Update yum repositories on your server

What is yum?

Yum is a tool that installs and updates software on Red Hat style Linux, such as CentOS, AlmaLinux and Rocky Linux. A repository is an online store of software. Yum reads a list of these stores. Each store has a small settings file. If the file is old or wrong, installs and updates fail.

You need root access for this guide. Root is the main administrator login of the server.

Tip: Yum is old. Newer systems use dnf, and yum is often just a link to it. The commands below work the same way with dnf.

Steps

1. Connect to your server with SSH.
2. List the stores yum knows.

   yum repolist

   This shows each active repository.
3. Clear old saved data.

   yum clean all

   This removes saved lists, so yum fetches new ones.
4. Build a fresh list.

   yum makecache

   This downloads the latest package lists.
5. Update the software.

   yum update

   This shows what will be updated. Read it, then type y to continue.

Add a new repository

1. Go to the settings folder.

   cd /etc/yum.repos.d/

2. Many repositories come as a package. For example, EPEL:

   yum install epel-release

   This adds the EPEL store.
3. Run yum repolist again to see it.

If a repository fails

• Read the error. It names the repository.
• Check that the server reaches the internet.
• CentOS 7 and 8 have reached end of life. Their old addresses moved. Update the baseurl lines in the files in /etc/yum.repos.d/ or move to a supported system.
• To skip a broken store once, use yum --disablerepo=name update.

Quick recap

• Yum gets software from repositories listed in /etc/yum.repos.d/.
• Run yum clean all and yum makecache to refresh.
• Add stores with packages like epel-release.
• Take a backup before big updates.