Puppet is a system for automating system administration tasks. Its automation saves you countless hours of frustration, monotony and reinventing the wheel. It lets you perform administrative task from a central systems to any number of systems running any variant of operating system.

For a more complete description visit Puppet Labs.

Installing the Puppet CentOS 6 packages

Install the Puppet Repository

# vi /etc/yum.repos.d/puppet.repo

[puppetlabs]
name=Puppet Labs Packages
baseurl=http://yum.puppetlabs.com/el/$releasever/products/$basearch/
enabled=1
gpgcheck=1
gpgkey=http://yum.puppetlabs.com/RPM-GPG-KEY-puppetlabs

Install the EPEL x86_64 YUM Repository

# rpm -Uvh http://download.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-5.noarch.rpm

Install the Puppet Master packages

# yum install puppet-server

Install the Puppet Client packages

# yum install puppet

A Simple Manifest: Managing Ownership of a File

Step 1: Create a minimal manifest file called site.pp in /etc/puppet/manifests with the following content:

# vi /etc/puppet/manifests/site.pp

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# /etc/puppet/manifests/site.pp
 
import "classes/*"
 
node default {
    include sudo
 }

Step 2: Next create the sudo.pp class in /etc/puppet/manifests/classes/ with the following content:

# vi /etc/puppet/manifests/classes/sudo.pp

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# /etc/puppet/manifests/classes/sudo.pp
 
class sudo {
    file { "/etc/sudoers":
        owner => "root",
        group => "root",
        mode  => 440,
    }
}

This class which will ensure that the owner, group, and mode of the /etc/sudoers file will be set consistently across all systems that belong to that class.

Step 3: Start the Puppet Master service and enable startup on boot

# service puppet-server start
# chkconfig puppet-server on

Configuring Puppet

Configure the puppet client to connect to the server and enable logging. Edit the file /etc/sysconfig/puppet and uncomment the PUPPET_LOG and PUPPET_SERVER line specifying the servers address.

# vi /etc/sysconfig/puppet

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# The puppetmaster server
PUPPET_SERVER=PuppetMaster
 
# If you wish to specify the port to connect to do so here
#PUPPET_PORT=8140
 
# Where to log to. Specify syslog to send log messages to the system log.
PUPPET_LOG=/var/log/puppet/puppet.log
 
# You may specify other parameters to the puppet client here
#PUPPET_EXTRA_OPTS=--waitforcert=500

The client will automatically pull configuration from the server every 30 minutes, start it as a service and enable startup on boot

# service puppet start
# chkconfig puppet on

Sign the SSL key request from the Puppet Client

In order for the two systems to communicate securely we need to create signed SSL certificates. You should be logged into both the Puppet Master and Puppet machines for this next step.

# puppetca --list
server2.example.co.za

# puppetca --sign server2.example.co.za
Signed server2.example.co.za

Percona XtraDB Cluster is a new high availability and high scalability solution for MySQL users. XtraDB Cluster integrates Percona Server with the Galera library of high availability solutions in a single product package. Percona XtraDB is an enhanced version of the InnoDB storage engine for MySQL and MariaDB. It has much faster performance than InnoDB and better scalability on modern hardware.

This tutorial is how to setup a 3-node XtraDB cluster, assuming you are running CentOS Linux 6.2 64-bit.

Install Percona’s CentOS 6 repositories:

# rpm -Uhv http://repo.percona.com/testing/centos/6/os/noarch/percona-testing-0.0-1.noarch.rpm
# rpm -Uhv http://www.percona.com/downloads/percona-release/percona-release-0.0-1.x86_64.rpm

Install Percona XtraDB Cluster packages:

# yum install Percona-XtraDB-Cluster-server Percona-XtraDB-Cluster-client

XtraDB Cluster requires a couple of TCP ports to operate. Easiest way:

# service iptables stop

If you want to open only specific ports, you need to open 3306, 4444, 4567, 4568 ports.

