timeout (process_timeout) 0.5% ( 0.6) <kernel core> : neigh_table_init_no_netlink (neigh_periodic_timer) And when the maximum throughput of about 25MB/s is reached: Wakeups-from-idle per second : 11175.5 interval: 10.0s no ACPI power usage estimate available Top causes for wakeups: 99.9% (22097.4) <interrupt> : eth0 0.0% ( 5.0) iftop : schedule_timeout (process_timeout) 0.0% ( 2.0) <kernel core> : clocksource_register (clocksource_watchdog) 0.0% ( 1.0) dhcdbd : schedule_timeout (process_timeout) 0.0% ( 0.6) <kernel core> : neigh_table_init_no_netlink (neigh_periodic_timer) Notice the 20000 interrupts per second. Could this be the cause for the high CPU usage and low throughput? If so, how can I improve the situation? As a reference, the other computers in the network can usually transfer at 50+MB/s without problems. A computer with a Core 2 CPU generates only 5000 interrupts per second when it's transferring at 110MB/s. The number of interrupts is about 20 times less than the Atom system (if interrupts scale linearly with throughput.) And a minor question: How can I find out what is the driver in use for eth0?

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• Complete machine freezes...at a loss

  - by user28818

  Guys, We built around 12 machines a few months ago to run Ubuntu. They each have the following specs: ASUS Z8NA-D6 motherboard Dual quad core Intel(R) Xeon(R) CPU E5520 @ 2.27GHz OCZ Mod Extreme Pro 500W power supply 12 GB Kingston RAM Nvidia GeForce 9800 GT graphics card My machine ran well for awhile. However, it started experiencing random lockups. These lockups are not X lockups, they are complete system freezes. The nic stops responding, the magic sysrq buttons won't work. The machine is dead. I first suspected RAM. Memtest86 didn't find anything, but I replaced the RAM anyway. Still, lockups. So I replaced the graphics card. Still, more lockups. They became more and more frequent and started to happen 2-3 times a day. So I replaced the motherboard and power supply in one fell swoop. Suddenly, no more lockups! Woohoo! Except, a week later, in the morning, the machine wouldn't wake up. I reset it, started it up, and the log files showed the last entry at around 11 pm the evening before. This has started occurring with more frequency...now just about every morning I come in, the machine is locked up, and has been since the night before. Yesterday, in the 3 weeks since I replaced the motherboard and power supply, the machine actually locked up on in in mid-work. This is the first time since replacing the two (MB and PS) that this happened while I was using it. All others occurred while I was away. I'm at a loss. Nothing is in syslog or message that would indicate a problem around the time of the lockup. Temps are good...I use lmsensors to monitor and have a script that writes the output to file every minute. They never get that high. The only thing I haven't replaced at this point is the case and the harddrives. I doubt either could be the cause. What would you do if you were in my shoes? Is there a troubleshooting approach I'm missing? For the record, all of the other machines, all eleven of them, don't have any problems. They're all running the same version of Ubuntu (Lucid) that I am. Thanks!

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• Will spreading your servers load not just consume more recourses

  - by Saif Bechan

  I am running a heavy real-time updating website. The amount of recourses needed per user are quite high, ill give you an example. Setup Every visit The application is php/mysql so on every visit static and dynamic content is loaded. Recourses: apache,php,mysql Every second (no more than a second will just be too long) The website needs to be updated real-time so every second there is an ajax call thats updates the website. Recourses: jQuery,apache,php,mysql Avarage spending for single user (spending one minute and visited 3 pages) Apache: +/- 63 requests / responsess serving static and dynamic content (img,css,js,html) php: +/- 63 requests / responses mysql: +/- 63 requests / responses jquery: +/- 60 requests / responses Optimization I want to optimize this process, but I think that maybe it would be just the same in the end. Before implementing and testing (which will take weeks) I wanted to have some second opinions from you guys. Every visit I want to start off with having nginx in the front and work as a proxy to deliver the static content. Recources: Dynamic: apache,php,mysql Static: nginx This will spread the load on apache a lot. Every Second For the script that loads every second I want to set up Node.js server side javascript with nginx in te front. I want to set it up that jquery makes a request ones a minute, and node.js streams the data to the client every second. Recources: jQuery,nginx,node.js,mysql Avarage spending for single user (spending one minute and visited 3 pages) Nginx: 4 requests / responsess serving mostly static conetent(img,css,js) Apache: 3 requests only the pages php: 3 requests only the pages node.js: 1 request / 60 responses jquery: 1 request / 60 responses mysql: 63 requests / responses Optimization As you can see in the optimisation the load from Apache and PHP are lifted and places on nginx and node.js. These are known for there light footprint and good performance. But I am having my doubts, because there are still 2 programs extra loaded in the memory and they consume cpu. So it it better to have less programs that do the job, or more. Before I am going to spend a lot of time setting this up I would like to know if it will be worth the while.

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• Echo 404 directly from nginx to improve performance

  - by user64204

  I am in charge of production servers serving static content for a website. Those servers are constantly being crawled by bots looking for potential exploits (which isn't that much of a problem security-wise because no application can be reached behind the web server) but generates thousands of 404 per day, sometimes per hour. I am looking into ways of blocking those requests but it's tricky (you want to make sure you don't block legitimate traffic and these bots are becoming more and more clever at looking like they're legit) and is going to take me a while to find an acceptable solution. In the meantime I would like to reduce the performance impact of serving those 404 pages. Indeed we're using nginx which by default is configured to serve it's 404 page from the disk (This can be changed using the error_page directive but in the end the 404 will either have to be served from disk or from another external source (e.g. upstream application which would be worst)) which isn't ideal. I ran a test with ab on my local machine with a basic configuration: in one case I echo a message directly from nginx so the disk isn't touched at all, in the other case I hit a missing page and nginx serves its 404 from disk. server { # [...] the default nginx stuff location / { } location /this_page_exists { echo "this page was found"; } } Here are the test results (my laptop has Intel(R) Core(TM) i7-2670QM + SSD in case you're wondering why they are so high): $ ab -n 500000 -c 1000 http://localhost/this_page_exists Requests per second: 25609.16 [#/sec] (mean) $ ab -n 500000 -c 1000 http://localhost/this_page_doesnt_exists Requests per second: 22905.72 [#/sec] (mean) As you can see, returning a value with echo is 11% ((25609-22905)÷22905×100) faster than serving the 404 page from disk. Accordingly I would like to echo a simple 404 Page not Found string from nginx. I tried many things so far but they all failed, essentially the idea was this: location / { try_files $uri @not_found; } location @not_found { echo "404 - Page not found"; } The problem is that as soon as the echo directive is used, the http response code is set to 200. I tried changing that by doing error_page 200 = 400 but that breaks the configuration. How can I serve a 404 page directly from nginx? (without hacking the source which may be might next step)

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• iTunes and Hulu Playback Choppy and Slow?

