Red Hat Package Management

A package in linux contains files and directories of the software we wish to use.  There are two different package types, .rpm used by Red Hat/CentOS/Fedora and .deb used by Debian/Ubuntun.  We are going to focus on the Red Hat version.  Each package in Red Hat is broken down into the following format:

package_name-version-release.arch.rpm


postfix-2.3.3-2.1.el5_2.i386.rpm

To download and install packages you obtain them from repositories.  Needless to say you should only use repositories and files from trusted sources.  The Red Hat Network (RHN) also provides packages and software updates from Red Hat clients.  It also provides a web interface which allows for snapshots, scheduled commands, and kickstart installations.  Instead of going into every single detail relating to rpm and yum (the frontend to rpm), we will look at common tasks and commands for system administration.

Querying Packages

To list all install packages on the system:

$rpm -qa

- or -

$rpmquery -a

Use commands like sort, grep, and wc to filter the results.

Check to see if Apache is installed:

$rpm -qa | grep httpd

If it returns the package then it is installed, otherwise nothing will be returned meaning it is not installed.

Also available is the yum commands which produce alot of output so make sure to pipe them:

$yum list | grep httpd

httpd.i386                 2.2.3-31.el5.centos.2         installed

Searching for Packages

To find a package to install:

$yum search httpd

Installing Packages

To install Apache with no prompts:

$yum -y install httpd.i386

You can also use rpm to install packages that you have downloaded:

$rpm -ivh mypackage.rpm

Removing Packages

To uninstall Apache:

$yum remove httpd

You can also do the same with the rpm command:

$rpm -e mypackage

Some other commands that may be useful include updating, upgrading, obtaining information on packages, and group installs.

$yum update


$yum check-update


$yum info


$yum groupinstall


$yum clean all

For those of you can don't like the command line you can also use the GUI tool that comes with Red Hat called pirut.  This is the package manager which can perform all the same commands that we have discussed via the command line.  The last part of package management that we will discuss deals with YUM repositories.  When handling a large number of systems and installs you will probably want to configure a local package repository (unless you happen to have a massive bandwidth pipe to the internet).  It also will help with dependency issues because it will make certain that all packages are using the versions.  to create a local repository follow these steps:

1) Download the needed package

$yum -y install createrepo

2) Create a directory for the repors

$mkdir -p /var/yum/repos.d && cd /var/yum/repos.d

3) Move all packages that you wish to be made available

4) Execute the createrepo command to convert the packages to local distribution

$createrepo -v .

5) Create the repo file for the repository

$nano /etc/yum.repos.d/server01.repo


[server01]
name=yum repository for server01
baseurl=ftp://server01/var/yum/repos.d/
enabled=1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-redhat-release

Finally you will need to make sure that your main yum configuration file is in order and specifies you local repositories as well.  You can find the file in /etc/yum.conf.  You now should have a pretty good handle on managing packages for your system.  There are obviously many other commands and options that you can use with yum or rpm however it is better to have a foundation and then work through the --help parameters.  This will show you all the options available and as always use the man pages for clarification of anything you may need.