How to safely downgrade or remove glibc with yum and rpm

Environment

• Red Hat Enterprise Linux 5
• Red Hat Enterprise Linux 6
• glibc, glibc-common, glibc-devel, glibc-headers, nscd

Issue

• A 3rd party application requires an older version of glibc than what's currently installed on the system.
• How to downgrade glibc
• How to remove glibc

Resolution

• Check for the required version by running:

# yum list --showduplicates glibc

• Downgrade the glibc package(s) to the previous version by running the following (if the requirement is a specific version, it would need to be appended to the package names below):

# yum downgrade glibc glibc-common glibc-devel glibc-headers nscd

Root Cause

• glibc is a library that provides core functionality that much of the system relies on. This particular package contains the most important sets of shared libraries: the standard C library and the standard math library. Without these two libraries, a Linux system will not function.
• While this can also be accomplished with RPM. Red Hat does not recommend manually removing glibc without a verified backup.