  - by Bart Silverstrim

  Specs: Windows XP, latest updates 1.7 ghz Pentium 4 1 gig ram DirectX 9.0c NVIDIA GeForce FX 5200 with 256 meg RAM OpenGL 2.1 The story: Okay, I had an older system laying around that I figured I would try turning into a mini-media system to connect to our TV. I put together a lot of older parts, got it into working order, etc. and hooked it up and voila'...slower, but usable system that displayed to the TV. It could run some things decently. I put in iTunes, it played video okay. Not great, but okay. Played Hulu and since we have a 1Mb download rate, the minimum for their site, there were some choppy moments when watching their shows, but I found that (sadly) changing resolution to 800x600 seemed to help with the issue when running full screen. I downloaded the application called Boxee and installed it. It wouldn't run; apparently the video card in the system supported OpenGL 1.2, and needed at least 1.4. I bought a cheap card, the 5200, with four times the memory in it and support for OpenGL 2.1. Installed, everything seemed fine. iTunes seemed to run fine, the video driver (PNY video card) came with OpenGL 2.1, and Boxee finally ran. I then upgraded to the latest drivers for the video card and ran the DirectX updater from MS. After that, the OpenGL Extension Viewer wouldn't run. It just stayed as an icon in the task bar. Also, any and all videos in iTunes stuttered and went out of sync horribly. Unwatchable. I tried watching Hulu video in Boxee, and it displayed video like it was a series of stills in a very bad powerpoint. Playing straightforward audio-only came through fine, no stutters no hiccups. I tried system restore to roll back updates to pre-directX updates (I thought that seemed to be the time that triggered the weird behavior), no joy. I tried uninstalling and reinstalling the video drivers. I installed updated audio drivers (ensoniq audiopci), nothing helped. I finally wiped the drive last night and tried reinstalling everything and restoring my iTunes content via an import from a backup. Fresh install, no updater on the video card or directx. the problem was still there although I haven't tested Hulu, the iTunes player is still stuttering like crazy if I play video, fine if I play audio. I know the processor isn't high in heft, but with one gig of RAM and the fact that it seemed to do okay before I thought that the problem must be software related. Has anyone else run into this sort of issue and have a solution other than "buy a new computer"? What specs seem to work with video at the low end for you? Right now the system is of little use other than keeping my music library and iTunes apps synced with my iPod.

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• SQL Transactional Replication snapshot not applying

  - by dmch2

  Hi, I'm using SQL Transactional Replication with pull subscriptions to replicate databases (hosting their own distribution database) from several servers across a VPN to a central server. I've got the first 2 databases working fine but the 3rd one is causing me problems. My subscription server is SQL 2008, the source systems are all SQL 2005. The source databases are a few 100Mb in size and contain audit data so are simply growing slowly by adding new records at approx 1kb a second. As far as the replication monitor, Agent logs and event logs show everything is working fine - except that no data appears in my subscription database. The distribution agent doesn't seem to want to read the snapshot (and hence the initial state and schema) from the publisher. New transactions aren't applied although they do seem to be arriving OK as the replication monitor shows things like '5 transactions with 10 commands were delivered'. I would expect (as in previous times) to see statements about data being BCPed in the replication monitor. The snapshot is on the publisher on a shared folder. The subscriber can view the snapshot OK (\\repldata) and the alt snapshot folder is pointing at it. But the distribution agent doesn't seem to be making an attempt to do read it. I tried changing the snapshot path to something that's incorrect and didn't even get an error saying that it couldn't access it. After lots of googling etc I found that sp_MSget_repl_commands is called by the subscriber on the distribution database on the publisher. Running a profiler I can see that it's only called for one agent Id. After a reinit it's called for sequence number 0x0 as expected so I thought that would mean it's would look for the snapshot. However, looking on the publisher I see that there's data for two agents - the snapshot agent and the log reader agent (which is being queries). So I guess I need to tell the distribution agent to get the data for both. But how? and more importantly - why? It worked fine on the other two servers I've replicated. I'm not an SQL novice but this is pretty much my first go at replication so don't be afraid to accuse me of missing something obvious/stupid! I can get log files (eg from the distribution agent) if you want but they don't seem to have any errors in them - it just starts up and starts applying log reader agent changes. Cheers Dave

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• How does an NTP host switch among the various modes?

  - by James A. Rosen

  The NTPv3 RFC describes five operating modes: Symmetric Active (1): A host operating in this mode sends periodic messages regardless of the reachability state or stratum of its peer. By operating in this mode the host announces its willingness to synchronize and be synchronized by the peer. Symmetric Passive (2): This type of association is ordinarily created upon arrival of a message from a peer operating in the symmetric active mode and persists only as long as the peer is reachable and operating at a stratum level less than or equal to the host; otherwise, the association is dissolved. However, the association will always persist until at least one message has been sent in reply. By operating in this mode the host announces its willingness to synchronize and be synchronized by the peer. Client (3): A host operating in this mode sends periodic messages regardless of the reachability state or stratum of its peer. By operating in this mode the host, usually a LAN workstation, announces its willingness to be synchronized by, but not to synchronize the peer. Server (4): This type of association is ordinarily created upon arrival of a client request message and exists only in order to reply to that request, after which the association is dissolved. By operating in this mode the host, usually a LAN time server, announces its willingness to synchronize, but not to be synchronized by the peer. Broadcast (5): A host operating in this mode sends periodic messages regardless of the reachability state or stratum of the peers. By operating in this mode the host, usually a LAN time server operating on a high-speed broadcast medium, announces its willingness to synchronize all of the peers, but not to be synchronized by any of them. It seems to me, though, that any host except a leaf node would probably be in several modes. For example, I might have a local area network with three NTP servers, each in Symmetric Active (1) mode with respect to one another. They would also each be clients (3) of one of the many public stratum two time servers. Lastly, they would all server as servers (4) to the many local clients. Is the point that they're only in a given mode for a moment during the synchronization? If so, how does a host know to switch? I'm only looking for enough depth here to discuss the issue in an educated manner, not to write a custom time server.

