varnishd

Varnish HTTP reverse proxy cache daemon

TLDR

Start with default backend

$ varnishd -a :80 -b localhost:8080

Start with VCL configuration

$ varnishd -a :80 -f /etc/varnish/default.vcl

Run in foreground

$ varnishd -F -a :80 -b localhost:8080

Set cache storage size

$ varnishd -a :80 -b localhost:8080 -s malloc,[256m]

Enable management interface

$ varnishd -a :80 -b localhost:8080 -T localhost:6082

Set default TTL

$ varnishd -a :80 -b localhost:8080 -t [120]

Set runtime parameters

$ varnishd -a :80 -b localhost:8080 -p thread_pools=[2]

varnishd is the Varnish HTTP accelerator daemon. It acts as a reverse proxy cache, accepting HTTP requests, forwarding them to backend servers, and caching responses to serve future requests faster.The daemon uses VCL (Varnish Configuration Language) to define caching policies, request routing, and response handling. VCL is compiled to C and loaded dynamically.Storage backends include malloc (memory) and file (disk-based with memory mapping). Multiple storage backends and listening addresses can be configured.The management interface allows runtime configuration changes, VCL loading, and statistics access via varnishadm.

PARAMETERS

-a address[:port]

Listen for client requests (default port: 80).

-b host[:port]

Backend server (default port: 80).

-f config

VCL configuration file.

-F

Run in foreground (don't fork).

-s [name=]type[,options]

Storage backend: malloc, file, persistent.

-t ttl

Default TTL for cached objects in seconds.

-T address[:port]

Management interface address.

-S secret-file

Authentication secret for management.

-n name

Instance name and working directory.

-p param=value

Set runtime parameter.

-r param[,param...]

Make parameters read-only.

-i identity

Server identity string.

-I clifile

Execute CLI commands from file on start.

-d

Enable debug mode (do not start worker process, accept CLI commands on stdin).

-j jail[,jailoptions]

Specify jailing technology for worker process.

INSTALL

sudo apt install varnish

sudo dnf install varnish

sudo apk add varnish

brew install varnish

nix profile install nixpkgs#varnish

CAVEATS

Requires either -b or -f option. VCL changes require reload through management interface. Memory storage is lost on restart. Running on port 80 requires root or capabilities.

HISTORY

Varnish was created by Poul-Henning Kamp and released in 2006. It was designed from scratch for modern hardware and operating systems, using techniques like memory-mapped files and kernel-level optimizations. It has become one of the most widely deployed HTTP accelerators.