/ - rtt - IT Resource

  • MySQL Using mytop Debug Source of High IO and Slow Performance


    mytop is one of my favorite tools and it is fairly simple aside from a few caveats and issues that persist to this day. To install it on Centos: yum -y install centos Configure ~/.mytop vi ~/.mytop user=root host=localhost db=test #port=3306 socket=/var/lib/mysql/mysql.sock header=1 color=1 Try runni........
  • systemd management using systemctl and journalctl to check systemd logs


    systemd is like the service manager for your Centos and other modern Linux distributions (including Debian/Mint/Ubuntu) allows you to enable services, stop them, restart them, check their status and even reboot your system. The key commands or arguments you will use with systemctl are the following: Unit Commands:   list-units [PATTERN...]         List loaded units &nbs........
  • Centos 7 python34 how to install the gi library


    Getting an error about gi missing when running a .py python script? Just install EPEL and install the python3-gobject package:  yum install python34-gobject........
  • Centos 7 - Convert Minimal to Graphical GUI GNOME or KDE Desktop


    Did you just install the minimal version by accident or want to install the GUI?  No need to reinstall just tell yum to do the work for you! You could actually have both installed and choose one as your preference on demand (although many people prefer GNOME's simplicity). Step 1.) Install Gnome and/or KDE. To install the GNOME Desktop on Centos 7: yum -y groups install "GNOME Desktop" To........
  • zenity popup messages, windows, dialogs, error messages calendars and more howto on Gnome Linux including Ubuntu, Linux Mint, Centos and more


    zenity is a nice utility as part of the gnome window manager that allows you to script from bash and retrieve the input from the user.  It could also be helpful in just notifying a user when they login with a popup window. I'll give an overview of what's available with zenity:   Application Options: --calendar Display calendar dialog --entry Display tex........
  • Linux How To Rename Files


    To remove all spaces from all files in the current directory linux rename remove spaces rename "s/ //g" * The above won't work in Centos but in Debian based distros as rename in Centos doesn't work that way. See this more comprehensive article.........
  • Linux Centos 7 HowTo Install Yarn


    https://yarnpkg.com/lang/en/docs/install/#centos-stable   curl --silent --location https://dl.yarnpkg.com/rpm/yarn.repo | tee /etc/yum.repos.d/yarn.repo If you need node.js: curl --silent --location https://rpm.nodesource.com/setup_6.x | bash - yum install nodejs yarn........
  • Centos 7 - How To Install NFS and Mount Remotely


    1.) First install nfs-utils [root@bcitcourse ~]# yum -y install nfs-utils Loaded plugins: fastestmirror base                                                         &n........
  • named [FAILED] - zone 1.168.192.in-addr.arpa/IN: not loaded due to errors. - bind error solution


    Centos when copying old files and restarting it seems load everything fine and then says [FAILED] with no log or other message. service restart named named   [FAILED] Check more thoroughly you may have missed the error if you have lots of zones!  service named restart|grep error zone 1.168.192.in-addr.arpa/IN: not loaded due to errors. zone 2.168.192.in-addr.arpa/IN: no........
  • No comments are allowed here Internal Server Error The server encountered an internal error or misconfiguration and was unable to complete your request.


    Internal Server Error The server encountered an internal error or misconfiguration and was unable to complete your request. Please contact the server administrator, root@localhost and inform them of the time the error occurred, and anything you might have done that may have caused the error. More information about this error may be available in the server error log. Apache/2.2.15 (CentOS) Server at testdomain.com Port 80........
  • Centos PXEBoot NetInstall Failure - Pane is dead


    ValueError: new value non-existent xfs filesystem is not valid as a default fs type Pane is dead From what I read this is misleading and has to do with the fact that the initrd and kernel are mismatched. This is a hard situation because for some older hardware I am using the Centos Plus kernel which has modules that I require for an older server/NIC.  This seems to have cropped up in the past few months and there is no simple fix........
  • Intel NUC J3455 Linux Kernel freeze slowness 4.4.98 errors


    It looks like this has something to do with APIC but I am not sure.  I have similar CPUs with a different MB and BIOS that work fine on the same type of kernel.  A lot of time the issue is because of the C-step setting in the BIOS. The same thing happened on the 2.6 kernel with Centos 6 but this is a homebrew 4.4 kernel so I am not sure why it is happening when even Centos 7 (3.2) kernel works OK. Solution - It comes down to the BIOS set........
  • How To Turn Any .iso file into a bootable USB drive


    This works for almost all ISO's I find (at least Linux based): sudo dd if=CentOS-6.9-x86_64-minimal.iso of=/dev/sdg bs=20M 20+1 records in 20+1 records out 427819008 bytes (428 MB) copied, 118.233 s, 3.6 MB/s   Of course change the .iso filename above and the /dev/sdg to your desired USB drive!........
  • curl: (35) Unknown SSL protocol error in connection Solution Centos


    curl: (35) Unknown SSL protocol error in connection The main solution is to update curl and nss.  If you are having an issue with curl through Apache/PHP you will need to restart PHP after. It's important to remember that this error could mean a lot of things but most often it simply means that curl and openssl may be outdated and only allow newer secure ways of connecting to SSL. In general here is how you would fix it in most c........
  • Unable to load dynamic library '/usr/lib64/php/modules/module.so' - /usr/lib64/php/modules/module.so: cannot open shared object file: No such file or directory in Unknown on line 0


    Getting this error on Centos 6 with PHP 5.3 when just running "php -v"   PHP Warning:  PHP Startup: Unable to load dynamic library '/usr/lib64/php/modules/module.so' - /usr/lib64/php/modules/module.so: cannot open shared object file: No such file or directory in Unknown on line 0 PHP Warning:  Cannot load module 'XCache' because conflicting module 'apc' is already loaded in Unknown on line 0 Solution:........
  • Centos 7 Password Reset


    In Centos 7 the days of editing the "kernel" line and adding "single" are gone.  On top of that sometimes after a new install passwords do not work (possibly because requirements were not met but the installer never mentioned this?). 1.) On bootup edit the bootline by entering GRUB. Type e Find the line that says "linux16 /vmlinuz" Edit the part that says "ro" and change with &q........
  • MySQL Cannot Update/Write to any database table solution


    This happened on Centos for no apparent reason with no obvious issue in the logs.  Data could be read fine but not written (possibly due to some corruption or out of memory issue in the OpenVZ container is the best guess).   All mysql update and insert queries failed freezing without any error log on any database and table. Tried to restart: service mysqld restart Timeout error occurred trying to stop MySQL........
  • Centos How To Update to Glibc 2.14 Plus


    Centos 6 requires GLIBC 2.12 however a lot of new programs you would want to compile may need a newer glibc.  You can't remove the old glibc since the whole OS is based on it but you can install the updated glibc alongside it and do an export pointing to your updated GLIBC. mkdir ~/glibc_install; cd ~/glibc_install wget http://ftp.gnu.org/gnu/glibc/glibc-2.14.tar.gz........
  • GCC 5 on Centos 6 - How To Install


    Install requirements: yum -y install gmp-devel mpfr-devel libmpc-devel glibc-devel glibc-devel.i686 zip unzip jar   Download, untar, configure, compile and install GCC http://mirrors.kernel.org/gnu/gcc/gcc-5.5.0/gcc-5.5.0.tar.gz tar -zxvf gcc-5.5.0.tar.gz cd gcc-5.5.0 ./configure make make install Now you need to cleanup th........
  • yum how to install old obsolete packages


    This is important as unfortunately Centos may designate a package obsolete and the replacement breaks everything (eg. you have a config file and the new replacement is not at all compatible with it and it breaks your application). This is where disabling obsoletes comes into play, it can be done from yum but it doesn't work at the time I find. yum --setopt=obsoletes=0 install someapp However I find it still installs the new app and not the one you ask for........
  • M2Crypto.SSL.Checker.WrongHost: Peer certificate subjectAltName does not match host, expected fedora-archive.ip-connect.vn.ua, got DNS:mirror.ip-connect.vn.ua


    You are using Centos 5 which is deprecated so nothing in yum will work until you follow this post to use the vault: http://realtechtalk.com/Centos_59_Working_Vault_Repo_file-1921-articles yum update Loaded plugins: fastestmirror Loading mirror speeds from cached hostfile  * epel: fedora-archive.ip-connect.vn.ua Traceback........
  • Centos 5.9 Working Vault Repo file


    Centos 5 is not supported running yum will produce an error like this: YumRepo Error: All mirror URLs are not using ftp, http[s] or file.  Eg. Invalid release/ removing mirrorlist with no valid mirrors: /var/cache/yum/base/mirrorlist.txt Error: Cannot find a valid baseurl for repo: base Solution - Update this file CentOS-Base.repo   # CentOS-Base.repo........
  • Disable SSH Password Authentication to Increase Security and Harden SSH Linux Unix Server Ubuntu Mint Centos Debian


    Just a note before you do this you should have a sure, guaranteed way into the system such as local, KVM or preferably publickey making bruteforce SSH absolutely impossible since there is no password to bruteforce and even if someone knew the password they wouldn't be able to login except from the local console (presumably you should make sure no one unauthorized has physical access). 1. Edit /etc/ssh/sshd_config Find the section like this:........
  • Centos 6.6/6.9 KVM VM Kernel Panic On Boot - Kernel panic - not syncing: Attempted to kill init!