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• SQL Server suddenly using only a small portion of CPU.

  - by hermiod

  We've got a Windows 2008 R2 server running SQL Server 2008. All of a sudden, the SQLServer process is refusing to go above 20% CPU usage. As of last week, when running a heavy query against the db it would rise to 100% usage as I would expect. We've had this server for a while and it seems strange that it would just suddenly have this limit. This limit is causing our queries to take a lot longer than they normally would. No one has (knowingly at least) made any changes to the server configuration. After a bit of investigation, I discovered the sys.dm_os_sys_memory view. This shows 'available physical memory is high' bu at the same time the available physical memory is 339552kb where as the total is 4193848kb. It is worth noting that this is a virtual server running on vmware. Is there a setting somewhere with in SQL Server that sets the maximum CPU usage? I've found the settings in resource governor, although this is currently off as it always has been. We have recently started using Spotlight for SQL Server by Quest Software. It's playback database was located on this server for a short time this morning, I first noticed the problem shortly afterwards, although I hadn't been doing any queries prior to this so I don't know if this is the point at which the problem began, however the database was working as expected on Friday afternoon. The Windows log shows that the following settings were applied to the SpotlightPlaybackDatabase when it was created. 02/21/2011 08:45:02,spid60,Unknown,Setting database option TORN_PAGE_DETECTION to ON for database SpotlightPlaybackDatabase. 02/21/2011 08:45:02,spid60,Unknown,Setting database option MULTI_USER to ON for database SpotlightPlaybackDatabase. 02/21/2011 08:45:02,spid60,Unknown,Setting database option READ_WRITE to ON for database SpotlightPlaybackDatabase. 02/21/2011 08:45:02,spid60,Unknown,Setting database option AUTO_UPDATE_STATISTICS to ON for database SpotlightPlaybackDatabase. 02/21/2011 08:45:02,spid60,Unknown,Setting database option AUTO_CREATE_STATISTICS to ON for database SpotlightPlaybackDatabase. 02/21/2011 08:45:02,spid60,Unknown,Setting database option ANSI_WARNINGS to OFF for database SpotlightPlaybackDatabase. 02/21/2011 08:45:02,spid60,Unknown,Setting database option CONCAT_NULL_YIELDS_NULL to ON for database SpotlightPlaybackDatabase. 02/21/2011 08:45:02,spid60,Unknown,Setting database option RECOVERY to SIMPLE for database SpotlightPlaybackDatabase. 02/21/2011 08:45:02,spid60,Unknown,Setting database option QUOTED_IDENTIFIER to OFF for database SpotlightPlaybackDatabase. 02/21/2011 08:45:02,spid60,Unknown,Setting database option AUTO_CLOSE to OFF for database SpotlightPlaybackDatabase. Could any of these settings changes modified the settings applied to the whole server?

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• Should I choose KVM/XEN over OpenVZ or use them together?

  - by Krystian

  I've got a dual xeon e5504 server, with [for now] only 8GB of ram. Storage is'n impressive either: 3x 146GB sas in raid5 + 500GB sata drives. Currently it works as a development server, but it's over speced for our needs and since our development methods changed through last 2 years we decided it will work as a production system for some of our applications + we would like to have a separate system for testing/research. Our apps are mainly web apps deployed on tomcats [plural as some of the apps require older versions] and connected to Postgres. I would like to have a production system, where only httpd+tomcat+db are setup and nothing else runs there. Sterile system. Apart from that, I would like a test system, where I can play with different JVM settings, deploy my test apps, play with tomcat/httpd settings and restart them without interfering with the production system. Apart from that, I would like to be able to play with different linux flavors, with newer kernels to test how they work etc. I know, this is not possible with OpenVZ and I would have to choose KVM for that. I am thinking about merging the two, and setting up a KVM to be able to work with different systems [linux only to be frank] + use openVZ to setup separate machines for my development needs. I would simply go with that, but reading here and there about the performance impact full virtualization has over containers and looking at the specs of my server makes me think twice about it. I don't want to loose too much performance, especially because of the nature of my apps [few JVMs running at the same time]. It will be my first time with virtualization, apart from using desktop virtualbox/vmserver. Although I am a fast learner I don't want to mess with the main system so much that it will break the production apps or make them crawl. Although they are more or less internal apps and they don't produce much load, they need to be stable. I've read, that KVM host is a normal linux installation and it allows to run normal processes on it. If that is so, does it allow to run openVZ as well? I mean... can I have KVM and OpenVZ running on the same system/kernel? Or do I have to setup another system to run OpenVZ containers? How much performance impact can this have for me? Will my hardware suffice? oh and one more thing... unfortunately I'm quite limited with the funds... I'm looking for a free solution only :/

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• How to store data on a machine whose power gets cut at random

