Configuring the Salt Minion

The Salt system is amazingly simple and easy to configure. The two components of the Salt system each have a respective configuration file. The salt-master is configured via the master configuration file, and the salt-minion is configured via the minion configuration file.

The Salt Minion configuration is very simple. Typically, the only value that needs to be set is the master value so the minion knows where to locate its master.

By default, the salt-minion configuration will be in /etc/salt/minion. A notable exception is FreeBSD, where the configuration will be in /usr/local/etc/salt/minion.

Minion Primary Configuration


Default: salt

The hostname or ipv4 of the master.

Default: salt

master: salt

The option can can also be set to a list of masters, enabling multi-master mode.

  - address1
  - address2

Changed in version 2014.7.0: The master can be dynamically configured. The master value can be set to an module function which will be executed and will assume that the returning value is the ip or hostname of the desired master. If a function is being specified, then the master_type option must be set to func, to tell the minion that the value is a function to be run and not a fully-qualified domain name.

master: module.function
master_type: func

In addition, instead of using multi-master mode, the minion can be configured to use the list of master addresses as a failover list, trying the first address, then the second, etc. until the minion successfully connects. To enable this behavior, set master_type to failover:

  - address1
  - address2
master_type: failover


New in version 2014.7.0.

Default: str

The type of the master variable. Can be str, failover or func.

master_type: failover

If this option is set to failover, master must be a list of master addresses. The minion will then try each master in the order specified in the list until it successfully connects. master_alive_interval must also be set, this determines how often the minion will verify the presence of the master.

master_type: func

If the master needs to be dynamically assigned by executing a function instead of reading in the static master value, set this to func. This can be used to manage the minion's master setting from an execution module. By simply changing the algorithm in the module to return a new master ip/fqdn, restart the minion and it will connect to the new master.


New in version 2014.7.0.

Default: 1048576

Passing very large events can cause the minion to consume large amounts of memory. This value tunes the maximum size of a message allowed onto the minion event bus. The value is expressed in bytes.

max_event_size: 1048576


New in version 2016.3.0.

Default: False

If the minion is in multi-master mode and the :conf_minion`master_type` configuration option is set to failover, this setting can be set to True to force the minion to fail back to the first master in the list if the first master is back online.

master_failback: False


New in version 2016.3.0.

Default: 0

If the minion is in multi-master mode, the :conf_minion`master_type` configuration is set to failover, and the master_failback option is enabled, the master failback interval can be set to ping the top master with this interval, in seconds.

master_failback_interval: 0


Default: 0

Configures how often, in seconds, the minion will verify that the current master is alive and responding. The minion will try to establish a connection to the next master in the list if it finds the existing one is dead.

master_alive_interval: 30


New in version 2014.7.0.

Default: False

If master is a list of addresses and :conf_minion`master_type` is failover, shuffle them before trying to connect to distribute the minions over all available masters. This uses Python's random.shuffle method.

master_shuffle: True


Default: False

If master is a list of addresses, shuffle them before trying to connect to distribute the minions over all available masters. This uses Python's random.randint method.

random_master: True


Default: 30

Set the number of seconds to wait before attempting to resolve the master hostname if name resolution fails. Defaults to 30 seconds. Set to zero if the minion should shutdown and not retry.

retry_dns: 30


Default: 4506

The port of the master ret server, this needs to coincide with the ret_port option on the Salt master.

master_port: 4506


Default: root

The user to run the Salt processes

user: root


Default: ''

The user to run salt remote execution commands as via sudo. If this option is enabled then sudo will be used to change the active user executing the remote command. If enabled the user will need to be allowed access via the sudoers file for the user that the salt minion is configured to run as. The most common option would be to use the root user. If this option is set the user option should also be set to a non-root user. If migrating from a root minion to a non root minion the minion cache should be cleared and the minion pki directory will need to be changed to the ownership of the new user.

sudo_user: root


Default: /var/run/

The location of the daemon's process ID file

pidfile: /var/run/


Default: /

This directory is prepended to the following options: pki_dir, cachedir, log_file, sock_dir, and pidfile.

root_dir: /


Default: /etc/salt/minion

The path to the minion's configuration file.

conf_file: /etc/salt/minion


Default: /etc/salt/pki/minion

The directory used to store the minion's public and private keys.

pki_dir: /etc/salt/pki/minion


Default: the system's hostname

See also

Salt Walkthrough

The Setting up a Salt Minion section contains detailed information on how the hostname is determined.