    I am not sure why this is happening neither the hostnode or VM changed.  All I did was reboot the hostnode and startup the Centos VM again, also note it happened with the original kernel on the VM and also the latest 6.9 kernel as of this writing as shown below. Host Node: Centos 6.9 Kernel: 2.6.32-696.6.3.el6.x86_64  Kernel: 2.6.32-042stab123.9 Same result in any kernel above........
  • Centos 7 How To Change Hostname


    Some guides still use the old Centos 6 style (do not use /etc/sysconfig/network). In Centos 7 the file is /etc/hostname echo "HOSTNAME=yourhostname.com" > /etc/hostname........
  • Migrate Centos 7 from Single HDD to mdadm RAID 10 array:


    Done on Centos 7.3 very important as clearly based on older guides it was a lot easier and more simpler!  Hint do not use grub2-install! One huge caveat if you are an oldschool user or sysadmin who has avoided UEFI booting The normal way will not work here if your Centos was using UEFI.  Newer systems use it by default. The easiest way to check is to do an fdisk -l if your sy........
  • Centos 7 A start job is running for dev-mapper-clx2droot.device (8min 44s / no limit)


    This error is usually because of some sort of encryption in this case a Seagate enclosure with encryption (even though not enabled) did not allow this hard drive to boot.........
  • Centos 7 Cudaminer Nvidia setup guide


    I am using a GTX 1060 but replace the download for the driver with the correct/current version for your particular card by visiting: http://www.nvidia.com/Download/index.aspx?lang=en-us   yum install automake curl openssl-devel libcurl-devel gcc gcc-c++ yum -y install kernel-devel-`uname -r` yum -y install unzip #the........
  • Centos/Linux Bash Script Warning when exiting/logging out of bash/shell/terminal for scripts running in the background


    This is mainly the case on Centos but applies to other distros and situations.  If you are running programs in the background with the &, at least in Centos it is usually not honored and if you quit or are disconnected the backgrounded programs will be sent sighup and be shut down.  The simplest way around this instead of using & is to start any programs or commands with "nohup" Eg. nohup yourscript.sh........
  • Apache SSL very slow response with Firefox Freezes/Loads Very slow when checking self-signed SSL certificate


    I was sure this was a Centos bug with OpenSSL, Apache, MySQL or even PHP.  I tried everything but nothing helped.  One clue is that if you check the Apache logs you will see nothing in the access logs until minutes later (this means Firefox has not even passed your request to the remote Apache/htttpd server). When even accepting the invalid certificate message that would show up minutes later when trying to "View the Certificate" Firefox would freeze.  This bu........
  • phpBB3 slow and internal dummy connection


    Using Apache 2.2 and PHP 5.6 PHPBB3 is very slow to respond.  Actually for some reason it takes so long to even register a log entry in access_log as in several seconds or a few minutes later it shows up in Apache.  All other vhosts and Apache access stops working and freezes until the request to access PHPBB3 slowly completes. It seems to randomly be slow if you stop using it whether for posting or reading the forums.  I've migrated to different machines including........
  • Centos 7 Migration Guide from Centos 6


    Centos 7 is no cakewalk, there are many fundamental features and basic utilities that are missing or even completely renamed or different! Another shocking thing is to check your NIC it is set by default to not turn on when booting! And by the way there is no more standard eth0 the NIC convention is now "enp0s3" vi /etc/sysconfig/network-scripts/ifcfg-enp0s3........
  • how to extract .xz file in Linux Centos/Debian/Ubuntu


    tar -xvJf somefile.tar.xz It is very annoying that so many are now using the .xz archive format as standard instead of .tar.gz but nevertheless above is how you would extract it with the "J" flag (not lower case j as that is for bz).........
  • What happens when you unplug 1 or more devices from an mdadm RAID array to simulate a failure in Linux Ubuntu/Centos/Debian?


    In short the two drives in the array were /dev/sdd and /dev/sde.  The kernel sees they were unplugged and have gone down as you can see below. mdadm caught the first one being unplugged /dev/sde and disabled the missing drive.  However when the final drive that was part of the array is unplugged it didn't notice at all.  Instead it complains about an IO error later for drives that the kernel knows do not exist anymore. [45817.162728] ata4: exception........
  • How to Execute PHP in .html files with Apache in Linux Centos/Debian/Ubuntu etc


    Add this to the .htaccess file #right/working: AddType application/x-httpd-php .html .htm   #wrong (won't work in many cases): AddHandler application/x-httpd-php5 .html .htm........
  • Using a proxy with yum in Centos 6


    Could not retrieve mirrorlist http://mirrorlist.centos.org/?release=6&arch=x86_64&repo=os error was 12: Timeout on http://mirrorlist.centos.org/?release=6&arch=x86_64&repo=os: (28, 'Operation too slow. Less than 1 bytes/sec transfered the last 30 seconds') Error: Cannot find a valid baseurl for repo: base You would think this should be fine and simple like using a proxy with most other software? However........
  • How Do you Open/Extract .WARC Internet Archive Files on Linux Ubuntu/Mint/Centos?


    Get the python "warc extractor" from here.  WARC just seems to be such an unnecessary and complicated format.  Why not use tar, rar, zip etc...?   ./warc-extractor.py -dump content !http:content-type:pdf yourfile.warc........
  • Centos 5 OpenSSL does not support TLS 1.2 Apache Error


    [Thu Jan 26 14:13:31 2017] [notice] caught SIGTERM, shutting down [Thu Jan 26 14:14:00 2017] [notice] suEXEC mechanism enabled (wrapper: /usr/sbin/suexec) [Thu Jan 26 14:14:00 2017] [error] Server certificate is expired: 'Server-Cert' [Thu Jan 26 14:14:00 2017] [notice] SSL FIPS mode disabled [Thu Jan 26 14:14:07 2017] [notice] suEXEC mechanism enabled (wrapper: /usr/sbin/suexec) [Thu Jan 26 14:14:07 2017] [error] Server certificate is expired: 'Server-Ce........
  • How to Properly Secure SSL/TLS Apache Settings against Heartbleed Poodle (TLS) Poodle (SSLv3) FREAK BEAST CRIME


    Many users still are not aware but simply patching OpenSSL does not secure you against many known and easy to exploit attacks that will render your encryption useless by an attacker. Use the following setings in /etc/httpd/conf.d/ssl.conf   SSLCipherSuite "EECDH+ECDSA+AESGCM EECDH+aRSA+AESGCM EECDH+ECDSA+SHA384 EECDH+ECDSA+SHA256 EECDH+aRSA+SHA384 EECDH+aRSA+SHA256 EECDH EDH+aRSA !CAMELLIA !SEED !3DES !RC4 !aNULL !eNULL !LOW !MD5 !EXP !PSK !........
  • ioncube loader install howto on PHP/Centos


    Disclaimer, before starting this I do not like ioncube, it is great to protect your source code, but a big pain to setup this extension since it has to be done manually.  Further, fi you do a PHP update ioncube may no longer work, causing important sites or services to not work (I wish authors would take another approach). 1.) Download from here: https://www.ioncube.com/loaders.php 2.) Extract the contents and co........
  • mcp55 NIC not working at boot on Centos 6.6-6.8


    forcedeth 0000:00:08.0: irq 25 for MSI/MSI-X forcedeth 0000:00:08.0: eth0: MSI enabled forcedeth 0000:00:08.0: eth0: no link during initialization ADDRCONF(NETDEV_UP): eth0: link is not ready forcedeth 0000:00:08.0: eth0: link up ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready Dec  1 18:21:32 box15 kernel: forcedeth: Reverse Engineered nForce ethernet driver. Version 0.64. Dec  1 18:21:32 box15 kernel........
  • Centos extremely secure iptables setup


    If you want to make sure only a certain IP can access your server for any service or protocol here is a way to do it (just be sure you have access to the IP(s) mentioned or you will be locked out).   iptables -F iptables -A INPUT -i lo -j ACCEPT iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT iptables -A INPUT -p tcp -s IP.IP.IP.IP -j ACCEPT iptables -A INPUT -j DROP serv........
  • mdadm change wrong device name md127 fix and solution in Linux


    md127 issue, it should be /dev/md3 per mdadm.conf Any time something is mounted as md127 it almost always means there is no entry for this mdadm array in the mdadm.conf in initramfs (which is separate from your actual /etc/mdadm.conf). cat /etc/mdadm.conf ARRAY /dev/md3 metadata=1.2 UUID=b6722845:381cc94e:7a2c5b5f:8e3b7c4f The reason for this is something strange, most Linux OS's bizarrely always keep their own copy of /etc/mdadm.con........
  • grubby fatal error: unable to find a suitable template solution Centos


    vzkernel-2.6.32-042stab116.2.x86_64.rpm                                                                           &n........
  • Linux How To Recover Partition Table from Kernel and Restore Centos/Debian etc..


