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• Git/Mercurial (hg) opinion

  - by Richard

  First, let me say I'm not a professional programmer, but an engineer who had a need for it and had to learn. I was always working alone, so it was just me and my seven splitted personalities ... and we worked okey as a team :) Most of my stuff is done in C/Fortran/Matlab and so far I've been learning git to manage it all. However, although I've had no unsolvable problems with it, I've never been "that" happy with it ... for everything I cannot do, I hae to look up a book. And, for some time now I've been hearning a lot of good stuff about hg. Now, a coleague of mine will have to work with me on a project (I almost feel sorry for him) and he's started learning hg (says he likes it more), and I'm considering the switch myself. We work almost exclusivly on Windows platform (although I manage relatively ok using unix tools and things that come from that part of the world). So, I was wondering, in a described scenario, what problems could I expect with the switch. I heard that hg is rather more user friendly towards windows users, regarding the user interfaces. How does it handle repositories ? Does it create them the same way as git does (just one subdirectory in a working directory) and can I just copy the whole project directory (including git repo) and just carry them somewhere with no extra thinking ? (I really liked that when I was choosing over git/svn). Are there any good books on it that you can recommend (something like Pro Git, only for Hg). What are good ways to implement hg into Visual Studio/GVim for Windows, or into Windows Explorer so I can work relatively easily (I would like to avoid using the command line for everything regarding it, like in git shell). Is there something else I should be aware of (please, on this don't point me to other questions ... they just give me a ton of info, and I'm not sure what is it that I should take as important, and what to disregard). I'm trying to cut some time, since I cannot spend all that time relearning hg, like I did for git. I've also heard git is c project, while mercurial is python ... is there any noticeable difference in speed. git was pretty speedy ... will I encounter some waiting while working. Notice: All my projects are of let's say, middle size ... mostly numerical simulations ... 10-15000 lines (medium size?)

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• Debugging IO limitation

  - by Martin F

  I have a Fedora box with some severe IO limitations which I have no idea how to debug. The server has a Areca Technology Corp. ARC-1130 12-Port PCI-X to SATA RAID Controller with 12 7200 RPM 1.5 TB disks and a Marvell Technology Group Ltd. 88E8050 PCI-E ASF Gigabit Ethernet Controller. uname -a output: 2.6.32.11-99.fc12.x86_64 #1 SMP Mon Apr 5 19:59:38 UTC 2010 x86_64 x86_64 x86_64 GNU/Linux The server is a file server running Nginx with the stub status module enabled, so I can see the current amount of connections. The problem present itself when I have a high number of simultaneous connections in a writing state. Usually around 350, at this very moment it's at 590 and the server is almost unusable and stuck at 230mbit/s. If I run stop and hit 1 to see CPU core usages I have all 4 cores with around 99% io wait, if I run iotop the nginx workers are the only processes producing any read load, currently at around 25MB/s. I have each of the workers bound to their own core. Initially I figured it was just the disks being bugged. But I've run fscheck and smartmontools checks and found no errors. I also ran an iozone test which you can see the result of here: http://www.pastie.org/951667.txt?key=fimcvljulnuqy2dcdxa Additionally, when the amount of connections are low I have no problem getting a good speed. If I wget over the local network it easily hits 60MB/sec. Right now I just tried putting a file in /dev/shm, then I symlinked a file from the public dir to it and used wget over the local network and only got 50KB/s. Also, if I try to cp /dev/shm/test /root/test it quickly copies around 740MB and then slows down HEAVILY. Again with iotop reporting 99% iowait. I'm not really sure how to go about figuring out what the problems are. It could be a natural disk limitation but then the file from /dev/shm ought to transfer so it seems there's a network limit, but that's fine when there's not many connections. Perhaps it's a TCP stack problem but I really have no idea how to check that. Any suggestions on how to proceed with debugging would be very welcome. If additional information is required then let me know and I'll try to get it. Thanks.

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• Kernel upgrade CentOS 5.3 mount: could not find filesystem '/dev/root'

  - by matt

  We have a CentOS 5.3 x64 server that by default runs kernel version 2.6.18-164.11.1 and we are attempting to upgrade the box to 2.6.31.12 The drive is LVM +ext3, and the problem I'm having is when I upgrade the kernel and attempt to boot from it, no matter what version of the kernel I use, I get /dev/root not found towards the end of the boot process, and the kernel panics, and than reboots. I'm installing the kernel exactly as it says in this doc. I've tried it "The centOS way " using make rpm and than installing that. I've updated my mkinitrd. The most interesting part of this problem is that it has been so frustrating that I decided to try and clean install centos on an identical machine without LVM, and the result is EXACTLY the same. After upgrading the kernel, I get /dev/root not found. Does anyone know how to fix this, or what information would be relevant to remedy it? I'm open to try anything at this point. One more interesting thing about this problem is that in the new version of the kernel, during boot it complains that dm-mapper is started twice, than panics right after that. I've tried this with other kernel versions, and the result is the same. What am I missing here? If you need any more files, please just ask. Linux cg 2.6.18-164.11.1.el5 #1 SMP Wed Jan 20 07:32:21 EST 2010 x86_64 x86_64 x86_64 GNU/Linux /dev/VolGroup00/LogVol00 / ext3 defaults 1 1 LABEL=/boot /boot ext3 defaults 1 2 tmpfs /dev/shm tmpfs defaults 0 0 devpts /dev/pts devpts gid=5,mode=620 0 0 sysfs /sys sysfs defaults 0 0 proc /proc proc defaults 0 0 /dev/VolGroup00/LogVol01 swap swap defaults 0 0 default=1 timeout=5 splashimage=(hd0,0)/grub/splash.xpm.gz hiddenmenu title CentOS (2.6.31.12-rt20) //NOT WORKING!!!! root (hd0,0) kernel /vmlinuz-2.6.31.12-rt20 ro root=/dev/VolGroup00/LogVol00 isolcpus=8,9,10,11,12,13,14,15 panic=10 initrd /initrd-2.6.31.12-rt20.img title CentOS (2.6.18-164.11.1.el5) //WORKING!! root (hd0,0) kernel /vmlinuz-2.6.18-164.11.1.el5 ro root=/dev/VolGroup00/LogVol00 isolcpus=8,9,10,11,12,13,14,15 panic=10 initrd /initrd-2.6.18-164.11.1.el5.img

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• Perl missing while installing nginx on centos

  - by Ahoura Ghotbi

  I am trying to install nginx on my server, however it keeps returning "./configure: error: perl 5.6.1 or higher is required" eventhough I have perl v5.8.8!!!! I have already downloaded perl and trying to configure it using the following command : ./configure --with-http_stub_status_module --with-http_perl_module --with-http_flv_module --add-module=nginx_mod_h264_streaming here is the output : [root@fst nginx-0.8.55]# ./configure --with-http_stub_status_module --with-http_perl_module --with-http_flv_module --add-module=nginx_mod_h264_streaming checking for OS + Linux 2.6.18-308.el5 x86_64 checking for C compiler ... found + using GNU C compiler + gcc version: 4.1.2 20080704 (Red Hat 4.1.2-52) checking for gcc -pipe switch ... found checking for gcc builtin atomic operations ... found checking for C99 variadic macros ... found checking for gcc variadic macros ... found checking for unistd.h ... found checking for inttypes.h ... found checking for limits.h ... found checking for sys/filio.h ... not found checking for sys/param.h ... found checking for sys/mount.h ... found checking for sys/statvfs.h ... found checking for crypt.h ... found checking for Linux specific features checking for epoll ... found checking for sendfile() ... found checking for sendfile64() ... found checking for sys/prctl.h ... found checking for prctl(PR_SET_DUMPABLE) ... found checking for sched_setaffinity() ... found checking for crypt_r() ... found checking for sys/vfs.h ... found checking for nobody group ... found checking for poll() ... found checking for /dev/poll ... not found checking for kqueue ... not found checking for crypt() ... not found checking for crypt() in libcrypt ... found checking for F_READAHEAD ... not found checking for posix_fadvise() ... found checking for O_DIRECT ... found checking for F_NOCACHE ... not found checking for directio() ... not found checking for statfs() ... found checking for statvfs() ... found checking for dlopen() ... not found checking for dlopen() in libdl ... found checking for sched_yield() ... found checking for SO_SETFIB ... not found configuring additional modules adding module in nginx_mod_h264_streaming + ngx_http_h264_streaming_module was configured checking for PCRE library ... found checking for system md library ... not found checking for system md5 library ... not found checking for OpenSSL md5 crypto library ... found checking for zlib library ... found checking for perl + perl version: v5.8.8 built for x86_64-linux-thread-multi ./configure: error: perl 5.6.1 or higher is required

