Centos 7 Yum Repository List

Yum, short for Yellowdog Updater Modified, is a command-line package-management utility for RPM-compatible Linux operating systems such as CentOS. It automatically computes dependencies and figures out what things should occur to install packages. Yum repositories are warehouses of Linux software (RPM package files). Each repository is a collection of software hosted on a remote server and intended to be used for installing and updating software packages within Linux distributions.

Default CentOS 7 Yum Repositories

CentOS 7 comes with several default repositories that are officially supported by the CentOS community. These repositories contain most of the necessary software for a standard installation and general use. The following are some of the default yum repositories available in CentOS 7:

base: Contains packages that form the core distribution.
updates: Provides updated packages to the base set of releases.
extras: Offers additional packages that do not conflict with the core distribution.
centosplus: Contains packages that actually upgrade certain base CentOS components, potentially affecting system stability.
contrib: Holds contributed packages from users that do not overlap with any of the core repositories.

Configuring Yum Repository Files

Each repository in CentOS is defined in a .repo file located in /etc/yum.repos.d/. These files contain the necessary information needed by YUM to manage the repositories. A typical repository configuration includes the name of the repository, the base URL where the packages are located, whether the repository is enabled or not, and the GPG key for security purposes.

[repositoryid]
name=Some name for this repository
baseurl=http://mirror.centos.org/centos/$releasever/os/$basearch/
enabled=1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7

Adding Additional Repositories

Users often need to add additional repositories to gain access to an even wider range of software. Some popular third-party repositories for CentOS include EPEL (Extra Packages for Enterprise Linux), IUS (Inline with Upstream Stable), and Remi’s repository. Here’s how you can add them:

EPEL: To add the EPEL repository, you can install the epel-release package:

sudo yum install epel-release

IUS: For IUS, you would first import the IUS repository GPG key and then install the IUS release package:

sudo yum install https://centos7.iuscommunity.org/ius-release.rpm

Remi: Similarly, to add Remi’s repository, you would run:

sudo yum install http://rpms.remirepo.net/enterprise/remi-release-7.rpm

Managing Yum Repositories

Managing yum repositories involves enabling or disabling repositories based on your needs. This can be done by editing the .repo files or using the yum-config-manager tool from the yum-utils package.

sudo yum install yum-utils
sudo yum-config-manager --enable 
sudo yum-config-manager --disable

List of Available Packages

To list all available packages from all enabled repositories, use the following command:

yum list available

This will give you a comprehensive list of all the packages that you can install using yum from the currently enabled repositories.

Searching for Packages

If you’re looking for a specific package, you can search through the yum repositories using:

yum search

This command will return a list of packages that match the search criteria along with a brief description for each.

Installing Packages from Yum Repositories

Once you have found the package you want to install, you can install it using the following command:

yum install

Yum will resolve any dependencies required by the package and prompt you for confirmation before proceeding with the installation.

Keeping Your System Updated

It’s important to keep your system up-to-date with the latest security patches and updates. You can update all packages to their latest versions with the following command:

yum update

For updating a specific package, simply specify the package name:

yum update

Security Considerations

When dealing with repositories, especially third-party ones, it’s crucial to ensure that they are secure and trusted. Always verify the GPG keys of the repositories to avoid installing malicious software. Most reputable repositories provide GPG keys which can be imported and set to be automatically checked during package installations.

FAQ Section

How do I list all enabled repositories in CentOS 7?

You can list all enabled repositories by running yum repolist enabled.

What should I do if a repository is not working?

First, check your internet connection and the repository URL in the .repo file for any typos. If the repository is down, you may need to find an alternative mirror or disable the repository temporarily.

Can I prioritize repositories in CentOS 7?

Yes, you can assign priority to repositories by installing the yum-plugin-priorities package and setting the ‘priority’ option in the repository’s .repo file.

Is it safe to use third-party repositories?

While many third-party repositories are widely used and trusted, there is always a risk when adding sources outside of the official CentOS repositories. Ensure you trust the source and understand the implications of installing third-party software.

How can I remove a package completely, including its dependencies?

To remove a package and its unused dependencies, you can use yum autoremove .

What is the difference between ‘yum update’ and ‘yum upgrade’?

Both commands essentially perform the same function of updating packages. However, ‘yum upgrade’ also removes obsolete packages, while ‘yum update’ does not.

References

CentOS Wiki: https://wiki.centos.org/Yum
Fedora Documentation: DNF System Administrator’s Guide
EPEL: https://fedoraproject.org/wiki/EPEL
IUS Project: https://ius.io/
Remi’s RPM Repository: https://rpms.remirepo.net/