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• How to monitor changes in the frequency of network latency spikes over time?

  - by dequis

  I'm currently trying to troubleshoot an issue with my network in which I get latency spikes up to 200 seconds (normally around 50 secs) in an apparently random way at apparently random moments of the day. While trying to find what part of my messy network needs to be blamed (outside of the scope of this question - discussed a bit on chat), I realized I have no reliable way to confirm that a change actually improved anything. So far, the main way in which i notice this is that irssi shows [Lag: 15 (??)] in the statusbar, increasing every 5 seconds, and all other connections seem to be affected too. Since this depends on my observations, it's not a very reliable method to know how often it really happens. Note that just sending ICMP pings is probably not enough, but that's just my guess. It might be a "bufferbloat" issue, it might be packet loss, it might only apply to persistent connections. I suspect this because a few months ago, when the issue started, I had a "ping" command running in background and it didn't show anything weird at all during the latency spikes. This seems to have changed now (pings don't go through), but still, I'd prefer something more robust.

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• Nginx + PHP5-FPM repeated cut outs 502

  - by James

  I've seen a number of questions here that highlight random 502 (Nginx + PHP-FPM = "Random" 502 Bad Gateway) and similar time outs when using Nginx + PHP-FPM. Even with all the questions, I'm still unable to find a solution. Using Ubuntu 10.10 + Nginx + PHP5-FPM + APC and every 1 out of 4 requests ends in a timeout and failure. This isn't a load issue or large traffic, it happens even in dev environment with one person. I am doing this across 3 1GB machines, each with the same configurations and same problems. fastcgi_params fastcgi_param QUERY_STRING $query_string; fastcgi_param REQUEST_METHOD $request_method; fastcgi_param CONTENT_TYPE $content_type; fastcgi_param CONTENT_LENGTH $content_length; fastcgi_param SCRIPT_NAME $fastcgi_script_name; fastcgi_param REQUEST_URI $request_uri; fastcgi_param DOCUMENT_URI $document_uri; fastcgi_param DOCUMENT_ROOT $document_root; fastcgi_param SERVER_PROTOCOL $server_protocol; fastcgi_param GATEWAY_INTERFACE CGI/1.1; fastcgi_param SERVER_SOFTWARE nginx/$nginx_version; fastcgi_param REMOTE_ADDR $remote_addr; fastcgi_param REMOTE_PORT $remote_port; fastcgi_param SERVER_ADDR $server_addr; fastcgi_param SERVER_PORT $server_port; fastcgi_param SERVER_NAME $server_name; fastcgi_param REDIRECT_STATUS 200; /etc/php5/fpm/main.conf ; FPM Configuration ; ;include=/etc/php5/fpm/*.conf ; Global Options ; pid = /var/run/php5-fpm.pid error_log = /var/log/php5-fpm.log ;log_level = notice ;emergency_restart_threshold = 0 ;emergency_restart_interval = 0 ;process_control_timeout = 0 ;daemonize = yes ; Pool Definitions ; include=/etc/php5/fpm/pool.d/*.conf /etc/php5/fpm/pool.d/www.conf [www] listen = 127.0.0.1:9000 ;listen.backlog = -1 ;listen.allowed_clients = 127.0.0.1 ;listen.owner = www-data ;listen.group = www-data ;listen.mode = 0666 user = www-data group = www-data ;pm.max_children = 50 pm.max_children = 15 ;pm.start_servers = 20 pm.min_spare_servers = 5 ;pm.max_spare_servers = 35 pm.max_spare_servers = 10 ;pm.max_requests = 500 ;pm.status_path = /status ;ping.path = /ping ;ping.response = pong request_terminate_timeout = 30 ;request_slowlog_timeout = 0 ;slowlog = /var/log/php-fpm.log.slow ;rlimit_files = 1024 ;rlimit_core = 0 ;chroot = chdir = /var/www ;catch_workers_output = yes

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• Chrome browser completely messing with network?