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• HAProxy + Percona XtraDB Cluster

  - by rottmanj

  I am attempting to setup HAproxy in conjunction with Percona XtraDB Cluster on a series of 3 EC2 instances. I have found a few tutorials online dealing with this specific issue, but I am a bit stuck. Both the Percona servers and the HAproxy servers are running ubuntu 12.04. The HAProxy version is 1.4.18, When I start HAProxy I get the following error: Server pxc-back/db01 is DOWN, reason: Socket error, check duration: 2ms. I am not really sure what the issue could be. I have verified the following: EC2 security groups ports are open Poured over my config files looking for issues. I currently do not see any. Ensured that xinetd was installed Ensured that I am using the correct ip address of the mysql server. Any help with this is greatly appreciated. Here are my current config Load Balancer /etc/haproxy/haproxy.cfg global log 127.0.0.1 local0 log 127.0.0.1 local1 notice maxconn 4096 user haproxy group haproxy debug #quiet daemon defaults log global mode http option tcplog option dontlognull retries 3 option redispatch maxconn 2000 contimeout 5000 clitimeout 50000 srvtimeout 50000 frontend pxc-front bind 0.0.0.0:3307 mode tcp default_backend pxc-back frontend stats-front bind 0.0.0.0:22002 mode http default_backend stats-back backend pxc-back mode tcp balance leastconn option httpchk server db01 10.86.154.105:3306 check port 9200 inter 12000 rise 3 fall 3 backend stats-back mode http balance roundrobin stats uri /haproxy/stats MySql Server /etc/xinetd.d/mysqlchk # default: on # description: mysqlchk service mysqlchk { # this is a config for xinetd, place it in /etc/xinetd.d/ disable = no flags = REUSE socket_type = stream port = 9200 wait = no user = nobody server = /usr/bin/clustercheck log_on_failure += USERID #only_from = 0.0.0.0/0 # recommended to put the IPs that need # to connect exclusively (security purposes) per_source = UNLIMITED } MySql Server /etc/services Added the line mysqlchk 9200/tcp # mysqlchk MySql Server /usr/bin/clustercheck # GNU nano 2.2.6 File: /usr/bin/clustercheck #!/bin/bash # # Script to make a proxy (ie HAProxy) capable of monitoring Percona XtraDB Cluster nodes properly # # Author: Olaf van Zandwijk <[email protected]> # Documentation and download: https://github.com/olafz/percona-clustercheck # # Based on the original script from Unai Rodriguez # MYSQL_USERNAME="testuser" MYSQL_PASSWORD="" ERR_FILE="/dev/null" AVAILABLE_WHEN_DONOR=0 # # Perform the query to check the wsrep_local_state # WSREP_STATUS=`mysql --user=${MYSQL_USERNAME} --password=${MYSQL_PASSWORD} -e "SHOW STATUS LIKE 'wsrep_local_state';" 2>${ERR_FILE} | awk '{if (NR!=1){print $2}}' 2>${ERR_FILE}` if [[ "${WSREP_STATUS}" == "4" ]] || [[ "${WSREP_STATUS}" == "2" && ${AVAILABLE_WHEN_DONOR} == 1 ]] then # Percona XtraDB Cluster node local state is 'Synced' => return HTTP 200 /bin/echo -en "HTTP/1.1 200 OK\r\n" /bin/echo -en "Content-Type: text/plain\r\n" /bin/echo -en "\r\n" /bin/echo -en "Percona XtraDB Cluster Node is synced.\r\n" /bin/echo -en "\r\n" else # Percona XtraDB Cluster node local state is not 'Synced' => return HTTP 503 /bin/echo -en "HTTP/1.1 503 Service Unavailable\r\n" /bin/echo -en "Content-Type: text/plain\r\n" /bin/echo -en "\r\n" /bin/echo -en "Percona XtraDB Cluster Node is not synced.\r\n" /bin/echo -en "\r\n" fi

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• 64-bit linux kernel only seeing 3 of 4GB after upgrade...

  - by Blaine

  Hey everyone. I am running Ubuntu 9.04 64-bit on my macbook. I had 2GB of ram before, and everything ran great. I just upgraded to 2x2GB (4GB), but my system only sees 3GB of it. OS X, which I am dual booting, sees all 4GB. Also, my video performance is incredibly lacking. Before the upgrade my compiz benchmark was full at 80fps, and now it is at 22fps with very choppy window dragging. Has anyone ever heard of this on a 64-bit kernel? I just don't quite understand what could be the issue. 10$ uname -a Linux macbook 2.6.28-15-generic #49-Ubuntu SMP Tue Aug 18 19:25:34 UTC 2009 x86_64 GNU/Linux $ free -m total used free shared buffers cached Mem: 2953 1031 1921 0 114 427 -/+ buffers/cache: 489 2463 Swap: 7812 0 7812 9$ lsmod Module Size Used by i915 77960 2 drm 123232 3 i915 binfmt_misc 18572 1 ppdev 16904 0 btusb 21784 2 bridge 63776 0 stp 11140 1 bridge bnep 22912 2 vboxnetadp 109356 0 vboxnetflt 116972 0 vboxdrv 1721612 1 vboxnetflt uvcvideo 69640 0 compat_ioctl32 18304 1 uvcvideo videodev 45184 2 uvcvideo,compat_ioctl32 v4l1_compat 23940 2 uvcvideo,videodev lp 19588 0 parport 49584 2 ppdev,lp snd_hda_intel 557492 3 snd_pcm_oss 52352 0 snd_mixer_oss 24960 1 snd_pcm_oss snd_pcm 99464 2 snd_hda_intel,snd_pcm_oss arc4 10240 2 snd_seq_dummy 11524 0 ecb 11392 2 snd_seq_oss 41984 0 snd_seq_midi 15744 0 snd_rawmidi 33920 1 snd_seq_midi snd_seq_midi_event 16512 2 snd_seq_oss,snd_seq_midi snd_seq 66272 6 snd_seq_dummy,snd_seq_oss,snd_seq_midi,snd_seq_midi_event ath9k 310584 0 snd_timer 34064 2 snd_pcm,snd_seq snd_seq_device 16276 5 snd_seq_dummy,snd_seq_oss,snd_seq_midi,snd_rawmidi,snd_seq mac80211 251528 1 ath9k iTCO_wdt 21712 0 iTCO_vendor_support 12420 1 iTCO_wdt joydev 20992 0 video 29204 0 snd 78920 15 snd_hda_intel,snd_pcm_oss,snd_mixer_oss,snd_pcm,snd_seq_oss,snd_rawmidi,snd_seq,snd_timer,snd_seq_device applesmc 37700 0 output 11648 1 video soundcore 16800 1 snd pcspkr 11136 0 cfg80211 43680 1 mac80211 appletouch 19972 0 isight_firmware 11520 0 input_polldev 12688 1 applesmc intel_agp 39408 1 snd_page_alloc 18704 2 snd_hda_intel,snd_pcm led_class 13064 2 ath9k,applesmc hid_apple 15872 0 usbhid 47040 0 ohci1394 42164 0 ieee1394 108288 1 ohci1394 sky2 63364 0 fbcon 49792 0 tileblit 11264 1 fbcon font 17024 1 fbcon bitblit 14464 1 fbcon softcursor 10368 1 bitblit Some information from dmesg: [ 795.820163] ACPI: EC: GPE storm detected, transactions will use polling mode [ 1762.709516] [drm:i915_getparam] *ERROR* Unknown parameter 6 [ 1763.078130] [drm:i915_getparam] *ERROR* Unknown parameter 6 [ 2362.760889] [drm:i915_getparam] *ERROR* Unknown parameter 6 [ 2416.352084] ACPI: EC: missing confirmations, switch off interrupt mode. [ 3718.721095] [drm:i915_getparam] *ERROR* Unknown parameter 6 [ 3719.108914] [drm:i915_getparam] *ERROR* Unknown parameter 6 [ 4318.773266] [drm:i915_getparam] *ERROR* Unknown parameter 6 [ 9513.813066] CE: hpet increasing min_delta_ns to 15000 nsec [ 9693.815684] npviewer.bin[6736]

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• grep simply fails when used on a few files