For example for 4567 port (substitute 10.0.0.1 by your IP):

# iptables -A INPUT -i eth0 -p tcp -m tcp –source 10.0.0.1/24 –dport 4567 -j ACCEPT

Now repeat on all XtraDB cluster nodes

Create /etc/my.cnf files

On the first XtraDB Cluster node (assume IP 10.0.0.10):

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[mysqld]
datadir=/mnt/data
user=mysql
 
binlog_format=ROW
 
wsrep_provider=/usr/lib64/libgalera_smm.so
 
wsrep_cluster_address=gcomm://
 
wsrep_slave_threads=2
wsrep_cluster_name=trimethylxanthine
wsrep_sst_method=rsync
wsrep_node_name=node1
 
innodb_locks_unsafe_for_binlog=1
innodb_autoinc_lock_mode=2

On the second XtraDB Cluster node:

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[mysqld]
datadir=/mnt/data
user=mysql
 
binlog_format=ROW
 
wsrep_provider=/usr/lib64/libgalera_smm.so
 
wsrep_cluster_address=gcomm://10.0.0.10
 
wsrep_slave_threads=2
wsrep_cluster_name=trimethylxanthine
wsrep_sst_method=rsync
wsrep_node_name=node2
 
innodb_locks_unsafe_for_binlog=1
innodb_autoinc_lock_mode=2

On the third XtraDB Cluster node:

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[mysqld]
datadir=/mnt/data
user=mysql
 
binlog_format=ROW
 
wsrep_provider=/usr/lib64/libgalera_smm.so
 
wsrep_cluster_address=gcomm://10.0.0.10
 
wsrep_slave_threads=2
wsrep_cluster_name=trimethylxanthine
wsrep_sst_method=rsync
wsrep_node_name=node3
 
innodb_locks_unsafe_for_binlog=1
innodb_autoinc_lock_mode=2

Start mysqld on the first node:

# service mysql start

When all nodes are in SYNCED stage your cluster is ready!

Connect to database on any node and create database:

# mysql
> CREATE DATABASE how2centos_test;

The new database will be propagated to all nodes.

CentOS 6.2 Downloads

You can download CentOS 6.2 via the web/ftp server or via BitTorrent (recommended) client.

CentOS 6.2 DVD ISO downloads

• Download CentOS 6.2 32 bit DVD ISO CentOS-6.2-i386-bin-DVD1.iso and CentOS-6.2-i386-bin-DVD2.iso
• Download CentOS 6.2 64 bit DVD ISO CentOS-6.2-x86_64-bin-DVD1.iso and CentOS-6.2-x86_64-bin-DVD2.iso

CentOS 6.2 DVD ISO Torrents

Torrent files for the DVD’s are available at the following location:

• Download CentOS 64 i386 torrent file
• Download CentOS 64 x86_64 torrent file

Yum is an automatic updater and package installer/remover for rpm-based systems. It automatically computes dependencies and figures out what things should occur in order to safely install, remove, and update rpm packages. Yum also efficiently and easily retrieves information on any package installed or available in a repository to the installer.

When trying to update your server via the yum command you might see the following error / warning message:

Warning: RPMDB altered outside of yum.

# yum install nethogs
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
* base: mirror.cogentco.com
* epel: mirror.cogentco.com
* extras: mirror.vcu.edu
* ius: mirror.rackspace.com
* updates: centos.aol.com
Setting up Install Process
Resolving Dependencies
–> Running transaction check
—> Package nethogs.x86_64 0:0.8.0-1.el6 set to be updated
–> Finished Dependency Resolution

Dependencies Resolved

====================================================================
 Package       Arch            Version          Repository     Size
====================================================================
Installing:
 nethogs      x86_64           0.8.0-1.el6      epel          28 k

Transaction Summary
====================================================================
Install       1 Package(s)
Upgrade       0 Package(s)

Total download size: 28 k
Installed size: 53 k
Is this ok [y/N]: y
Downloading Packages:
nethogs-0.8.0-1.el6.x86_64.rpm | 28 kB 00:00
Running rpm_check_debug
Running Transaction Test
Transaction Test Succeeded
Running Transaction

Warning: RPMDB altered outside of yum.

Installing : nethogs-0.8.0-1.el6.x86_64 1/1

Installed:
nethogs.x86_64 0:0.8.0-1.el6

Complete!

How do you fix this problem?

# yum clean all

After installing CentOS we sometimes see that the date is not in our desired timezone, instead it defaulted to the PST timezone.

Correcting your timezone is an easy operation, so here is a quick guide to change your CentOS timezone configuration file.

