The RPM Package Manager is used for distribution, installation, upgrading and removal of software on Red Hat Systems. Originally designed to be used in Red Hat Linux, the RPM is used by many GNU/Linux distributions. [1] The RPM system consists of a local database, the rpm executable, the rpm package files.
The local RPM database is maintained in /var/lib/rpm. The database stores information about installed packages such as file attributes and package prerequisites. Software to be installed using rpm is distributed through rpm package files, which are essentially compressed archives of files and associated dependency information.
Dependency Problems
When installing software via rpm, one of the problems that users face is dependency errors. The primary drawback of RPM is that it not able to resolve dependencies i.e. additional RPMs that have to be preinstalled before a certain RPM can be installed. In worst cases, the pre-required rpm itself requires another rpm to be preinstalled, and it would be up to the user to locate and install each of them.
Solving Dependency Problems with YUM
To solve the problems of dependency resolution and package locations, volunteer programmers at Duke University have developed Yellow do Update, Modified, or YUM for short. The system is based on repositories that hold RPMs and a repodata filelist. The yum application can call upon several repositories for dependency resolution, fetch the RPMs and install the needed packages. The following example illustrates the YUM installation procedure-
[root@prime ~]# yum install zsh
Dependencies Resolved
=================================================================
Package Arch Version Repository Size
=================================================================
Installing:
zsh i386 4.2.6-1 rhel-debuginfo 1.7 M
Transaction Summary
=================================================================
Install 1 Package(s)
Update 0 Package(s)
Remove 0 Package(s)
Total download size: 1.7 M
Downloading Packages:
Running Transaction Test
Finished Transaction Test
Transaction Test Succeeded
Running Transaction
Installing: zsh ######################### [1/1]
Installed: zsh.i386 0:4.2.6-1
Complete!
Configuring YUM
Installing RPMs
- createrepo (to create the repository)
- vasftpd (FTP would be used to transfer the necessary files from the Server to the client)
The IP address of my Server is 192.168.10.1 with hostname prime.example.org. The first thing that YUM requires is to prepare a repository from which it can access all the RPMs and call any of them as per necessary. To do this, the only required RPM is createrepo.rpm. The RPM can be found in the RHEL installation DVD in the Serverdirectory.
We would configure the YUM server in such manner that any client Red Hat machine can use the repository of prime.example.org to install RPMs. To do this, the client machine would use the FTP service. So, the ftp service must be installed and run if it is not already installed. These RPMs can easily be installed with the command-
[root@prime ~]# rpm -ivh createrepo-*.rpm
[root@prime ~]# rpm -ivh vsftpd-*.rpm
[root@prime ~]# service vsftpd restart
[root@prime ~]# chkconfig vsftpd on
Creating the Repository
Creating a repository can be done in the following procedure-
1. Copying the entire Serverdirectory to the hard drive. In this case, we copy the directory to FTP home directory /var/ftp/pub/Server
cp -r /mnt/Server /var/ftp/pub/Server
2. Creating the repodata directory that contains information about all the RPMs stored in the directory.
createrepo -v /var/ftp/pub/Server
Preparing the Configuration File
The YUM configuration file can be found in /etc/yum.repos.d/filename.repo. Even if the file name can be any, the file has to be named as filename.repo. We use the default /etc/yum.repos.d/rhel-debuginfo.repo as a reference. The lines in italic are added/modified by the user.
#cp /etc/yum.repos.d/rhel-debuginfo.repo /etc/yum.repos.d/MyYumServer.repo
#/etc/yum.repos.d/MyYumServer.repo
#repository name
[MyYumServer]
#the name can be any name
name=prime YUM server
#the location of the repository
#access protocol may be ftp://, http:// or file://
baseurl=ftp://192.168.10.1/pub/Server
#enabling or disabling the repository
enabled=1
#enabling or disabling gpg checking for digital signature
gpgcheck=0
#gpg key database
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-redhat-release
YUM Commands
The following list contains frequently used commands associated with YUM.
1. yum list - If configured correctly, this command returns the list of all available RPMs in the repository.
2. yum install rpm-name - This if the RPM exists in the repository, this command installs the required RPM and resolves any dependencies automatically if dependency RPMs also exist.
3. yum clean all - This command clears the YUM cache. Particularly useful if installation of an RPM is cancelled or illegally aborted.
3. yum remove rpm-name - This command will remove the package but will keep any configuration file. Usually the configuration file is renamed as filename.rpmsave
3. yum erase rpm-name - This command will remove the package including any configuration file.
Client End Configuration
To use the YUM server setup in prime.example.org, any Red Hat client in the network needs to modify the file /etc/yum.repos.d/rhel-debuginfo.repo configuration file as below. The lines in italic are added/modified by the user.
#cp /etc/yum.repos.d/rhel-debuginfo.repo /etc/yum.repos.d/myyum.repo
#host: client.example.org
#/etc/yum.repos.d/rhel-debuginfo.repo
#repository name
[myyum]
#the name can be any name
name= prime YUM repository
#the location of the repository
#access protocol may be ftp://, http:// or file://
baseurl=ftp://192.168.10.1/pub/Server
#enabling or disabling the repository
enabled=1
#enabling or disabling gpg checking for digital signature
gpgcheck=0
#gpg key database
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-redhat-release
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