  - by kiasecto

  I have a bizare problem with Google Chrome on a intel core i5 running windows 7 32bit. Whenever chrome is installed, access to other computers in the home group becomes really slow - such as opening shares. Its becomes really slow to resolve windows names. Something goes hay-wire with the local network - pining local machines which is usually 0mS pings I get random timeouts and random successes. Whenever I try to load a local address inside of chrome (including localhost, 192.168.0.1 etc) - it always says something in the status bar about resolving proxy and times out after about 5 seconds, then seems to work fine. If I go to settings inside of chrome, it just brings up the internet explorer connection settings, where I have not set any proxy settings. One I uninstall chrome, all these problems go away. Network shares and name resolvings work instantly, pings to any machines never have a problem. Localhost and other network IP address work fine in all other browsers. Anyone heard of this problem before and know what it might be? I even tried re-installing winodws 7 and the problem came straight back when chrome was loaded on again.

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• (Zywall USG 300) NAT bypassed when accessing in-house-server From LAN Via domain name

  - by mschr

  My situations is like this; i host a number of websites from within our joint network solution. On the network is basically 3 categories: the known public, registered via mac, given static dhcp lease the anonymous lan connections, given lease from specific dhcp range switches, unix hosts firewall Now, consider following hosts which are of interest 111.111.111.111 (Zywall USG 300 WAN) 192.168.1.1 (ZyWall USG 300 LAN) load balances and bw monitors plus handles NAT 192.168.1.2 (Linux www) serves mydomain1.tld and mydomain2.tld 192.168.123.123 (Random LAN client) accesses mydomain1.tld from LAN 23.234.12.253 (Random External client) accesses mydomain1.tld via WAN DNS A records are setup so that both mydomain1.tld and mydomain2.tld points to 111.111.111.111 - and the Linux www serves the http parts with VirtualHost configurations, setting up the document roots pr ServerName, this is not so interesting though.. NAT rule translates 111.111.111.111:80 to 192.168.1.2:80 (1:1 NAT) Our problem follows; When accessing http://mydomain1.tld from outside (23.234.12.253 example host) the joint network - everything is fine, zywall receives requests via port 80 and maps it to the linux host' httpd. However - once trying to go through the NAT from LAN side (in-house, 192.168.123.123 example host) then one gets filtered in the Zywall port 80 firewall. I know this only because port 443 is open for administration interface and https://mydomain1.tld prompts for zywall login. So my conclusion is, that the LAN that accesses 111.111.111.111 in fact are routed to 192.168.1.1 whilst bypassing the NAT table. I need to know how to setup NAT / Policy Route, so that LAN WAN LAN will function with proper network translations instead of doing the 'quick nameserver lookup' or whatever this might be.

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• What is the IPv6 equivalent to IPv4 RFC1918 addresses?

  - by Kumba

  Having a hard time wrapping my head around IPv6 here. A lot of the lingo seems targeted at enterprise-level IPv6 deployments, discussing link-local, site-local, global unicast, scopes, etc. Not a lot of solid information on really small networks, like home networks. I want to check my thinking and make sure I am getting the correct translations from IPv4-speak to IPv6-speak. The first question is, what's the equivalent of RFC1918 for IPv6? Initial searches suggested there was no equivalent. Then I stumbled upon Unique Local Addresses (RFC4193), and that states that all ULA's should be assigned the prefix fc00, followed by a 40-bit random number in the routing prefix. This random number is to "prevent collisions when two IPv6 networks are interconnected" -- again, another reference to an enterprise-level function. If I have a small local LAN at home, numbered using 192.168.4.0/24, what's my equivalent in IPv6's ULA scope? Assuming I will never, ever, tie that IPv6 address into the real internet (a router will NAT & firewall it), can I ignore the RFC to an extent and go with fc00::4:0/120? It also seems that any address in fc00::/7 are to be globally routable. Does this mean I'll need extra protections so my router would not automatically start advertising these private IPv6 addresses to the world? Second question, what's this link-local thing? Reading suggests a default-assigned address in the fe80::/10 range that has the last 64bits of the address comprised of the interface's MAC address. Seems to be required, too, but I'm annoyed by the constant discussion of it in relation to enterprise networks. Third question, what is scope id for? Seems to be yet another term tossed around in relation to enterprise networks, especially when interconnecting them, but almost no explanation on the smaller home network level. Can I see a scope ID AND CIDR notation used together? I.e., fc00::4:0/120%6, or are scope IDs only supposed to be applied to a single /128 IPv6 address?

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• Screen Flickering: Hardware or Software?

