• [error] (28)No space left on device: Cannot create SSLMutex Apache Solution Linux CentOS Ubuntu Debian Mint


    Have you got this error from Apache? [notice] suEXEC mechanism enabled (wrapper: /usr/sbin/suexec) [error] (28)No space left on device: Cannot create SSLMutex At first glance it appears that you may be out of disk space but the issue is ipc or interprocess communication. This will clear out the ipcs processes so things can work, this often happens during high traffic and may be a sign of DDOS. The command below will fix it, it will list al........
  • Save money on bandwidth by disabling reflective rpc queries in Linux CentOS RHEL Ubuntu Debian


    Even today we see a lot of servers that have different services and ports open for rpc and this creates not only potential inward vulnerabilities but perhaps more common, the abuse of your network resources in reflective rpc queries. To stop this problem, you should disable and remove all services relating to rpc or at least block all relevant ports for the service. Surprisingly, there are still some providers and OS installs in Linux that install these services and leave them........
  • Linux How To Access Original Contents of Directory Mounted Debian Mint CentOS Redhat Solution


    Let's say you have a directory /mnt/raid which has files and directories inside it, but nothing is mounted to it. Then you mount a block device such as /dev/sdh to /mnt/raid Even though /mnt/raid has files and directories there, you can only see the mounted contents of /mnt/raid. How do we access the original contents? Just do a bind mount of the root filesystem to another location. mkdir /bindmount mount --bind / /b........
  • Linux How To echo as root solution to use tee permission denied solution Ubuntu Debian Mint Redhat CentOS


    The issue is when you need to echo something as root/sudo, that it doesn't work. You can never do a sudo echo to an output file as you'd expect. Take an example to clear out wasted RAM buffers/cache like this: sudo echo 1 > /proc/sys/vm/drop_caches -bash: /proc/sys/vm/drop_caches: Permission denied The solution is to run tee as sudo/root What we do is echo 1, but then pipe it to the "tee" command as sudo........
  • ecryptfs how to change default mount location from Private Ubuntu Debian Centos How


    In a lot of distros like Debian, ecryptfs will mount itself in /home/yourusername/Private This is controlled by Private.mnt which may contain the mount path like this: /home/yourusername/Private Change the default mount location of ecryptfs by modifying this file: home/.ecryptfs/yourusername/.ecryptfs/Private.mnt After you unmount and relogin, you should find ecryptfs is now mo........
  • RHEL 8 CentOS 8, Alma Linux 8, Rocky Linux 8 System Not Booting with RAID or on other servers/computers Solution for dracut and initramfs missing kernel modules


    This seems to have changed for RHEL 8 where a normal dracut to update your initramfs creates a system that only boots for the running kernel. For example if you have Kernel 5 and then chroot into a RHEL 8 variant which uses kernel 4.18, and run dracut, it seems that by default the system will be unbootable. It is also the case that if you move your RAID array or drives to another server that it will be unbootable, because dracut seems to only include modules needed for the curre........
  • Linux How to Check Which NIC is Onboard eth0 or eth1 Ubuntu Centos Debian Mint


    So say you happen to have 2 NICs of the exact same chipset, they will generally show up as the same name, with possibly a different revision in lspci. Normally this is not an issue if you have a server with 4 NICs, generally the eth0 to eth3 appears from left to the right (or right to left on some vendors) so it doesn't take much figuring out. Generally if you have different chipsets for different NICs, it should be easy to know which one is eth0 or the first NIC in the OS.........
  • Stop ls in Linux Debian Mint CentOS Ubuntu from applying quotes around filenames and directory names


    Later versions of ls try to be helpful and smart to prevent errors in dealing with files with spaces that were tradtionally a pain. However if you need the raw/real filenames, this can break scripts or if you are pasting into a csv etc.... How do you make ls not add the quotes? Add the capital "-N" switch ls -N You could also add an alias to make it more permanent Do this to add it to ~/........
  • grub blank screen how to manually boot kernel and initrd Linux Ubuntu Debian Centos won't boot solution


    You probably didn't do an "update-grub" and grub no longer has any proper menu entries, but before you can fix it let's try to get grub booting anyway. If you get this lovely black grub screen here's how you can get things booting. In my case I have a gpt partition with partition 1 and 2. Partion 1 is just my EFI / ESPand partion 2 /dev/sda2 is my root which includes /boot. You will have to adjust this if you had a separate /boot partition.........
  • GRUB error: invalid arch-independent ELF magic. Solution How To Fix Linux Centos Ubuntu Mint