  - by Reid

  I've been trying for about the past 30 minutes to get this to work properly. grep is not exactly the most difficult thing to use, so I'm somewhat baffled as to why this won't work. The files I'm trying to use grep on are simple XHTML log files. Their names are in the format [email protected], though I don't think that should matter, and inside is simple XHTML. I copied one such log file to be testfile so you can see the output of some commands and why it's baffling to me: [~/.chatlogs_windows/dec] > whoami reid [~/.chatlogs_windows/dec] > type grep grep is /bin/grep [~/.chatlogs_windows/dec] > uname -a Linux reid-pc 2.6.35-22-generic #33-Ubuntu SMP Sun Sep 19 20:32:27 UTC 2010 x86_64 GNU/Linux [~/.chatlogs_windows/dec] > head -1 /etc/issue Linux Mint 10 Julia [~/.chatlogs_windows/dec] > ls -Alh | grep testfile -rw-r--r-- 1 reid reid 63K 2011-01-10 12:45 testfile [~/.chatlogs_windows/dec] > tail -3 testfile </body> </html> [~/.chatlogs_windows/dec] > file testfile testfile: XML document text [~/.chatlogs_windows/dec] > grep html testfile [~/.chatlogs_windows/dec] > grep body testfile [~/.chatlogs_windows/dec] > grep "</html>" testfile [~/.chatlogs_windows/dec] > grep "</body>" testfile [~/.chatlogs_windows/dec] > cat testfile | grep html [~/.chatlogs_windows/dec] > cat testfile | wc -l 231 [~/.chatlogs_windows/dec] > cat testfile | tail -3 </body> </html> [~/.chatlogs_windows/dec] > chmod a+rw testfile && ls -Alh | grep testfile -rw-rw-rw- 1 reid reid 63K 2011-01-10 12:45 testfile [~/.chatlogs_windows/dec] > grep html testfile That's what I'm attempting to do. I want to just use grep -ri query . in ~/.chatlogs_windows, which normally works perfectly for me... but for some reason, it completely fails at going through these files. If it matters, I copied these files off of my Windows 7 partition. But I chown'd them and gave myself all the appropriate permissions, and other programs (like cat) seem to read them just fine. I also copied testfile to testfile_unix and converted the line endings and tried that, but it didn't work either. I'm using zsh, but I tried it on bash and that failed too. Also, grep works normally: I tried it out on my documents folder and it worked flawlessly. If you need any more information, just let me know. I tried googling around, but I found no reason for grep to simply not work. Thanks in advance.

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• Why does unpartitioned Hitachi HDS5C3020 drive start consuming 50% more power 15 minutes after boot?

  - by Pro Backup

  In a Debian 6.0.6 system there are 74 pieces of 2TB Toshiba DT01ABA200 drives. These drives are identified as Hitachi HDS5C3020BLE630 drives running firmware revision MZ4OAAB0. 64 Drives attached via HP SAS expander cards to an LSI 2008 SAS controller, another 5 drives are connected directly to the mainboard, 4 drives are connected to a Sil based PCI controller and last 1 drive is only powered and has no data cable connected. The controller LSI and Sil card's their onboard BIOS are both disabled and the mpt2sas and sata_sil modules are removed from the Linux debian 2.6.32-5-amd64 #1 SMP Sun Sep 23 10:07:46 UTC 2012 x86_64 GNU/Linux kernel. The mpt2sas module is loaded after boot using a modprobe command in /etc/rc.local. These 74 drives are not partitioned, neither formatted and also not mounted. The system consumes: with 0 drives: 70.6 - 70.9 Watt (also 15 minutes after boot); with 74 drives: 330 - 360 Watt, just after boot (is equivalent to 3.5 - 3.9W per drive in idle state); with 74 drives: 420 - 466 Watt, each time in the 15th minute of uptime (is equivalent to 4.7 - 5.3W per drive in idle state). The drive specification lists 4.7W as read/write, and 3.3W as idle power consumption. The increased power consumption is most likely on the 5V line, because after roughly 1 minute an "over current protection" (OCP) of the power supply (PSU) shuts down the power. The used PSU is a single rail model with an OCP of 122A on the 12V line and 55A on the 5V line. Regression: It doesn't matter whether the drive its APM value is set to disabled or 1 (maximum power saving). The operating system records no read/write activity in /proc/diskstats. The values there are identical (28 read, 0 write operations) as immediately after the modprobe operation. Can't test what happens when booting into the mainboard it's BIOS - to exclude any OS intervention - because the Super Micro X8SI6-F mainboard running firmware 06/27/12 has a bug that incorrectly reads a +74.0 C CPU sensor temperature as "High" in BIOS mode, and shuts down the power after 1 minute. What might be causing the drive read/write activity on all drives in the 15th minute after boot and how to prevent it from happening?

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• Hybrid gmail MX + postfix for local accounts

  - by krunk

  Here's the setup: We have a domain, mydomain.com. Everything is on our own server, except general email accounts which are through gmail. Currently gmail is set as the MX record. The server also has various email aliases it needs to support for bug trackers and such. e.g. [email protected] |/path/to/issuetracker.script I'm struggling with a setup that allows the following, both locally and from user's email clients. guser1 - has a gmail account and a local account guser2 - only has a gmail account bugs - has a pipe alias in /etc/aliases for issue tracker Scenarios mail to [email protected] from local host (crons and such) needs to go to gmail account mail to [email protected] from local host mail to [email protected] needs to be piped to the local issue tracker script So, the first stab was creating a transport map. In this scenario, the our server would be set as teh MX and guser* destined emails are sent to gmail. Put the gmail users in a map like so: [email protected] smtp:gmailsmtp:25 [email protected] smtp:gmailsmtp:25 Problems: Ignores extensions such as [email protected] Only works if append_at_myorigin = no (if set to yes, gmail refuses to connect with: E4C7E3E09BA3: to=, relay=none, delay=0.05, delays=0.02/0.01/0.02/0, dsn=4.4.1, status=deferred (connect to gmail-smtp-in.l.google.com[209.85.222.57]:25: Connection refused)) since append_at_myorigin is set to no, all received emails have (unknown sender) The second stab was to set explicit localhost aliases in /etc/aliases and do a domain wide forward on mydomain. This too requires setting the local server as the MX: root: root@localhost # transport mydomain.com smtp:gmailsmtp:25 Problems: * If I create a transport map for a domain that matches "$myhostname", the aliases file is never parsed. So when a local user (or daemon) sends an email like: mail -s "testing" root < text.txt Postfix ignores the /etc/alias entry and maps to [email protected] and attempts to send it to the gmail transport mapping. Third stab: Create a subdomain for the bugs, something like bugs.mydomain.com. Set the MX for this domain to local server and leave the MX for mydomain.com to the Gmail server. Problems: * Does not solve the issue with local accounts. So when the bug tracker responds to an email from [email protected], it uses a local transport and the user never receives the email. % postconf -n alias_database = hash:/etc/aliases alias_maps = hash:/etc/aliases append_at_myorigin = no append_dot_mydomain = no biff = no config_directory = /etc/postfix inet_interfaces = all mailbox_command = procmail -a "$EXTENSION" mailbox_size_limit = 0 mydestination = $myhostname, localhost.$myhostname, localhost myhostname = mydomain.com mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128 myorigin = /etc/mailname readme_directory = no recipient_delimiter = + relayhost = smtp_tls_cert_file = /etc/ssl/certs/kspace.pem smtp_tls_enforce_peername = no smtp_tls_key_file = /etc/ssl/certs/kspace.pem smtp_tls_note_starttls_offer = yes smtp_tls_scert_verifydepth = 5 smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache smtp_use_tls = yes smtpd_banner = $myhostname ESMTP $mail_name (Debian/GNU) smtpd_recipient_restrictions = permit_mynetworks, reject_invalid_hostname, reject_non_fqdn_sender, reject_non_fqdn_recipient, reject_unknown_sender_domain, reject_unknown_recipient_domain, reject_unauth_destination smtpd_tls_ask_ccert = yes smtpd_tls_req_ccert = no smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache tls_random_source = dev:/dev/urandom transport_maps = hash:/etc/postfix/transport

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• MySQL foreign key creation with alter table command