  - by Wesley

  I have a Samsung N120 netbook (upgraded to 2GB DDR2 RAM) and there has been a screen flickering issue for some time now. However, I have not been able to accurately determine whether it is a software or hardware issue. Here are some of the symptoms: The flicker is white-colored and shows up as vertical lines. Flickering or not, there may be occasionally some random blue patterns (no image distortion) The screen tends to flicker more when the screen is not tilted back all the way. When tilting the screen back and forth, the screen will usually flicker. Some images on the screen may randomly distort without full-on flickering. The screen will flicker only on certain websites, but not on others. A certain part of a webpage may constantly be distorted randomly, even when scrolling. While flickering, the mouse will not move though I'm moving my finger along the touchpad. A connected external monitor does not have any problems. The flickering is completely random and does not seem to follow any CPU/GPU usage trends. Flickering usually gets worse when the screen brightness is turned higher. There will be flickering on battery and while plugged in. Search up "Samsung N120 - Screen Flickering" on YouTube for an idea of what the flickering looks like. However, there is no visible distortions and the flickering seems to stop when the screen has dimmed. Since the problems started, I tried formatting and using Windows 7, then formatted again and went back to Windows XP. The screen was also replaced sometime during this past summer. The uninstallation of the Samsung Battery Manager (on the original install of XP) seemed to reduce the flicker partially, but eventually got worse. So, what could possibly be the problem?

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• How to interpret iozone values

  - by Henno

  I ran a test to measure my I/O IOPS on Linux: iozone -s 4g -r 2k -r 4k -r 8k -r 16k -r 32k -O -b /tmp/results.xls iozone claims that output is in operations per second yet the numbers are too big for that to be plausible. I'm observing some 320 CMDs/s maximum on vmware esx console (esxtop, then v). File size set to 4194304 KB Record Size 2 KB Record Size 4 KB Record Size 8 KB Record Size 16 KB Record Size 32 KB OPS Mode. Output is in operations per second. Command line used: iozone -s 4g -r 2k -r 4k -r 8k -r 16k -r 32k -O -b tmpresults.xls Time Resolution = 0.000001 seconds. Processor cache size set to 1024 Kbytes. Processor cache line size set to 32 bytes. File stride size set to 17 * record size. random random bkwd record stride KB reclen write rewrite read reread read write read rewrite read fwrite frewrite fread freread 4194304 2 19025 5580 27581 29848 284 198 415 1103217 1498 18541 4340 24245 25618 4194304 4 15650 21942 18962 21068 252 1198 193 976164 1677 22802 23093 21089 21232 4194304 8 11121 11638 10273 10165 247 1196 202 625020^C The test ran for 15 hours before I pressed ^C. Is that ordinary expectation for such command line (dedicated 4 drive RAID10 LUN, 10k RPM SAS drives in EMC CX300)?

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• How to make a Linux software RAID1 detect disc corruption?

  - by Paul

  This is one of the nightmare days: A virtualized server running on a Linux SW-RAID1 runs a VM that exhibits random segfaults in seemingly random codechunks. While debugging I find that a file gives different md5sums on each and every run. Digging deeper I find this: The raw disc partitions that make up the RAID1 mirror contain 2 bit-differences and ca. 9 sectors are completely empty on one disc and filled with data on the other disc. Obviously Linux gives back a sector from a undeterministically chosen disc of the mirror set. So sometimes the same sector is returned OK, sometimes the corrupted is given back. The docs say: RAID cannot and is not supposed to guard against data corruption on the media. Therefore, it doesn't make any sense either, to purposely corrupt data (using dd for example) on a disk to see how the RAID system will handle that. It is most likely (unless you corrupt the RAID superblock) that the RAID layer will never find out about the corruption, but your filesystem on the RAID device will be corrupted. Thanks. That will help me sleep. :-/ Is there a way to have Linux at least detect this corruption by using sector checksumming or something like that? Would this be detected in a RAID5 setup? Is this the moment I wish I used ZFS or btrfs (once it becomes usable without uber-admin capabilities)?

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• How can I format an SD card with a more robust Linux-usable filesystem with a specific cluster size for better write performace?

