>.... > [root@localhost mark]# sudo -u squid /usr/sbin/squid -NCd 1 >... That's not the way to go, and not what I asked. You need to make sure that the one who is defined as cache_effective_user can execute ..../squidGuard. Since the user is apparently called 'squid' you need to, Either fully login as "squid'' and test this, I advise to test it that way *really*. If you want to test it from root-originating-shells then, 1) # su - squid 2) squid % _path_to_squidguard/squidGuard the latter should not give a permission error. squid.pid contains the process id of the squid process. Starting as 'squid' using the sudo stuff is bogus, because, indeed, then you run into other problems such as the pid file which can not be written, e.g. because this file is owned by root. M.