Explicitly declare the id for this minion to use. Since Salt uses detached ids it is possible to run multiple minions on the same machine but with different ids.



New in version 0.17.2.

Default: True

Caches the minion id to a file when the minion's :minion_conf:`id` is not statically defined in the minion config. This setting prevents potential problems when automatic minion id resolution changes, which can cause the minion to lose connection with the master. To turn off minion id caching, set this config to False.

For more information, please see Issue #7558 and Pull Request #8488.

minion_id_caching: True


Default: None

Append a domain to a hostname in the event that it does not exist. This is useful for systems where socket.getfqdn() does not actually result in a FQDN (for instance, Solaris).



Default: /var/cache/salt/minion

The location for minion cache data.

This directory may contain sensitive data and should be protected accordingly.

cachedir: /var/cache/salt/minion


Default: True

Verify and set permissions on configuration directories at startup.

verify_env: True


When set to True the verify_env option requires WRITE access to the configuration directory (/etc/salt/). In certain situations such as mounting /etc/salt/ as read-only for templating this will create a stack trace when state.apply is called.


Default: False

The minion can locally cache the return data from jobs sent to it, this can be a good way to keep track of the minion side of the jobs the minion has executed. By default this feature is disabled, to enable set cache_jobs to True.

cache_jobs: False


Default: False

The minion can locally cache rendered pillar data under cachedir/pillar. This allows a temporarily disconnected minion to access previously cached pillar data by invoking salt-call with the --local and --pillar_root=:conf_minion:cachedir/pillar options. Before enabling this setting consider that the rendered pillar may contain security sensitive data. Appropriate access restrictions should be in place. By default the saved pillar data will be readable only by the user account running salt. By default this feature is disabled, to enable set minion_pillar_cache to True.

minion_pillar_cache: False


Default: (empty)

Statically assigns grains to the minion.

    - webserver
    - memcache
  deployment: datacenter4
  cabinet: 13
  cab_u: 14-15


Default: False

The minion can locally cache grain data instead of refreshing the data each time the grain is referenced. By default this feature is disabled, to enable set grains_cache to True.

grains_cache: False


New in version 2016.3.0.

Default: False

The grains can be merged, instead of overridden, using this option. This allows custom grains to defined different subvalues of a dictionary grain. By default this feature is disabled, to enable set grains_deep_merge to True.

grains_deep_merge: False

For example, with these custom grains functions:

def custom1_k1():
    return {'custom1': {'k1': 'v1'}}

def custom1_k2():
    return {'custom1': {'k2': 'v2'}}

Without grains_deep_merge, the result would be:

  k1: v1

With grains_deep_merge, the result will be:

  k1: v1
  k2: v2


New in version 2015.8.10.

Default: True

Determines whether or not the salt minion should run scheduled mine updates. If this is set to False then the mine update function will not get added to the scheduler for the minion.

mine_enabled: True


New in version 2015.8.10.

Default: False

Determines whether or not scheduled mine updates should be accompanied by a job return for the job cache.

mine_return_job: False


Default: Empty

Designate which functions should be executed at mine_interval intervals on each minion. See this documentation on the Salt Mine for more information. Note these can be defined in the pillar for a minion as well.

mine_functions: []
    interface: eth0
    cidr: ''


Default: /var/run/salt/minion

The directory where Unix sockets will be kept.

sock_dir: /var/run/salt/minion


Default: ''

Backup files replaced by file.managed and file.recurse under cachedir.

backup_mode: minion


Default: 10

The number of seconds to wait until attempting to re-authenticate with the master.

acceptance_wait_time: 10


Default: 0

The maximum number of seconds to wait until attempting to re-authenticate with the master. If set, the wait will increase by acceptance_wait_time seconds each iteration.

acceptance_wait_time_max: 0


Default: 10

When the master key changes, the minion will try to re-auth itself to receive the new master key. In larger environments this can cause a syn-flood on the master because all minions try to re-auth immediately. To prevent this and have a minion wait for a random amount of time, use this optional parameter. The wait-time will be a random number of seconds between 0 and the defined value.

random_reauth_delay: 60


New in version 2014.7.0.