  - by Harvey

  Goal: microSD card formatted... for best write performance for use only with embedded Linux for better reliability (random power failures may occur) using an 64kB cluster size I'm using an 8GB microSD card for data storage inside an embedded Linux/ARM device. The SD card is not removable. I've been using ext3 instead of the pre-installed FAT32 because it seems to better handle random power failures during writes. However, I kept noticing that my write performance is always best with the pre-installed FAT32 from Kingston. If I reformat the card with FAT32, the performance still suffers. After browsing wikipedia, I stumbled upon the following comment saying that some cards are optimized for specific cluster sizes. In my case, the Kingston comes pre-formatted for an 64kB cluster size. Risks of reformatting Reformatting an SD card with a different file system, or even with the same one, may make the card slower, or shorten its lifespan. Some cards use wear leveling, in which frequently modified blocks are mapped to different portions of memory at different times, and some wear-leveling algorithms are designed for the access patterns typical of the file allocation table on a FAT16 or FAT32 device.[60] In addition, the preformatted file system may use a cluster size that matches the erase region of the physical memory on the card; reformatting may change the cluster size and make writes less efficient.

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• files have no ownership permissions and can't assign ownership

  - by Force Flow

  I'm having problems with file permissions on a server 2008 R1 server. Office 2010 tmp files are being created, and don't have any security permissions assigned. They aren't being deleted, I can't assign ownership, and I can't delete them. I downloaded and ran the sysinternals tool handle.exe. When running it for the first time, handle64.exe was created, but not assigned any permissions. I cannot assign ownership and cannot delete it. Seemingly random files in random places don't seem to have any permissions assigned. Access is denied when attempting to change ownership to administrator or the administrators group. If I try to replace inheritable permissions of the folder these files are in, access is denied for the files with no permissions. I attempted to use subinacl to view the ownership information on the files that had no permissions, but access was denied here as well. I also tried setting the owner with setacl in an elevated cmd window, but access was denied as well. This problem only surfaced in the last few days, and I'm unsure as what the cause is or how to correct it.

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• Solution to easily share large files with non-tech-savvy users?

  - by Tim

  Hey all, We've got a server setup at work which we'd like to use to exchange large files with known clients easily. We're looking into software to facilitate this, but somewhow typing "large file hosting" into Google gives questionable results.. ;) We've come up with the following requirements, and I hope any of you can points us in the direction of a solution that offers this functionality, or is malleable to our needs. Synchronization / revision management is of no concern, it's mostly single large (up to 1+ GB) file uploads & downloads we'll need. We'd like to make the downloads expire & be removed after a certain number of days / downloads, to limit the amount of cleanup we'd have to do. The data files exchanged sometimes hold confidential information, so the URLs generated should be random and not publicly visible. Our users are of the less technically savvy variety, so a simple webform would be best over a desktop client (because we also have to support a mix of operating systems). As for use of the system we'd either like to send out generated random URLs for them to upload their files, or have an easy way manage & expire users. Works on a linux (Ubuntu) server (so nothing .Net-related please) Does anyone know of software that fits the above criteria? We've already seen a few instances of this within the scientific community, but nothing we could use directly.. Best regards, Tim

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• Solution to easily share large files with non-tech-savvy users?

  - by Tim

  Hey all, We've got a server setup at work which we'd like to use to exchange large files with known clients easily. We're looking into software to facilitate this, but somewhow typing "large file hosting" into Google gives questionable results.. ;) We've come up with the following requirements, and I hope any of you can points us in the direction of a solution that offers this functionality, or is malleable to our needs. Synchronization / revision management is of no concern, it's mostly single large (up to 1+ GB) file uploads & downloads we'll need. We'd like to make the downloads expire & be removed after a certain number of days / downloads, to limit the amount of cleanup we'd have to do. The data files exchanged sometimes hold confidential information, so the URLs generated should be random and not publicly visible. Our users are of the less technically savvy variety, so a simple webform would be best over a desktop client (because we also have to support a mix of operating systems). As for use of the system we'd either like to send out generated random URLs for them to upload their files, or have an easy way manage & expire users. Works on a linux (Ubuntu) server (so nothing .Net-related please) Does anyone know of software that fits the above criteria? We've already seen a few instances of this within the scientific community, but nothing we could use directly.. Best regards, Tim

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• Perfectly reproducable select statement default ordering issue....

