# The Top File

## Introduction

Most infrastructures are made up of groups of machines, each machine in the group performing a role similar to others. Those groups of machines work in concert with each other to create an application stack.

To effectively manage those groups of machines, an administrator needs to be able to create roles for those groups. For example, a group of machines that serve front-end web traffic might have roles which indicate that those machines should all have the Apache webserver package installed and that the Apache service should always be running.

In Salt, the file which contains a mapping between groups of machines on a network and the configuration roles that should be applied to them is called a `top file`.

Top files are named `top.sls` by default and they are so-named because they always exist in the "top" of a directory hierarchy that contains state files. That directory hierarchy is called a `state tree`.

## A Basic Example

Top files have three components:

- Environment: A state tree directory containing a set of state files to configure systems.

- Target: A grouping of machines which will have a set of states applied to them.

- State files: A list of state files to apply to a target. Each state file describes one or more states to be configured and enforced on the targeted machines.

The relationship between these three components is nested as follows:

- Environments contain targets

- Targets contain states

Putting these concepts together, we can describe a scenario in which all minions with an ID that begins with `web` have an `apache` state applied to them:

    base:          # Apply SLS files from the directory root for the 'base' environment
      'web*':      # All minions with a minion_id that begins with 'web'
        - apache   # Apply the state file named 'apache.sls'

## Environments

Environments are directory hierarchies which contain a top file and a set of state files.

Environments can be used in many ways, however there is no requirement that they be used at all. In fact, the most common way to deploy Salt is with a single environment, called `base`. It is recommended that users only create multiple environments if they have a use case which specifically calls for multiple versions of state trees.

## Getting Started with Top Files

Each environment is defined inside a salt master configuration variable called, `file_roots` .

In the most common single-environment setup, only the `base` environment is defined in `file_roots` along with only one directory path for the state tree.

    file_roots:
      base:
        - /srv/salt

In the above example, the top file will only have a single environment to pull from.

Next is a simple single-environment top file placed in `/srv/salt/top.sls`, illustrating that for the environment called `base`, all minions will have the state files named `core.sls` and `edit.sls` applied to them.

    base:
      '*':
        - core
        - edit

Assuming the `file_roots` configuration from above, Salt will look in the `/srv/salt` directory for `core.sls` and `edit.sls`.

## Multiple Environments

In some cases, teams may wish to create versioned state trees which can be used to test Salt configurations in isolated sets of systems such as a staging environment before deploying states into production.

For this case, multiple environments can be used to accomplish this task.

To create multiple environments, the `file_roots` option can be expanded:

    file_roots:
      dev:
        - /srv/salt/dev
      qa:
        - /srv/salt/qa
      prod:
        - /srv/salt/prod

In the above, we declare three environments: `dev`, `qa` and `prod`. Each environment has a single directory assigned to it.

Our top file references the environments:

    dev:
      'webserver*':
        - webserver
      'db*':
        - db
    qa:
      'webserver*':
        - webserver
      'db*':
        - db
    prod:
      'webserver*':
        - webserver
      'db*':
        - db

As seen above, the top file now declares the three environments and for each, target expressions are defined to map minions to state files. For example, all minions which have an ID beginning with the string `webserver` will have the webserver state from the requested environment assigned to it.

In this manner, a proposed change to a state could first be made in a state file in `/srv/salt/dev` and then be applied to development webservers before moving the state into QA by copying the state file into `/srv/salt/qa`.

## Choosing an Environment to Target

The top file is used to assign a minion to an environment unless overridden using the methods described below. The environment in the top file must match valid fileserver environment (a.k.a. `saltenv`) in order for any states to be applied to that minion. When using the default fileserver backend, environments are defined in `file_roots`.

The states that will be applied to a minion in a given environment can be viewed using the `state.show_top` function.

Minions may be pinned to a particular environment by setting the `environment` value in the minion configuration file. In doing so, a minion will only request files from the environment to which it is assigned.

The environment may also be dynamically selected at runtime by passing it to the `salt`, `salt-call` or `salt-ssh` command. This is most commonly done with functions in the `state` module by using the `saltenv` argument. For example, to run a `highstate` on all minions, using only the top file and SLS files in the `prod` environment, run: `salt '*' state.highstate saltenv=prod`.

Note

Not all functions accept `saltenv` as an argument, see the documentation for an individual function documentation to verify.