    I've seen this bizarrely happen on a newly partitioned and custom installed Linux install, particularly if you did not properly unmount before rebooting. You can find reports of it happening on various How to fix the error: invalid arch-independent ELF magic. You need to boot into Live/Rescue mode, chroot into your OS properly and then do a grub-install on each drive that nee........
  • Centos 7 not mounting /etc/fstab partitions


    If you are doing a custom deployment and image, make sure that when you rsync'd or tar'd that you didn't mess up the symlnk of /etc/mtab to /proc/self/mounts ln --force -s /proc/self/mounts /etc/mtab Will fix this........
  • CentOS 7 / 8 cannot boot with with mdadm RAID array solution


    This article about migrating to a CentOS 7 /8 RAID mdadm array has a lot of info but I wanted to focus specifically on what newer versions of CentOS 7 require to boot mdadm and what changes are necessary on CentOS 7.8+ CentOS 7 / 8 mdadm RAID booting requirements This assumes you are chrooting into an existing install or using it to get a new deployment ready. However, these steps can........
  • Error: Failed to download metadata for repo 'appstream': Cannot prepare internal mirrorlist: No URLs in mirrorlist Solution for Centos8 yum package install error


    Are you getting this error in CentOS 8 when trying to use yum to install a package? Error: Failed to download metadata for repo 'appstream': Cannot prepare internal mirrorlist: No URLs in mirrorlist What we need to do is not use the automatic mirror list and manually set the base URL Solution sed -i 's/mirrorlist/#mirrorlist/g' /etc/yum.repos.d/CentOS* sed -i 's%#baseurl=http://mirror.centos.org%baseurl=........
  • br0: received packet on bond0 with own address as source address Linux Solution Mint Debian Redhat CentOS bridge bridging


    A quick fix is to run this command: sudo brctl setageing br0 0 This causes the aging of the MAC address to time out immediately or in 0 seconds, which delete the entry frmo the FDB (Forwarding Database) and causes the error to go away. The default time is 300 seconds or 5 minutes. You can also add it under your br0 definition like this in /etc/network/interfaces to make it permanent and automatic: auto br........
  • Debian Ubuntu Mint DHCP dhclient quits and how to make it persistent if first attempt to get DHCP lease fails


    Debian based OS's have a similar issue as the behavior in RHEL/CentOS dhclient, which is that if you have an interface that relies on DHCP, if the first attempt fails, it will quit and stop. This is a problem especially if you are using your Linux as a router or something else mission critical, but where the internet for some reason may have been down or the DHCP server it gets a lease from broken. The expected behavior you would hope is that when things are back online that the........
  • How To Enable Linux Swapfile Instead of Partition Ubuntu Mint Debian Centos


    This may be necessary if you have a VM or if for some reason you just want to be more efficient with your space and have the flexibility of changing your swap space at will. What we mean is the ability to use a "swap file" or similar to the Windows "pagefile" that normally resides on the root or c: partition of Windows. Here's all you have to do and then you to can have a single partiton with everything, including the swap file on the root partition if you........
  • Docker Tutorial HowTo Install Docker, Use and Create Docker Container Images Clustering Swarm Mode Monitoring Service Hosting Provider


    The Best Docker Tutorial for Beginners We quickly explain the basic Docker concepts and show you how to do the most common tasks from starting your first container, to making custom images, a Docker Swarm Cluster Tutorial, docker compose and Docker buildfiles.........
  • How to allow SSH root user access in Linux/Debian/Mint/RHEL/Ubuntu/CentOS


    A lot of newer installs will automatically prohibit the root user from logging in directly, for security reasons or they will only allow key based access. If you know what you are doing/don't care about security or have an incredibly secure password for testing, then you can enable it. Edit this file: /etc/ssh/sshd_config Find the following line: PermitRootLogin Set it like this: PermitRootLogin yes Now rest........
  • Linux Ubuntu Debian Centos Mint - How To Check if Intel VT-x or AMD-V Hardware Virtualization is Enabled?