  - by Dave

  Hi, I've recently been chasing an issue with a client's db... solution found, but impossible to recreate. Essentially, we're doing a Select * from mytable where ArbitraryColumn = 75 Where MyTable has an Identity column, called 'MyIndentityColumn' - incremented by one in each insert. Naturally, and normally I would assume that the order returned would be the order in which they are inserted (bad assumption, but one which was forced onto me, through an inherited application - which has been patched). Essentially, I would like suggestions as to why the database, when restored to my local machine (same OS, same SQL server version - 200 sp3) same collation, and same backup instance restored on it, as a test DB on the client site. When I perform the above select, I get them in order of insert (i.e. identity column ordered ascending). On the client, it seems random (but the same 'random' order each time)... A few other points: I have the same collation on my test server as client Same DB backup restored to a test only I can access Same SQL server version and service pack Same OS Test DB is a new DB - new log and MDF... I have the problem 'solved' by adding an explicit order by clause but I want to undertand the cause of the issue, given the exact nature of my attempts to recreate it beuing futile, and perfectly recreatable on the client server... Thanks in advance, Dave

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• Weird problem with Visual C++ 2010 Express

  - by Robert Vella

  This has happened before on my Vista Premium installation, and now it's happening on my Windows 7 Home Premium installation. Basically everytime I install Visual Studio Express 2010, it works fine for a random amount of time but then suddenly starts to hide from my sight -- that's the best way I can explain it. VS does not crash, and from what I can tell it does not freeze either; It continues to work, I can even "minimize" and "maximize" it; I simply cannot see it nor can I interact with it any meaningful way. Also: After the "crash" there are no logs in: Root\Program Files (x86)\Microsoft Visual Studio 10.0\Microsoft Visual C++ 2010 Express - ENU. Nor any other files created at the time of the crash. There are no traces in the event viewer. The program seems to be functioning perfectly in the process manager. If I reinstall Visual C++, it works normally for a seemingly random period of time before going cookoo again. I am stumped. This has never happened to me before, with any other program. And yet I doubt it really is a problem with Visual C++; More like something general that seems to have picked on it for some reason. Still, after a clean install with a new OS, I'm kinda thinking there's something wrong here. Any help would be appreciated, altough I suspect that the answer to this question will make me feel embarassed. P.S. Not sure if it helps, but I think around the same time I started having problems (On both installations) with windows turning off the display when I leave the computer, and then seemingly crashing when it turns it on again -- in fact when I interact with it it seems to be responding to my commands without actually display anything.

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• how do I fix a wrong UUID in grub.cfg?

  - by mozerella

  I run Debian Wheezy alone on my PC and I recently copied the root partition to another with rsync as I found that worked well (I also know about dd and ddrescue but they leave unusable space on the new partition). I generated a new random UUID for the new partition with sudo tune2fs -U random /dev/hda9 and also updated fstab / and /home entries. Then as I know so little about GRUB I used a gui (GRUB Customizer) to probe for the new OS and add an entry to GRUB and the MBR -it makes an /etc/grub.d entry then updates GRUB. On startup, the GRUB list contains the new OS (on sda9) but it boots the first OS (which I copied from -sda5). /boot/grub/grub.cfg contains the new debian OS but it looks like this set root='(hd0,msdos9)' search --no-floppy --fs-uuid --set=root 64662470-0e58-4dfd-90ac-43227d773556 linux /boot/vmlinuz-3.2.0-2-amd64 root=UUID=cc3bca0d-aee4-4b9c-95c2-57212cc36d4d ro quiet initrd /boot/initrd.img-3.2.0-2-amd64 the 1st uuid is of sda9, but the 2nd uuid there is of sda5. I can change the 2nd uuid at startup (with E) and it boots sda9. So how can I get grub.cfg corrected so that the sda9 GRUB list entry boots from sda9 permanently?

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• Need help toubleshooting PC

  - by brux

  I have had problems since my dog pee'd on my computer. Problem: loads windows fine, at random intervals from 5 minutes to 30 minutes it restarts itself. There is nothing in the event log such as errors, no BSOD, just cold restart. after restarting - sometimes- it POST's and restarts itself at the end of POST. It will do this many times and then finally load windows. The cycle then begins again, it will restart eventually. What I have done: I thought it was HDD at first, since this is the only part of the computer which actually got wet with any fluid ( the case is off the PC and the dog pee'd down the front where the HDD is located). Seatool, the seagate HDD tool, found errors when I ran it inside windows, so I ran it in DOS mode from boo-table USB and ran it. It found the same number of errors and fixed them all. I ran the scan again and it says "Good". I loaded windows and ran the scan and it also said "Good there. So the HDD appears to be fine but the problem persists, random restarts. What else could this be? I have taken the computer apart and cleaned everything and also taken the PSU apart and cleaned it thoroughly. The problem still persists, what should my next steps be?