  - by user313338

  I created some tables using MySQL Workbench, and then did forward ‘forward engineer’ to create scripts to create these tables. BUT, the scripts lead me to a number of problems. One of which involves the foreign keys. So I tried creating separate foreign key additions using alter table and I am still getting problems. The code is below (the set statements, drop/create statements I left in … though I don’t think they should matter for this): SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0; SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0; SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='TRADITIONAL'; DROP SCHEMA IF EXISTS `mydb` ; CREATE SCHEMA IF NOT EXISTS `mydb` DEFAULT CHARACTER SET latin1 COLLATE latin1_swedish_ci ; -- ----------------------------------------------------- -- Table `mydb`.`User` -- ----------------------------------------------------- DROP TABLE IF EXISTS `mydb`.`User` ; CREATE TABLE IF NOT EXISTS `mydb`.`User` ( `UserName` VARCHAR(35) NOT NULL , `Num_Accts` INT NOT NULL , `Password` VARCHAR(45) NULL , `Email` VARCHAR(45) NULL , `User_ID` INT NOT NULL AUTO_INCREMENT , PRIMARY KEY (`User_ID`) ) ENGINE = InnoDB; -- ----------------------------------------------------- -- Table `mydb`.`User_Space` -- ----------------------------------------------------- DROP TABLE IF EXISTS `mydb`.`User_Space` ; CREATE TABLE IF NOT EXISTS `mydb`.`User_Space` ( `User_UserName` VARCHAR(35) NOT NULL , `User_Space_ID` INT NOT NULL AUTO_INCREMENT , PRIMARY KEY (`User_Space_ID`), FOREIGN KEY (`User_UserName`) REFERENCES `mydb`.`User` (`UserName`) ON UPDATE CASCADE ON DELETE CASCADE) ENGINE = InnoDB; SET SQL_MODE=@OLD_SQL_MODE; SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS; SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS; The error this produces is: Error Code: 1005 Can't create table 'mydb.user_space' (errno: 150) Anybody know what the heck I’m doing wrong?? And anybody else have problems with the script generation done by mysql workbench? It’s a nice tool, but annoying that it pumps out scripts that don’t work for me. [As an fyi here’s the script it auto-generates: SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0; SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0; SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='TRADITIONAL'; DROP SCHEMA IF EXISTS `mydb` ; CREATE SCHEMA IF NOT EXISTS `mydb` DEFAULT CHARACTER SET latin1 COLLATE latin1_swedish_ci ; -- ----------------------------------------------------- -- Table `mydb`.`User` -- ----------------------------------------------------- DROP TABLE IF EXISTS `mydb`.`User` ; CREATE TABLE IF NOT EXISTS `mydb`.`User` ( `UserName` VARCHAR(35) NOT NULL , `Num_Accts` INT NOT NULL , `Password` VARCHAR(45) NULL , `Email` VARCHAR(45) NULL , `User_ID` INT NOT NULL AUTO_INCREMENT , PRIMARY KEY (`User_ID`) ) ENGINE = InnoDB; -- ----------------------------------------------------- -- Table `mydb`.`User_Space` -- ----------------------------------------------------- DROP TABLE IF EXISTS `mydb`.`User_Space` ; CREATE TABLE IF NOT EXISTS `mydb`.`User_Space` ( `User_Space_ID` INT NOT NULL AUTO_INCREMENT , PRIMARY KEY (`User_Space_ID`) , INDEX `User_ID` () , CONSTRAINT `User_ID` FOREIGN KEY () REFERENCES `mydb`.`User` () ON DELETE NO ACTION ON UPDATE NO ACTION) ENGINE = InnoDB; SET SQL_MODE=@OLD_SQL_MODE; SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS; SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS; ** Thanks!]

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• How to generate and encode (for use in GA), random, strict, binary rooted trees with N leaves?

  - by Peter Simon

  First, I am an engineer, not a computer scientist, so I apologize in advance for any misuse of nomenclature and general ignorance of CS background. Here is the motivational background for my question: I am contemplating writing a genetic algorithm optimizer to aid in designing a power divider network (also called a beam forming network, or BFN for short). The BFN is intended to distribute power to each of N radiating elements in an array of antennas. The fraction of the total input power to be delivered to each radiating element has been specified. Topologically speaking, a BFN is a strictly binary, rooted tree. Each of the (N-1) interior nodes of the tree represents the input port of an unequal, binary power splitter. The N leaves of the tree are the power divider outputs. Given a particular power divider topology, one is still free to map the power divider outputs to the array inputs in an arbitrary order. There are N! such permutations of the outputs. There are several considerations in choosing the desired ordering: 1) The power ratio for each binary coupler should be within a specified range of values. 2) The ordering should be chosen to simplify the mechanical routing of the transmission lines connecting the power divider. The number of ouputs N of the BFN may range from, say, 6 to 22. I have already written a genetic algorithm optimizer that, given a particular BFN topology and desired array input power distribution, will search through the N! permutations of the BFN outputs to generate a design with compliant power ratios and good mechanical routing. I would now like to generalize my program to automatically generate and search through the space of possible BFN topologies. As I understand it, for N outputs (leaves of the binary tree), there are $C_{N-1}$ different topologies that can be constructed, where $C_N$ is the Catalan number. I would like to know how to encode an arbitrary tree having N leaves in a way that is consistent with a chromosomal description for use in a genetic algorithm. Also associated with this is the need to generate random instances for filling the initial population, and to implement crossover and mutations operators for this type of chromosome. Any suggestions will be welcome. Please minimize the amount of CS lingo in your reply, since I am not likely to be acquainted with it. Thanks in advance, Peter

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• How to obtain a pointer out of a C++ vtable?

  - by Josh Haberman

  Say you have a C++ class like: class Foo { public: virtual ~Foo() {} virtual DoSomething() = 0; }; The C++ compiler translates a call into a vtable lookup: Foo* foo; // Translated by C++ to: // foo->vtable->DoSomething(foo); foo->DoSomething(); Suppose I was writing a JIT compiler and I wanted to obtain the address of the DoSomething() function for a particular instance of class Foo, so I can generate code that jumps to it directly instead of doing a table lookup and an indirect branch. My questions are: Is there any standard C++ way to do this (I'm almost sure the answer is no, but wanted to ask for the sake of completeness). Is there any remotely compiler-independent way of doing this, like a library someone has implemented that provides an API for accessing a vtable? I'm open to completely hacks, if they will work. For example, if I created my own derived class and could determine the address of its DoSomething method, I could assume that the vtable is the first (hidden) member of Foo and search through its vtable until I find my pointer value. However, I don't know a way of getting this address: if I write &DerivedFoo::DoSomething I get a pointer-to-member, which is something totally different. Maybe I could turn the pointer-to-member into the vtable offset. When I compile the following: class Foo { public: virtual ~Foo() {} virtual void DoSomething() = 0; }; void foo(Foo *f, void (Foo::*member)()) { (f->*member)(); } On GCC/x86-64, I get this assembly output: Disassembly of section .text: 0000000000000000 <_Z3fooP3FooMS_FvvE>: 0: 40 f6 c6 01 test sil,0x1 4: 48 89 74 24 e8 mov QWORD PTR [rsp-0x18],rsi 9: 48 89 54 24 f0 mov QWORD PTR [rsp-0x10],rdx e: 74 10 je 20 <_Z3fooP3FooMS_FvvE+0x20> 10: 48 01 d7 add rdi,rdx 13: 48 8b 07 mov rax,QWORD PTR [rdi] 16: 48 8b 74 30 ff mov rsi,QWORD PTR [rax+rsi*1-0x1] 1b: ff e6 jmp rsi 1d: 0f 1f 00 nop DWORD PTR [rax] 20: 48 01 d7 add rdi,rdx 23: ff e6 jmp rsi I don't fully understand what's going on here, but if I could reverse-engineer this or use an ABI spec I could generate a fragment like the above for each separate platform, as a way of obtaining a pointer out of a vtable.

