Actions Plugin

Description

This plugin allows defining actions to be executed through libdnf5 callbacks hooks. Each action is hooked to one specific callback. Actions for pre_transaction and post_transaction callbacks may define a (glob-like) filtering rule on the package NEVRA or package files, as well as whether the package is incoming or outgoing.

Configuration

The plugin does not extend the standard configuration. However, it reads “actions” files.

The actions files are read from <libdnf5_plugins_config_dir>/actions.d/ directory. Only files with “.actions” extension are read.

Actions file format

Empty lines and lines that start with a ‘#’ character (comment line) are ignored.

Each non-comment line defines an action and consists of five items separated by colons: callback_name:package_filter:direction:options:command.

callback_name

  • pre_base_setup

  • post_base_setup

  • repos_configured (added in version 1.0.0)

  • repos_loaded (added in version 1.0.0)

  • pre_add_cmdline_packages (added in version 1.0.0)

  • post_add_cmdline_packages (added in version 1.0.0)

  • pre_transaction

  • post_transaction

package_filter

A (glob-like) filtering rule applied on the package NEVRA (also in the shortened forms) or package files.

Empty filter means executing the command once with no information about the package. The “*” filter means executing the command for each package in the transaction that matches the direction filter. The filter can be non-empty only for pre_transaction and post_transaction callbacks.

direction

Filters packages by their direction (coming into the system/going out of the system) in a transaction. If empty, the filter is not applied. The filter can only be non-empty when combined with a non-empty package_filter.

  • in - packages coming to the system (downgrade, install, reinstall, upgrade)

  • out - packages going out of the system (upgraded, downgraded, reinstalled, removed, replaced/obsoleted)

options

Options are separated by spaces. A space within an option can be written using escaping.

  • enabled=<value> - the value specifies when the action is enabled (added in version 0.3.0)

    • 1 - action is always enabled

    • host-only - the action is only enabled for operations on the host

    • installroot-only - the action is only enabled for operations in the alternative “installroot”

command

Any executable file with arguments.

Arguments are separated by spaces. A space within an argument can be written using escaping. Escaping can also be used to prevent substitution and to pass special characters \a, \b, \f, \n, \r, \t, \v. Unescaping of arguments is done after substitution.

The following variables in the command will be substituted:

  • ${pid} - process ID

  • ${plugin.version} - version of the actions plugin (added in version 0.3.0)

  • ${conf.<option_name>} - option from base configuration

  • ${var.<variable_name>} - variable

  • ${tmp.<actions_plugin_variable_name>} - variable exists only in actions plugin context

  • ${pkg.<package_attribute_name>} - value of the package attribute

    • ${pkg.name} - package name

    • ${pkg.arch} - package arch

    • ${pkg.version} - package version

    • ${pkg.release} - package release

    • ${pkg.epoch} - package epoch

    • ${pkg.na} - package name.architecture

    • ${pkg.evr} - package epoch-version-release

    • ${pkg.nevra} - package nevra (0 epoch is hidden)

    • ${pkg.full_nevra} - package full nevra (epoch is always present) ${name}-${epoch}:${ver}-${rel}.${arch}

    • ${pkg.repo_id} - package repository id

    • ${pkg.license} - package license

    • ${pkg.location} - the change of package state in the transaction:

    • ${pkg.vendor} - package vendor

    • ${pkg.action} - action performed on the package:

      • I - newly installed package

      • U - package installed as an upgrade

      • D - package installed as an downgrade

      • R - package used for reinstallation

      • E - erased (removed) package from the system (was upgraded/downgraded/reinstalled/removed)

      • O - replaced (obsoleted) package

The command will be evaluated for each package that matched the package_filter and the direction. However, after variable substitution, any duplicate commands will be removed and each command will only be executed once per transaction. The commands are executed in sequence. There is no parallelism. Argument substitution is performed after the previous command has completed. This allows the substitution to use the results of the previous commands. The order of execution of the commands follows the order in the action files, but may differ from the order of packages in the transaction. In other words, when you define several action lines for the same package_filter and direction these lines will be executed in the order they were defined in the action file when the package_filter and direction matches a package. However, the order of when a particular package_filter is invoked depends on the position of the corresponding package in the transaction.