## Shorthand

If you assign only one SLS to a system, as in this example, a shorthand is also available:

    base:
      '*': global
    dev:
      'webserver*': webserver
      'db*':        db
    qa:
      'webserver*': webserver
      'db*':        db
    prod:
      'webserver*': webserver
      'db*':        db

## Advanced Minion Targeting

In the examples above, notice that all of the target expressions are globs. The default match type in top files (since version 2014.7.0) is actually the compound matcher, not the glob matcher as in the CLI.

A single glob, when passed through the compound matcher, acts the same way as matching by glob, so in most cases the two are indistinguishable. However, there is an edge case in which a minion ID contains whitespace. While it is not recommended to include spaces in a minion ID, Salt will not stop you from doing so. However, since compound expressions are parsed word-by-word, if a minion ID contains spaces it will fail to match. In this edge case, it will be necessary to explicitly use the `glob` matcher:

    base:
      'minion 1':
        - match: glob
        - foo

The available match types which can be set for a target expression in the top file are:

Match Type | Description
--- | ---
glob | Full minion ID or glob expression to match multiple minions (e.g. `minion123` or `minion*`)
pcre | Perl-compatible regular expression (PCRE) matching a minion ID (e.g. `web[0-3].domain.com`)
grain | Match a grain, optionally using globbing (e.g. `kernel:Linux` or `kernel:*BSD`)
grain_pcre | Match a grain using PCRE (e.g. `kernel:(Free|Open)BSD`)
list | Comma-separated list of minions (e.g. `minion1,minion2,minion3`)
pillar | Pillar match, optionally using globbing (e.g. `role:webserver` or `role:web*`)
pillar_pcre | Pillar match using PCRE (e.g. `role:web(server|proxy)`
pillar_exact | Pillar match with no globbing or PCRE (e.g. `role:webserver`)
ipcidr | Subnet or IP address (e.g. `172.17.0.0/16` or `10.2.9.80`)
data | Match values kept in the minion's datastore (created using the `data` execution module)
range | Range cluster
compound | Complex expression combining multiple match types (see here)
nodegroup | Pre-defined compound expressions in the master config file (see here)

Below is a slightly more complex top file example, showing some of the above match types:

    # All files will be taken from the file path specified in the base
    # environment in the ``file_roots`` configuration value.

    base:
        # All minions which begin with the strings 'nag1' or any minion with
        # a grain set called 'role' with the value of 'monitoring' will have
        # the 'server.sls' state file applied from the 'nagios/' directory.

        'nag1* or G@role:monitoring':
            - nagios.server

        # All minions get the following three state files applied

        '*':
            - ldap-client
            - networking
            - salt.minion

        # All minions which have an ID that begins with the phrase
        # 'salt-master' will have an SLS file applied that is named
        # 'master.sls' and is in the 'salt' directory, underneath
        # the root specified in the ``base`` environment in the
        # configuration value for ``file_roots``.

        'salt-master*':
            - salt.master

        # Minions that have an ID matching the following regular
        # expression will have the state file called 'web.sls' in the
        # nagios/mon directory applied. Additionally, minions matching
        # the regular expression will also have the 'server.sls' file
        # in the apache/ directory applied.

        # NOTE!
        #
        # Take note of the 'match' directive here, which tells Salt
        # to treat the target string as a regex to be matched!

        '^(memcache|web).(qa|prod).loc$':
            - match: pcre
            - nagios.mon.web
            - apache.server

        # Minions that have a grain set indicating that they are running
        # the Ubuntu operating system will have the state file called
        # 'ubuntu.sls' in the 'repos' directory applied.
        #
        # Again take note of the 'match' directive here which tells
        # Salt to match against a grain instead of a minion ID.

        'os:Ubuntu':
            - match: grain
            - repos.ubuntu

        # Minions that are either RedHat or CentOS should have the 'epel.sls'
        # state applied, from the 'repos/' directory.

        'os:(RedHat|CentOS)':
            - match: grain_pcre
            - repos.epel

        # The three minions with the IDs of 'foo', 'bar' and 'baz' should
        # have 'database.sls' applied.

        'foo,bar,baz':
            - match: list
            - database

        # Any minion for which the pillar key 'somekey' is set and has a value
        # of that key matching 'abc' will have the 'xyz.sls' state applied.

        'somekey:abc':
            - match: pillar
            - xyz

## How Top Files Are Compiled

When a highstate is executed and an environment is specified (either using the `environment` config option or by passing the saltenv when executing the highstate), then that environment's top file is the only top file used to assign states to minions, and only states from the specified environment will be run.