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• 2xAMD Opteron 6128 with libvirt, Physical CPU 13 doesn't exist

  - by yak

  I need help with libvirt(?) problem. Server specs: ProLiant DL165 G7 2x AMD Opteron(tm) Processor 6128 System: Debian GNU/Linux testing (wheezy) 3.2.0-3-amd64 libvirt 0.9.12-5 kvm 1:1.1.2+dfsg-2 $ grep processor /proc/cpuinfo | wc -l 16 $ virsh nodeinfo setlocale: No such file or directory CPU model: x86_64 CPU(s): 16 CPU frequency: 800 MHz CPU socket(s): 2 Core(s) per socket: 4 Thread(s) per core: 1 NUMA cell(s): 1 Memory size: 66114200 KiB $ virsh capabilities .. <topology> <cells num='4'> <cell id='0'> <cpus num='4'> <cpu id='0'/> <cpu id='1'/> <cpu id='2'/> <cpu id='3'/> </cpus> </cell> <cell id='1'> <cpus num='4'> <cpu id='4'/> <cpu id='5'/> <cpu id='6'/> <cpu id='7'/> </cpus> </cell> <cell id='2'> <cpus num='4'> <cpu id='12'/> <cpu id='13'/> <cpu id='14'/> <cpu id='15'/> </cpus> </cell> <cell id='3'> <cpus num='4'> <cpu id='8'/> <cpu id='9'/> <cpu id='10'/> <cpu id='11'/> </cpus> </cell> </cells> </topology> .. $ virsh vcpupin vm 0 13,12,11,10,9,8,7,6,5 error: Physical CPU 13 doesn't exist. error: cpulist: Invalid format. Question? Why my VM Guests use only first 8 CPUs and next 8 are idling? $ for host in virsh list | awk '{print $2}'; do virsh vcpuinfo $host; done | grep ^CPU: | sort | uniq CPU: 0 CPU: 1 CPU: 2 CPU: 3 CPU: 4 CPU: 5 CPU: 6 CPU: 7 Any ideas how to change it?

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• Reasons for missing IP info in `last` output on pts logins?

  - by Mike Pennington

  I have five CentOS 6 linux systems at work, and encountered a rather strange issue that only seems to happen with my userid across all the linux systems I have... This is an example of the problem from entries I excepted from the last command... mpenning pts/19 Fri Nov 16 10:32 - 10:35 (00:03) mpenning pts/17 Fri Nov 16 10:21 - 10:42 (00:21) bill pts/15 sol-bill.local Fri Nov 16 10:19 - 10:36 (00:16) mpenning pts/1 192.0.2.91 Fri Nov 16 10:17 - 10:49 (12+00:31) kkim14 pts/14 192.0.2.225 Thu Nov 15 18:02 - 15:17 (4+21:15) gduarte pts/10 192.0.2.135 Thu Nov 15 12:33 - 08:10 (11+19:36) gduarte pts/9 192.0.2.135 Thu Nov 15 12:31 - 08:10 (11+19:38) kkim14 pts/0 :0.0 Thu Nov 15 12:27 - 15:17 (5+02:49) gduarte pts/6 192.0.2.135 Thu Nov 15 11:44 - 08:10 (11+20:25) kkim14 pts/13 192.0.2.225 Thu Nov 15 09:56 - 15:17 (5+05:20) kkim14 pts/12 192.0.2.225 Thu Nov 15 08:28 - 15:17 (5+06:49) kkim14 pts/11 192.0.2.225 Thu Nov 15 08:26 - 15:17 (5+06:50) dspencer pts/8 192.0.2.130 Wed Nov 14 18:24 still logged in mpenning pts/18 alpha-console-1. Mon Nov 12 14:41 - 14:46 (00:04) You can see two of my pts login entries above that do not have a source IP address associated with them. My CentOS machines have as many as six other users that share the systems, but the mpenning userid is the only one that has this issue. Approximately 5% of my logins see this issue, but no other usernames exhibit this behavior. Questions Given the kind of scripts I keep on these systems (which control much of our network infrastructure), I'm a little spooked by this and would like to understand what would cause my logins to occasionally miss source addresses. Is there anything (other than malicious activity) that would reasonably explain the behavior? Other than bash history timestamping, are there other things I can do to track the issue down? Informational Since this started happening, I enabled bash history time-stamping (i.e. HISTTIMEFORMAT="%y-%m-%d %T " in .bash_profile) and also added a few other bash history hacks; however, that does not give clues to what happened during the previous occurrences. All the systems run CentOS 6.3... [mpenning@typo ~]$ uname -a Linux typo.local 2.6.32-279.9.1.el6.x86_64 #1 SMP Tue Sep 25 21:43:11 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux [mpenning@typo ~]$ EDIT If I use last -i mpenning, I see entries like this... mpenning pts/19 0.0.0.0 Fri Nov 16 10:32 - 10:35 (00:03) mpenning pts/17 0.0.0.0 Fri Nov 16 10:21 - 10:42 (00:21)

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• Sarg report error

  - by amyassin

  I have a proxy server that runs Ubuntu Server 11.10, Squid 2.7.STABLE9. I installed sarg (version 2.3.1 Sep-18-2010) to generate reports using the ordinary apt-get install, and added a cron job to generate a report of the day every 5 minutes (that will overwrite the 5-minutes-older one): */5 * * * * /root/proxy_report.sh And the content of /root/proxy_report.sh is: #!/bin/bash /usr/bin/sarg -nd `date +"%d/%m/%Y"` > /dev/null 2>&1 And I added another cron job to generate a full report every hour at :32 (not to collide with the 5 minutes job): */32 * * * * /root/proxy_report_full.sh And the content of /root/proxy_report_full.sh is : #!/bin/bash /usr/bin/sarg -n > /dev/null 2>&1 And I added a small script to remove the yesterday full report (the full report that ends in yesterday that won't be overwritten by the new today full report) in /etc/rc.local to run at startup: /usr/bin/rm_yesterday.sh &>> /var/log/rm_yesterday Where /usr/bin/rm_yesterday.sh: #!/bin/bash find /var/www/sarg/ | grep `date -d Apr1 +"%Y%b%d"`-* | grep -v `date +"%Y%b%d"` | xargs rm -rf * Apr1 is the starting date of the proxy... ** I've placed it in /usr/bin to be mounted early at startup... That arrangement went OK for about a month and a half, except for one time I noticed some errors and reports wasn't generated, and fixed that by making an offset (the two minutes in 32 of the second cron job). However, it then started not to generate reports anymore. By manually trying to generate it it gives the following error: root@proxy-server:~# sarg -n SARG: getword_atoll loop detected after 3 bytes. SARG: Line="154 192.168.10.40 TCP_MISS/200 39 CONNECT www.google.com" SARG: Record="154 192.168.10.40 TCP_MISS/200 39 CONNECT www.google.com" SARG: searching for 'x2f' SARG: getword backtrace: SARG: 1:sarg() [0x8050a4a] SARG: 2:sarg() [0x8050c8b] SARG: 3:sarg() [0x804fc2e] SARG: 4:/lib/i386-linux-gnu/libc.so.6(__libc_start_main+0xf3) [0x129113] SARG: 5:sarg() [0x80501c9] SARG: Maybe you have a broken date in your /var/log/squid/access.log file When I looked to /var/log/squid/ folder, I noticed that it contains some rotated logs: root@proxy-server:~# ls /var/log/squid/ access.log access.log.1 cache.log cache.log.1 store.log store.log.1 So maybe sarg installed logrotate with it? Or it comes with the standard Ubuntu? I don't remember I installed it manuallly. The question is: What could've gone wrong? Does it have something to do with rotating the log? How can I trace the error and start generating reports again?

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• PHP Sessions suddenly not working

  - by styrken

  Out of no where my php sessions does not work anymore. The server have been running fine for several months. I'am running Ubuntu 11.10 (GNU/Linux 3.0.0-14-server x86_64) with nginx/1.0.11 and php 5.3.19-1~dotdeb.0 Session info copied from phpinfo() Session Support enabled Registered save handlers files user memcached Registered serializer handlers php php_binary wddx Directive Local Value Master Value session.auto_start Off Off session.bug_compat_42 Off Off session.bug_compat_warn Off Off session.cache_expire 180 180 session.cache_limiter nocache nocache session.cookie_domain no value no value session.cookie_httponly Off Off session.cookie_lifetime 0 0 session.cookie_path / / session.cookie_secure Off Off session.entropy_file no value no value session.entropy_length 0 0 session.gc_divisor 1000 1000 session.gc_maxlifetime 1440 1440 session.gc_probability 0 0 session.hash_bits_per_character 5 5 session.hash_function 0 0 session.name PHPSESSID PHPSESSID session.referer_check no value no value session.save_handler files files session.save_path /tmp /tmp session.serialize_handler php php session.use_cookies On On session.use_only_cookies On On session.use_trans_sid 0 0 I have setup the following php script to test with: error_reporting(E_ALL); ini_set('display_errors', true); error_log($_SERVER['REMOTE_ADDR'] . ' visited test page'); if(session_start()) echo "Session started <br />"; else echo "Session failed <br />"; echo '<a href="?', time(), '">refresh</a>', "\n"; echo '<pre>'; echo 'session id: ', session_id(), "\n"; $sessionfile = ini_get('session.save_path') . '/' . 'sess_'.session_id(); echo 'session file: ', $sessionfile, ' '; if ( file_exists($sessionfile) ) { echo 'size: ', filesize($sessionfile), "\n"; echo '# ', file_get_contents($sessionfile), ' #'; } else { echo ' does not exist'; } echo PHP_EOL; $_SESSION['number'] = (int) @$_SESSION['number'] + 1; var_dump($_SESSION); echo "</pre>\n"; session_write_close(); echo 'done.'; It tells me that the session file exists, but my session id changes on each refresh.. What is going wrong? There is no output to any error logs at all.. :/ Please help!