Firstly you’ll need to know your timezone and/or country, a list can be found in /usr/share/zoneinfo/

The more generic procedure to change the timezone is to create a symlink to file /etc/localtime

# ln -sf /usr/share/zoneinfo/Africa/Johannesburg /etc/localtime

OR you can copy and replace the current localtime setting

# cp /usr/share/zoneinfo/Africa/Johannesburg /etc/localtime

To verify that your timezone is changed use the date command:

# date

A quick solution to duplicate packet installation. This tutorial will show you how to remove all i386 packages from CentOS 5 x86_64 server

# yum remove \*.i\?86

You can update your CentOS 6 system to the latest version or to a specific version of the BIOS and firmware available in the Dell Linux online repository. You can inventory your CentOS 6 system, scan the repository for matching firmware with newer version using repository management software such as yum.

Firmware-tools are used to update BIOS and firmware on your system. Using a repository management software, you can easily update your BIOS and firmware to the latest or specific versions on your system.

Setting Up/Bootstrapping the Repository

To setup/bootstrap the Dell Linux online repository on your CentOS 6 sever, run the following command at the command prompt:

# wget -q -O - http://linux.dell.com/repo/hardware/latest/bootstrap.cgi | bash

The system is configured to access the Dell Linux online repository using supported repository management software. The Dell GPG keys and libsmbios (BIOS library) are also installed.

Installing Firmware Tools

# yum install dell_ft_install

Downloading Applicable Firmware

# yum install $(bootstrap_firmware)

You can also inventory your system for the list of existing versions of BIOS and firmware using the following command:

# inventory_firmware

Updating BIOS and Firmware Using CLI

Run the following command to inventory the system and scan the repository for new versions of components:

# update_firmware

This command provides information about the existing versions of components on your system and the list of component versions that are available to be installed.

To install all applicable BIOS and firmware updates on your system, run the following command:

# update_firmware --yes

Once the devices are updated, the “Execution Success” message is displayed.

Automatically Update Firmware

By default, installing a BIOS or firmware RPM does not apply the update to the hardware. The update is manually applied using the update_firmware command. However, you can automatically update the hardware during RPM installation by configuring the /etc/firmware/firmware.conf file.

To automatically install BIOS and firmware updates, ensure that rpm_mode is set to auto in the firmware.conf file as shown:

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[main]
 
# Automatically install BIOS updates when an RPM BIOS Update file is installed
# values: 'auto', 'manual'
# default: 'manual'
rpm_mode=auto

Viewing Log Information

# cat /var/log/firmware-updates.log

CentOS 6 Channel Bonding allows administrators to bind multiple network interfaces together into a single channel using the bonding kernel module and a special network interface called a channel bonding interface. Channel bonding enables two or more network interfaces to act as one, simultaneously increasing the bandwidth and providing redundancy.

CentOS 6 Channel Bonding

Channel bonding (also known as “Ethernet bonding”) is a computer networking arrangement in which two or more network interfaces on a host computer are combined for redundancy or increased throughput.

mode=0 (Balance-rr) – This mode provides load balancing and fault tolerance.
mode=1 (active-backup) – This mode provides fault tolerance.
mode=2 (balance-xor) – This mode provides load balancing and fault tolerance.
mode=3 (broadcast) – This mode provides fault tolerance.
mode=4 (802.3ad) – This mode provides load balancing and fault tolerance.
mode=5 (balance-tlb) – Prerequisite: Ethtool support in the base drivers for retrieving the speed of each slave.
mode=6 (balance-alb) – Prerequisite: Ethtool support in the base drivers for retrieving the speed of each slave.

Note: Always append extra configuration in case of a rollback.