  - by Sevas

  I have a virtual machine (Debian) running on a physical machine host. The virtual machine acts as a buffer for data that it frequently receives over the local network (the period for this data is 0.5s, so a fairly high throughput). Any data received is stored on the virtual machine and repeatedly forwarded to an external server over UDP. Once the external server acknowledges (over UDP) that it has received a data packet, the original data is deleted from the virtual machine and not sent to the external server again. The internet connection that connects the VM and the external server is unreliable, meaning it could be down for days at a time. The physical machine that hosts the VM gets its power cut several times per day at random. There is no way to tell when this is about to happen and it is not possible to add a UPS, a battery, or a similar solution to the system. Originally, the data was stored on a file-based HSQLDB database on the virtual machine. However, the frequent power cuts eventually cause the database script file to become corrupted (not at the file system level, i.e. it is readable, but HSQLDB can't make sense of it), which leads to my question: How should data be stored in an environment where power cuts can and do happen frequently? One option I can think of is using flat files, saving each packet of data as a file on the file system. This way if a file is corrupted due to loss of power, it can be ignored and the rest of the data remains intact. This poses a few issues however, mainly related to the amount of data likely being stored on the virtual machine. At 0.5s between each piece of data, 1,728,000 files will be generated in 10 days. This at least means using a file system with an increased number of inodes to store this data (the current file system setup ran out of inodes at ~250,000 messages and 30% disk space used). Also, it is hard (not impossible) to manage. Are there any other options? Are there database engines that run on Debian that would not get corrupted by power cuts? Also, what file system should be used for this? ext3 is what is used at the moment. The software that runs on the virtual machine is written using Java 6, so hopefully the solution would not be incompatible.

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• What DNS server to use for dynamic load-balancing of website?

  - by Marki555

  I will have 2 servers in different datacenters (different countries) and I want to use DNS load-balancing mainly for High Availability of website hosted on those 2 servers. It is just ad tracking site, which records hit in local database and returns few lines on html code. I want to return 2 A records each time because of DNS pinning in browsers (if one server fails, browser will try second A record which it has already cached). Both servers will be acting also as DNS servers for redundancy. Now comes my proposed solution: I will use BIND and have both servers as a master for that zone. On each server there will be running script, which will periodically test availability (http) of both servers and remove IP from DNS in case of failure. Now the questions :) 1) Is BIND suitable for this solution? I think BIND performance is good and it is easy to manipulate the zone file via script. And as I will modify the zone only in case of failure/maintenance, the modifications (and thus bind reload) won't be often. 2) I plan to use TTL of 5 minutes. The website will have about 1000-3000 req/s but from distinct clients (each IP only 1-3 requests), so I think the DNS load won't be too much. I suppose their ISPs will cache the responses for those 5 mins. Is there any reason to lower the TTL even more? 3) Is my master-master approach good? Or should I make one of the servers master and the other one slave? Right now each server can monitor both itself and the other one. If only webservice fails, both DNS nodes will notice it. If the whole server fails, then the remaining DNS node will notice it and the failed node will not answer DNS queries anyway. 4) Is it a big issue when one NS server does not respond to queries? If yes, I can make a third DNS, so anytime at least 2 of them would accept queries... 5) Should I rewrite the zone file via script, or just use dynamic DNS update (for example via nsupdateutility)?

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• Low FPS in some games, but hardware not fully used

  - by Mario De Schaepmeester

  I just did a little funny experiment in the game/sim "Train Simulator 2013". I normally have good FPS in it (around 30) at full settings. What I did was make a really, really long train so that the calculations the sim needed to make were enormous (the sim is quite realistic, it takes all things into account like speed/acceleration, G-forces, comfort levels, possible wheel slip and many more, and most of those things on each carriage seperately). This resulted in only 14FPS as reported by the game, but it felt more like 8FPS or so. I have a Logitech G15 keyboard which has an LCD, and it allows me to monitor CPU/RAM and video card load on it. The strange thing is, all CPU cores were busy, but the total load was only about 60% maximum at all times. The video card was only on 30% load (possibly an important note, the memory was full, which is however not unusual for the game in question). The RAM had plenty of room and there weren't many operations as it didn't grow or shrink much. I just have the feeling that the game would run smoother if it used more of my hardware power. Why is it not doing so? I had the same in another game, The Elder Scrolls: Morrowind when using more than 100 mods (that all use scripting) and a few high res texture mods, + a full-on graphics improvement program. The engine is very old (2003), and so I thought this might be the cause (not being optimised for multithreading). I had thought of possible causes, like: The operating system doesn't let the games use all the resources. It doesn't make use of multi-threading appropriately. To eliminate the former, I tried a CPU stress tool and that got 100% CPU juice as I let it run, so the OS is not the problem. I gave its thread the "higher" priority though. My actual question In both games, I did things the engine was not really built to do or support. Can those games' framerate be limited cause of their own engine not being able to cope? What is the real reason and more importantly, can I help it? And in any case, could something actually be wrong with my hardware? It's all reasonably new, a couple of months, and I (almost) never experience any other trouble. Modern and much more demanding games work absolutely fine. Specs CPU: AMD Phenom II 965 X4 @ 3.4gHz RAM: 8GB of DDR3 RAM Video: MSI GTX560 (nVidia chip) with 1GB of GDDR5 memory OS: Windows 7 Ultimate 64 bit Nothing overclocked.

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• Apache's htcacheclean doesn't scale: How to tame a huge Apache disk_cache?

  - by flight

  We have an Apache setup with a huge disk_cache (500.000 entries, 50 GB disk space used). The cache grows by 16 GB every day. My problem is that the cache seems to be growing nearly as fast as it's possible to remove files and directories from the cache filesystem! The cache partition is an ext3 filesystem (100GB, "-t news") on an iSCSI storage. The Apache server (which acts as a caching proxy) is a VM. The disk_cache is configured with CacheDirLevels=2 and CacheDirLength=1, and includes variants. A typical file path is "/htcache/B/x/i_iGfmmHhxJRheg8NHcQ.header.vary/A/W/oGX3MAV3q0bWl30YmA_A.header". When I try to call htcacheclean to tame the cache (non-daemon mode, "htcacheclean-t -p/htcache -l15G"), IOwait is going through the roof for several hours. Without any visible action. Only after hours, htcacheclean starts to delete files from the cache partition, which takes a couple more hours. (A similar problem was brought up in the Apache mailing list in 2009, without a solution: http://www.mail-archive.com/[email protected]/msg42683.html) The high IOwait leads to problems with the stability of the web server (the bridge to the Tomcat backend server sometimes stalls). I came up with my own prune script, which removes files and directories from random subdirectories of the cache. Only to find that the deletion rate of the script is just slightly higher than the cache growth rate. The script takes ~10 seconds to read the a subdirectory (e.g. /htcache/B/x) and frees some 5 MB of disk space. In this 10 seconds, the cache has grown by another 2 MB. As with htcacheclean, IOwait goes up to 25% when running the prune script continuously. Any idea? Is this a problem specific to the (rather slow) iSCSI storage? Should I choose a different file system for a huge disk_cache? ext2? ext4? Are there any kernel parameter optimizations for this kind of scenario? (I already tried the deadline scheduler and a smaller read_ahead_kb, without effect).

