When one installs rar in Red Hat Linux,

yum install rar

and then attempts to run rar or unrar, one is likely to get a failure with the diagnostic

rar: /lib/libc.so.6: version `GLIBC_2.7' not found (required by rar)

In various fora, the recommendation has been to install a newer version of glibc or somesuch. Such updating would be a signally bad idea, likely to disable the operating system.

Instead, note that the rar package came with rar_static. Use that in place of rar. (If it makes you happier, you could delete rar and rename or alias rar_static with rar.)