How to Fix Yum 404 Errors Caused by Missing $releasever Variable on CentOS

Problem Phenomenon

When running yum install on a CentOS system, every package installation returns a 404 error, initially suggesting a broken repository.

Error Output

Loaded plugins: fastestmirror, security
http://***.***.360.cn:/addops/$releasever/os/x86_64/repodata/repomd.xml: [Errno 14] PYCURL ERROR 22 - "The requested URL returned error: 404 Not Found"
Trying other mirror.
Error: Cannot retrieve repository metadata (repomd.xml) for repository: ADDOPS-base. Please verify its path and try again

Analysis

The URL contains the variable $releasever (displayed as %24releasever ) which is not expanded, leading to the 404. The variable is defined by the distroverpkg setting in /etc/yum.conf , which points to the centos-release package.

On the affected machine the centos-release package is missing, so $releasever cannot be resolved.

Solution

Temporarily replace $releasever with the actual version number (e.g., 6 ) in the repository configuration, install the centos-release package, then restore the original variable.

Useful Tips

/usr/bin/python -c 'import yum, pprint; yb = yum.YumBase(); pprint.pprint(yb.conf.yumvar, width=1)'

This Python one‑liner prints the current yum variables, showing releasever: '6' .

yum whatprovides centos-release

Shows which package provides centos-release and its repository information.

Conclusion

Mastering yum and understanding its variables is a fundamental skill for any operations engineer.