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• Issue using a "used" SSD as a Windows 8.1 Boot Drive

  - by EpiGrad

  So, I'm something of a Mac person, but decided to take a stab at this whole "build yourself a PC" thing - right now, the thing is assembled, posts just fine, and can get to the BIOS. The problem is the drive I want to use - I intended to use a 80 GB Corsair SSD I've had sitting around as the boot drive, and a new Samsung SSD for games and the like. So I boot using a Windows 8.1 install USB stick, and if the Samsung drive is plugged in, it happily offers to install Windows on it. The Corsair drive though, it's flipped out - I reformatted it as a blank NTFS drive (it was HFS for Mac purposes) and the BIOS can't see it, nor can the Windows installer. What's wrong, and how do I fix it? The tools at my disposal are: The current ASUS BIOS that came with my motherboard (a Z87I-Deluxe), a Mac running the latest OS X which can also boot to Windows 7 if needed via either Parallels or Bootcamp. Update 1: Update: Based on a friend's suggestion to switch SATA ports, Windows 8.1's installer can now see the drive as Drive 0, Partition 1, a 83.8 GB "Primary" partition. But when I click it and hit "Next", I get the following error: "We couldn't create a new partition or locate an existing one. For more information, see the Setup log files" - not that it gives any clue how to access those. Update 2: Following a trail of Google suggestions, I ended up going into advanced tools and just reformatting the drive as follows: Start DISKPART. Type LIST DISK and identify your SSD disk number (from 0 to n disks). Type SELECT DISK <n> where <n> is your SSD disk number. Type CLEAN Type CREATE PARTITION PRIMARY Type ACTIVE Type FORMAT FS=NTFS QUICK Type ASSIGN Type EXIT twice (one to get out of DiskPart, the other to exit the command line tool) Per these instructions. This goes well enough, but now I can select the disk for installation, and I get a new error: "Windows 8 cannot be installed to this disk. The selected disk has an MBR partition table. On EFI systems, Windows can only be installed to GP disks." So, Googling that, I do the following: select disk 0 clean convert gpt exit ...and we might have fixed it. Windows is at least trying to install now.

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• ssh, "Last Login", `last` and OS X

  - by allentown

  I have hit the googles as much as I can on this, being specific to OS X, I am not finding an answer. Nothing is wrong, but curiosity levels are high. $ssh [email protected] Password: Last login: Wed Apr 7 21:28:03 2010 from my-laptop.local ^lonely tylenol^ Line 1 is my command line 2 is the shell asking for the password line 3 is where my question comes from line 4 comes out of /etc/motd I can find nothing in ~/ of an of the .bash* files that contains the string "Last Login", and would like to alter it. It performs some type of hostname lookup, which I can not determine. If I ssh to another host: $ssh [email protected] Last login: Wed Apr 7 21:14:51 2010 from 123-234-321-123-some.cal.isp.net.example hi there, you are on box 456 line 1 is my command line 2 is again, where my question comes from line 3 is from /etc/motd *The dash'd IP address is not reversed On this remote host, I have ~/.ssh and it's corresponding keys set up, so there was no password request Where is the "Last Login:" coming from, where does the date stamp come from, and most importantly, where does the hostname come from? While on [email protected] (box 456) $echo hostname remote.location.example456.com Or with dig, to make sure I have rDNS/PTR set up, for which I am not authoritative, but my ISP has correctly set... $dig -x 123.234.321.123 PTR remote.location.example456.com or $dig PTR 123.321.234.123.in-addr.arpa. +short remote.location.example456.com. my previous hostname used to be 123-234-321-123-some.cal.isp.net.example, which I set with hostname -s remote.location.example456.com, because it was obnoxious to see such a long name. That solves the value of $echo hostname which now returns remote.location.example456.com. Mac OS X, 10.6 is this case, does seem to honor: touch ~/.hushlogin If leave that file empty, I get nothing on the shell when I login. I want to know what controls the host resolution of the IP, and how it is all working. For example, running last reports a huge list of my logins, which have obtusely long hostnames, when they would be preferable to just be remote.location.example456.com. More confusing to me, reading the man page for wtmp and lastlog, it looks like lastlog is not used on OS X, /var/log/lastlog does not exist. Actually, none of these exist on 10.5 or 10.6: /var/run/utmp The utmp file. /var/log/wtmp The wtmp file. /var/log/lastlog The lastlog file. If I am to assume that the system is doing some kind of reverse lookup, I certainly do not know what it is, as it is not an accurate one.

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• Troubleshooting Network Speeds -- The Age Old Inquiry

  - by John K

  I'm looking for help with what I'm sure is an age old question. I've found myself in a situation of yearning to understand network throughput more clearly, but I can't seem to find information that makes it "click" We have a few servers distributed geographically, running various versions of Windows. Assuming we always use one host (a desktop) as the source, when copying data from that host to other servers across the country, we see a high variance in speed. In some cases, we can copy data at 12MB/s consistently, in others, we're seeing 0.8 MB/s. It should be noted, after testing 8 destinations, we always seem to be at either 0.6-0.8MB/s or 11-12 MB/s. In the building we're primarily concerned with, we have an OC-3 connection to our ISP. I know there are a lot of variables at play, but I guess I was hoping the experts here could help answer a few basic questions to help bolster my understanding. 1.) For older machines, running Windows XP, server 2003, etc, with a 100Mbps Ethernet card and 72 ms typical latency, does 0.8 MB/s sound at all reasonable? Or do you think that slow enough to indicate a problem? 2.) The classic "mathematical fastest speed" of "throughput = TCP window / latency," is, in our case, calculated to 0.8 MB/s (64Kb / 72 ms). My understanding is that is an upper bounds; that you would never expect to reach (due to overhead) let alone surpass that speed. In some cases though, we're seeing speeds of 12.3 MB/s. There are Steelhead accelerators scattered around the network, could those account for such a higher transfer rate? 3.) It's been suggested that the use SMB vs. SMB2 could explain the differences in speed. Indeed, as expected, packet captures show both being used depending on the OS versions in play, as we would expect. I understand what determines SMB2 being used or not, but I'm curious to know what kind of performance gain you can expect with SMB2. My problem simply seems to be a lack of experience, and more importantly, perspective, in terms of what are and are not reasonable network speeds. Could anyone help impart come context/perspective?

