yum is a package management tool, used to install, uninstall or update the Linux (CentOS, RHEL, Fedora etc.) packages. You can use yum with root privilege only.

To install a package:

yum install packagename

To update a package, if already install or to install a package:

yum update packagename

To reinstall a installed package:

yum reinstall packagename

To remove a installed package:

yum remove packagename

To see the list of package groups:

yum grouplist

To install all the packages of a group:

yum groupinstall packagegroupname

To update all the packages of a group:

yum groupupdate packagegroupname

To remove all the packages of a group:

yum groupremove packagegroupname

If you want to exclude some packages from group to install or update or remove, use “–exclude” option:

yum groupinstall packagegroupname –exclude=excludepackagename

To clean the cache of packages database:

yum clean all

Now some little tricky commands.

To disable all the repository & enable the given repositories only & then again same yum commands:

yum –disablerepo=\* –enablerepo=myreponame1,myreponame2 install packagename

You can get the reponame from the repo files inside the /etc/yum.repo.d directory. For example, the CentOS.repo file’s content is showing the reponame inside the square brackets “[ ]” as base & update. To select all the repo,”\*” is used.

[base]
name=CentOS-$releasever – Base
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os
#baseurl=http://mirror.centos.org/centos/$releasever/os/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5

#released updates
[updates]
name=CentOS-$releasever – Updates
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=updates
#baseurl=http://mirror.centos.org/centos/$releasever/updates/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5

“yum clean all” command does not clean the cache of disabled repositories, clean the cache by enabling all the repositories, remove all the cache:

yum –enablerepo=\* clean all

you can also remove the directory /var/cache/yum/* to clean all the cache of repositories.

There are so many other commands & combination in yum. If you like to share, please write as a comment.

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