Default: 7

The number of attempts to authenticate to a master before giving up. Or, more technically, the number of consecutive SaltReqTimeoutErrors that are acceptable when trying to authenticate to the master.

auth_tries: 7


New in version 2016.3.0.

Default: 1

The number of attempts to connect to a master before giving up. Set this to -1 for unlimited attempts. This allows for a master to have downtime and the minion to reconnect to it later when it comes back up. In 'failover' mode, which is set in the master_type configuration, this value is the number of attempts for each set of masters. In this mode, it will cycle through the list of masters for each attempt.

master_tries is different than auth_tries because auth_tries attempts to retry auth attempts with a single master. auth_tries is under the assumption that you can connect to the master but not gain authorization from it. master_tries will still cycle through all of the masters in a given try, so it is appropriate if you expect occasional downtime from the master(s).

master_tries: 1


New in version 2014.7.0.

Default: 7

The number of attempts to authenticate to a master before giving up. Or, more technically, the number of consecutive SaltReqTimeoutErrors that are acceptable when trying to authenticate to the master.

auth_tries: 7


New in version 2014.7.0.

Default: 60

When waiting for a master to accept the minion's public key, salt will continuously attempt to reconnect until successful. This is the timeout value, in seconds, for each individual attempt. After this timeout expires, the minion will wait for acceptance_wait_time seconds before trying again. Unless your master is under unusually heavy load, this should be left at the default.

auth_timeout: 60


New in version 2014.7.0.

Default: False

If authentication fails due to SaltReqTimeoutError during a ping_interval, this setting, when set to True, will cause a sub-minion process to restart.

auth_safemode: False


Default: 1000

The interval in milliseconds that the socket should wait before trying to reconnect to the master (1000ms = 1 second).

recon_default: 1000


Default: 10000

The maximum time a socket should wait. Each interval the time to wait is calculated by doubling the previous time. If recon_max is reached, it starts again at the recon_default.

Short example:
  • reconnect 1: the socket will wait 'recon_default' milliseconds
  • reconnect 2: 'recon_default' * 2
  • reconnect 3: ('recon_default' * 2) * 2
  • reconnect 4: value from previous interval * 2
  • reconnect 5: value from previous interval * 2
  • reconnect x: if value >= recon_max, it starts again with recon_default
recon_max: 10000


Default: True

Generate a random wait time on minion start. The wait time will be a random value between recon_default and recon_default + recon_max. Having all minions reconnect with the same recon_default and recon_max value kind of defeats the purpose of being able to change these settings. If all minions have the same values and the setup is quite large (several thousand minions), they will still flood the master. The desired behavior is to have time-frame within all minions try to reconnect.

recon_randomize: True


Default: 1

The loop_interval sets how long in seconds the minion will wait between evaluating the scheduler and running cleanup tasks. This defaults to 1 second on the minion scheduler.

loop_interval: 1


Default: True

Some installations choose to start all job returns in a cache or a returner and forgo sending the results back to a master. In this workflow, jobs are most often executed with --async from the Salt CLI and then results are evaluated by examining job caches on the minions or any configured returners. WARNING: Setting this to False will disable returns back to the master.

pub_ret: True


Default: 5

The default timeout for a minion return attempt.

return_retry_timer: 5


Default: 10

The maximum timeout for a minion return attempt. If non-zero the minion return retry timeout will be a random int between return_retry_timer and return_retry_timer_max

return_retry_timer_max: 10


Default: True

The connection to the master ret_port is kept open. When set to False, the minion creates a new connection for every return to the master.

cache_sreqs: True


Default: ipc

Windows platforms lack POSIX IPC and must rely on slower TCP based inter- process communications. Set ipc_mode to tcp on such systems.

ipc_mode: ipc


Default: 4510

Publish port used when ipc_mode is set to tcp.

tcp_pub_port: 4510


Default: 4511

Pull port used when ipc_mode is set to tcp.

tcp_pull_port: 4511


Default: zeromq

Changes the underlying transport layer. ZeroMQ is the recommended transport while additional transport layers are under development. Supported values are zeromq, raet (experimental), and tcp (experimental). This setting has a significant impact on performance and should not be changed unless you know what you are doing! Transports are explained in Salt Transports.

transport: zeromq


Default: ''

The key fingerprint of the higher-level master for the syndic to verify it is talking to the intended master.

syndic_finger: 'ab:30:65:2a:d6:9e:20:4f:d8:b2:f3:a7:d4:65:50:10'

Minion Module Management


Default: [] (all modules are enabled by default)

The event may occur in which the administrator desires that a minion should not be able to execute a certain module. The sys module is built into the minion and cannot be disabled.

