..
	Copyright (c) 2012-2021 Varnish Software AS
	SPDX-License-Identifier: BSD-2-Clause
	See LICENSE file for full text of license

.. _users-guide-command-line:

Required command line arguments
-------------------------------

There a two command line arguments you have to set when starting Varnish, these are:

* what TCP port to serve HTTP from, and
* where the backend server can be contacted.

If you have installed Varnish through using a provided operating system bound package,
you will find the startup options here:

* Debian, Ubuntu: `/etc/default/varnish`
* Red Hat, Centos: `/etc/sysconfig/varnish`
* FreeBSD: `/etc/rc.conf` (See also: /usr/local/etc/rc.d/varnishd)


'-a' *listen_address*
^^^^^^^^^^^^^^^^^^^^^

The '-a' argument defines what address Varnish should listen to, and service HTTP requests from.

You will most likely want to set this to ":80" which is the Well
Known Port for HTTP.

You can specify multiple addresses separated by a comma, and you
can use numeric or host/service names if you like, Varnish will try
to open and service as many of them as possible, but if none of them
can be opened, `varnishd` will not start.

Here are some examples::

	-a :80
	-a localhost:80
	-a 192.168.1.100:8080
	-a '[fe80::1]:80'
	-a '0.0.0.0:8080,[::]:8081'

.. XXX:brief explanation of some of the more complex examples perhaps? benc

If your webserver runs on the same machine, you will have to move
it to another port number first.

'-f' *VCL-file* or '-b' *backend*
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Varnish needs to know where to find the HTTP server it is caching for.
You can either specify it with the '-b' argument, or you can put it in your own VCL file, specified with the '-f' argument.

Using '-b' is a quick way to get started::

	-b localhost:81
	-b thatotherserver.example.com:80
	-b 192.168.1.2:80

Notice that if you specify a name, it can at most resolve to one IPv4
*and* one IPv6 address.

For more advanced use, you will want to specify a VCL program with ``-f``,
but you can start with as little as just::

	backend default {
		.host = "localhost:81";
	}

which is, by the way, *precisely* what '-b' does.

Optional arguments
^^^^^^^^^^^^^^^^^^

For a complete list of the command line arguments please see
:ref:`varnishd(1) options <ref-varnishd-options>`.