    We've all done this at some point, you work on the wrong shell window and this was my first time making this mistake but I deleted a partition table in fdisk, recreated it and saved it with "wq" and even ran partprobe!  If you haven't rebooted yet then you can still recover your partition table, otherwise you're in big trouble. Fortunately since it was a live system and in use the kernel still had to use the old table like below:........
  • OpenVZ Migration Hostnode Containers from Centos 5 to Centos 6


    migrating from an old OpenVZ (Centos 5) to new OpenVZ (Centos 6) Also if migrating from 32-bit HN to 64-bit your RAM will probably be much bigger than it should be! 16x bigger eg. 32bit HN:              total       used       free     shared    buffers     cached Mem:&nb........
  • SELinux targeted policy relabel is required


    You may get this after a long time of not rebooting but especially if you have rsync'd a / partition or deployed an image to another VPS or computer, you will often have this issue. The good thing it usually just takes a reboot. Here is more info from Centos........
  • Apache Centos Stopping httpd: [ OK ] Starting httpd: [Wed Jun 29 19:29:44 2016] [warn] _default_ VirtualHost overlap on port 80, the first has precedence [Wed Jun 29 19:29:44 2016] [warn] _default_ Virtual


    Stopping httpd:                                            [  OK  ] Starting httpd: [Wed Jun 29 19:29:44 2016] [warn] _default_ VirtualHost overlap on port 80, the first has precedence [Wed Jun 29 19:29:44 2016] [warn] _default_ VirtualHost overlap on........
  • Script runs fine from shell but not from cron job in Linux/Unix Debian/Ubuntu/Mint/Centos


    Usually the cause is inexplicable because some things just don't work correctly even when calling all commands by their full path. Usually adding the following to your crontab file at the top will fix/solve the issue: SHELL=/bin/sh PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin  ........
  • Centos and obfsproxy install errors


    pip install obfsproxy /usr/lib/python2.6/site-packages/pip/_vendor/requests/packages/urllib3/util/ssl_.py:90: InsecurePlatformWarning: A true SSLContext object is not available. This prevents urllib3 from configuring SSL appropriately and may cause certain SSL connections to fail. For more information, see https://urllib3.readthedocs.org/en/latest/security.html#insecureplatformwarning.   InsecurePlatformWarning You are using pip version 7.1.0, however version 8.1.1 i........
  • There was a problem importing one of the Python modules required to run yum. The error leading to this problem was:


    There was a problem importing one of the Python modules required to run yum. The error leading to this problem was:    No module named yum Please install a package which provides this module, or verify that the module is installed correctly. It's possible that the above module doesn't match the current version of Python, which is: 2.7.9 (default, Apr 21 2016, 16:51:58) [GCC 4.4.7 20120313........
  • find: missing argument to '-mtime'


    This is using find and -mtime in Centos Linux, it simply takes "n" (which is a day) as a number and you can specifiy a + or - to say older or less than a certain age. # (show everything older than 1 day) find . -mtime +1  ........
  • Cannot load /etc/httpd/modules/mod_file_cache.so into server: /etc/httpd/modules/mod_file_cache.so:


    Stopping httpd:                                            [FAILED] Starting httpd: httpd: Syntax error on line 73 of /etc/httpd/conf/httpd.conf: Cannot load /etc/httpd/modules/mod_file_cache.so into server: /etc/httpd/modules/mod_file_cache.so: cannot open shared obje........
  • Error: database disk image is malformed - yum error solution and fix


    I got this when running yum on a Centos 6 machine: Error: database disk image is malformed It was easily fixed with the following command: yum clean all........
  • Linux Debian/Ubuntu/Centos How To Force Internet Traffic Through PPTP L2TP OpenVPN Account Only


    The following assumes the computer is local/physical to you and/or it always has a LAN IP so it can be accessed on site without having a default gateway. The key to this is not to set a default gateway for your computer or you can set a script on boot or other time to delete the gateway (where eth0 is the NIC you are using): route del default eth0 50.80.20.2 is the VPN server you connect to 192.168.1.1 is your........
  • Mount a SMB Samba share in fstab Linux Debian/Ubuntu/Centos


    Add the following to fstab where 192.168.1.125/Media is the samba share and where /home/homeuser/Downloads is where you want to mount. Change user and pass to what is needed (if no pass is required it still works fine with the below). //192.168.1.125/Media /home/homeuser/Downloads cifs        user=guest,pass=bla 0 0 mount: wrong fs type, bad option, bad superblock on //192.168.1.125/Media, &nbs........
  • Centos Add Multiple IP Addresses in a range without manually setting each static IP


    This is actually very simple and this example assumes your network device is "eth0" In Centos your network config would be the following: /etc/sysconfig/network-scripts/ifcfg-eth0 Take the same path and just add a "-range0" So to add a range create the following file: /etc/sysconfig/network-scripts/ifcfg-eth0-range0 IPADDR_START=192.168.1.50 IPADD........
  • Centos installing grub problems suspect gpt problem


    grub> root (hd0,0) root (hd0,0)  Filesystem type is ext2fs, partition type 0xfd grub> setup (hd0) setup (hd0) But if you do: root (hd1,0) setup (hd1) it does work, I think hd0/sda had a GPT partition that was not removed properly (what I did was just dd bs=512 count=1 the partition table from another drive since the partition table should be identical).  Checking if "/boot/grub/........
  • linux bash mass rename tool Centos/Debian/Ubuntu


    Say you have a bunch of files like this: file-01.jpg file-02.jpg ............... What if you want to mass rename them? the rename tool can work just like sed For Debian based distros: Note "file" is what we search for and "newname" is what we replace it with, so substitute according to your requirements. rename s/file/newname/ name-file-*.jpg For R........
  • How to manually mount Linux disk image partition without using losetup


    In this case we want to mount partition #2 fdisk -lu Centos-6.6-x86_64.img You must set cylinders. You can do this from the extra functions menu. Disk Centos-6.6-x86_64.img: 0 MB, 0 bytes 255 heads, 63 sectors/track, 0 cylinders, total 0 sectors Units = sectors of 1 * 512 = 512 bytes                 Device Boot &nbs........
  • Debian 8 Jessie in Linux OpenVZ Container does not work on Centos host


    It sounds like this is corrected in later versions of the OpenVZ kernel but I am not sure, it may also be that a much newer kernel is needed and Centos may not have a recent enough kernel. *Debain 7.0 however does work fine as a temporary fix or work around. Debian 8 OpenVZ no IP and networking not working: lo        Link encap:Local Loopback     ........
  • mdadm real example of recovery and rebuilding of the array on Centos 6


    In this example we have 2 drives in a RAID array and /dev/sdb is the one that failed.  /dev/sda1 is also the /boot partition which we tell grub to install on /dev/sdb eg install root (hd0,0) /dev/sda1 on the new drive /dev/sdb (hd1)   First copy the partition table from /dev/sda to /dev/sdb dd if=/dev/sda of=/dev/sdb bs=512 count=1 Run partprobe to detect the new partition table partprobe........
  • Centos 6 how to guide convert LVM non-RAID into mdadm 1/10 RAID array live without reinstalling


    Here is the scenario you or a client have a remote machine that was installed as a standard/default minimal Centos 6.x machine on a single disk with LVM for whatever reason.  Often many people do not know how to install it to a RAID array so it is common to have this problem and why reinstall if you don't need to?  In some cases on a remote system you can't easily reinstall without physical or KVM access. So in this case you add a second physical or disk or already ha........
  • Centos cannot login by console or ssh session closed immediately


    In my case I could login with the initial install but I rsync'd everything over while preserving ownership and permissions to another RAID partition and booted from that.was fine before. The problem is that you are kicked out the second you login and the problem was SELINUX for some reason (perhaps it noticed something strange when it was moved to the new partition) login: pam_unix(login:session): session opened for user root by LOGIN(uid=0) login: ROOT LOG........
  • openvz yum problem Centos 6.5 cannot find file on mirror:


    #solution Edit /etc/yum.repos.d/openvz.repo For the first two entries comment out #mirrorlist and uncomment #baseurl and then it worked openvz yum problem Centos 6.5 cannot find file on mirror: yum update Loaded plugins: fastestmirror Determining fastest mirrors  * openvz-kernel-rhel6: mirrors.ustc.edu.cn  * openvz-utils: mirrors.ustc.edu.cn base      ........
  • Centos/obfsproxy errors


    I never did get it working, it is too bad as obfsproxy should really be an option and integrated into the OpenVPN client and server or something similar:   yum -y install python-pip python-devel No package python-pip available. #install the EPEL repo python-pip install obfsproxy python-pip install obfsproxy -bash: python-pip: command not found pip install obfsproxy    &........
  • Centos yum mirror problem error "[Errno 14] PYCURL ERROR 22 - "The requested URL returned error: 404 Not Found""


    [Errno 14] PYCURL ERROR 22 - "The requested URL returned error: 404 Not Found" The above happened when for some reason all the mirrors in my cache didn't have the files (some mirrors only keep the latest version of Centos). I tried to block them all but that didn't help because it seemed the mirrors were all hardcoded no matter what I tried. Here is how to fix it and reset your mirror list in Centos cd /var/cac........
  • Unable to configure RSA server private key SSL Library Error: 185073780 error:0B080074:x509 certificate routines:X509_check_private_key:key values mismatch


    [Tue Jun 23 02:05:52 2015] [error] Unable to configure RSA server private key [Tue Jun 23 02:05:52 2015] [error] SSL Library Error: 185073780 error:0B080074:x509 certificate routines:X509_check_private_key:key values mismatch The above is an accurate description of what is wrong. In our case the client made a simple mistake of thinking the localhost.crt and localhost.key (default key locations for Apache SSL in Centos) were in the same directory but they we........
  • Centos OpenDKIM & Postfix Setup Guidel