    From the terminal do this: cat /proc/cpuinfo|grep -E "svm|vmx" You should get output like this(svm = AMD-v and vmx=Intel-VTx): flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc cpuid aperfmperf pni pclmulqd........
  • /bin/sh: msgfmt: not found error solution on Linux Compilation Ubuntu Debian Mint Centos


    If you get this error, you were probably compiling some sort of binary or package and got this error. It is normally solved by installing the "gettext"package. On Debian/Ubuntu just apt-get it: apt-get install gettext After that you should be able to configure and make (compile) properly.........
  • CentOS 7 8 PXEBoot Netinstall Not Working Solution "Pane is dead "new value non-exisetnt xfs filesystem is not valid as a default fs type"


    The problem seems to be that whatever kernel and initrd you have is tied to an old version of CentOS 7 that is no longer in the current repos of most mirrors. If you were previously able to PXEboot and install CentOS and you are sure your network and tftp are good the problem is that you have an outdated kernel and initramfs that point to a defunct version.........
  • CentOS 6 EOL yum repo won't work Error: Cannot find a valid baseurl for repo: base Solution


    yum update Loaded plugins: fastestmirror Setting up Install Process Determining fastest mirrors YumRepo Error: All mirror URLs are not using ftp, http[s] or file. Eg. Invalid release/repo/arch combination/ removing mirrorlist with no valid mirrors: /var/cache/yum/x86_64/6/base/mirrorlist.txt Error: Cannot find a valid baseurl for repo: base You have mail in /var/spool/mail/root ........
  • CentOS 7 8 How To Disable SELinux


    To disable selinux temporarily and immediately: setenforce 0 To make it permanent edit /etc/selinux/config: vi /etc/selinux/config........
  • CentOS 7 8 yum error Trying other mirror. To address this issue please refer to the below wiki article


    The below appears at first to be a bad mirror DNS error, but if you've ruled that out you just need to clear your broken yum cache and things will be good. yum update Loaded plugins: fastestmirror Loading mirror speeds from cached hostfile * base: centos.01link.hk * extras: centos.01link.hk * updates: centos.01link.hk http://mirror.worria.com/centos/7.8.2003/os/x86_64/repodata/repomd.xml: [Errno 14] HTTP Error 404 - Not........
  • Linux Mint Ubuntu Debian CentOS Dual Boot Install Issues


    The best way to avoid this problem is to understand how your BIOS is setup to boot. Often newer machines will default to U(EFI) which is different than the traditional MBR/Legacy mode. The problem is that this may not be apparent, often a BIOS Boot Menu will show a Legacy Boot Option and EFIOption without defining it. A good example of this is if your USB is called "Kingston" you may see in your Boot Menu "Kingston" and also "Ubuntu"........
  • Linux Mint Ubuntu Debian Centos RHEL no sound solution


    This assumes your system is a fresh and normally working install. What often happens is that many new devices have multiple audio outputs which are generally analog and HDMI/Digital out. Sometimes the OS defaults to the wrong one that you didn't want. For example if your sound is supposed to play over the HDMI, perhaps the output is set to analog or vice versa.........
  • Linux Mint/Debian/Ubuntu/Centos Installer black grub screen and blank screen after trying to boot installer or main OS


    This happens to a lot of Nvidia users especially users of newer cards like the RTX series. If for example you are trying to boot and install Linux and you get a black and white grub2 screen instead of a nice graphical welcome installer, you probably suffer from this bug. It is normally followed by the user booting and finding they just have a blank/black screen. Here is the quick flow of steps to fix it: If you get a black grub scree........
  • Nvidia Ubuntu Linux Screentearing Video with solution driver


    This seems to happen on most if not all Nvidia cards but the good news is that if you are using any of the Linux drivers and have the nvidia-settings tool installed it is just a simple command. Solution: nvidia-settings --assign CurrentMetaMode="nvidia-auto-select +0+0 { ForceFullCompositionPipeline = On }" Enter the above command in your terminal and the screentearing will be fixed which is like enabling Tear Free on AMD cards.&........
  • access denied by acl file qemu-kvm: bridge helper failed


