Varnish Command Line Interface

Manual section



Varnish has a command line interface (CLI) which can control and change most of the operational parameters and the configuration of Varnish, without interrupting the running service.

The CLI can be used for the following tasks:


You can upload, change and delete VCL files from the CLI.


You can inspect and change the various parameters Varnish has available through the CLI. The individual parameters are documented in the varnishd(1) man page.


Bans are filters that are applied to keep Varnish from serving stale content. When you issue a ban Varnish will not serve any banned object from cache, but rather re-fetch it from its backend servers.

process management

You can stop and start the cache (child) process though the CLI. You can also retrieve the latest stack trace if the child process has crashed.

If you invoke varnishd(1) with -T, -M or -d the CLI will be available. In debug mode (-d) the CLI will be in the foreground, with -T you can connect to it with varnishadm or telnet and with -M varnishd will connect back to a listening service pushing the CLI to that service. Please see varnishd for details.


Commands are usually terminated with a newline. Long command can be entered using shell-style here document (here-document or heredoc). The format of here document is:

<< word
     here document

word can be any continuous string chosen to make sure it doesn’t appear naturally in the following here document. Often EOF or END is used.

When using the here document style of input there are no restrictions on length. When using newline-terminated commands maximum length is limited by the varnishd parameter cli_buffer.

When commands are newline terminated they get tokenized before parsing so if you have significant spaces enclose your strings in double quotes. Within the quotes you can escape characters with . The n, r and t get translated to newlines, carriage returns and tabs. Double quotes themselves can be escaped with a backslash.

To enter characters in octals use the \nnn syntax. Hexadecimals can be entered with the \xnn syntax.


auth <response>


backend.list [-p] [<backend_pattern>]

List backends. -p also shows probe status.

backend.set_health <backend_pattern> [auto|healthy|sick]

Set health status on the backends.

ban <field> <operator> <arg> [&& <field> <oper> <arg> …]

Mark obsolete all objects where all the conditions match.


List the active bans.

The output format is:

  • Time the ban was issued.

  • Objects referencing this ban.

  • C if ban is completed = no further testing against it.

  • if lurker debugging is enabled:

    • R for req.* tests

    • O for obj.* tests

    • Pointer to ban object

  • Ban specification

help [<command>]

Show command/protocol help.

panic.clear [-z]

Clear the last panic, if any, -z will clear related varnishstat counter(s)

Return the last panic, if any.

param.set <param> <value>

Set parameter value. [-l] [<param>]

Show parameters and their values.

ping [<timestamp>]

Keep connection alive.


Close connection.


Start the Varnish cache process.


Check status of Varnish cache process.


Stop the Varnish cache process.


List storage devices.

vcl.discard <configname|label>

Unload the named configuration (when possible).

vcl.inline <configname> <quoted_VCLstring> [auto|cold|warm]

Compile and load the VCL data under the name provided.

Multi-line VCL can be input using the here document Syntax.

vcl.label <label> <configname>

Apply label to configuration.


List all loaded configuration.

vcl.load <configname> <filename> [auto|cold|warm]

Compile and load the VCL file under the name provided. [-v] <configname>

Display the source code for the specified configuration.

vcl.state <configname> [auto|cold|warm]

Force the state of the named configuration.

vcl.use <configname|label>

Switch to the named configuration immediately.

Backend Pattern

A backend pattern can be a backend name or a combination of a VCL name and backend name in “VCL.backend” format. If the VCL name is omitted, the active VCL is assumed. Partial matching on the backend and VCL names is supported using shell-style wilcards, e.g. asterisk (*).


backend.list def*
backend.list b*.def*
backend.set_health default sick
backend.set_health def* healthy
backend.set_health * auto

Ban Expressions

A ban expression consists of one or more conditions. A condition consists of a field, an operator, and an argument. Conditions can be ANDed together with “&&”.

A field can be any of the variables from VCL, for instance req.url, or obj.http.set-cookie.

Operators are “==” for direct comparison, “~” for a regular expression match, and “>” or “<” for size comparisons. Prepending an operator with “!” negates the expression.