    #from epel repo yum -y install opendkim chkconfig opendkim on cd /etc/opendkim/keys opendkim-genkey -vd mail.server.com opendkim-genkey: generating private key opendkim-genkey: private key written to default.private opendkim-genkey: extracting public key opendkim-genkey: DNS TXT record written to default.txt  ........
  • dir2slideshow Centos rpm requirements


    yum -y install dvdauthor ffmpeg mjpegtools sox bc   rpm -ivh dvd-slideshow-0.8.4-2.noarch.rpm Preparing...                ########################################### [100%]    1:dvd-slideshow          ########################################### [100%] /usr/bin/dir2slideshow: line 553: bc: command not f........
  • No package fuse-encfs available. yum


    It looks like newer versions of Centos no longer have encfs so you have to compile it, only it does not work and fails so those wanting encfs should probably use any other OS which supports it better.........
  • Centos scp or sftp program missing solution/what rpm provides them


    You need the "openssh-clients" package which contains sftp and scp. yum -y install openssh-clients........
  • How to install grub on virtio KVM with Linux


    I messed up the bootloader by accident on a standard Centos 6.3 install because I turned the /dev/vda1 boot partition into an mdadm raid 1.  This was all done correctly aside from one point I didn't realize was an issue metadata=00.90 is the only thing that will allow you to boot (otherwise grub won't work and you won't boot). So the next step is rescue mode from a CD right? The problem you will find is that grub does not detect your hard drives, this is I believe is be........
  • Centos automatic ifcfg-eth0 scripts based on list of IPs from bash


    <p>It's a basic script that reads the file &quot;ips.txt&quot; in the current directory and then creates a corresponding ifcfg file</p> <p>&nbsp;</p> <p>&nbsp;</p> <p><code>#!/bin/bash<br /> GATEWAY=192.168.1.1</code></p> <p><code>NETMASK=255.255.255.0</code></p> <p>device=eth0</p> <p><code><br /> counter=0<br /> for ips in `cat ips.txt`; do<br........
  • Directadmin compile error solution cc: Internal error: Killed (program cc1)


    cc: Internal error: Killed (program cc1) Please submit a full bug report. See <http://bugzilla.redhat.com/bugzilla> for instructions. make: *** [ext/fileinfo/libmagic/apprentice.lo] Error 1 make: *** Waiting for unfinished jobs.... Stopping crond:                                  ........
  • bash shellshock how to manually patch when there is no update for Centos/Debian/Ubuntu/Fedora


    wget http://ftp.gnu.org/gnu/bash/bash-4.3.tar.gz tar xzvf bash-4.3.tar.gz cd bash-4.3/ wget --no-directories --level 1 --recursive http://ftp.gnu.org/gnu/bash/bash-4.3-patches/ for patch in `ls bash43-*|grep -v .sig$`; do echo applying "$patch" patch -p0 < $patch done ./configure;make;make install #it will install to /usr/bin/bash but if your bash is somewhere else you need to overwrite the old one.........
  • yum error "Error: database disk image is malformed" solution


    yum -y install mathtools Loaded plugins: fastestmirror Loading mirror speeds from cached hostfile  * base: centos.mirror.rafal.ca  * epel: mirror.steadfast.net  * extras: mirror.agmn.ca  * rpmforge: repoforge.mirror.constant.com  * updates: centosb5.centos.org extras                         ........
  • yum Centos 386 and 64 bit conflict resolution


    This can happen when you install RPMForge or other repos with the wrong architecture and here's how you fix it (simply uninstalling won't usually fix it): solution yum clean all yum -y install openvpn Loaded plugins: fastestmirror, presto Loading mirror speeds from cached hostfile  * base: mirror.its.sfu.ca  * extras: centos.mirror.nexicom.net  * rpmforge: mirror.cpsc.ucalgary.ca  * up........
  • OpenVZ Quick Install Copy & Paste for Centos 6


    yum -y install wget wget -P /etc/yum.repos.d/ http://ftp.openvz.org/openvz.repo rpm --import http://ftp.openvz.org/RPM-GPG-Key-OpenVZ yum -y install vzkernel vzctl After that just reboot and you may also have to enable ip_forward in /etc/sysctl.conf........
  • yum error installing php solution - exclude php from being installed from third party repos


    Error: Package: php-Monolog-dynamo-1.7.0-1.el6.noarch (epel)            Requires: php-aws-sdk Error: php-pecl-zendopcache conflicts with 1:php-eaccelerator-0.9.6.1-1.el6.x86_64 Error: php-xcache conflicts with php-pecl-apc-3.1.9-2.el6.x86_64 Error: php-pecl-zendopcache conflicts with php-pecl-apc-3.1.9-2.el6.x86_64 Error: Package: php-horde-Horde-Vfs-2.1.2-2.el6.noarch (epel)    &n........
  • Centos 6 server crash - " kernel:[735188.961824] Kernel panic - not syncing: Fatal exception in interrupt Write failed: Broken pipe"


     kernel:[735188.961824] Kernel panic - not syncing: Fatal exception in interrupt Write failed: Broken pipe I'm not sure what is causing this and have never seen it on any server before.........
  • Centos Howto Upgrade to PHP 5.3 from 5.2


    It's not as simple as "yum install" as you can see below and it doesn't stop there.  yum install php53 Loaded plugins: fastestmirror Loading mirror speeds from cached hostfile  * rpmforge: mirror.us.leaseweb.net  * extras: centos.mirror.rafal.ca  * updates: centos.mirror.nexicom.net  * base: centos.mirror.nexicom.net  * addons: centos.mirror.nexicom.net Setting up Install Process........
  • Linux Centos 6 Weird Kernel Panic


    Kernel panic - not syncing: Attempted to kill init! Pid: 1, comm: init Not tained: 3.2.51-3.el6.x86_64 #1 Call Trace:  panic+0x8c/0x1a2 forget_original_parent+0x34d/0x360 exit_notify+0x12/0x140 do_exit+0x1d8/0x400 do_group_exit_+0x50/0xc0 sys_exit_group+0x12/0x20 system_call_fastpath+0x16/0x1b panic occurred, switching back to text console........
  • Centos 6 samba server not showing up in WORKGROUP


    This is different than Centos 5, you have two services btu they are called "smb" and "nmb". You need to enable and start "nmb" in order for your samba server to be listed. chkconfig nmb on; chkconfig smb on service nmb start;service smb start........
  • kvm centos cannot compile error


    ./configure ./configure: cannot locate gcc 3.x. please install it or specify with --qemu-cc yum -y install gcc make ./configure ./configure: cannot locate gcc 3.x. please install it or specify with --qemu-cc yum -y install compat-gcc-* ./configure Error: Could not find alsa Make sure to have the alsa libs and headers installed. yum -y install alsa-lib-devel ./configure........
  • KVM on Centos 6.3 cannot boot FreeBSD 9.2 AMD64


    <p>On the same OS with the same kernels basically I cannot boot FreeBSD installer, I&nbsp;believe the issue is the host CPU.</p> <p>One host runs an Intel and works, while an Opteron 2373 does not work despite suggestions from this thread: <a href="http://149.20.54.209/showthread.php?t=36761">http://149.20.54.209/showthread.php?t=36761</a></p> <p>I've tried cpu options like &quot;kvm64&quot; &quot;Opteron_G3&quot; and none........
  • Openvz OOM Centos Issue Memory Config Settings Solution


    Linux box13. 2.6.32-042stab076.5 #1 SMP Mon Mar 18 20:41:34 MSK 2013 x86_64 x86_64 x86_64 GNU/Linux even setting privvmpages to a specific setting DOES not affect "free -m" in containers. This is probably a kernel issue  23:36:29 up 159 days,  7:12,  4 users,  load average: 0.42, 0.44, 0.33 [root@box13 ~]# free -m              total  &n........
  • rpmforge Centos 6 how to install


    rpm --import http://apt.sw.be/RPM-GPG-KEY.dag.txt i686: rpm -ivh http://packages.sw.be/rpmforge-release/rpmforge-release-0.5.2-2.el6.rf.i686.rpm x64: rpm -ivh http://packages.sw.be/rpmforge-release/rpmforge-release-0.5.2-2.el6.rf.x86_64.rpm  ........
  • Centos 5,6,7 Install EPEL from Fedora for extra packages Howto


    http://fedoraproject.org/wiki/EPEL#How_can_I_use_these_extra_packages.3F Visit the above URL, choose your version and architecture and install it.  EPEL has a lot of missing and extra packages that rpmforge does not. For Centos 5  #update EPEL for Centos 5 is now archived and not really supported but can be downloaed from here:........
  • PHP Security - Enable Safe Mode to increase security


    Everyone should be running with safe_mode on in /etc/php.ini (on Centos) as it makes exploiting your system more difficult is PHP can't execute anything on the system if a script is exploited. For example with Safe_Mode on the only executable files on the system are ones in the safe_mode_exec_dir = /safephp This is crucial, if you must execute anything from PHP then you have to copy the binary and assign to the user that Apache runs your site under.&........
  • PHP5 Centos 6 displays part of code from PHP file for some scripts