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• Achieving A 1600 x 900 Resolution For (Guest OS) Ubuntu Under (Host OS) Windows 7

  - by panamack

  I am running Ubuntu 11.10 as a guest OS using VirtualBox 4.1.16 installed on Windows 7 Ultimate. On my laptop I'd like to be able to run Ubuntu in full screen mode at 1600 x 900. I only have options within the virtual machine to select 4:3 display settings such as 1600 x 1200, 1440 x 1050 etc. I have guest additions installed. At the windows command prompt, I tried typing: VBoxManage setextradata "Virtual Ubuntu Coursera ESSAAS" "CustomVideoMode1" "1600x900x16" This didn't work, still no 1600 x 900 res available in Ubuntu. I tried this having read the following section of the VirtualBox help (this also says something about a 'video mode hint feature' not sure what this means): 9.7. Advanced display configuration 9.7.1. Custom VESA resolutions Apart from the standard VESA resolutions, the VirtualBox VESA BIOS allows you to add up to 16 custom video modes which will be reported to the guest operating system. When using Windows guests with the VirtualBox Guest Additions, a custom graphics driver will be used instead of the fallback VESA solution so this information does not apply. Additional video modes can be configured for each VM using the extra data facility. The extra data key is called CustomVideoMode with x being a number from 1 to 16. Please note that modes will be read from 1 until either the following number is not defined or 16 is reached. The following example adds a video mode that corresponds to the native display resolution of many notebook computers: VBoxManage setextradata "VM name" "CustomVideoMode1" "1400x1050x16" The VESA mode IDs for custom video modes start at 0x160. In order to use the above defined custom video mode, the following command line has be supplied to Linux: vga = 0x200 | 0x160 vga = 864 For guest operating systems with VirtualBox Guest Additions, a custom video mode can be set using the video mode hint feature. UPDATE 02.06.12 I've just tried creating a new virtual machine using the same original disk image I had been given. This had Guest Additions v 4.1.6 installed and provided me with the 1600 x 900 full screen display I want. It's after I then install Guest Additions v 4.1.16 (the version included with my VirtualBox installation) that my only choices are 4:3 displays e.g. 1600 x 1200. Seems this is the cause.

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• Local dns for testing websites using mobile devices

  - by Morpheu5

  Hi. I have no idea where to start from so sorry in advance if this topic has already been discussed. I usually develop web sites using my laptop as a development server, and recently I needed to test a web site using various mobile devices that can connect via wifi. Having no real AP, I set up a ad-hoc network using my laptop's wireless card and the devices can correctly browse the Internet and access the laptop's web server. The setup is as follows: subnet: 192.168.1.0/24 gateway to the Internet (wired adsl router/modem): 192.168.1.1 laptop: 192.168.1.64 (eth0, wired if connected to the gateway) and 192.168.1.32 (eth1, wifi if somewhat bridged to eth0) mobile devices (same for all, I only use one of them at any time for simplicity): 192.168.1.11 with default gw 192.168.1.1 Now, if I open either 192.168.1.32 or 192.168.1.64 from the mobile devices, I correctly get the default host of my Apache configuration. However I usually work with virtual hosts for many practical reasons, one of which being Drupal's peculiar implementation of multi-sites. For those who don't know how this works, Drupal takes the request's hostname and searches into its sites/ subdirectories for an appropriate configuration file. So, for example, suppose I request www.example.com, then Drupal would search for a config file in the following directories: sites/www.example.com/ sites/example.com/ sites/com/ sites/default/ So I decided to adopt the following style of virtual hosts: if the website I'm working on will be accessible using www.example.com I set up a sites/www.example.com/ directory and create a virtual host for local.www.example.com so Drupal have no trouble finding it. I've been told this is suboptimal from a dns point of view since I'd have to create an authoritative entry for example.com and turn Bind on only when I'm supposed to access the local copy, which is weird. However, if this is the only path I can follow, I still have some problems with Bind's configuration, as I couldn't find any guide that tells me in a clear, noob-friendly way, how to set up such an entry. On the other hand, I was wondering if I could set up an authoritative entry for local, so I could access www.example.com.local and tell in some way (which I don't even know if this is possible) Apache to put www.example.com instead of www.example.com.local in the relevant environment variable. Anyway, I have a last problem, sort of: when I launch Bind in debug mode with high verbosity, and make 192.168.1.32 as the primary dns for the devices, the output doesn't say anything about requests being made from the devices to Bind, so I'm not even sure it comes into play. As you can see, I'm a complete noob at these matters, but I'm eager to learn, so any help/pointer will be appreciated.

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• What else can I do to secure my Linux server?