The argument could be a quoted string, a regexp, or an integer. Integers can have “KB”, “MB”, “GB” or “TB” appended for size related fields.

VCL Temperature

A VCL program goes through several states related to the different commands: it can be loaded, used, and later discarded. You can load several VCL programs and switch at any time from one to another. There is only one active VCL, but the previous active VCL will be maintained active until all its transactions are over.

Over time, if you often refresh your VCL and keep the previous versions around, resource consumption will increase, you can’t escape that. However, most of the time you want only one to pay the price only for the active VCL and keep older VCLs in case you’d need to rollback to a previous version.

The VCL temperature allows you to minimize the footprint of inactive VCLs. Once a VCL becomes cold, Varnish will release all the resources that can be be later reacquired. You can manually set the temperature of a VCL or let varnish automatically handle it.


If you are going to write a script that talks CLI to varnishd, the include/cli.h contains the relevant magic numbers.

One particular magic number to know, is that the line with the status code and length field always is exactly 13 characters long, including the NL character.

The varnishapi library contains functions to implement the basics of the CLI protocol, see the vcli.h include file.

Authentication with -S

If the -S secret-file is given as argument to varnishd, all network CLI connections must authenticate, by proving they know the contents of that file.

The file is read at the time the auth command is issued and the contents is not cached in varnishd, so it is possible to update the file on the fly.

Use the unix file permissions to control access to the file.

An authenticated session looks like this:

critter phk> telnet localhost 1234
Trying ::1...
Connected to localhost.
Escape character is '^]'.
107 59

Authentication required.

auth 455ce847f0073c7ab3b1465f74507b75d3dc064c1e7de3b71e00de9092fdc89a
200 279
Varnish Cache CLI 1.0
varnish-trunk revision dc360a4

Type 'help' for command list.
Type 'quit' to close CLI session.
Type 'start' to launch worker process.

The CLI status of 107 indicates that authentication is necessary. The first 32 characters of the response text is the challenge “ixsl…mpg”. The challenge is randomly generated for each CLI connection, and changes each time a 107 is emitted.

The most recently emitted challenge must be used for calculating the authenticator “455c…c89a”.

The authenticator is calculated by applying the SHA256 function to the following byte sequence:

  • Challenge string

  • Newline (0x0a) character.

  • Contents of the secret file

  • Challenge string

  • Newline (0x0a) character.

and dumping the resulting digest in lower-case hex.

In the above example, the secret file contained foon and thus:

critter phk> cat > _
critter phk> hexdump -C _
00000000  69 78 73 6c 76 76 78 72  67 6b 6a 70 74 78 6d 63  |ixslvvxrgkjptxmc|
00000010  67 6e 6e 73 64 78 73 76  64 6d 76 66 79 6d 70 67  |gnnsdxsvdmvfympg|
00000020  0a 66 6f 6f 0a 69 78 73  6c 76 76 78 72 67 6b 6a  |.foo.ixslvvxrgkj|
00000030  70 74 78 6d 63 67 6e 6e  73 64 78 73 76 64 6d 76  |ptxmcgnnsdxsvdmv|
00000040  66 79 6d 70 67 0a                                 |fympg.|
critter phk> sha256 _
SHA256 (_) = 455ce847f0073c7ab3b1465f74507b75d3dc064c1e7de3b71e00de9092fdc89a
critter phk> openssl dgst -sha256 < _

The sourcefile lib/libvarnish/cli_auth.c contains a useful function which calculates the response, given an open filedescriptor to the secret file, and the challenge string.


Load a multi-line VCL using shell-style here document:

vcl.inline example << EOF
vcl 4.0;

backend www {
    .host = "";
    .port = "8080";

Ban all requests where req.url exactly matches the string /news:

ban req.url == "/news"

Ban all documents where the serving host is “” or “”, and where the Set-Cookie header received from the backend contains “USERID=1663”:

ban ~ "^(?i)(www\\.)$" && obj.http.set-cookie ~ "USERID=1663"


This manual page was originally written by Per Buer and later modified by Federico G. Schwindt, Dridi Boukelmoune, Lasse Karstensen and Poul-Henning Kamp.