Action standard output format

The standard output of each executed action (command) is captured and processed. Each line of output can set the value or unset one actions plugin variable. It can also change the value of an option from the base configuration or a variable.

Output line format

  • tmp.<actions_plugin_variable_name>=<value> - sets the value of action plugins variable <actions_plugin_variable_name>

  • tmp.<actions_plugin_variable_name> - removes the action plugins variable if it exists

  • conf.<option_name>=<value> - sets the value of option <option_name> in the base configuration

  • var.<variable_name>=<value> - sets value of the vatiable <variable_name>

An example actions file:

# Prints header with process id
pre_base_setup::::/usr/bin/sh -c echo\ -------------------------------------\ >>/tmp/actions-trans.log
pre_base_setup::::/usr/bin/sh -c date\ >>/tmp/actions-trans.log
pre_base_setup::::/usr/bin/sh -c echo\ libdnf5\ pre_base_setup\ was\ called.\ Process\ ID\ =\ '${pid}'.\ >>/tmp/actions-trans.log
pre_base_setup:::enabled=installroot-only:/usr/bin/sh -c echo\ run\ in\ alternative\ "installroot":\ installroot\ =\ '${conf.installroot}'\ >>/tmp/actions-trans.log

# Prints the value of the configuration option "defaultyes".
pre_base_setup::::/bin/sh -c echo\ 'pre_base_setup:\ conf.defaultyes=${{conf.defaultyes}}'\ >>\ {context.dnf.installroot}/actions.log

# Prints a message that the "post_base_setup" callback was called.
post_base_setup::::/usr/bin/sh -c echo\ libdnf5\ post_base_setup\ was\ called.\ >>/tmp/actions-trans.log

# Prints the information about the start of the transaction.
# Since package_filter is empty, it executes the commands once.
pre_transaction::::/usr/bin/sh -c echo\ Transaction\ start.\ Packages\ in\ transaction:\ >>/tmp/actions-trans.log

# Logs all packages (package action, full_nevra, repo id) in transaction into a file.
# Uses the shell command "echo" and redirection to a file.
pre_transaction:*:::/usr/bin/sh -c echo\ '${pkg.action}'\ '${pkg.full_nevra}'\ '${pkg.repo_id}'\ >>/tmp/actions-trans.log

# Prints the date and time and information about the end of the transaction.
# Since package_filter is empty, it executes the commands once.
post_transaction::::/usr/bin/sh -c date\ >>/tmp/actions-trans.log
post_transaction::::/usr/bin/sh -c echo\ Transaction\ end.\ Repositories\ used\ in\ the\ transaction:\ >>/tmp/actions-trans.log

# Logs all the repositories from which packages were used in the transaction to install on the system.
# Each repository will be listed only once, even if multiple packages from the same repository were used.
# The same command (after variables substitution) is executed only once per transaction.
post_transaction:*:in::/usr/bin/sh -c echo\ '${pkg.repo_id}'\ >>/tmp/actions-trans.log

# ==============================================================================================
# The next two actions emulate the DNF4 snapper plugin. It uses the "snapper" command-line proram.

# Creates pre snapshot before the transaction and stores the snapshot number in the "tmp.snapper_pre_number" variable.
pre_transaction::::/usr/bin/sh -c echo\ "tmp.snapper_pre_number=$(snapper\ create\ -t\ pre\ -p)"

# If the variable "tmp.snapper_pre_number" exists, it creates post snapshot after the transaction and removes the variable "tmp.snapper_pre_number".
post_transaction::::/usr/bin/sh -c [\ -n\ "${tmp.snapper_pre_number}"\ ]\ &&\ snapper\ create\ -t\ post\ --pre-number\ "${tmp.snapper_pre_number}"\ ;\ echo\ tmp.snapper_pre_number