  - by eric01

  I want to put a web application on my Linux server: I will first explain to you what the web app will do and then I will tell you what I did so far to secure my brand new Linux system. The app will be a classified ads website (like gumtree.co.uk) where users can sell their items, upload images, send to and receive emails from the admin. It will use SSL for some pages. I will need SSH. So far, what I did to secure my stock Ubuntu (latest version) is the following: NOTE: I probably did some things that will prevent the application from doing all its tasks, so please let me know of that. My machine's sole purpose will be hosting the website. (I put numbers as bullet points so you can refer to them more easily) 1) Firewall I installed Uncomplicated Firewall. Deny IN & OUT by default Rules: Allow IN & OUT: HTTP, IMAP, POP3, SMTP, SSH, UDP port 53 (DNS), UDP port 123 (SNTP), SSL, port 443 (the ones I didn't allow were FTP, NFS, Samba, VNC, CUPS) When I install MySQL & Apache, I will open up Port 3306 IN & OUT. 2) Secure the partition in /etc/fstab, I added the following line at the end: tmpfs /dev/shm tmpfs defaults,rw 0 0 Then in console: mount -o remount /dev/shm 3) Secure the kernel In the file /etc/sysctl.conf, there are a few different filters to uncomment. I didn't know which one was relevant to web app hosting. Which one should I activate? They are the following: A) Turn on Source Address Verification in all interfaces to prevent spoofing attacks B) Uncomment the next line to enable packet forwarding for IPv4 C) Uncomment the next line to enable packet forwarding for IPv6 D) Do no accept ICMP redirects (we are not a router) E) Accept ICMP redirects only for gateways listed in our default gateway list F) Do not send ICMP redirects G) Do not accept IP source route packets (we are not a router) H) Log Martian Packets 4) Configure the passwd file Replace "sh" by "false" for all accounts except user account and root. I also did it for the account called sshd. I am not sure whether it will prevent SSH connection (which I want to use) or if it's something else. 5) Configure the shadow file In the console: passwd -l to lock all accounts except user account. 6) Install rkhunter and chkrootkit 7) Install Bum Disabled those services: "High performance mail server", "unreadable (kerneloops)","unreadable (speech-dispatcher)","Restores DNS" (should this one stay on?) 8) Install Apparmor_profiles 9) Install clamav & freshclam (antivirus and update) What did I do wrong and what should I do more to secure this Linux machine? Thanks a lot in advance

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• NGINX SSL Certificate Not Working

  - by LeSamAdmin

  I've been working on SSL stuff and getting nowhere from like 4 tutorials... I've bought an SSL for pingrglobe.com, and now trying to apply it to my servers. Here's my nginx code: http { server { listen 80; server_name pingrglobe.com; rewrite ^(.*) http://www.pingrglobe.com$1 permanent; } server { listen 443; ssl on; ssl_certificate /etc/nginx/ssl/pingrglobe.crt; ssl_certificate_key /etc/nginx/ssl/pingrglobe.key; #enables SSLv3/TLSv1, but not SSLv2 which is weak and should no longer be used. ssl_protocols SSLv3 TLSv1; #Disables all weak ciphers ssl_ciphers ALL:!aNULL:!ADH:!eNULL:!LOW:!EXP:RC4+RSA:+HIGH:+MEDIUM; server_name www.pingrglobe.com; root /var/www/pingrglobe.com; index index.html index.php; location / { try_files $uri $uri/ @extensionless-php; add_header Access-Control-Allow-Origin *; } rewrite ^/blog/blogpost/(.+)$ /blog/blogpost?post=$1 last; rewrite ^/viewticket/(.+)/(.*)$ /viewticket?tid=$1&$2 last; rewrite ^/vemail/(.+)$ /vemail?eid=$1 last; rewrite ^/serversettings/(.+)$ /serversettings?srvid=$1 last; rewrite ^/notification/(.+)$ /notification?id=$1 last; rewrite ^/viewreport/(.+)$ /viewreport?srvid=$1 last; rewrite ^/removeserver/(.+)$ /removeserver?srvid=$1 last; rewrite ^/staffviewticket/(.+)/(.*)$ /staffviewticket?tid=$1&$2 last; rewrite ^/activate/(.*)/(.*)/(.*)$ /activate?user=$1&code=$2&email=$3 last; rewrite ^/activate2/(.*)/(.*)/(.*)$ /activate2?user=$1&code=$2&email=$3 last; rewrite ^/passwordtoken/(.+)/(.*)/(.*)$ /passwordtoken?user=$1&token=$2&email=$3 last; location ~ \.php$ { try_files $uri =404; fastcgi_pass unix:/var/run/php5-fpm.sock; fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name; include fastcgi_params; } location @extensionless-php { rewrite ^(.*)$ $1.php last; } location ~ /\. { deny all; } } } SSL doesn't work as you see here: https://www.pingrglobe.com

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• SQL Express 2008 R2 on Amazon EC2 instance: tons of free memory, poor performance

  - by gravyface

  The old SQL Express 2005 was running on a low-end single Xeon CPU Dell server, RAID 5 7200 disks, 2 GB RAM (SBS 2003). I have not done any baseline measurements on the old physical server, but the Web app is used by half a dozen people (maybe 2 concurrently), so I figured "how bad can an Amazon EC2 instance be?". It's pretty horrible: a difference of 8 seconds of load time on one screen. First of all, I'm not a SQL guru, but here's what I've tried: Had a Small Instance, now running a c1.medium (High Cpu Medium) Windows 2008 32-bit R2 EBS-backed instance running IIS 7.5 and SQL Express 2008 R2. No noticeable improvement. Changed Page File from fixed 256 to Automatic. Setup a Striped Mirror from within Disk Management with two attached 1 GB EBS volumes. Moved database and transaction log, left everything else on the boot EBS volume. No noticeable change. Looked at memory, ~1000 MB of physical memory free (1.7 GB total). Changed SQL instance to use a minimum of 1024 RAM; restarted server, no change in memory usage. SQL still only using ~28MB of RAM(!). So I'm thinking: this database is tiny (28MB), why isn't the whole thing cached in RAM? Surely that would speed up performance. The transaction log is 241 MB. Seems kind of large in comparison -- has this not been committed? Is it a cause of performance degradation? I recall something about Recovery Models and log sizes somewhere in my travels, but not positive. Another thing: the old server was running SQL Express 2005. Not sure if that has any impact, but I tried changing the compatibility level from SQL 2000 to 2008, but that had no effect. Anyways, what else can I try here? Seems ridiculous to throw more virtual hardware at this thing. I know I/O is going to be rough on EBS volumes, but surely others are successfully running small .NET/SQL apps on reasonably priced instances?