Configuring Channel Bonding

# cd /etc/sysconfig/network-scripts/

# vi ifcfg-bond0

We’ll be using mode=6 (balance-alb)

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DEVICE=bond0
USERCTL=no
BOOTPROTO=none
ONBOOT=yes
IPADDR=10.0.0.10
NETMASK=255.255.0.0
NETWORK=10.0.0.0
BONDING_OPTS="miimon=100 mode=balance-alb"
TYPE=Unknown
IPV6INIT=no

# vi ifcfg-eth0

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DEVICE=eth0
BOOTPROTO=none
ONBOOT=yes
MASTER=bond0
SLAVE=yes
USERCTL=no

# vi ifcfg-eth1

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DEVICE=eth1
BOOTPROTO=none
ONBOOT=yes
MASTER=bond0
SLAVE=yes
USERCTL=no

# vi ifcfg-eth2

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DEVICE=eth2
BOOTPROTO=none
ONBOOT=yes
MASTER=bond0
SLAVE=yes
USERCTL=no

Due to the fact that /etc/modprobe.conf has been deprecated in CentOS 6, the process of bonding network interfaces has changed a bit.

Now instead of defining your bond in your /etc/modprobe.conf, you define it in /etc/modprobe.d/bonding.conf

# vi /etc/modprobe.d/bonding.conf

Append the following onto the end out your modprobe config file

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alias bond0 bonding

# servive network restart

You need to be aware that by disabling SELinux you will be removing a security mechanism on your CentOS system. Think about this carefully, and if your system is on the Internet and accessed by the public, then think about it some more.

Applications should be fixed to work with SELinux, rather than disabling the OS security mechanism.

You could even switch to Permissive mode where every operation is allowed. Operations that would be denied are allowed and a message is logged identifying that it would be denied.

If you really need to disable SELinux on CentOS 6 please consider the following:

# vi /etc/selinux/config

Change SELINUX=enforcing

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# This file controls the state of SELinux on the system.
# SELINUX= can take one of these three values:
#     enforcing - SELinux security policy is enforced.
#     permissive - SELinux prints warnings instead of enforcing.
#     disabled - No SELinux policy is loaded.
SELINUX=enforcing
# SELINUXTYPE= can take one of these two values:
#     targeted - Targeted processes are protected,
#     mls - Multi Level Security protection.
SELINUXTYPE=targeted

to SELINUX=disabled

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# This file controls the state of SELinux on the system.
# SELINUX= can take one of these three values:
#       enforcing - SELinux security policy is enforced.
#       permissive - SELinux prints warnings instead of enforcing.
#       disabled - SELinux is fully disabled.
SELINUX=disabled
# SELINUXTYPE= type of policy in use. Possible values are:
#       targeted - Only targeted network daemons are protected.
#       strict - Full SELinux protection.
SELINUXTYPE=targeted

This will disable SELinux on your next reboot.

To diable SELinux, without having to reboot, you can use the setenforce command like so:

# setenforce 0

This will revert to enforcing once you reboot

The assumption for installing PHP 5.3 on CentOS 5.7 tutorial is that you are running as root and have a basic understanding of the software required but if you follow this tutorial you should be able to complete the task successfully.

Lets begin by installing yum-priorities to enforce ordered protection of repositories, by associating priorities to repositories.

# yum install yum-priorities

Installing PHP 5.3 on CentOS 5.7 x86_64

Install the EPEL x86_64 YUM Repository

# rpm -Uvh http://download.fedoraproject.org/pub/epel/5/x86_64/epel-release-5-4.noarch.rpm

Install the IUS x86_64 YUM Repository

# rpm -Uvh http://dl.iuscommunity.org/pub/ius/stable/Redhat/5/x86_64/ius-release-1.0-10.ius.el5.noarch.rpm

# yum install php53u php53u-common php53u-devel

# php -v
PHP 5.3.8 (cli) (built: Aug 23 2011 06:33:32)
Copyright (c) 1997-2011 The PHP Group
Zend Engine v2.3.0, Copyright (c) 1998-2011 Zend Technologies

Installing PHP 5.3 on CentOS 5.7 i386

Install the EPEL i386 YUM Repository

# rpm -Uvh http://download.fedoraproject.org/pub/epel/5/i386/epel-release-5-4.noarch.rpm

Install the IUS i386 YUM Repository

# rpm -Uvh http://dl.iuscommunity.org/pub/ius/stable/Redhat/5/i386/ius-release-1.0-10.ius.el5.noarch.rpm

# yum install php53u php53u-common php53u-devel

# php -v
PHP 5.3.8 (cli) (built: Aug 23 2011 06:33:32)
Copyright (c) 1997-2011 The PHP Group
Zend Engine v2.3.0, Copyright (c) 1998-2011 Zend Technologies