This setting can also tune the minion. Because all modules are loaded into system memory, disabling modules will lover the minion's memory footprint.

Modules should be specified according to their file name on the system and not by their virtual name. For example, to disable cmd, use the string cmdmod which corresponds to salt.modules.cmdmod.

  - test
  - solr


Default: [] (all returners are enabled by default)

If certain returners should be disabled, this is the place

  - mongo_return


Default: []

A list of extra directories to search for Salt modules

  - /var/lib/salt/modules


Default: []

A list of extra directories to search for Salt returners

  - /var/lib/salt/returners


Default: []

A list of extra directories to search for Salt states

  - /var/lib/salt/states


Default: []

A list of extra directories to search for Salt grains

  - /var/lib/salt/grains


Default: []

A list of extra directories to search for Salt renderers

  - /var/lib/salt/renderers


Default: False

Set this value to true to enable auto-loading and compiling of .pyx modules, This setting requires that gcc and cython are installed on the minion.

cython_enable: False


New in version 2015.8.0.

Default: False

Set this value to true to enable loading of zip archives as extension modules. This allows for packing module code with specific dependencies to avoid conflicts and/or having to install specific modules' dependencies in system libraries.

enable_zip_modules: False


Default: (empty)

A module provider can be statically overwritten or extended for the minion via the providers option. This can be done on an individual basis in an SLS file, or globally here in the minion config, like below.

  service: systemd

State Management Settings


Default: yaml_jinja

The default renderer used for local state executions

renderer: yaml_jinja


Default: True

Controls the verbosity of state runs. By default, the results of all states are returned, but setting this value to False will cause salt to only display output for states that failed or states that have changes.

state_verbose: True


Default: full

The state_output setting changes if the output is the full multi line output for each changed state if set to 'full', but if set to 'terse' the output will be shortened to a single line.

state_output: full


Default: True

autoload_dynamic_modules turns on automatic loading of modules found in the environments on the master. This is turned on by default. To turn off auto-loading modules when states run, set this value to False.

autoload_dynamic_modules: True

Default: True

clean_dynamic_modules keeps the dynamic modules on the minion in sync with the dynamic modules on the master. This means that if a dynamic module is not on the master it will be deleted from the minion. By default this is enabled and can be disabled by changing this value to False.

clean_dynamic_modules: True


Default: None

Normally the minion is not isolated to any single environment on the master when running states, but the environment can be isolated on the minion side by statically setting it. Remember that the recommended way to manage environments is to isolate via the top file.

environment: dev


Default: merge

When no specific fileserver environment (a.k.a. saltenv) has been specified for a highstate, all environments' top files are inspected. This config option determines how the SLS targets in those top files are handled.

When set to merge, the targets for all SLS files in all environments are merged together. A given environment's SLS targets for the highstate will consist of the collective SLS targets specified for that environment in all top files. The environments will be merged in no specific order, for greater control over the order in which the environments are merged use env_order.

When set to same, then for each environment, only that environment's top file is processed, with the others being ignored. For example, only the dev environment's top file will be processed for the dev environment, and any SLS targets defined for dev in the base environment's (or any other environment's) top file will be ignored. If an environment does not have a top file, then the top file from the default_top config parameter will be used as a fallback.

top_file_merging_strategy: same


Default: []

When top_file_merging_strategy is set to merge, and no environment is specified for a highstate, this config option allows for the order in which top files are merged to be explicitly defined.

  - base
  - dev
  - qa


Default: base

When top_file_merging_strategy is set to same, and no environment is specified for a highstate, this config option specifies a fallback environment in which to look for a top file if an environment lacks one.

default_top: dev

File Directory Settings


Default: remote

The client defaults to looking on the master server for files, but can be directed to look on the minion by setting this parameter to local.

file_client: remote


Default: False

When using a local file_client, this parameter is used to allow the client to connect to a master for remote execution.

use_master_when_local: False



  - /srv/salt

When using a local file_client, this parameter is used to setup the fileserver's environments. This parameter operates identically to the master config parameter of the same name.