    PHP5 Centos 6 displays part of code from PHP file for some scripts Solution edit /etc/php.ini change  short_open_tag = Off to: short_open_tag = On Then restart Apache and it should be resolved (assuming the scripts failing used <? and ?>)  ........
  • Dell Perc 6/i cannot downgrade


    I flashed an LSI Logic firmware to it and it broke the BIOS (cannot do Ctrl+R) for booting purposes but allows other functionality to work normally. I tried downgrading to a Dell firmware for Perc 6i but it won't work, not even with MegaCli wget http://downloads.dell.com/FOLDER00416606M/1/SAS-RAID_Firmware_W83M2_LN32_6.3.1-0003_A14.BIN --2013-08-26 12:53:39--  http://downloads.dell.com/FOLDER00416606M/1/SAS-RAID_Firmware_W83M2_LN32_6.3.1-0003_A14.BIN Resolvi........
  • rpmforge Centos 6 x64 howto install


    rpm --import http://apt.sw.be/RPM-GPG-KEY.dag.txt rpm -ivh http://packages.sw.be/rpmforge-release/rpmforge-release-0.5.2-2.el6.rf.x86_64.rpm Retrieving http://packages.sw.be/rpmforge-release/rpmforge-release-0.5.2-2.el6.rf.x86_64.rpm Preparing...                ########################################### [100%]    1:rpmforge-release       #############........
  • pxe-32 tftp open timeout


    pxe-32 tftp open timeout   The solution was to enable tftp in xinetd with "chkconfig tftp on". See the troubleshooting below:   chkconfig --list NetworkManager     0:off    1:off    2:off    3:off    4:off    5:off    6:off acpid              0:off&n........
  • iptables centos error getsockopt failed strangely: Invalid argument


    iptables -t nat -A PREROUTING -p udp -m multiport --dports 20,123,443 -j REDIRECT --to-port 53 getsockopt failed strangely: Invalid argument........
  • rtorrent: symbol lookup error: rtorrent: undefined symbol: _ZN7torrent10ThreadBase8m_globalE solution


    The solution is strange but simple and works each time on Centos: yum downgrade libtorrent........
  • How to use the Linux mail command to attach a file


    The key here is to use the "uuencode" command but note that we specify the file name twice (this must be done at least on Centos or it won\'t work). The first file.zip is the actual file we want to send. The second file.zip i........
  • Install PECL APC on RHEL/Centos HowTo


    pecl install apc........
  • OpenVZ Container Can't Restart, stuck in mounted state


    When trying to reboot this Centos 5 container, it gets stuck as "mounted" and requires a manual start command, here is what dmesg shows:   [424458.173252] VE10000: no allowed mount options found for device 0:21 [424458.177970] proc: unrecognized mount option "relatime" or missing value [424460.297663] CT: 10000: stopped [426663.466433] CT: 10000: started........
  • init: tty (/dev/tty2) main process (1031) terminated with status 1 init: tty (/dev/tty2) main process ended, respawning


    After some fsck issues I can't boot my Centos 6.4, this just keeps repeating over and over. init: tty (/dev/tty2) main process (1031) terminated with status 1 init: tty (/dev/tty2) main process ended, respawning Disabling SELinux through Single User mode fixed this.........
  • Solution ERROR 1146 (42S02): Table ‘mysql.servers’ doesn’t exist - when running flush privileges


    flush privileges; ERROR 1146 (42S02): Table ‘mysql.servers’ doesn’t exist This happened to me on a system running Centos with the REMI repo and a new version of Mysql 5 (which the official Centos/RHEL does not support on version 5). The solution is just to run this program "mysql_upgrade", after that flush privileges will work. mysql_upgrade........
  • Centos Net Install Format


    After booting the net install, eg. over tftp here's the format you need to install the OS when it asks for the URL: http://mirror.centos.org/centos-6/6.4/os/x86_64/ Obviously change the URL and path to match the architecture and version that you're looking for and you'll be good to go.........
  • Directadmin error/** Found 7 pre-existing rpmdb problem(s), 'yum check' output follows: e2fsprogs-devel-1.41.12-3.el6.i686 has missing requires of e2fsprogs-libs = ('0', '1.41.12', '3.el6') e2fsprogs-devel-1.41.12-3.el6.i686 has missing requires of l


    Solution To The Following: yum -y install zlib-devel yum -y install e2fsprogs* *** Cannot find /usr/include/et/com_err.h.  (yum install libcom_err-devel) *** Installation didn't pass, halting install. Once requirements are met, run the following to continue the install:   cd /usr/local/directadmin/scripts   ./install.sh Common pre-install commands:  http://help.directadmin.com/it........
  • How to log all PHP based E-mails for abuse


    Step #1 - Create Wrapper Script vi /usr/local/bin/phpsendmail #!/usr/bin/php <?php //changed by realtechtalk.com to make the log readable /**   This script is a sendmail wrapper for php to log calls of the php mail() function.   Author: Till Brehm, www.ispconfig.org   (Hopefully) secured by David Goodwin <david @ _palepurple_.co.uk> */........
  • Centos 6 RTL8111/8168B r8169 link up and down error solution/fix


    02:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168B PCI Express Gigabit Ethernet controller (rev 03) For whatever reason it seems the r8169 driver that ships and has shipped with most Linux distros for years is still flawed and does not work properly on these cards, causing 100mbit connectivity when it should be 1gbit and even worse, causing random network dropouts.  The r8169 driver in Linux kernels is simply not meant to be used on th........
  • KVM support Ubuntu 12.04 or 12.10


    This seems to be a verified bug on KVM with no solution.  I wasn't able to get through the installer with Ubuntu 12.04, it would crash while "configuring apt".  I was able to install it with Ubuntu 12.10 but it crashes randomly at times. This happens with the latest Centos 6.3 kernel and KVM package, I even compiled the latest version from the KVM website and used that, but the results are still the same. Here's some links to discussion about the bugs:........
  • kvm cannot boot xen guest using lvm


    This booting error is because the Xen PV guest image uses the Xen kernel, this is not compatible with anything but a host running a Xen kernel. I did a kpartx -av virtual.img and then it created some partitions that showed up in fdisk. I mounted it and did a chroot into it and removed the xen kernel and installed a normal kernel but Xen still shows the same kernel in Grub (only the Xen one). This is strange but it seems like this Xen PV guest has some sort of hidden or........
  • Setup PXE Boot using Centos and dhcpd, tftp and syslinux


    This is something I often setup for clients because it's very helpful for people in datacenters, this allows custom OS installs on demand, you can customize it more by using kickstart etc.. but here's a base I use before customizing more: This little script below will install everything you need to get booting by PXE Linux. It also assumes you set a local IP (be sure not to overwrite your existing IP) on eth0:0 (note the :0) as 192.168.1.10 and it........
  • Disable SELinux How To Tutorial Solution


    Here is a quick script that works on most Centos versions to disable the virus/SELinux from blocking basic functionality. The first echo 0 statement disables SELinux instantly but it will still be enabled on reboot. The second line disables it permanently. #!/bin/bash #disable SELinux Immediately echo 0 > /selinux/enforce #disable SELinux Permanently sed -i 's/SELINUX=enforcing/SELINUX=disabled/g' /etc/selinux/config........
  • KVM/QEMU Base/Template Images and the power they provide


     qemu-img create -b centos.5-8.x86.20120308.qcow2 -f qcow2 ../kvmguests/25000-centos5.8x86.qcow2 Formatting '../kvmguests/25000-centos5.8x86.qcow2', fmt=qcow2, backing_file=centos.5-8.x86.20120308.qcow2, size=10485760 kB -b the source/base image -f format is qcow2 and the location of the destination image What is so special about this?  It's even quicker than creating a template with OpenVZ but this is an actual OS. It saves time a........
  • Centos 5 and OpenVZ won't boot after kernel install


    For whatever reason the current OpenVZ yum repo file enables the RHEL6 version of OpenVZ, why is this bad?  Because if you're running Centos 5 it still defaults to using the kernel from RHEL6 which won't work on RHEL5/Centos 5. I only realized this after wondering why I couldn't boot into OpenVZ that it was using one meant for RHEL6. To fix the problem you have to edit /etc/yum.repos.d/openvz.repo and disable the "[openvz-kernel-rhel6]" section by changing........
  • Creating tunnel gives the error ioctl: no such device


    ip tunnel add tun3 mode gre remote 192.58.1.5 ttl 64 ioctl: no such device I solved this on Centos by loading the ip_gre module: modprobe ip_gre On Debian I believe it is the "sit" module.........
  • ip_conntrack: table full, dropping packet. solution for Linux RHEL/Centos/Debian


    ip_conntrack: table full, dropping packet. A lot of clients I've seen have this issue, it really seems the default level is way too small.  Once this connection tracking table becomes full then packets get dropped which is obviously a bad thing. One thing to be mindful of though is that 350 bytes of memory are used per entry so there is some justification for not keeping it too high.  However, if you have multiple servers running or high traffic daemons........
  • Linux/Centos how to block SSH bruteforce/dictionary attacks automatically with denyhosts


    A lot of people become nervous (and understandably so) when checking their auth or security logs, in Centos /var/log/secure and see dozens, hundreds of even thousands of attempted logins to various services, especially SSH. Of course you could manually block these people/IPs but no one has time to read the logs like that, what if some program or script could do it for you? This is what denyhosts does for you, it checks the logs and based on a certain number of failed SSH attem........
  • Centos how to upgrade from PHP 5.2 to 5.3 without downtime