The remainder of this section applies to cases in which a highstate is executed without an environment specified.

With no environment specified, the minion will look for a top file in each environment, and each top file will be processed to determine the SLS files to run on the minions. By default, the top files from each environment will be merged together. In configurations with many environments, such as with GitFS where each branch and tag is treated as a distinct environment, this may cause unexpected results as SLS files from older tags cause defunct SLS files to be included in the highstate. In cases like this, it can be helpful to set `top_file_merging_strategy` to `same` to force each environment to use its own top file.

    top_file_merging_strategy: same

Another option would be to set `state_top_saltenv` to a specific environment, to ensure that any top files in other environments are disregarded:

    state_top_saltenv: base

With GitFS, it can also be helpful to simply manage each environment's top file separately, and/or manually specify the environment when executing the highstate to avoid any complicated merging scenarios. `gitfs_saltenv_whitelist` and `gitfs_saltenv_blacklist` can also be used to hide unneeded branches and tags from GitFS to reduce the number of top files in play.

When using multiple environments, it is not necessary to create a top file for each environment. The easiest-to-maintain approach is to use a single top file placed in the `base` environment. This is often infeasible with GitFS though, since branching/tagging can easily result in extra top files. However, when only the default (`roots`) fileserver backend is used, a single top file in the `base` environment is the most common way of configuring a highstate.

The following minion configuration options affect how top files are compiled when no environment is specified, it is recommended to follow the below four links to learn more about how these options work:

- `state_top_saltenv`

- `top_file_merging_strategy`

- `env_order`

- `default_top`

## Top File Compilation Examples

For the scenarios below, assume the following configuration:

/etc/salt/master:

    file_roots:
      base:
        - /srv/salt/base
      dev:
        - /srv/salt/dev
      qa:
        - /srv/salt/qa

/srv/salt/base/top.sls:

    base:
      '*':
        - base1
    dev:
      '*':
        - dev1
    qa:
      '*':
        - qa1

/srv/salt/dev/top.sls:

    base:
      'minion1':
        - base2
    dev:
      'minion2':
        - dev2
    qa:
      '*':
        - qa1
        - qa2

Note

For the purposes of these examples, there is no top file in the `qa` environment.

### Scenario 1 - `dev` Environment Specified

In this scenario, the highstate was either invoked with `saltenv=dev` or the minion has `environment: dev` set in the minion config file. The result will be that only the `dev2` SLS from the dev environment will be part of the highstate, and it will be applied to minion2, while minion1 will have no states applied to it.

If the `base` environment were specified, the result would be that only the `base1` SLS from the `base` environment would be part of the highstate, and it would be applied to all minions.

If the `qa` environment were specified, the highstate would exit with an error.

### Scenario 2 - No Environment Specified, `top_file_merging_strategy` is "merge"

In this scenario, assuming that the `base` environment's top file was evaluated first, the `base1`, `dev1`, and `qa1` states would be applied to all minions. If, for instance, the `qa` environment is not defined in /srv/salt/base/top.sls, then because there is no top file for the `qa` environment, no states from the `qa` environment would be applied.

### Scenario 3 - No Environment Specified, `top_file_merging_strategy` is "same"

Changed in version 2016.11.0: In prior versions, "same" did not quite work as described below (see here). This has now been corrected. It was decided that changing something like top file handling in a point release had the potential to unexpectedly impact users' top files too much, and it would be better to make this correction in a feature release.

In this scenario, `base1` from the `base` environment is applied to all minions. Additionally, `dev2` from the `dev` environment is applied to minion2.

If `default_top` is unset (or set to `base`, which happens to be the default), then `qa1` from the `qa` environment will be applied to all minions. If `default_top` were set to `dev`, then both `qa1` and `qa2` from the `qa` environment would be applied to all minions.

### Scenario 4 - No Environment Specified, `top_file_merging_strategy` is "merge_all"

Added in version 2016.11.0.

In this scenario, all configured states in all top files are applied. From the `base` environment, `base1` would be applied to all minions, with `base2` being applied only to `minion1`. From the `dev` environment, `dev1` would be applied to all minions, with `dev2` being applied only to `minion2`. Finally, from the `qa` environment, both the `qa1` and `qa2` states will be applied to all minions. Note that the `qa1` states would not be applied twice, even though `qa1` appears twice.