    - /srv/salt
    - /srv/salt/dev/services
    - /srv/salt/dev/states
    - /srv/salt/prod/services
    - /srv/salt/prod/states


New in version 2014.1.0.

Default: False

By default, the Salt fileserver recurses fully into all defined environments to attempt to find files. To limit this behavior so that the fileserver only traverses directories with SLS files and special Salt directories like _modules, set fileserver_limit_traversal to True. This might be useful for installations where a file root has a very large number of files and performance is impacted.

fileserver_limit_traversal: False


Default: md5

The hash_type is the hash to use when discovering the hash of a file on the local fileserver. The default is md5, but sha1, sha224, sha256, sha384, and sha512 are also supported.

hash_type: md5

Pillar Settings



  - /srv/pillar

When using a local file_client, this parameter is used to setup the pillar environments.

    - /srv/pillar
    - /srv/pillar/dev
    - /srv/pillar/prod


Default: None

Isolates the pillar environment on the minion side. This functions the same as the environment setting, but for pillar instead of states.

pillarenv: None


New in version 2014.7.0.

Default: 100

Set a hard-limit on the size of the files that can be pushed to the master. It will be interpreted as megabytes.

file_recv_max_size: 100

Security Settings


Default: False

Open mode can be used to clean out the PKI key received from the Salt master, turn on open mode, restart the minion, then turn off open mode and restart the minion to clean the keys.

open_mode: False


Default: ''

Fingerprint of the master public key to validate the identity of your Salt master before the initial key exchange. The master fingerprint can be found by running "salt-key -F master" on the Salt master.

master_finger: 'ba:30:65:2a:d6:9e:20:4f:d8:b2:f3:a7:d4:65:11:13'


Default: False

Enables verification of the master-public-signature returned by the master in auth-replies. Please see the tutorial on how to configure this properly Multimaster-PKI with Failover Tutorial

New in version 2014.7.0.

verify_master_pubkey_sign: True

If this is set to True, master_sign_pubkey must be also set to True in the master configuration file.


Default: master_sign

The filename without the .pub suffix of the public key that should be used for verifying the signature from the master. The file must be located in the minion's pki directory.

New in version 2014.7.0.

master_sign_key_name: <filename_without_suffix>


Default: False

If verify_master_pubkey_sign is enabled, the signature is only verified if the public-key of the master changes. If the signature should always be verified, this can be set to True.

New in version 2014.7.0.

always_verify_signature: True


Default: []

If cmd_blacklist_glob is enabled then any shell command called over remote execution or via salt-call will be checked against the glob matches found in the cmd_blacklist_glob list and any matched shell command will be blocked.


This blacklist is only applied to direct executions made by the salt and salt-call commands. This does NOT blacklist commands called from states or shell commands executed from other modules.

New in version Carbon.

  - 'rm * '
  - 'cat /etc/* '


Default: []

If cmd_whitelist_glob is enabled then any shell command called over remote execution or via salt-call will be checked against the glob matches found in the cmd_whitelist_glob list and any shell command NOT found in the list will be blocked. If cmd_whitelist_glob is NOT SET, then all shell commands are permitted.


This whitelist is only applied to direct executions made by the salt and salt-call commands. This does NOT restrict commands called from states or shell commands executed from other modules.

New in version Carbon.

  - 'ls * '
  - 'cat /etc/fstab'

Thread Settings

Default: True

If multiprocessing is enabled when a minion receives a publication a new process is spawned and the command is executed therein. Conversely, if multiprocessing is disabled the new publication will be run executed in a thread.

multiprocessing: True

Minion Logging Settings


Default: /var/log/salt/minion

The minion log can be sent to a regular file, local path name, or network location. See also log_file.


log_file: /var/log/salt/minion
log_file: file:///dev/log
log_file: udp://loghost:10514


Default: warning

The level of messages to send to the console. See also log_level.

log_level: warning


Default: info

The level of messages to send to the log file. See also log_level_logfile. When it is not set explicitly it will inherit the level set by log_level option.

log_level_logfile: warning


Default: %H:%M:%S

The date and time format used in console log messages. See also log_datefmt.

log_datefmt: '%H:%M:%S'


Default: %Y-%m-%d %H:%M:%S

The date and time format used in log file messages. See also log_datefmt_logfile.

log_datefmt_logfile: '%Y-%m-%d %H:%M:%S'


Default: [%(levelname)-8s] %(message)s

The format of the console logging messages. See also log_fmt_console.