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• How can I inject clips [ads] in a playlist every x minutes (even if previous clip is not over)

  - by azera

  Sorry for the title, I find it quite hard to describe what I want to do in a single sentence We have a few TV here linked to our computer, which we use to display clips about what we do in our sport center, what you should do to stay in good form ect ... It's running non stop, actually though vlc + playlist. Those main clips are 1-2 hours long and we have about 20 of them looping randomly all day. We would like to inject ads for some of our sponsiored products every now and then during the playlist, like say one ad every 15 minute. Does any one know how we can do that, while keeping the main clip random order ? I thought about encoding the whole thing as a single movie with ads inserted, but then it's not random. So we can put the ads in the playlist itself right ? Except clips are several hours long and we want that more often than that. Cutting the main clips in several pieces seems to work but that kind of sucks as new clips are made every month. If any one has an idea, thanks a lot

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• I have a perl script that is supposed to run indefinitely. It's being killed... how do I determine who or what kills it?

  - by John O

  I run the perl script in screen (I can log in and check debug output). Nothing in the logic of the script should be capable of killing it quite this dead. I'm one of only two people with access to the server, and the other guy swears that it isn't him (and we both have quite a bit of money riding on it continuing to run without a hitch). I have no reason to believe that some hacker has managed to get a shell or anything like that. I have very little reason to suspect the admins of the host operation (bandwidth/cpu-wise, this script is pretty lightweight). Screen continues to run, but at the end of the output of the perl script I see "Killed" and it has dropped back to a prompt. How do I go about testing what is whacking the damn thing? I've checked crontab, nothing in there that would kill random/non-random processes. Nothing in any of the log files gives any hint. It will run from 2 to 8 hours, it would seem (and on my mac at home, it will run well over 24 hours without a problem). The server is running Ubuntu version something or other, I can look that up if it matters.

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• Need help ttoubleshooting PC

  - by brux

  I have had problems since my dog pee'd on my computer. Problem: loads windows fine, at random intervals from 5 minutes to 30 minutes it restarts itself. There is nothing in the event log such as errors, no BSOD, just cold restart. after rstarting - sometimes- it POST's and restarts itself at the end of POST. It will do this many times and then finally load windows. The cycle then begins again, it will restart eventually. What i have done: I thought it was HDD at first, since this is the only part of the coputer which actually got wet with any fluid ( the case is off the PC and the dog pee'd down the front where the HDD is located). Seatool, the seagate HDD tool, found errors when I ran it inside windows, so I ran it in DOS mode from bootable USB and ran it. It found the same number of errors and fixed them all. I ran the scan again and it says "Good". I loaded windows and ran the scan and it also said "Good there. So the HDD apears to be fine but the problem persists, random restarts. What else could this be? I have taken the computer apart and cleaned everything and also taken the PSU apart and cleaned it thoughrouly. The problem still persists, what should my next steps be? Thanks in advance.

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• What are the typical methods used to scale up/out email storage servers?

  - by nareshov

  Hi, What I've tried: I have two email storage architectures. Old and new. Old: courier-imapds on several (18+) 1TB-storage servers. If one of them show signs of running out of disk space, we migrate a few email accounts to another server. the servers don't have replicas. no backups either. New: dovecot2 on a single huge server with 16TB (SATA) storage and a few SSDs we store fresh mails on the SSDs and run a doveadm purge to move mails older than a day to the SATA disks there is an identical server which has a max-15min-old rsync backup from the primary server higher-ups/management wanted to pack in as much storage as possible per server in order to minimise the cost of SSDs per server the rsync'ing is done because GlusterFS wasn't replicating well under that high small/random-IO. scaling out was expected to be done with provisioning another pair of such huge servers on facing disk-crunch issues like in the old architecture, manual moving of email accounts would be done. Concerns/doubts: I'm not convinced with the synchronously-replicated filesystem idea works well for heavy random/small-IO. GlusterFS isn't working for us yet, I'm not sure if there's another filesystem out there for this use case. The idea was to keep identical pairs and use DNS round-robin for email delivery and IMAP/POP3 access. And if one the servers went down for whatever reasons (planned/unplanned), we'd move the IP to the other server in the pair. In filesystems like Lustre, I get the advantage of a single namespace whereby I do not have to worry about manually migrating accounts around and updating MAILHOME paths and other metadata/data. Questions: What are the typical methods used to scale up/out with the traditional software (courier-imapd / dovecot)? Do traditional software that store on a locally mounted filesystem pose a roadblock to scale out with minimal "problems"? Does one have to re-write (parts of) these to work with an object-storage of some sort - such as OpenStack object storage?