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• FTP script needs blank line

  - by Ones and Zeroes

  I am trying to determine the reason for some FTP servers requiring a blank line in the script as follows: open server.com username ftp_commands bye Refer to blank line required after username credentials. Example from: FTP from batch file another reference to the same: http://newsgroups.derkeiler.com/Archive/Comp/comp.sys.ibm.as400.misc/2008-05/msg00227.html Also discussed here: archive.midrange.com/midrange-l/200601/msg00048.html "The behavior I'm observing is the same as if I didn't specify the password to login." with an answer referring to our same fix... archive.midrange.com/midrange-l/200601/msg00053.html and archive.midrange.com/midrange-l/200601/msg00065.html Note: It is my experience that FTP questions attract uncouth responses. Admittedly FTP is outdated, but many clients still have legacy systems, which they cannot upgrade or replace. The reason thereof should not be discussed here. The intention of this question is to invite a positive response. Please do not respond if you disagree with the above. If you have never encountered this same issue, please do not respond. I suspect this may be limited to FTP scripts executed from Windows machines, but have been told that this happens often and with many different servers. My specific interest is to understand what may cause this as I have a real world example of a production system suddenly requiring this as a workaround fix, after running for many years without issue. The server belongs to a third party who claims no change on their end. Server details unknown and cannot be determined. Any help or encouragement from someone who has come across the same, would be appreciated. ps. Sorry for the many words and references to painful responses, but I have asked similar questions on serverfault and elsewhere and unfortunately got back kneejerk responses to FTP and respondents debating the validity of the question. I would truly not ask, or re-post this question online if I had a better understanding of the issue. I know of people who have seen this issue, but don't know what causes it. I am wary that this question would again turn into another irrelevant discussion. Please, I ask very nicely: Please do not respond if you have not encountered a similar issue. FURTHER EDIT: Please do not suggest changing the product. The problem is not the blank line requirement. We know this fixes the issue. The problem is not being able to explain the reason for the blank line in the first place. Slight difference, but a critical point to note wrt the answering of this question.

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• How to make Nginx fire 504 immediately is server is not available?

  - by Georgiy Ivankin

  I have Nginx set up as a load balancer with cookie-based stickiness. The logic is: If the cookie is NOT there, use round-robbing to choose a server from cluster. If the cookie is there, go to the server that is associated with the cookie value. Server is then responsible for setting the cookie. What I want to add is this: If the cookie is there, but server is down, fallback to round-robbing step to choose next available server. So actually I have load balancing and want to add failover support on top of it. I have managed to do that with the help of error_page directive, but it doesn't work as I expected it to. The problem: 504 (and the fallback associated with it) fires only after 30s timeout even if the server is not physically available. So what I want Nginx to do is fire a 504 (or any other error, doesn't matter) immediately (I suppose this means: when TCP connection fails). This is the behavior we can see in browsers: if we go directly to server when it is down, browser immediately tells us that it can't connect. Moreover, Nginx seems to be doing this for 502 error: if I intentionally misconfigure my servers, Nginx fires 502 immediately. Configuration (stripped down to basics): http { upstream my_cluster { server 192.168.73.210:1337; server 192.168.73.210:1338; } map $cookie_myCookie $http_sticky_backend { default 0; value1 192.168.73.210:1337; value2 192.168.73.210:1338; } server { listen 8080; location @fallback { proxy_pass http://my_cluster; } location / { error_page 504 = @fallback; # Create a map of choices # see https://gist.github.com/jrom/1760790 set $test HTTP; if ($http_sticky_backend) { set $test "${test}-STICKY"; } if ($test = HTTP-STICKY) { proxy_pass http://$http_sticky_backend$uri?$args; break; } if ($test = HTTP) { proxy_pass http://my_cluster; break; } return 500 "Misconfiguration"; } } } Disclaimer: I am pretty far from systems administration of any kind, so there may be some basics that I miss here. EDIT: I'm interested in solution with standard free version of Nginx, not Nginx Plus. Thanks.

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• Wrapping a point-to-point link

  - by user3712955

  I'm using a pair of IP radios (non-WiFi) to bridge my office engineering LAN (172.0.0.0/8) to a lab in another building. The radios work fine, but they expose a web management interface I'd like to hide, and they also generate traffic (ARP, STP, and more) that I need to keep off my (very, very clean) LAN segments. I have some ARM-Linux boards (similar to Beagle/Panda/RasPi) running Ubuntu, and I've put one at each end of the link, between the radio and the LAN. Each of the boards has 2 wired Ethernet interfaces, eth0 and eth1. The LAN segments are connected to eth0, and the radios are connected to eth1. I'd like to accomplish the following: Keep radio-originated traffic off my LAN segments! Hide all services provided by the radio (web, ssh, etc.) Transparently pass all traffic between the LAN segments (including things like ARP). The above also applies to the ARM-Linux boards: No stray traffic my LAN from them either! I'd like the system to look like a switch: LAN packets arriving at one eth0 appear at the other. And neither eth0 should have an IP address: The working system should behave like a CAT6 cable with some latency (instead of ARM boards and radios). Unfortunately, I'm confused about how to properly configure the ARM Ubuntu systems. What I'm guessing I need is a bridge on each board (br0?) and a VLAN (vlan0 or eth0.0?) to isolate the LAN traffic from everything else as it passes through the ARM boards and the radios. Then I need some kind of a firewall to block sending anything out eth0 that isn't from the other eth0 (via the VLAN). I've looked at the ip and ebtables commands (especially -t broute). While the concepts sorta-kinda make sense, I'm completely lost in the details. Edit: In the perverse case that a system on one of my LAN segments has the same IP address as one of the radios, or as eth1 on the ARM-Ubuntu boards, a VLAN won't work. Which I believe means I need to tunnel all traffic between the two eth0 interfaces to get that "like a wire" behavior. Help? Finally, I'd like to have a way to temporarily expose services on the ARM boards (ssh) and the radios (web) for maintenance purposes. Ideally, it would expose an IP address with ssh available on port 22. Once connected, I figure I'd start an X11 session and run a browser on the ARM board to access the radios. Or something. I could login via the console to enable/disable this, or perhaps could use a GPIO to trigger a script. I feel I've identified most of the pieces needed to make all this happen, but I have no idea how to combine them to make a working system. Thanks!

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