Squid: The Definitive Guide

If you start Squid as root , it changes the process' user ID to the username specified by cache_effective_user . By default, Squid sets the process' group ID to the group associated with the cache_effective_user . You can set the cache_effective_group directive if you want Squid to use some other group ID.

You only need to set this directive if you're starting Squid as root . If you start Squid as a non- root user, this directive is ignored.