    This may sound silly but there will be conflicts/issues with the default Centos repository so you have to use a third party like remi (I prefer not to do this but it's the only option unless you migrate your sites/data to another server or can stand some downtime-not an option IMHO on a production server). You may need to upgrade to PHP 5.3 to run Joomla or many other reasons. Your host needs to use PHP 5.2.4 or higher to run this version of Jo........
  • ntpd[7047]: can't open /var/lib/ntp/drift.TEMP: Permission denied solution


    ntpd[7047]: can't open /var/lib/ntp/drift.TEMP: Permission denied chown ntp.ntp /var/lib/ntp/ The solution is shown above and changes the ownership to ntp.ntp which is what the ntpd daemon/server is running as.  This is based on Centos but the same idea will apply on any other OS.  You can do a "ps aux|grep ntpd" to see what it is running as in the case it's running as a different user. After that this annoying message wil........
  • Slow KVM Virtual Machine Performance Solved - Choose the right architecture with the CPU flag


    I am running a 64-bit host and was running a 32-bit XP guest which was crawling no matter what I was doing with it,in fact it frequently used 100% CPU power while having no real work load.  I experienced with this other guests and wondered why KVM was slow compared to say Xen or Virtualbox. This is because you need to use the "-cpu" flag. For a full list of options run: /usr/libexec/qemu-kvm -cpu ? x86    ........
  • Centos Complete RPM/ISO Archive is at http://vault.centos.org


    This is so handy, especially if you need things like old kernels etc..., this is the main and practically only place you'll ever find what you need.   http://vault.centos.org........
  • pcnet32: eth0: transmit timed out, status 97fb, resetting - NIC card problem solution


    I've encountered this problem before and I believe it  may affect other drivers (I could test but I don't have time).  This was happening on my custom Linux system with the pcnet32 driver. pcnet32: eth0: transmit timed out, status 97fb, resetting (and some other kernel module tracing in dmesg) Basically it means the card is connected (it shows connected in full duplex etc.. and recognized if the cable is disconnected too) but no packets can be sent or received........
  • Directadmin Install Segfault Error


    ************************************* *                                   * *   All parts have been installed   * *                        ........
  • Xen non-HVM container won't work/boot anymore


    One of my test Centos 5 containers was on a partition that filled up and it threw all sorts of errors and stopped responding but now I can't boot it again anymore. All the console shows is the Linux Penguin on the top left corner and the xm console says "usbcore: registered new driver hub" and has halted there. Centos 5 Xen container stuck/frozen won't boot on "usbcore: registered new driver hub" Another great way of troubleshooting is booting fro........
  • How To Burn ISO Image using cdrtools/dvdrtools for Linux/Unix Ubuntu/Debian/RHEL/Centos etc..


    It really is as simple as: cdrecord -v dev=/dev/sr0 pathtoyourisoimage.iso -v is for verbose, I prefer it but if you don't you won't see as much output like below (I like to know the details and exactly what's happening) dev=/dev/sr0 specifies the device name of your burner (they say not to use it and to specify some weird annoying device string but using the raw /dev has always worked for me and is how it should have been implemented from the start IMHO)........
  • scp not found - solution


    Some minimal installs of Centos may be missing the scp command, which is actually part of the "openssh-clients" package. scp not found yum install openssh-clients........
  • screen Cannot open your terminal '/dev/pts/2' - please check.


    The solution to this screen issue is simple. This happened to me in Centos 5 as a user, but I also su'd to it and I don't have any password for it. I've read some people say this is more common when su'ing. The solution is simple though, just give others rw access to the corresponding pts whether it's 0,1,2 etc..: As root do chmod o+rw /dev/pts/2  ........
  • rpmforge: [#### ] 471/10722Segmentation fault yum[18934]: segfault at 0000000000000000 rip 00002ade62153a30 rsp 00007fff76f9fe58 error 4


    A few days ago this happened on multiple Centos 5 servers and apparently anyone using rpmforge was affected by this error and there was no solution other than disabling that repo to fix it. To some this highlighted a few points, that there is a reason RHEL exists with full paid support, and also that this could be a vulnerability and huge flaw with yum.  A yum search or install should not segfault just because the rpmforge repo goes down. Fortunately it came back up........
  • ifup eth0 SIOCSIFFLAGS: Cannot allocate memory Failed to bring up eth0 Centos Network won't work after kernel update and reboot


    ifup eth0 SIOCSIFFLAGS: Cannot allocate memory Failed to bring up eth0 This is on a Centos 5.5 machine with OpenVZ kernel 2.6.18-238.12.1.el5.028stab091.1PAE, I updated 3 systems with the same hardware to the same kernel and for some reason the network didn't come back. This only happened once the first time I booted into the new kernel and hasn't happened again but this is a serious issue for those running systems from remote locations such as a datacente........
  • Centos Solution to "Warning: Unable to open /dev/fd0 read-write (Read-only file system). /dev/fd0 has been opened read-only."


    Warning: Unable to open /dev/fd0 read-write (Read-only file system).  /dev/fd0 has been opened read-only. That's a very annoying error, it's simply because Centos for some reason thinks it's wise to load the "floppy" kernel module, who has a floppy drive?  I haven't seen or used a floppy for over 12 years! It's more than just annoying, if you probe the drives attached to your system, eg. with grub or partprobe, it keeps trying to locate a flopp........
  • Openvz YUM Error Solution to "[Errno -1] Metadata file does not match checksum Trying other mirror."


    It's weird because I have a nearly identical box and setup and I can update the ovzkernel-PAE* just fine but on this box it doesn't work. I only get this error with the openvz.repo and not others such as Centos-Base.repo With my other server it works normally: ================ Setting up Update Process Resolving Dependencies --> Running transaction check ---> Package ovzkernel-PAE.i686 0:2.6.18-238.12.1.el5.0........
  • Apache High CPU Usage Enable Mod_Status Guide Solution - Find Cause of High CPU Usage Script/Domain


    mod_status is a great way to track down the source of high CPU usage and to find what vhost/script is the cause of it. It gives you a live view of bandwith usage, CPU usage, and memory usage broken down by domain/vhost and script/URI. Enable mod_status vi /etc/httpd/conf/httpd.conf ExtendedStatus On <Location /server-status> SetHandler server-status Order Deny,Allow Deny from all All........
  • vnstat setup guide/tutorial


    yum -y install vnstat chown nobody.nobody -R /var/lib/vnstat/ #replace venet0 below with your desired interface sudo -u nobody vnstat -u -i venet0 #edit: vi /etc/sysconfig/vnstat #VNSTAT_OPTIONS="-i venet0" # only use the sed below if you are using venet0 instead of eth0 or replace accordingly sed -i 's/eth0/venet0/g' /etc/sysconfig/vnstat   [root@monitor]# yum install vn........
  • Enable SPAMASSASSIN on Postfix in 5 minutes


    Centos 5 Postfix and SPAMASSASSIN Tutorial yum install spamassassin chkconfig spamassassin on vi /etc/mail/spamassassin/local.cf ############## #required_hits 5 #report_safe 0 #rewrite_header Subject [SPAM] #5 is the least restrictive (means only the most obvious SPAM is caught. 0 is obviously the most restrictive/sensitive and would have lots of false positives require........
  • updatedb/mdadm caused a kernel panic?


    Jan 16 04:02:03 centosbox syslogd 1.4.1: restart. Jan 16 04:07:34 centosbox kernel: INFO: task updatedb:20771 blocked for more than 300 seconds. Jan 16 04:07:34 centosbox kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. Jan 16 04:07:34 centosbox kernel: updatedb      D F78BE050  6476 20771  20766                &n........
  • Installing Webmin & Enabling SSL


    Webmin Setup Centos 5: wget http://downloads.sourceforge.net/project/webadmin/webmin/1.530/webmin-1.530-1.noarch.rpm?r=http%3A%2F%2Fwww.webmin.com%2Fstandard.html&ts=1294339690&use_mirror=surfnet [1] 24229 [2] 24230 [root@host ~]# --2011-01-06 21:48:20--  http://downloads.sourceforge.net/project/webadmin/webmin/1.530/webmin-1.530-1.noarch.rpm?r=http%3A%2F%2Fwww.webmin.com%2Fstandard.html Resolving downloads.sourceforge.net... 216.34.181.........
  • mdadm Centos 5 automatic resync


    This made me nervous but it's clearly a cronjob based on the messages log that happens every Sunday at about 4:22. I actually can't find any evidence of it in cron.d cron.daily but it is there somewhere obviously. What I don't get is why doesn't this cronjob do a datacheck like Ubuntu's cronscript does?  When you unnecessarily rebuild the array you lose your redundancy during that point which makes your data extremely vulnerable. *Update I did a grep of &q........
  • SSH delay problem UseDNS and disabling GSSAPI does not help


    The normal solution doesn't help or apply here:   ssh -v user@192.168.5.41 OpenSSH_4.3p2 Debian-9etch3, OpenSSL 0.9.8c 05 Sep 2006 debug1: Reading configuration data /etc/ssh/ssh_config debug1: Applying options for * debug1: Connecting to 192.168.5.41 [192.168.5.41] port 22. debug1: Connection established. debug1: permanently_set_uid: 0/0 debug1: identity file /root/.ssh/identity type -1 debug1: i........
  • Ubuntu/Debian DRBD 8.0 Setup Guide