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• Thinkpad speaker turns mute - Linux Codec issue?

  - by Curlew

  At some point a few days ago the speakers on my Lenovo Thinkpad T410 (Model number: 2537A11) suddenly stopped working randomly. This error happens every time I watch a video or listen to a music file. The sound just abruptly stops. At the moment, I can't produce a single sound no matter what I do. I am using Debian GNU/Linux on this laptop and there doesn't appear to be anything else wrong (the fan is working, no abnormal heat (staying around ~40°C), no other obvious errors or problems). Here is the output of a nice program someone pointed me to: martin@martin:~/Downloads$ sudo python run.py --monitor Using temporary directory: /dev/shm/hda-analyzer You may remove this directory when finished or if you like to download the most recent copy of hda-analyzer tool. Downloading file hda_analyzer.py Downloading file hda_guilib.py Downloading file hda_codec.py Downloading file hda_proc.py Downloading file hda_graph.py Downloading file hda_mixer.py Downloaded all files, executing hda_analyzer.py Watching 1 cards ====================================== Sound is working normally and then it stops and the following lines appear: Diff for codec 0/0 (0x14f15069): --- +++ @@ -164,17 +164,17 @@ Power: setting=D0, actual=D0 Node 0x1f [Pin Complex] wcaps 0x400501: Stereo Pincap 0x00000010: OUT Pin Default 0x901701f0: [Fixed] Speaker at Int N/A Conn = Analog, Color = Unknown DefAssociation = 0xf, Sequence = 0x0 Misc = NO_PRESENCE Pin-ctls: 0x40: OUT - Power: setting=D0, actual=D0 + Power: setting=D3, actual=D3 Connection: 2 0x10* 0x11 Node 0x20 [Pin Complex] wcaps 0x400781: Stereo Digital Pincap 0x00000010: OUT Pin Default 0x40f001f0: [N/A] Other at Ext N/A Conn = Unknown, Color = Unknown DefAssociation = 0xf, Sequence = 0x0 Misc = NO_PRESENCE And now there is also an error in the dmesg output hda-intel: IRQ timing workaround is activated for card #0. Suggest a bigger bdl_pos_adj. I changed the bdl_pos_adj to various numbers (-1, 0, 64, 1024) and either there is no change at all or dmesg reports that the adjustment is too big. I wonder if this bdl_pos_adj is the real reason for the error. Here is my hardware information provided by alsa-info.sh website. Okay, i did some serious testing and even installed Windows and now i officially conclude that this is a hard-ware related issue with my Laptop speakers. Reason: The error occurs in my installed Debian Linux, an Ubuntu Live distribution and Windows XP No error-message appears in all of the OS. The sound just keeps running and i can't hear a thing. I tested different setups, including OSS, ALSA and the pulseaudio server on top If i use my new usb-headphones i can hear sound all the time without any sudden silences. So obviously, although hard to believe, my laptop speakers are not okay (never heard of similar cases). I'll award the bounty to anyone who can point me to good tutorials or the procedure how to exchange my T410 speakers (i still have warranty. The laptop was bought in Germany, but now i am in Denmark). Or to someone who can explain me the output from hda-analyzer (big log above).

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• Can't validate mine, sudo nor root in Debian "Jessie" Gnome anymore?

  - by Janar

  I'm Debian beginner & GUI guy in a bit of trouble? Can't login as sudo/gksu/root/su nor as (main/super)user after removed user password via Gnome-user-settings. History of actions (Probably irrelevant though) Installed Debian "Jessie" GNU/Linux with xFce GUI (en-US) as only OS. HardWare is ThinkPad w510. Skipped root user password in setup, to get sudo for superuser easily. Logged in (as always had) with Gnome (3.4.x), not once with xFCE. (installed Xfce. Installed xFce only to achieve more control (easier management) over packages this way, to set-up gnome much more by mine likes. Added more jessie repros (same ones as in Wheesy stable by default but for Jessie as, Jessie only had repros for security updates by default). Installed lots of gtk(3) & gnome(3) based soft; (- restarted again after this) Installed propietary graphics card driver for mine nvidia quadro. (- restarted once again after that one) Installed more stuff related to mine work/school/devel. The actual problem Had a plan to restart again, but wanted to set up auto-login first, instead set user password to none (don't ask why / perhaps caused by being awake for a looooong time), noticed it, and set also to auto-login, but couldn't undo mine previous mistake to create new password for me. As mine password is set to none I would have expected that simply return in pass prompt for emty password field would do, but it won't authenticate. I tried Alt+F2 "gksu gedit" as well as: sudo wget "https://www.some-page.eu/file.ext" and "su" in terminals, none has applied (quite logical actually - as I'm sudoer and highest ranked super user, besides only user in computer). Current stand Everything worked & still works nice after this accident, besides this password prompts part. To spoked to log-out nor restart. Synaptic package-manager is still open with root rights (only one, that has left open prior to the issue and not closed since, just in case). Goggled for help and read some manuals/faqs/how-tos - mostly lead to sudoers file management, but not found one specifically for mine issue - so still not any smarter. Really hope, that I don't have to redo OS inst all over again, by just one stupid mistake. Thanks for your reply :-)

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• Do You Really Know Your Programming Languages?

  - by Kristopher Johnson

  I am often amazed at how little some of my colleagues know or care about their craft. Something that constantly frustrates me is that people don't want to learn any more than they need to about the programming languages they use every day. Many programmers seem content to learn some pidgin sub-dialect, and stick with that. If they see a keyword or construct that they aren't familiar with, they'll complain that the code is "tricky." What would you think of a civil engineer who shied away from calculus because it had "all those tricky math symbols?" I'm not suggesting that we all need to become "language lawyers." But if you make your living as a programmer, and claim to be a competent user of language X, then I think at a minimum you should know the following: Do you know the keywords of the language and what they do? What are the valid syntactic forms? How are memory, files, and other operating system resources managed? Where is the official language specification and library reference for the language? The last one is the one that really gets me. Many programmers seem to have no idea that there is a "specification" or "standard" for any particular language. I still talk to people who think that Microsoft invented C++, and that if a program doesn't compile under VC6, it's not a valid C++ program. Programmers these days have it easy when it comes to obtaining specs. Newer languages like C#, Java, Python, Ruby, etc. all have their documentation available for free from the vendors' web sites. Older languages and platforms often have standards controlled by standards bodies that demand payment for specs, but even that shouldn't be a deterrent: the C++ standard is available from ISO for $30 (and why am I the only person I know who has a copy?). Programming is hard enough even when you do know the language. If you don't, I don't see how you have a chance. What do the rest of you think? Am I right, or should we all be content with the typical level of programming language expertise? Update: Several great comments here. Thanks. A couple of people hit on something that I didn't think about: What really irks me is not the lack of knowledge, but the lack of curiosity and willingness to learn. It seems some people don't have any time to hone their craft, but they have plenty of time to write lots of bad code. And I don't expect people to be able to recite a list of keywords or EBNF expressions, but I do expect that when they see some code, they should have some inkling of what it does. Few people have complete knowledge of every dark corner of their language or platform, but everyone should at least know enough that when they see something unfamiliar, they will know how to get whatever additional information they need to understand it.

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• Why is domU faster than dom0 on IO?