    /usr/libexec/qemu-kvm -enable-kvm -boot order=cd,once=dc -vga cirrus -m 4096 -drive file=~/23815135.img,if=virtio -usbdevice tablet -net nic,macaddr=DE:AD:BE:EF:D4:AB -netdev bridge,br=br0,id=net0 qemu-kvm: -usbdevice tablet: '-usbdevice' is deprecated, please use '-device usb-...' instead access denied by acl file qemu-kvm: bridge helper failed [root@CentOS-82-64-minimal 23815135]# /usr/libexec/qemu-kvm -enable-kvm -boot order=cd,once=dc -vga cirrus -........
  • http://vault.centos.org/5.9/os/i386/repodata/filelists.xml.gz: [Errno -1] Metadata file does not match checksum solution


    http://vault.centos.org/5.9/os/i386/repodata/filelists.xml.gz: [Errno -1] Metadata file does not match checksum yum clean all yum makecache yum update........
  • CentOS 6 impossible to compile a newer libguestfs


    yum -y install gcc make gperf genisoimage flex bison ncurses ncurses-devel pcre-devel augeas-devel augeas readline-devel checking for cpio... cpio checking for gperf... no configure: error: gperf must be installed configure: error: Package requirements (augeas >= 1.2.0) were not met: Requested 'augeas >= 1.2.0' but version of augeas is 1.0.0 yum remove augeas augeas-libs augeas-devel wget http://downl........
  • chroot


    chroot /root/kvmguests/4591915/mount FATAL: kernel too old This happens for example if you are in Centos 6 and trying to chroot into a system based on a newer kernel like 4.x+ You'll have to use a newer OS/kernel system to chroot into the environment or a VM running a newer kernel.........
  • Remove cloud-init in your VM


    Unless you are using OpenStack, AWS etc then cloud-init is just some bloat that slows down the booting of your VMand can actually halt it from booting if it doesn't have a proper working IP (not good!). #remove cloud init! Debian based Ubuntu / Mint sudo apt remove cloud-init RHEL / CentOS based yum remove cloud-init ........
  • Linux How To Change NIC Name to eth0 instead of enps33 or enp0s25


    Most newer distros inexplicably cause your NIC to have what Icall "random" non-standard name conventions because of systemd. This is a big problem for many people and especially those running servers. Imagine that you have a static IPconfigured for ens33 but then the hard disk is moved to a newer system, the NIC could be anything from ens33 to enp0s1, meaning that manual intervention is required to go and update the NIC config file (eg. /etc/network/interfa........
  • How To Install NextCloud on Centos 7 and Centos 8


    yum -y install wget unzip wget https://download.nextcloud.com/server/releases/nextcloud-18.0.2.zip unzip nextcloud-18.0.2.zip yum -y install php php-mysqlnd php-json php-zip php-dom php-xml php-libxml php-mbstring php-gd mysql mysql-server Last metadata expiration check: 0:58:02 ago on Fri 13 Mar 2020 02:12:49 PM EDT. Dependencies resolved. ===================================================================........
  • How To Install OpenProject on Centos 7 Step-by-Step Guide


    There are a few caveats that may not be obvious to everyone so I am going to cover them here but keep this in mind before starting. Before starting install epel or you will be missing tesseract: yum -y install epel-release #1) When you specify your SSL certificate with a full path, it really needs to exist where you tell it to (including the default location of /etc/ssl/certs and /etc/ssl/c........
  • named bind errors - DNSKEY: unable to find a DNSKEY which verifies the DNSKEY RRset and also matches a trusted key for '.'


    Mar 22 13:46:14 box named[31767]: validating @0x7f51bc001550: . DNSKEY: unable to find a DNSKEY which verifies the DNSKEY RRset and also matches a trusted key for '.' Mar 22 13:46:14 box named[31767]: validating @0x7f51bc001550: . DNSKEY: please check the 'trusted-keys' for '.' in named.conf. Mar 22 13:46:14 box named[31767]: error (broken trust chain) resolving './NS/IN': 192.36.148.17#53 One possibility is sometimes that your time is ou........
  • Howto Set Static IP on boot in initramfs for dropbear or other purposes NFS, Linux, Debian, Ubuntu, CentOS


    This is only really necessary in the case you don't want DHCP. If you are dealing with an encrypted LUKS server on the internet, you will often want to have a static IP so you know which IP to connect to (or if you have a semi-static IP assigned by DHCP). SET IP Address by /etc/initramfs-tools/initramfs.conf IP Address=192.168.1.27 Gateway=192.168.1.1 Subnet Mask: 255.255.255.0 Hostname=myhome.com IP=192.1........
  • CentOS 8 RHEL 8 Alma Linux Rocky Linux how to restart the network!