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• User receives group membership error to terminal server even though has rights

  - by BlueToast

  http://www.hlrse.net/Qwerty/TSLoginMembership.png To log on to this remote computer, you must be granted the Allow log on through Terminal Services right. By default, members of the Remote Desktop Users group have this right. If you are not a member of the Remote Desktop Users group or another group that has this right, or if the Remote Desktop User group does not have this right, you must be granted this right manually. Only as of today a particular user began receiving this message for a second terminal server they use; otherwise, they have never had any problems authenticating into this server. We have no restrictions on simultaneous and multiple logins. On each terminal server, we have a group and security group like "_Users" locally in the Builtin\Remote Desktop Users group. For this particular user, on this particular terminal server we have locally given him Administrator, Remote Desktop Users, and Users membership; in AD we have given him DOMAIN\Administrator, Builtin\Remote Desktop Users, DOMAIN\_Users. It still gives us that error message. We gave him membership to another terminal server (random) by simply making him member of another DOMAIN\_Users group -- successfully able to login to that random terminal server. So, from scratch we created an AD account 'dummy' (username) with only Domain Users membership. Tried to login to this particular server, no success. So I added 'dummy' to DOMAIN\_Users group, and then was successfully able to login. Other users from this user's department are able to login to this particular server just fine as well. We checked the Security logs on this particular server, and while it is logging everything, the only thing it appears to not log are these failed login attempts from this particular user who receives this error message. We have tried rebooting the server, and the user is still receiving that error message.

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• Korean characters not appearing in Korean Windows XP computer

  - by user13267

  I am using a Korean software (with a partial English interface) in a Korean Version of Windows XP SP 3 However, in parts of the software, even when I change the interface to Korean, Korean letters show up as random characters, as shown here: This is happening at others parts of the software as well, and I am not sure what is the difference between the places where this is happening, and places where this is not happening. For example, a command button where Korean letters are showing up properly is shown below: This software is a video conferencing software and has a chat feature as well. When I type into the chat box, i can see the Korean letters appear properly at my side, but when I press Enter and send the message, it changes into random characters as shown above in the chat box. What could be the issue here? Could it be a missing font in my computer? Since this is a Korean Windows installation I was hoping everything would work properly by default. What can be done here? EDIT 1: I asked some other people who are using this software, and they think that the problem is at my end, and playing around with the Regional and Language Settings might solve the problem. Also, they suggested I install all the language packs related to Korean display. But it looks like all the language packs have been installed, and my location is set to Korea in Regional and Language Settings in Control Panel, and I still have this problem. Also, I have had similar problems with displaying Korean on an English Windows XP computer. This answer suggested some solutions, but I still do not quite understand exactly what I have to do (at that time I had not fixed the problem, as I later on changed the computer). If I follow that answer, what fonts exactly do I need to install?

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• Why does my ftp(e)s server fails like half of the time

