cache_effective_user

In the interest of security, Squid doesn't allow itself to run as root. If you start the process as root, Squid changes its effective userid to a nonprivileged user. This user ID must have write permission to the cache directories and log file directory.

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

cache_effective_user username

cache_effective_user nobody

cache_effective_user squid