  - by Paco

  I have installed debian 7 on a physical machine. This is the configuration of the machine: 3 hard drives using RAID 5 Strip element size: 1M Read policy: Adaptive read ahead Write policy: Write Through /boot 200 MB ext2 / 15 GB ext3 SWAP 10GB LVM rest (~500GB) emphasized text I installed postgresql, created a big database (over 1GB). I have an SQL request that takes a lot of time to run (a SELECT statement, so it only reads data from the database). This request takes approximately 5.5 seconds to run. Then, I installed XEN, created a domU, with another debian distro. On this OS, I also installed postgresql, with the same database. The same SQL request takes only 2.5 seconds to run. I checked the kernel on both dom0 and domU. uname-a returns "Linux debian 3.2.0-4-amd64 #1 SMP Debian 3.2.41-2+deb7u2 x86_64 GNU/Linux" on both systems. I checked the kernel parameters, which are approximately the same. For those that are relevant, I changed their values to make them match on both systems using sysctl. I saw no changes (the requests still take the same amount of time). After this, I checked the file systems. I used ext3 on domU. Still no changes. I installed hdparm, and ran hdparm -Tt on both systems, on all my partitions on both systems, and I get similar results. Now, I am stuck, I don't know what is different, and what could be the cause of such a big difference. Additional Info: Debian runs on a Dell server PowerEdge 2950 postgresql: 9.1.9 (both dom0 and domU) xen-linux-system: 3.2.0 xen-hypervisor: 4.1 Thanks EDIT: As Krzysztof Ksiezyk suggested, it might be due to some file caching system. I ran the dd command to test both the read and write speed. Here is domU: root@test1:~# dd if=/dev/zero of=/root/dd count=5MB bs=1MB ^C2020+0 records in 2020+0 records out 2020000000 bytes (2.0 GB) copied, 18.8289 s, 107 MB/s root@test1:~# dd if=/root/dd of=/dev/null count=5MB bs=1MB 2020+0 records in 2020+0 records out 2020000000 bytes (2.0 GB) copied, 15.0549 s, 134 MB/s And here is dom0: root@debian:~# dd if=/dev/zero of=/root/dd count=5MB bs=1MB ^C1693+0 records in 1693+0 records out 1693000000 bytes (1.7 GB) copied, 8.87281 s, 191 MB/s root@debian:~# dd if=/root/dd of=/dev/null count=5MB bs=1MB 1693+0 records in 1693+0 records out 1693000000 bytes (1.7 GB) copied, 0.501509 s, 3.4 GB/s What can be the cause of this caching system? And how can we "fix" it? Can we apply it to dom0? EDIT 2: I switched my virtual disk type. To do so I followed this article. I did a dd if=/dev/vg0/test1-disk of=/mnt/test1-disk.img bs=16M Then in /etc/xen/test1.cfg, I changed the disk parameter to use file: instead of phy: it should have removed the file caching, but I still get the same numbers (domU being much faster for Postgres)

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• tc rules block traffic from some hosts at network

  - by user139430

  I have a problem I can not solve. The script, which sets the rules for traffic shaping is blocking the traffic from some hosts.If I remove all the rules, then it works. I can not understand why? Here is my script... #!/bin/sh cmdTC=/sbin/tc rateLANDl="60mbit" ceilLANDl="60mbit" rateLANUl="40mbit" ceilLANUl="40mbit" quantLAN="1514" # Nowaday bandwidth limit set to 100mbit. # We devide it with 60mbit download and 40mbit upload bandthes. rateHiDl="30mbit" ceilHiDl="60mbit" rateHiUl="20mbit" ceilHiUl="40mbit" quantHi="1514" rateLoDl="30mbit" ceilLoDl="60mbit" rateLoUl="20mbit" ceilLoUl="40mbit" quantLo="1514" devNIF=eth0 devFIF=ifb0 modprobe ifb ip link set $devFIF up 2>/dev/null #exit 0 ################################################################################################ # Remove discuiplines from network and fake interfaces ################################################################################################ $cmdTC qdisc del dev $devNIF root 2>/dev/null $cmdTC qdisc del dev $devFIF root 2>/dev/null $cmdTC qdisc del dev $devNIF ingress 2>/dev/null if [ "$1" = "down" ]; then exit 0 fi ################################################################################################ # Create discuiplines for network interface ################################################################################################ $cmdTC qdisc add dev $devNIF root handle 1:0 htb default 12 # Create classes for network interface $cmdTC class add dev $devNIF parent 1:0 classid 1:1 htb rate ${rateLANDl} ceil ${ceilLANDl} quantum ${quantLAN} $cmdTC class add dev $devNIF parent 1:1 classid 1:11 htb rate ${rateHiDl} ceil ${ceilHiDl} quantum ${quantHi} $cmdTC class add dev $devNIF parent 1:1 classid 1:12 htb rate ${rateLoDl} ceil ${ceilLoDl} quantum ${quantLo} $cmdTC qdisc add dev $devNIF parent 1:11 handle 111: sfq perturb 10 $cmdTC qdisc add dev $devNIF parent 1:12 handle 112: sfq perturb 10 # Create filters for network interface $cmdTC filter add dev $devNIF protocol all parent 1:0 u32 match ip dst 10.252.2.0/24 flowid 1:11 $cmdTC filter add dev $devNIF protocol all parent 111: handle 111 flow hash keys dst divisor 1024 baseclass 1:11 $cmdTC filter add dev $devNIF protocol all parent 112: handle 112 flow hash keys dst divisor 1024 baseclass 1:12 ################################################################################################ # Create discuiplines for fake interface ################################################################################################ $cmdTC qdisc add dev $devFIF root handle 1:0 htb default 12 # Create classes for network interface $cmdTC class add dev $devFIF parent 1:0 classid 1:1 htb rate ${rateLANUl} ceil ${ceilLANUl} quantum ${quantLAN} $cmdTC class add dev $devFIF parent 1:1 classid 1:11 htb rate ${rateHiUl} ceil ${ceilHiUl} quantum ${quantHi} $cmdTC class add dev $devFIF parent 1:1 classid 1:12 htb rate ${rateLoUl} ceil ${ceilLoUl} quantum ${quantLo} $cmdTC qdisc add dev $devFIF parent 1:11 handle 111: sfq perturb 10 $cmdTC qdisc add dev $devFIF parent 1:12 handle 112: sfq perturb 10 # Create filters for network interface $cmdTC filter add dev $devFIF protocol all parent 1:0 u32 match ip src 10.252.2.0/24 flowid 1:11 $cmdTC filter add dev $devFIF protocol all parent 111: handle 111 flow hash keys src divisor 1024 baseclass 1:11 $cmdTC filter add dev $devFIF protocol all parent 112: handle 112 flow hash keys src divisor 1024 baseclass 1:12 ################################################################################################ # Create redirect discuiplines from network to fake interface ################################################################################################ $cmdTC qdisc add dev $devNIF handle ffff:0 ingress $cmdTC filter add dev $devNIF parent ffff:0 protocol all u32 match u32 0 0 action mirred egress redirect dev $devFIF Here is my /etc/modules: loop ifb ppp_mppe nf_conntrack_pptp nt_conntrack_proto_gre nf_nat_pptp nf_nat_proto_gre The system is Linux wall 2.6.32-5-amd64 #1 SMP Sun Sep 23 10:07:46 UTC 2012 x86_64 GNU/Linux

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• Are there any modern GUI toolkits which implement a heirarchical menu buffer zone?

  - by scomar

  In Bruce Tognazzini's quiz on Fitt's Law, the question discussing the bottleneck in the hierarchical menu (as used in almost every modern desktop UI), talks about his design for the original Mac: The bottleneck is the passage between the first-level menu and the second-level menu. Users first slide the mouse pointer down to the category menu item. Then, they must carefully slide the mouse directly across (horizontally) in order to move the pointer into the secondary menu. The engineer who originally designed hierarchicals apparently had his forearm mounted on a track so that he could move it perfectly in a horizontal direction without any vertical component. Most of us, however, have our forarms mounted on a pivot we like to call our elbow. That means that moving our hand describes an arc, rather than a straight line. Demanding that pivoted people move a mouse pointer along in a straight line horizontally is just wrong. We are naturally going to slip downward even as we try to slide sideways. When we are not allowed to slip downward, the menu we're after is going to slam shut just before we get there. The Windows folks tried to overcome the pivot problem with a hack: If they see the user move down into range of the next item on the primary menu, they don't instantly close the second-level menu. Instead, they leave it open for around a half second, so, if users are really quick, they can be inaccurate but still get into the second-level menu before it slams shut. Unfortunately, people's reactions to heightened chance of error is to slow down, rather than speed up, a well-established phenomenon. Therefore, few users will ever figure out that moving faster could solve their problem. Microsoft's solution is exactly wrong. When I specified the Mac hierarchical menu algorthm in the mid-'80s, I called for a buffer zone shaped like a <, so that users could make an increasingly-greater error as they neared the hierarchical without fear of jumping to an unwanted menu. As long as the user's pointer was moving a few pixels over for every one down, on average, the menu stayed open, no matter how slow they moved. (Cancelling was still really easy; just deliberately move up or down.) This just blew me away! Such a simple idea which would result in a huge improvement in usability. I'm sure I'm not the only one who regularly has the next level of a menu slam shut because I don't move the mouse pointer in a perfectly horizontal line. So my question is: Are there any modern UI toolkits which implement this brilliant idea of a < shaped buffer zone in hierarchical menus? And if not, why not?!

