squid

Start squid

$ squid

$ squid -k parse

$ squid -k reconfigure

$ squid -k shutdown

$ squid -v

$ squid -N

$ squid -d [5]

$ squid -k rotate && rm -rf [/var/spool/squid/*] && squid -z

squid [-k command] [-f config] [-N] [options]

squid is a caching proxy server supporting HTTP, HTTPS, FTP, and other protocols. It operates as both a forward proxy for client internet access and a reverse proxy (accelerator) for web servers, caching frequently requested content to reduce bandwidth usage and improve response times.
The server uses Access Control Lists (ACLs) to filter traffic, authenticate users, restrict access to specific sites or content types, and enforce bandwidth limits. Cache storage is configurable with both memory and disk backends, supporting hierarchical caching with parent and sibling proxies.
Configuration is managed through a comprehensive configuration file that defines listening ports, ACL rules, cache policies, authentication schemes, and logging behavior. The -k flag sends management commands to a running instance for operations like configuration reload, log rotation, and graceful shutdown.

-k COMMAND

Send command to running squid.

Configuration file.

No daemon mode.

Debug level.

Create swap directories.

Show version.

/etc/squid/squid.conf

Main configuration file defining listening ports, ACL rules, cache policies, authentication helpers, and logging settings.

Default disk cache directory for cached web content.

Log directory containing access.log, cache.log, and store.log.

parse - Check config
reconfigure - Reload config
shutdown - Graceful stop
interrupt - Immediate stop
rotate - Rotate logs

Configuration is complex. ACL order matters. HTTPS interception needs certificates.

Squid originated from the Harvest project at the University of Colorado in 1996. It became the most widely deployed caching proxy.

nginx(1), apache(1), privoxy(1)