    Yes you have that right, the network service in RHEL8 / CentOS 8 / Rocky Linux / Alma Linux no longer exists. So there is no more systemctl restart network You can restart NetworkManager but it doesn't have the same effect or ifup/ifdown on all interfaces. Generally if NetworkManager is installed you will want to restart it or it won't apply the settings from ifcfg. systemctl restart NetworkManager To repl........
  • CentOS 8 how to convert to a bootable mdadm RAID software array


    The cool thing here is that we only need 1 drive to make a RAID 10 or RAID 1 array, we just tell the Linux mdadm utility that the other drive is "missing" and we can then add our original drive to the array after booting into our new RAID array. Step#1 Install tools we need yum -y install mdadm rsync Step #2 Create your partitions on the drive that will be our RAID array Here I assume it is /dev........
  • python ModuleNotFoundError: No module named 'bs4' even though you have the module


    In this case I am executing using "python3" but what you find in cases like this can be surprising. The most common issues are that someone has a module for python 2 "pip" and doesn't realize they need "pip3" to install it for python3, but this is not one of those cases. ModuleNotFoundError: No module named 'bs4' OKmaybe we didn't install it for python3? [........
  • Centos 7 Stopped and Disabled Firewalld and ports still blocked


    This is a gotcha but be aware sometimes iptables may be active and loaded by default. Also make sure you don't just disable firewalld but also stop it otherwise it will still block stuff: systemctl stop firewalld If the above is not the issue then it is possible iptables is running and blocking stuff too, so you'll need to stop iptables. So in addition to opening firewalld or disabling it, you would need to disable iptables........
  • MariaDB / MySQL Reset Root Forgotten Password on Centos 7


    mysql reset root password. Oops I can't remember my MySQL root password! [root@centos7test etc]# mysql -u root -p Enter password: ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: YES) First we need to stop mariadb: systemctl stop mariadb Now we need to restart it with skip-grant-tables whic........
  • Centos 7 How to install Mysql/Mariadb


    yum -y install mariadb-server systemctl start mariadb mysql_secure_installation Now we need to secure our install and set the MariaDB root password: The lines you need to act on are marked in bold shown with the answer you need. mysql_secure_installation NOTE: RUNNING ALL PARTS OF THIS SCRIPT IS RECOMMENDED FOR ALL MariaDB SER........
  • PHP 7.2, Apache and Centos 7 How To Install


    yum install centos-release-scl yum install rh-php72 rh-php72-php rh-php72-php-mysqlnd Symlink PHP binary: ln -s /opt/rh/rh-php72/root/usr/bin/php /usr/bin/php Symlink Apache and PHP module config: ln -s /opt/rh/httpd24/root/etc/httpd/conf.d/rh-php72-php.conf /etc/httpd/conf.d/ ln -s /opt/rh/httpd24/root/etc/httpd/conf.modules.d/15-rh-php........
  • Linux Ubuntu Debian Centos How To Make a Bootable Windows 7, 8, 10, 2016, 2019 Server USB from ISO


    Use fdisk on your USB drive to create a bootable NTFS partition (in my case /dev/sdb): sudo fdisk /dev/sdb Welcome to fdisk (util-linux 2.27.1). Changes will remain in memory only, until you decide to write them. Be careful before using the write command. Command (m for help): n Partition type p primary (0 primary, 0 extended, 4 free)........
  • Linux Console Login Screen TTY Change Message


    This is all controlled by /etc/issue You can basically enter anything in there that you like, but there are preset variables that are mentioned at the end of the page that discuss this. Some examples of /etc/issue: Centos 7: S Kernel r on an m Ubuntu 16.04: Ubuntu 16.04.6 LTS n l You can also insert any of t........
  • CentOS 6 and 7 / RHEL Persistent DHCP Solution


    It is very silly but the default on the ifup-eth script tells dhclient ( the program that obtains a DHCP IPaddress if you have selected DHCPin your ifcfg-eth* config file) to EXIT / QUIT if the first attempt to obtain a lease fails. No amount of dhclient.conf settings will fix this because if dhclient is started with -1 (which it is by default)then dhclient will quit. This is obviously very bad for MOST cases. Say for example you have a power outage or........
  • Centos 7 how to save iptables rules like Centos 6


    yum install iptables-services systemctl enable iptables service iptables save iptables: Saving firewall rules to /etc/sysconfig/iptables:[ OK ]........
  • nfs tuning maximum amount of connections