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• Linux clock loses 10 minutes every week

  - by PaKempf

  One of my linux server's clock loses 10 minutes every now and then, nearly every week. I update the time so it stays correct, and although it doesn't really bother me, i'd like to fix it. I've been searching around a bit. Nothing can be responsible in the crontab, and i can't find any related message in the logs. Some people seem to use ntp to fix that kind of issue, but i'd prefer not to use an unecessary component on it. Uname result : Linux unis-monitor 2.6.32-5-686 #1 SMP Mon Feb 25 01:04:36 UTC 2013 i686 GNU/Linux Cat message : cat messages Jul 14 06:25:06 unis-monitor rsyslogd: [origin software="rsyslogd" swVersion="4.6.4" x-pid="882" x-info="http://www.rsyslog.com"] rsyslogd was HUPed, type 'lightweight'. Jul 15 06:25:05 unis-monitor rsyslogd: [origin software="rsyslogd" swVersion="4.6.4" x-pid="882" x-info="http://www.rsyslog.com"] rsyslogd was HUPed, type 'lightweight'. Cat syslog cat syslog Jul 15 06:25:05 unis-monitor rsyslogd: [origin software="rsyslogd" swVersion="4.6.4" x-pid="882" x-info="http://www.rsyslog.com"] rsyslogd was HUPed, type 'lightweight'. Jul 15 06:39:01 unis-monitor /USR/SBIN/CRON[15272]: (root) CMD ( [ -x /usr/lib/php5/maxlifetime ] && [ -d /var/lib/php5 ] && find /var/lib/php5/ -type f -cmin +$(/usr/lib/php5/maxlifetime) -delete) Jul 15 07:09:01 unis-monitor /USR/SBIN/CRON[15465]: (root) CMD ( [ -x /usr/lib/php5/maxlifetime ] && [ -d /var/lib/php5 ] && find /var/lib/php5/ -type f -cmin +$(/usr/lib/php5/maxlifetime) -delete) Jul 15 07:17:01 unis-monitor /USR/SBIN/CRON[15521]: (root) CMD ( cd / && run-parts --report /etc/cron.hourly) Jul 15 07:39:01 unis-monitor /USR/SBIN/CRON[15662]: (root) CMD ( [ -x /usr/lib/php5/maxlifetime ] && [ -d /var/lib/php5 ] && find /var/lib/php5/ -type f -cmin +$(/usr/lib/php5/maxlifetime) -delete) Jul 15 08:09:01 unis-monitor /USR/SBIN/CRON[15855]: (root) CMD ( [ -x /usr/lib/php5/maxlifetime ] && [ -d /var/lib/php5 ] && find /var/lib/php5/ -type f -cmin +$(/usr/lib/php5/maxlifetime) -delete) Jul 15 08:17:01 unis-monitor /USR/SBIN/CRON[15911]: (root) CMD ( cd / && run-parts --report /etc/cron.hourly) Jul 15 08:39:01 unis-monitor /USR/SBIN/CRON[16052]: (root) CMD ( [ -x /usr/lib/php5/maxlifetime ] && [ -d /var/lib/php5 ] && find /var/lib/php5/ -type f -cmin +$(/usr/lib/php5/maxlifetime) -delete) Jul 15 09:09:01 unis-monitor /USR/SBIN/CRON[16273]: (root) CMD ( [ -x /usr/lib/php5/maxlifetime ] && [ -d /var/lib/php5 ] && find /var/lib/php5/ -type f -cmin +$(/usr/lib/php5/maxlifetime) -delete) So if you have any clue of where to look or what i could use to monitor those date change ? Here is some more infos : the server is a virtual server hosted on HyperV on a win 2012 server. Don't know if it changes anything, seen the other servers hosted don't have this issue...

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• Why is Linux choosing the wrong source ip address

  - by Scheintod

  and what to do to let it choose the right one? This all happens inside an OpenVZ container: The Host is Debian/Wheezy with Redhat/OpenVZ Kernel: root@mycl2:~# uname -a Linux mycl2 2.6.32-openvz-042stab081.5-amd64 #1 SMP Mon Sep 30 16:40:27 MSK 2013 x86_64 GNU/Linux The container has two (virtual) network interfaces. One in public and one in private address-space: root@mycl2:~# ifconfig lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) venet0 Link encap:UNSPEC HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00 inet addr:127.0.0.2 P-t-P:127.0.0.2 Bcast:0.0.0.0 Mask:255.255.255.255 UP BROADCAST POINTOPOINT RUNNING NOARP MTU:1500 Metric:1 RX packets:475 errors:0 dropped:0 overruns:0 frame:0 TX packets:775 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:32059 (31.3 KiB) TX bytes:56309 (54.9 KiB) venet0:0 Link encap:UNSPEC HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00 inet addr:80.123.123.29 P-t-P:80.123.123.29 Bcast:80.123.123.29 Mask:255.255.255.255 UP BROADCAST POINTOPOINT RUNNING NOARP MTU:1500 Metric:1 venet0:1 Link encap:UNSPEC HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00 inet addr:10.0.1.29 P-t-P:10.0.1.29 Bcast:10.0.1.29 Mask:255.255.255.255 UP BROADCAST POINTOPOINT RUNNING NOARP MTU:1500 Metric:1 The route to the private network is set manually: root@mycl2:~# route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 10.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0 venet0 0.0.0.0 0.0.0.0 0.0.0.0 U 0 0 0 venet0 Tring to ping others on the private network leads to the wrong source address been choosen: root@mycl2:~# ip route get 10.0.1.26 10.0.1.26 dev venet0 src 80.123.123.29 cache mtu 1500 advmss 1460 hoplimit 64 Why is this and what can I do about it? EDIT: If I create the route with (thanks to Joshua) ip route add 10.0.0.0/8 dev venet0 src 10.0.1.29 it is working. But according to man ip-route the src parameter should only set the source-ip if this route is chosen. But if this route is chosen then the source-ip would be that anyway.

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• What server setup for a small web development company? [closed]

  - by Giordano

  I co-own a company with a friend of mine and we have decided to buy a new server to support our business (our current server is an Asus EEE Box, working great but too limited :) ). I should mention that we are web developers but occasionally we do small-office sys admin. Thus, 99% of time we work on GNU/Linux (mainly Ubuntu) but from time to time we need to setup a Windows environment to assist some customers (e.g. setup a temporary SQL Server 2008). Our requirements: Low budget: we don't want the cheapest solution out there but we can't afford to spend too much. Budget could be ~1000-1500€ (before VAT) Robustness: we would like to setup a RAID array and maybe have an external disk where we can store backups Virtualization: we need to be able to setup few servers for development. The scenario is something like this (~8 appliances running in parallel): Redmine + GIT server Bacula server FTP server 3-4 virtual appliances that could be set up on demand to test our applications or support a customer. The appliances could be: LAMP, Tomcat+PostgreSQL, SQL Server Support: if something breaks down it shouldn't be too difficult to find a replacement. Now, given the main requirements, there are some doubts we need to clarify: Do you suggest to buy a prepackaged solution (for example a customized Dell PowerEdge T110 or T310) or to assemble the server by ourselves (buy the separate components)? What RAID configuration do you suggest? I was thinking of RAID1 (probably cheaper) or RAID5. should we buy a hardware RAID controller or is it ok to use a software RAID (mdadm)? In case, which controller do you suggest? What processor do you suggest (Intel Xeon, i3, i5, i7, AMD)? How much RAM? (I was thinking at least 8GB, ~1GB per appliance) What virtualization software do you recommend? VMWare seems to be the best choice, but what about XEN or KVM? We don't want to buy licenses at the moment so we would like to consider only free options. What OS do you recommend? We know Ubuntu, Debian, Gentoo very well (we would like to use Ubuntu Server), however it seems a lot of people goes for CentOS. Thanks in advance if you can help us with this! It's our first "serious" server so many doubts popped up :) Please feel free to add further recommendations if you have some to share ;) Have a nice day

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