    I've only used it on Centos, so I thought I'd make a quick Debian guide: Install the DRBD Package apt-get install drbd8-utils Reading package lists... Done Building dependency tree       Reading state information... Done The following packages were automatically installed and are no longer required:   libswfdec-0.8-0 Use 'apt-get autoremove' to remove them. The following........
  • VirtualBox Convert Import/Boot .vmdk VMWare Hard Disk/Drive Image Won't Work


    I wanted to Import/Use a .vmdk hard disk image file from VMWare.  Generally you can just "point" VirtualBox to it and use it and it will work but I found an exception. One of my Centos 4.4 x64 images wouldn't boot.  I had two copies, an older one and the newer one.  The older one booted as normal (once I changed the VirtualBox driver to IDE from SATA).  The newer one stopped at the "GRUB loading" message no matter what I tried. As far as........
  • yum in Centos 5/Xen halts and exits suddenly


    yum exits in the middle The problem is this VPS seems to be an OpenVZ template from HyperVM.  The only way to make it work was to disable i386 packages since this was an x64 kernel.  That shouldn't be necessary but it was the only way to make yum stop quitting after the first package or two.  I couldn't find any issue by checking the logs either. echo y|yum install vim-minimal telnet expect jwhois net-tools slocate iptables elinks gawk L........
  • yum error with some versions of Centos Refusing to automatically import keys when running unattended. Use "-y" to override.


    Refusing to automatically import keys when running unattended. Use "-y" to override. When using echo y|yum install gcc Fix with rpm --import /etc/pki/rpm-gpg/RPM-GPG-KEY*........
  • Buffer I/O error on device fd0, logical block 0


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  • Openvz Quick Install for CentOS 5 Tutorial


    cd /etc/yum.repos.d wget http://download.openvz.org/openvz.repo rpm --import  http://download.openvz.org/RPM-GPG-Key-OpenVZ yum install ovz-kernel-PAE Now remember to set /etc/sysctl.conf to "net.ipv4.ip_forward = 1" You can apply the change immediately by running sysctl -w net.ipv4.ip_forward = 1 but remember that you still have to set sysctl.conf sysctl -p will load and apply any changes to s........
  • DRBD WFConnection Problem/Solution


    This has stumped me  a few times because I keep forgetting that Centos 5.5 comes with a default iptables configuration that ends up blocking DRBD traffic, I tried all the normal things and couldn't understand why I couldn't make my normal DRBD config work.  So if you have WFConnection problems and have tried the normal "mailing list" fixes, check your firewall status first! Both Nodes Say the Following: version: 8.3.8 (api:88/prot........
  • VirtualBox Error Failed to start the virtual machine Centos 5.5 Mirror. Medium '/home/testuser/.VirtualBox/HardDisks/Centos 5.5 Mirror.vdi' is not accessible. UUID {a1a9fad7-0402-4867-b8f3-39fb49454bc5} of the medium '/home/testuser/.VirtualBox/HardD


    Virtualbox Error I tried to copy a .vdi of one container to use in another one, basically to clone instead of having to install the OS again. Failed to start the virtual machine Centos 5.5 Mirror. Medium '/home/testuser/.VirtualBox/HardDisks/Centos 5.5 Mirror.vdi' is not accessible. UUID {a1a9fad7-0402-4867-b8f3-39fb49454bc5} of the medium '/home/testuser/.VirtualBox/HardDisks/Centos 5.5 Mirror.vdi' does not match the value {4945a0e8-0ed5-4736-9088-bcaf........
  • Installing Virtualbox on Centos 5.5


    wget http://download.virtualbox.org/virtualbox/3.2.8/VirtualBox-3.2-3.2.8_64453_rhel5-1.i386.rpm rpm -i http://download.virtualbox.org/virtualbox/3.2.8/VirtualBox-3.2-3.2.8_64453_rhel5-1.i386.rpm error: Failed dependencies:     libGLU.so.1 is needed by VirtualBox-3.2-3.2.8_64453_rhel5-1.i386     libSDL-1.2.so.0 is needed by VirtualBox-3.2-3.2.8_64453_rhel5-1.i386     libXmu.so.6 is needed b........
  • VirtualBox/VBOX Centos 5.5 Installation Kernel Freeze Problem "NET: Registered protocol family 2" And Solution


    NET: Registered protocol family 2 The above is the last thing that I ever saw, I tried pci=routeirq etc.. and it wouldn't work. The solution is to enable IOAPIC in the VBOX Settings Just enable "IOAPIC" in the settings for your Centos Guest and you'll find the kernel boots just fine.  I wonder if a physical system might stall in this same way if the BIOS has IOAPIC disabled which many people do as a troubleshooting method.  ........
  • Shutdown/Power/Halt In Debian/Ubuntu/Centos Guide Systems Doesn't Work


    Different distributions such as Debian and Centos behave differently when trying to shutdown your system. shutdown -H now on Debian does not do what you'd expect.  The system won't power down, it will halt and do everything but power down. shutdown -PH now will do the job though (actually power the system off).  This is important to test especially if you are not near the system.  If you just use -P it forcefully shuts off which is not........
  • jailkit for chroot ssh account security tutorial and fix for error


    This was done on Centos but I think it's easier on Debian machines, the paths that it is set to use are tailored towards Debian, so there is some fiddling that needs to be done on Centos. This is for chrooting ssh, but jailkit has other uses than just SSH jails but I won't cover them in this writeup. 1. Install jailkit yum install jailkit 2. Setup Jail Home mkdir /home/jail chown root:root /home/ja........
  • Centos How To Add Static Network Route


    route add -net 192.16.5.0 netmask 255.255.255.0 eth0 Of course adjust as you need (eg. the 192.16.5.0 should be changed to the subnet you need access to and eth0 should be changed to the network device that you want that subnet routed through).   I also use the /etc/sysconfig/rc.local script and add the above into it (remember that this route only gets added AFTER all other init scripts have finished though).........
  • Linux Centos/RHEL can't find php/apache/httpd/mysql/ftp/exim/sendmail ?


    I wasted a lot of time wondering why I could never find those packages. Check the /etc/yum.conf file and at the bottom look for the "exclude=" line.  Below is what I found in mine exclude=apache* httpd* mod_* mysql* MySQL* da_* *ftp* exim* sendmail* php* bind-chroot* Just remove those entries or uncomment that line and you'll get access to the missing applications.........
  • How To Set DHCP/Static IP Address in Centos/RHEL/Fedora & Debian/Ubuntu/Kubuntu/MEPIS Set DHCP/Static IP Address


    Basically the two main types of distros are Debian and RHEL/Centos based.  I'm just going to give a quick overview of how the configuration of IP interfaces works in Debian/Centos based distros. *Just one thing to remember, when setting IPs statically you have to manually specify a DNS server in /etc/resolv.conf (since DHCP is what normally does it automatically) Debian/Ubuntu/Kubuntu/MEPIS The IP (DHCP &........
  • mdadm force/fix proper md127 name


    I have an md0 arary that my Centos install refers to.  I feel this is half the reason why it won't boot anymore. I saw the initrd for Centos was assembling it as md127 even though it was known as md0. The reason for this is because I used mdadm --assemble --scan to detect the array on a LiveCD.  I had no idea this name would stick (but now I realize the name is permanently stored in the metadata once you mount md127 or whatever random name assemble gives it).  W........
  • Debian 5.04 RAID 1 mdadm boot problem GRUB error


    I successfully created a single RAID 1 partition which includes /boot inside it and my root directory through the Debian installer.  It said GRUB installed successfully but when I try booting the OS it seems GRUB can't read anything. When trying to boot from GRUB GRUB Loading stage 1.5. GRUB loading, please wait... Error 2 I get "Error 2" when trying to boot Debian.  I also notice from a LiveCD that........
  • Centos 5.5 RAID 1 boot issue


    I installed 5.5 with a 300GB RAID 1 partition (boot is also on this partition).  It booted up fine the first few times until after I used a Live CD and accessed the array, and it became named /dev/md127 for some reason. Now whenI boot into CentOS I get a kernel panic and different errors, once I got "invalid superblock", even though the array is fine (it didn't happen again, probably because I was sure to dismount and stop the mdadm array properly). Here's what........
  • Compile PHP 5.3.2 on Centos 5 and CPanel/WHM because of error - Fatal error: Call to > undefined function imagecreatefromjpeg()


    This function and others may not work with the stock PHP install on Centos/CPanel:  Fatal error:  Call to > undefined function imagecreatefromjpeg() Even with libjpeg-devel installed it won't work because PHP was not compiled with jpeg support, so we have to do the dirty work ourselves :) Here is the command/yum's I did to install missing libraries for PHP that configure will complain about (yes it is a one by one process). yum install bzip2-........
  • Unixbench Score on Core i5 750 with OpenVZ Kernel vs Xen/Openvz


    This was unbelievable how much the Xen kernel slows things down, keep in mind both tests were done on the hostnode, one was with the Openvz-Xen hybrid kernel and the other was just OpenVZ.  You can see the performance difference is nearly 300% better when not using the Xen kernel. OpenVZ-Xen Kernel Test Results (I was wondering what was wrong/so slow with my Core i5!)    #    #  #    #  #  #  &n........
  • SSH Automatic/Passwordless Logon - Setup Public Key Encryption In Single Command