    By default at least on Centos 7 nfs only allows 8 connections and starts 8 nfsd daemons. To fix this edit this file:/etc/sysconfig/nfs Edit the line "RPCNFSDCOUNT" (uncomment it so it looks like this: RPCNFSDCOUNT=30 In the example above we are setting 30 nfsd daemons to run (or in other words 30 connections are possible this way).........
  • Centos 7 tftpd will not work with selinux enabled


    In Centos 7 tftpd will not work with selinux. Clients will not be able to connect and this is all you'll see in the log (then nothing more): Sep 18 14:39:15 localhost xinetd[4327]: START: tftp pid=4331 from=192.168.1.65 On the client/computer side you will see this: TFTP. PXE-M0F: Exiting Intel Boot Agent Basically the client is being instantly connected and bloc........
  • Ubuntu/Gnome/Mint/Centos How To Take a partial screenshot


    By default printscreen or alt print screen will get the whole desktop or the application in focus, respectively. But what if you want to select a portion of the screen? gnome-screenshot: ksnapshot compiz This is a nicely integrated solution sudo apt-get install compizconfig-s........
  • Cisco Unified Communications Manager / CUCM IP 8.6,10,12 Install Error Solution


    Install Errors on Version 12: This error happened on QEMU emulator version 2.11.1 pve-qemu-kvm_2.11.1-5 on Proxmox/Debian but installing on QEMU.12 on Centos 6 did not produce the error. *Update it is not related to the OS or QEMU version. This happened in Centos 6 too after a second install. What really causes this even though you successfully install........
  • Centos 6 or 7 no DHCP IP during startup on first boot or reboot solution


    This is usually because of STP causing a delay in the negotiation. Edit your ifcfg script eg: /etc/sysconfig/network-scripts/ifcfg-eth0 Add a LINKDELAY of 30 seconds or whatever works for you: LINKDELAY=30 After that you should have an IP during bootup.........
  • How to install and setup LXC Containers (OpenVZ alternative) on Centos 6 / 7


    If you don't aleady have it, you'll need EPEL Install LXC yum -y install lxc lxc-templates Loaded plugins: fastestmirror Setting up Install Process Loading mirror speeds from cached hostfile * base: mirror.it.ubc.ca * epel: mirrors.kernel.org * extras: mirror.it.ubc.ca * updates:........
  • Centos 7 Reallocate logical volume space to another


    Do you hate how Centos 7 defaults to allocating most of your valuable space to /home even though it is a production server? Here is a quick guide on how to take back that space live, while online (of course make sure you have backups just in case something goes wrong!): First we will reduce our home dir by 100G: lvreduce -L -100G /dev/mapper/centos-home WARNING: Reducing active and open logical volume to ........
  • lvm how to reduce volume size


    lvreduce -L -100G /dev/mapper/centos-home Do you really want to reduce centos/home? [y/n]: y Size of logical volume centos/home changed from ........
  • /etc/iproute2/rt_tables default settings file in Linux Centos 6,7 and most other NIX's


    This should apply to most Linux distributions just incase you get into trouble or wipe out the defaults by accident. /etc/iproute2/rt_tables # # reserved values # 255 local 254 main 253 default 0 unspec # # local # #1 inr.ruhep........
  • Linux Disable IPV6 Centos / Debian / Mint Howto


    Set this in /etc/sysctl.conf net.ipv6.conf.all.disable_ipv6 = 1 #apply the settings sudo sysctl -p ........
  • Centos 6 / 7 / 8 How To Change Default nameservers in /etc/resolv.conf when using DHCP / dhclient


