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Version: VAST v3.1


VAST offers several mechanisms to adjust configuration options on startup.

  1. Command-line arguments
  2. Environment variables
  3. Configuration files
  4. Compile-time defaults

These mechanisms are sorted by precedence, i.e., command-line arguments override environment variables, which override configuration file settings.

Compile-time defaults can only be changed by rebuilding VAST from source.

Command Line

VAST has a hierarchical command structure of this form:

vast [opts] cmd1 [opts1] cmd2 [opts2] ...

Both long --long=X and short -s X exist. Boolean options do not require explicit specification of a value, and it suffices to write --long and -s to set an option to true.

Hierarchical Options

Each command has its own dedicated set of options. Options are not global and only valid for their respective command. Consider this example:

vast --option foo # option applies to command 'vast'
vast foo --option # option applies to command 'foo'

Get help

You get short usage instructions for every command by adding the help sub-command or providing the option --help (which has the shorthand -h):

vast help
vast --help
vast -h

The same help pattern applies to (sub-)commands:

vast export help
vast export --help
vast export -h

Environment Variables

In addition to the command line, VAST offers environment variables as an equivalent mechanism to provide options. This comes in handy when working with non-interactive deployments where the command line is hard-coded, such as in Docker containers.

An environment variable has the form KEY=VALUE, and we discuss the format of KEY and VALUE below. VAST processes only environment variables having the form VAST_{KEY}=VALUE. For example, VAST_ENDPOINT= translates to the the command line option --endpoint= and YAML configuration vast.endpoint:

Regarding precedence, environment variables override configuration file settings, and command line arguments override environment variables.


There exists a one-to-one mapping from configuration file keys to environment variable names. Here are two examples:

  • vast.import.batch-size 👈 configuration file key
  • VAST_IMPORT__BATCH_SIZE 👈 environment variable

A hierarchical key of the form vast.x.y.z maps to the environment variable VAST_X__Y__Z. More generally, the KEY in VAST_{KEY}=VALUE adheres to the following rules:

  1. Double underscores map to the . separator of YAML dictionaries.

  2. Single underscores _ map to a - in the corresponding configuration file key. This is unambiguous because VAST does not have any options that include a literal underscore.

From the perspective of the command line, the environment variable key VAST_X__Y__Z maps to vast x y --z. Here are two examples with identical semantics:

VAST_IMPORT__BATCH_SIZE=42 vast import json < data
vast import --batch-size=42 json < data
CAF and plugin Settings

To provide CAF and plugin settings, which have the form caf.x.y.z and in the configuration file, the environment variable must have the form VAST_CAF__X__Y__Z and VAST_PLUGINS__NAME__X__Y__Z respectively.

The configuration file is an exception in this regard: vast.caf. and vast.plugins. are invalid key prefixes. Instead, CAF and plugin configuration file keys have the prefixes caf. and plugins., i.e., they are hoisted into the global scope.


While all environment variables are strings on the shell, VAST parses them into a typed value internally. In general, parsing values from the environment follows the same syntactical rules as command line parsing.

In particular, this applies to lists. For example, VAST_PLUGINS="sigma,pcap" is equivalent to --plugins=foo,bar.

VAST ignores environment variables with an empty value because the type cannot be inferred. For example, VAST_PLUGINS= will not be considered.

Configuration files

VAST's configuration file is in YAML format. On startup, VAST attempts to read configuration files from the following places, in order:

  1. <sysconfdir>/vast/vast.yaml for system-wide configuration, where sysconfdir is the platform-specific directory for configuration files, e.g., <install-prefix>/etc.

  2. ~/.config/vast/vast.yaml for user-specific configuration. VAST respects the XDG base directory specification and its environment variables.

  3. A path to a configuration file passed via --config=/path/to/vast.yaml.

If there exist configuration files in multiple locations, options from all configuration files are merged in order, with the latter files receiving a higher precedence than former ones. For lists, merging means concatenating the list elements.

Plugin Configuration Files

In addition to vast/vast.yaml, VAST loads vast/plugin/<plugin>.yaml for plugin-specific configuration for a given plugin named <plugin>. The same rules apply as for the regular configuration file directory lookup.

Bare Mode

Sometimes, users may wish to run VAST without side effects, e.g., when wrapping VAST in their own scripts. Run with --bare-mode to disable looking at all system- and user-specified configuration paths.


VAST's plugin architecture allows for flexible replacement and enhancement of functionality at various pre-defined customization points. There exist dynamic plugins that ship as shared libraries and static plugins that are compiled into libvast.

Install plugins

Dynamic plugins are just shared libraries and can be placed at a location of your choice. We recommend putting them into a single directory and add the path to the vast.plugin-dirs configuration option..

Static plugins do not require installation since they are compiled into VAST.

Load plugins

The onfiguration key vast.plugins specifies the list of plugins that should load at startup. The all plugin name is reserved. When all is specified VAST loads all available plugins in the configured plugin directories. If no vast.plugins key is specified, VAST will load all plugins by default. To load no plugins at all, specify a vast.plugins configuration key with no plugin values, e.g. the configuration file entry plugins: [] or launch parameter --plugins=.

Since dynamic plugins are shared libraries, they must be loaded first into the running VAST process. At startup, VAST looks for the vast.plugins inside the vast.plugin-dirs directories configured in vast.yaml. For example:

- .
- /opt/foo/lib
- example
- /opt/bar/lib/

Before executing plugin code, VAST loads the specified plugins via dlopen(3) and attempts to initialize them as plugins. Part of the initilization is passing configuration options to the plugin. To this end, VAST looks for a YAML dictionary under plugins.<name> in the vast.yaml file. For example:

# <configdir>/vast/vast.yaml
option: 42

Alternatively, you can specify a plugin/<plugin>.yaml file. The example configurations above and below are equivalent. This makes plugin deployments easier, as plugins can be installed and uninstalled alongside their respective configuration.

# <configdir>/vast/plugin/example.yaml
option: 42

After initialization with the configuration options, the plugin is fully operational and VAST will call its functions at the plugin-specific customization points.

Show plugins

You can get a list of all plugins and their respective version by running vast version:

"VAST": "v1.4.1-97-gced115d91-dirty",
"CAF": "0.17.6",
"Apache Arrow": "2.0.0",
"PCAP": "libpcap version 1.9.1",
"jemalloc": null,
"plugins": {
"example": "v0.4.1-g14cee3e48-dirty"

The version of a plugin consists of three optional parts, separated by dashes:

  1. The CMake project version of the plugin
  2. The Git revision of the last commit that touched the plugin
  3. A dirty suffix for uncommited changes to the plugin

Plugins created with the recommended scaffolding use the above version number format.