Package Management with Yum (RHEL Based)

1. Introduction to Yum

Yum (Yellowdog Updater Modified) is the primary package management tool for Red Hat Enterprise Linux (RHEL) and its derivatives like CentOS and Fedora. It allows you to install, update, and remove software packages while automatically handling dependencies.

2. Basic Yum Commands

Searching for packages: yum search keyword
Getting information about a package: yum info package_name
Installing a package: sudo yum install package_name
Removing a package: sudo yum remove package_name
Updating all packages: sudo yum update
Updating a specific package: sudo yum update package_name

3. Working with Repositories

Yum uses repositories to fetch package information and the packages themselves.

Listing enabled repositories: yum repolist
Listing all repositories (including disabled): yum repolist all
Adding a new repository: Create a .repo file in /etc/yum.repos.d/ with the following structure:

[repository_id]
name=Repository Name
baseurl=http://repository.url
enabled=1
gpgcheck=1
gpgkey=http://repository.url/RPM-GPG-KEY

Enabling/disabling a repository:
sudo yum-config-manager --enable repository_id
sudo yum-config-manager --disable repository_id

4. Managing Package Groups

Yum can install predefined groups of packages.

Listing available groups: yum group list
Getting info about a group: yum group info "group_name"
Installing a group: sudo yum group install "group_name"
Removing a group: sudo yum group remove "group_name"

5. Yum Cache Management

Yum maintains a cache to speed up operations.

Cleaning all cached packages and metadata: sudo yum clean all
Cleaning only cached packages: sudo yum clean packages
Cleaning only cached metadata: sudo yum clean metadata

6. Advanced Yum Features

Downloading a package without installing: yumdownloader package_name
Installing a local RPM package with Yum (to resolve dependencies): sudo yum localinstall package_name.rpm
Checking for available updates: yum check-update
Listing installed packages: yum list installed
Listing available packages: yum list available

7. Yum History

Yum keeps a history of transactions, allowing you to undo or redo actions.

Viewing Yum history: yum history list
Undoing a transaction: sudo yum history undo transaction_id
Redoing a transaction: sudo yum history redo transaction_id

8. Yum Configuration

The main Yum configuration file is /etc/yum.conf Here are some important settings:

cachedir: Directory where Yum stores its cache files
keepcache: Whether to keep the cache after successful operations
debuglevel: Level of debugging output
gpgcheck: Whether to perform GPG signature checking on packages
plugins: Whether to enable Yum plugins

9. Yum Plugins

Yum's functionality can be extended with plugins. Some useful plugins include:

yum-plugin-fastestmirror: Finds the fastest mirror for downloads
yum-plugin-security: Allows security-related operations
yum-plugin-versionlock: Locks specified packages to a particular version

To install a plugin: sudo yum install plugin_name

10. Troubleshooting

If you encounter issues with Yum, try these steps:

Clear the Yum cache: sudo yum clean all
Rebuild the Yum cache: sudo yum makecache
Check for conflicting transactions: sudo yum-complete-transaction --cleanup-only
Verify the package database: sudo yum check

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