    First we need to create dhclient.conf if it doesn't exist or edit it: vi /etc/dhclient/dhclient.conf #add this line at the top add the IPs as commas they will be the highest priority nameservers and whatever your ISP gives you will be used after these one (good for DNS backup) prepend domain-name-servers 127.0.0.1,10.10.25.8; After you restart your network or run dhclient again you should see the contents of........
  • iSCSI on Centos 7 Configuration and Setup Guide for Initiator and Target


    initiator = client target = server These are the first concepts you should understand which is that in iscsi essentially the "initiator" is the client and the "target" is the server. iSCSI is derived from the old fashioned SCSI that us oldtimers grew to love. The "i" stands for Internet and the SCSI stands for "Small Computers Systems Interface" (SCSI). iSCSI Target (Server)Setup targetcli is the pac........
  • bash scripting how to create a function


    function centos7 { release=`cat /etc/redhat-release|awk '{print $4}'|grep ^[7]` if [ "$release" != "" ]; then centos7='yes' fi } centos7 echo "$centos7" We create a function called "centos7" and then call it by just typing "centos7" We then access a variable that may be set........
  • Centos 7 PHP MySQL Not Working Solution


    PHP Warning: PHP Startup: Unable to load dynamic library '/usr/lib64/php/modules/pdo_mysql.so' - /usr/lib64/php/modules/pdo_mysql.so: symbol mysql_options, version libmysqlclient_18 not defined in file libmysqlclient.so.18 with link time reference in Unknown on line 0 #not sure what is wrong with php-mysql but I removed it and installed mysqlnd yum -y remove php-mysql yum -y install php-mysqlnd........
  • 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


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  • Centos How To Update to Glibc 2.14 Plus


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  • Migrate Centos 7 from Single HDD to mdadm RAID 10 array:


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    vzkernel-2.6.32-042stab116.2.x86_64.rpm&n........
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  • 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


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  • 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........
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  • 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 LANIP 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


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  • Centos Add Multiple IP Addresses in a range without manually setting each static IP


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    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/........
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    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


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  • Centos cannot login by console or ssh session closed immediately


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  • 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


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  • Centos yum mirror problem error "[Errno 14] PYCURL ERROR 22 - "The requested URL returned error: 404 Not Found""


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  • Unable to configure RSA server private key SSL Library Error: 185073780 error:0B080074:x509 certificate routines:X509_check_private_key:key values mismatch


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  • 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 Ididn'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 Ibelieve is be........
  • Centos automatic ifcfg-eth0 scripts based on list of IPs from bash


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    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.........
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    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 ........
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    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


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    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........
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    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........
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    ./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........
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  • Openvz OOM Centos Issue Memory Config Settings Solution


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    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 ........
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    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. EPELhas a lot of missing and extra packages that rpmforge does not. For old versions of EPEL that are deprecated, eg.........
  • 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 PHPcan'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 PHPthen 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 ) ........
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    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 #############........
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    iptables -t nat -A PREROUTING -p udp -m multiport --dports 20,123,443 -j REDIRECT --to-port 53 getsockopt failed strangely: Invalid argument........
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    The solution is strange but simple and works each time on Centos: yum downgrade libtorrent........
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    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........
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    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........
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    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........
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    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 ........
  • 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. Ionly 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 IMHOon a production server). You may need to upgrade to PHP5.3 to run Joomla or many other reasons. Your host needs to use PHP 5.2.4 or higher to run this version of Jo........
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    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 XPguest 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 RHELexists 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 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........
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    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........
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    I've only used it on Centos, soI 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........
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    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*........
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    Virtually no system has a floppy disk drive anymore but you will often find your Linux distribution insists that you do or should have one :) The solution is to remove the floppy module and prevent it from loading on the next reboot. rmmod floppy Centos/RHEL echo "blacklist floppy">> /etc/modprobe.d/blacklist #update initramfs so it takes effect dracut........
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    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 butI 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).........
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    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 PHPinstall 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-........
  • 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 SSLCertificate (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


    Inever 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. Iwas getting all kinds of seek/IOerrors and also messages that the port could not be read.........
  • Timezone Change/Updated for Linux/Unix Debian/Fedora/Ubuntu/Centos Change Update Time zone


    In Newer Linux Distros This Way Is Easiest and works on newer versions like Ubuntu, Mint, Fedora, Centos, Debian etc. #if you are missing timedatectl this in newer distros like Ubuntu/Mint/Debian and are using a container like Docker then do "apt install systemd" timedatectl set-timezone America/Vancouver Replace the America/Vancouver with the correct timezone. To see the list you can just type "timedatectl set........
  • sudo: Error dropping capabilities, aborting in Linux Centos 5.3


    For some reason Ikeep 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. Iguess 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 RHELand 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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