Log colors are enabled in log_fmt_console rather than the color config since the logging system is loaded before the minion config.

Console log colors are specified by these additional formatters:

%(colorlevel)s %(colorname)s %(colorprocess)s %(colormsg)s

Since it is desirable to include the surrounding brackets, '[' and ']', in the coloring of the messages, these color formatters also include padding as well. Color LogRecord attributes are only available for console logging.

log_fmt_console: '%(colorlevel)s %(colormsg)s'
log_fmt_console: '[%(levelname)-8s] %(message)s'


Default: %(asctime)s,%(msecs)03d [%(name)-17s][%(levelname)-8s] %(message)s

The format of the log file logging messages. See also log_fmt_logfile.

log_fmt_logfile: '%(asctime)s,%(msecs)03d [%(name)-17s][%(levelname)-8s] %(message)s'


Default: {}

This can be used to control logging levels more specifically. See also log_granular_levels.


Default: False

To diagnose issues with minions disconnecting or missing returns, ZeroMQ supports the use of monitor sockets to log connection events. This feature requires ZeroMQ 4.0 or higher.

To enable ZeroMQ monitor sockets, set 'zmq_monitor' to 'True' and log at a debug level or higher.

A sample log event is as follows:

[DEBUG   ] ZeroMQ event: {'endpoint': 'tcp://', 'event': 512,
'value': 27, 'description': 'EVENT_DISCONNECTED'}

All events logged will include the string ZeroMQ event. A connection event should be logged as the minion starts up and initially connects to the master. If not, check for debug log level and that the necessary version of ZeroMQ is installed.


Default: False

Set the global failhard flag. This informs all states to stop running states at the moment a single state fails

failhard: False

Include Configuration


Default: minion.d/*.conf

The minion can include configuration from other files. Per default the minion will automatically include all config files from minion.d/*.conf where minion.d is relative to the directory of the minion configuration file.


Salt creates files in the minion.d directory for its own use. These files are prefixed with an underscore. A common example of this is the _schedule.conf file.


Default: not defined

The minion can include configuration from other files. To enable this, pass a list of paths to this option. The paths can be either relative or absolute; if relative, they are considered to be relative to the directory the main minion configuration file lives in. Paths can make use of shell-style globbing. If no files are matched by a path passed to this option then the minion will log a warning message.

# Include files from a minion.d directory in the same
# directory as the minion config file
include: minion.d/*.conf

# Include a single extra file into the configuration
include: /etc/roles/webserver

# Include several files and the minion.d directory
  - extra_config
  - minion.d/*
  - /etc/roles/webserver

Frozen Build Update Settings

These options control how salt.modules.saltutil.update() works with esky frozen apps. For more information look at


Default: False (Update feature is disabled)

The url to use when looking for application updates. Esky depends on directory listings to search for new versions. A webserver running on your Master is a good starting point for most setups.

update_url: ''


Default: [] (service restarting on update is disabled)

A list of services to restart when the minion software is updated. This would typically just be a list containing the minion's service name, but you may have other services that need to go with it.

update_restart_services: ['salt-minion']

Standalone Minion Windows Software Repo Settings


To use these config options, the minion must be running in masterless mode (set file_client to local).


Changed in version 2015.8.0: Renamed from win_repo to winrepo_dir. Also, this option did not have a default value until this version.

Default: C:\salt\srv\salt\win\repo

Location on the minion where the winrepo_remotes are checked out.

winrepo_dir: 'D:\winrepo'


Changed in version 2015.8.0: Renamed from win_repo_cachefile to winrepo_cachefile. Also, this option did not have a default value until this version.

Default: winrepo.p

Path relative to winrepo_dir where the winrepo cache should be created.

winrepo_cachefile: winrepo.p


Changed in version 2015.8.0: Renamed from win_gitrepos to winrepo_remotes. Also, this option did not have a default value until this version.

New in version 2015.8.0.

Default: ['']

List of git repositories to checkout and include in the winrepo


To specify a specific revision of the repository, prepend a commit ID to the URL of the the repository:

  - '<commit_id>'

Replace <commit_id> with the SHA1 hash of a commit ID. Specifying a commit ID is useful in that it allows one to revert back to a previous version in the event that an error is introduced in the latest revision of the repo.