A package declares its relationship to some trigger(s) by including a triggers file in its control archive (i.e. DEBIAN/triggers during package creation).
This file contains directives, one per line. Leading and trailing whitespace and everything after the first # on any line will be trimmed, and empty lines will be ignored.
The trigger control directives currently supported are:
Specifies that the package is interested in the named trigger. All triggers in which a package is interested must be listed using this directive in the triggers control file. The "noawait" variant does not put the triggering packages in triggers-awaited state. This should be used when the functionality provided by the trigger is not crucial.
Arranges that changes to this package's state will activate the specified trigger. The trigger will be activated at the start of the following operations: unpack, configure, remove (including for the benefit of a conflicting package), purge and deconfigure. The "noawait" variant does not put the triggering packages in triggers-awaited state. This should be used when the functionality provided by the trigger is not crucial.
If this package disappears during the unpacking of another package the trigger will be activated when the disappearance is noted towards the end of the unpack. Trigger processing, and transition from triggers-awaited to installed, does not cause activations. In the case of unpack, triggers mentioned in both the old and new versions of the package will be activated.
Unknown directives are an error which will prevent installation of the package.
The "-noawait" variants should always be favored when possible since triggering packages are not put in triggers-awaited state and can thus be immediately configured without requiring the processing of the trigger. If the triggering packages are dependencies of other upgraded packages, it will avoid an early trigger processing run and make it possible to run the trigger only once as one of the last steps of the upgrade.
The "-noawait" variants are only supported since dpkg 1.16.1, and will lead to errors if used with an older dpkg. It is thus recommended to add a "Pre-Depends: dpkg (>= 1.16.1)" to any package that wish to use those directives.
The "-await" alias variants are only supported since dpkg 1.17.21, and will lead to errors if used with an older dpkg. It is thus recommended to add a "Pre-Depends: dpkg (>= 1.17.21)" to any package that wish to use those directives.