  - by user1092608

  I have this discussion at work regarding our ftp server running via vsftpd. Initially, we have opted to serve ftpes instead of sftp because this seemed the most flexible and straightforward solution for our server to have secure file transmission. Afterwards, our ftp server seems to be a source of issues for our end users. Half of the time, users complain about not working ftp connections. I must say, i tested our FTP trough different infrastructures (=in the field, at random times at random places) and indeed, sometimes behind some configurations (=no idea how they are configured, because the 'field' testing), i recieve errors. Some of the are: Error: Failed to retrieve directory listing (filezilla) Furthermore, behind my basic home configuration, everything seems to be running fine. I (think I) did all the basic configuration checks (passive mode?, firewall for all ports?, ...) and can't seem to find the source. Being a bunch of techies at our small office, yet knowing nothing about infrastructure, some start suggesting that ftps protocol could be the source of issues. ("No, i only knew sftp so far" "Ftps is not widespread"). I, however, strongly doubt this hypothesis, since reading around on the www, asking questions on serverfault, everyone seems to deny this. So, as I would like to avoid reconfiguring, since this involves messing around in our SSH service, our virtual user setup and ftp service, i would need some advice on 1) what could be potentially the general cause? 2) do you have some general tips? 3) would you mind having a look at my configuration file? ----- General Settings ----- write_enable=YES dirmessage_enable=YES nopriv_user=ftpsecure ftpd_banner="Welcome to XXXX FTP!" hide_ids=YES hide_file=.* max_per_ip=10 max_clients=10 local_enable=YES local_umask=022 chroot_local_user=YES secure_chroot_dir=/usr/share/empty userlist_enable=NO userlist_deny=YES userlist_file=/etc/vsftp_deny_users guest_enable=YES guest_username=ftpvirtual virtual_use_local_privs=YES user_sub_token=$USER local_root=/srv/ftp/ftpvirtual/$USER anonymous_enable=NO syslog_enable=NO xferlog_enable=YES xferlog_file=/var/log/vsftpd_xfer.log connect_from_port_20=YES pam_service_name=vsftpd listen=YES listen_port=21 pasv_enable=YES pasv_min_port=30000 pasv_max_port=30030 pasv_address=foo ssl_enable=YES rsa_cert_file=/etc/vsftpd.pem rsa_private_key_file=/etc/vsftpd.pem force_local_data_ssl=YES force_local_logins_ssl=YES ssl_tlsv1=YES ssl_sslv2=YES ssl_sslv3=YES ssl_ciphers=HIGH anon_mkdir_write_enable=NO anon_root=/srv/ftp anon_upload_enable=NO idle_session_timeout=900 log_ftp_protocol=NO dsa_cert_file=/etc/vsftpd.pem Thanks

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• RAIDs with a lot of spindles - how to safely put to use the "wasted" space

  - by kubanczyk

  I have a fairly large number of RAID arrays (server controllers as well as midrange SAN storage) that all suffer from the same problem: barely enough spindles to keep the peak I/O performance, and tons of unused disk space. I guess it's a universal issue since vendors offer the smallest drives of 300 GB capacity but the random I/O performance hasn't really grown much since the time when the smallest drives were 36 GB. One example is a database that has 300 GB and needs random performance of 3200 IOPS, so it gets 16 disks (4800 GB minus 300 GB and we have 4.5 TB wasted space). Another common example are redo logs for a OLTP database that is sensitive in terms of response time. The redo logs get their own 300 GB mirror, but take 30 GB: 270 GB wasted. What I would like to see is a systematic approach for both Linux and Windows environment. How to set up the space so sysadmin team would be reminded about the risk of hindering the performance of the main db/app? Or, even better, to be protected from that risk? The typical situation that comes to my mind is "oh, I have this very large zip file, where do I uncompress it? Umm let's see the df -h and we figure something out in no time..." I don't put emphasis on strictness of the security (sysadmins are trusted to act in good faith), but on overall simplicity of the approach. For Linux, it would be great to have a filesystem customized to cap I/O rate to a very low level - is this possible?

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• Isn't a hidden volume used when encrypting a drive with TrueCrypt detectable?

  - by neurolysis

  I don't purport to be an expert on encryption (or even TrueCrypt specifically), but I have used TrueCrypt for a number of years and have found it to be nothing short of invaluable for securing data. As relatively well known free, open-source software, I would have thought that TrueCrypt would not have fundamental flaws in the way it operates, but unless I'm reading it wrong, it has one in the area of hidden volume encryption. There is some documentation regarding encryption with a hidden volume here. The statement that concerns me is this (emphasis mine): TrueCrypt first attempts to decrypt the standard volume header using the entered password. If it fails, it loads the area of the volume where a hidden volume header can be stored (i.e. bytes 65536–131071, which contain solely random data when there is no hidden volume within the volume) to RAM and attempts to decrypt it using the entered password. Note that hidden volume headers cannot be identified, as they appear to consist entirely of random data. Whilst the hidden headers supposedly "cannot be identified", is it not possible to, on encountering an encrypted volume encrypted using TrueCrypt, determine at which offset the header was successfully decrypted, and from that determine if you have decrypted the header for a standard volume or a hidden volume? That seems like a fundamental flaw in the header decryption implementation, if I'm reading this right -- or am I reading it wrong?

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