There are two things I’ve learned about Ubuntu 10.04 if you’re running Squid. Upstart doesn’t properly handle squid’s shutdown process properly. You need to issue squid -k shutdown *twice* if you want it to shutdown.

Two, the /etc/default/squid.conf SQUID_MAXFD is not listened to either, you must set this in /etc/squid/squid.conf instead.

https://bugs.launchpad.net/ubuntu/+source/squid/+bug/580590