    This is a very simple solution, but most guides out there make you login twice (once to scp the key) and once to put the key in authorized_keys.  There's no need for that.  If you don't already have a ~/.ssh/id_rsa.pub just type "ssh-keygen -t rsa" and keep hitting enter until it's done :) Just use this code to easily enable passwordless login with SSHD key=`cat ~/.ssh/id_rsa.pub`;ssh user@192.168.5.25 "echo $key >> ~/.ssh/auth........
  • Picking an FTPD (vsftpd) Server in Linux Centos/Debian


    I decided on using yum to help me decide even though I normaly use proftpd I decided to see what else I could find. yum search ftp Loaded plugins: fastestmirror Loading mirror speeds from cached hostfile  * rpmforge: ftp-stud.fht-esslingen.de  * base: mirrors.netdna.com  * updates: updates.interworx.info  * addons: yum.singlehop.com  * extras: mirrors.netdna.com rpmforge   ........
  • OpenVZ backup container to a single file while it's running using "vzdump"


    Proxmox has made this free utility to backup running OpenVZ containers.  It's a great program which is actually just a PERL script but gets the job done.  This program is not 100% required because all it really does is cp -a from your container's path as far as I know but it is still good to have uniformity to how you backup your containers. For RPM distros such as Centos/RHEL/Fedora etc.. download and install this: wget http://www.proxmox.com/cms_proxm........
  • CentOS (most Linux) no-RAID to software RAID-1 guide


    CentOS (most Linux) no-RAID to software RAID-1 guidehttp://lists.centos.org/pipermail/centos/2006-January/018624.html........
  • Centos 4.3 x64 & VMWare Server Beta


    Centos 4.3 x64 & VMWare Server Beta[code:1:6d0b2c8c2f] The correct version of one or more libraries needed to run VMware Server may be missing. This is the output of ldd /usr/bin/vmware: linux-gate.so.1 => (0xffffe000) libm.so.6 => /lib/tls/libm.so.6 (0xf7fbd000) libdl.so.2 => /lib/libdl.so.2 (0xf7fb9000) libpthread.so.0 => /lib/tls/libpthread.so.0 (0xf7fa7000) libX11.so.6 => not f........
  • Upgrade Release Kernel Tips


    Upgrade Release Kernel TipsThis is for CentOS 3.1 to 3.8 but the methodology will apply everywhere. I ran into a problem first of all with a non-booting system after running #yum update centos-release It took me to 3.8 and upgraded all the other packages [b:7e931c835d]BUT[/b:7e931c835d] because of some stupid flags enabled in /etc/yum.conf the KERNEL WASN'T UPGRADED SO AFTER BOOTING, WELL IT DIDN'T BOOT OF COURSE :) H........
  • Setup Static IP Address ONBOOT


    Setup Static IP Address ONBOOTAssuming you are using eth0 Note this will work for any version of CentOS and basically any version of Redhat Linux or Redhat based distribution. You would need to create a new file [code:1:02f8d34c30] /etc/sysconfig/network-scripts/ifcfg-eth0:0[/code:1:02f8d34c30] DEVICE=eth0:0 the ":0" at the end specifies alias 0 we could actually change this to ":99" or "........
  • Need identd for port 113 ? Install authd


    Need identd for port 113 ? Install authdyum install authd Happy identing :)Actually it's not that simple. It installs as an "xinetd" service and is disabled and turned off by deafult. To enable it run: [code:1:8c94df8319] chkconfig --level 3 auth on service xinetd restart [/code:1:8c94df8319] This will set identd aka authd to start by default. service xinetd resta........
  • /usr/bin/ld: cannot open crt1.o: No such file or directory


    /usr/bin/ld: cannot open crt1.o: No such file or directory[quote:812bec9db7]/usr/bin/ld: cannot open crt1.o: No such file or directory collect2: ld returned 1 exit status[/quote:812bec9db7] This is annoying and in my case it happened on Centos AMD 64 when compiling a 32bit program with GCC. Install glibc-devel.i386 (make sure you get the i386 version and not the native 64 bit version which is likely already installed). The joys of 3........
  • Updating yum repos for DAG /etc/yum.repos.d


    Updating yum repos for DAG /etc/yum.repos.dIn /etc/yum.repos.d [quote:96456b2ab9]Create any file such as "CentOS-Dag.repo" in /etc/yum.repos.d[/quote:96456b2ab9] Add the following to the above file: [code:1:96456b2ab9] [dag] name=Dag RPM Repository For Red Hat Enterprise Linux baseurl=http://dag.atrpms.net/redhat/el$releasever/en/$basearch/dag/ http://dag.freshrpms.net/redhat/e........
  • Create/Enable SSL Certificates for Apache on Linux/Unix Systems eg. Redhat,Centos,Debian


    Shortcut/Easiest Way To Create A Self-Signed Key: openssl req -new -x509 -nodes -days 1530 -out server.crt -keyout server.key Using the above, you instantly create a self-signed certificate valid for 1530 days and you can simply skip to step #5.) below. If You Need a Real SSL Certificate (eg. Equifax/Openssl) then you need to create a CSR request (you'll need to follow Steps 1.) and 2.) in order to create the CSR.  You then upload the CSR Certi........
  • How To Enable 3rd/third party packages in RHEL/Redhat/Centos 4/5 Linux via RPMForge


    It's a bit of a pain that many basic third party tools that aren't put of the main Centos/RHEL repositories are not available unless you compile them or install the RPMForge Repo. *Updated 08/29 with new download location changed from apt.sw.be to rpmforge.sw.be Here's a quick, simple/cut&paste way to do it: wget http://rpmforge.sw.be/redhat/el5/en/i386/rpmforge/RPMS/rpmforge-release-0.5.1-1.el5.rf.i386.rpm rpm -i rpmforge........
  • Tyan S2735-8M Maximum Hard Drive Limit/Not Working/Doesn't work with 1TB 1000GB hard drives


    I never saved any of the logs, but basically no matter what OS (Linux) I used, I could not get my 1000GB hard drive to work (Seagate SATA).  The BIOS recognizes the drive and fdisk -l shows the hard drive as it should. The tricky thing is that different OS's will give you different results, but don't be fooled.  You can't use these larger drives for long.  I was getting all kinds of seek/IO errors and also messages that the port could not be read.........
  • Timezone Change/Updated for Linux/Unix Debian/Fedora/Ubuntu/Centos Change Update Time zone


    This way should work on all Linux machines, at least RHEL/Debian (Ubuntu) based distros but most likely all and also should work on many Unix style machines I believe. Many OS's have tools to update the timezone, but most of them (even if command line) require several bloated packages and even Xorg/KDE based packages etc.. Your time zone info file is actually in /etc/localtime if you open this file in vi/vim/pico you'll see it's gibberish (binary code or another encodin........
  • sudo: Error dropping capabilities, aborting in Linux Centos 5.3


    For some reason I keep getting this error when trying to run a sudo command eg: sudo -u someuser somecommand sudo: Error dropping capabilities, aborting My version of sudo is: sudo-1.6.9p17-3.el5_3.1 and I've heard that version 1.7 fixes everything.  The only thing is yum does not think sudo has any update.  I guess the new version has not been committed to the RPM repository yet. This is really a huge and ann........
  • How To Save iptables firewall rules Centos/Redhat/Fedora Linux


    This is something that annoys a lot of people, fortunately the Redhat style OS's are the most simple in this respect.  I disagree that Debian's way makes sense, it is more of a hackish approach in how they implement iptables. Anyway, for those who are using Redhat/Centos style OS's it is very simple. Set your rules from the shell/command prompt and to save the iptables firewall rules so they are remember/loaded on boot just run this command: service iptables........
  • Samba SMB Error - Server not using user level security and no password supplied. tree connect failed: NT_STATUS_WRONG_PASSWORD


    Server not using user level security and no password supplied. tree connect failed: NT_STATUS_WRONG_PASSWORD That happens when trying to use smbclient to connect to a share.  The weird thing is that I can authnenticate just fine from Windows XP. It is partially my mistake, I forgot this share does have a password.  I've tried authenticating with the correct user and also with "Guest" because this works in Windows.  In Linux I ........
  • Configuring OCFS2 Clustered File System on Debian Based Linux including Ubuntu and Kubuntu


    There's a lot of information and guides on OCFS2 for RHEL and Centos Linux but the package setup and configuration is slightly different and this has thrown some people off. Installing OC2FS You should install the following packages to get started: apt-get install ocfs2-tools ocfs2console Configure OC2FS In RHEL/Centos the main configuration file is located in /etc/sysconfig/o2cb However in Debian based Linux it is located........
  • Writing/Burning a data CD-R/DVD-R or DVD+RW in Unix/Linux


    There's a lot of outdated information and confusion for system administrator's out there. One annoying task for many an Administrator has been backing up data in Linux.  You don't need any GUI tools such as K3B or GnomeBaker.  Both are excellent tools but for veteran command line users working remotely, using the keyboard is a great and possibly automated way to save yourself pain and hassle. At a later date we'll cover how scripting can automatically backup certain........
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