dpkg: How to use trigger?

debhelper, debian, dpkg, triggers

Solution

What you are looking for is dpkg-triggers.

One solution with use of debhelper to build the debian packages is this:

Step 1)

Create file `debian/<serverPackageName>.triggers` (replace `<serverPackageName>` with name of your server package).

Step 1a)

Define a trigger that watch the directory of your pool. The content of file would be:

`interest /path/to/my/pool`

Step 1b)

But you can also define a named trigger, which have to be fired explicit (see step 3).

content of file:

`interest cdn-pool-changed`

The name of the trigger cdn-pool-changed is free. You can take what ever you want.

Step 2)

Add handler for trigger to file `debian/<serverPackageName>.postinst` (replace `<serverPackageName>` with name of your server package).

Example:

#!/bin/sh

set -e

case "$1" in
    configure)
    ;;

    triggered)
        #here is the handler 
        /etc/init.d/<serverPackageName> restart
    ;;

    abort-upgrade|abort-remove|abort-deconfigure)
    ;;

    *)
        echo "postinst called with unknown argument \`$1'" >&2
        exit 1
    ;;
esac

#DEBHELPER#

exit 0

Replace `<serverPackageName>` with name of your server package.

Step 3) (only for named triggers, step 1b) )

Add in every content package the file `debian/<contentPackageName>.triggers` (replace `<contentPackageName>` with names of your content packages).

content of file:

`activate cdn-pool-changed`

Use same name for trigger you defined in step 1.

More detailed Information

The best description for dpkg-triggers I could found is "How to use dpkg triggers". The corresponding git repository with examples you can get here:

`git clone git://anonscm.debian.org/users/seanius/dpkg-triggers-example.git`

Problem

I wrote a little CDN server that rebuilds its registry pool when new `pool-content-packages` are installed into that registry pool. Instead of having each `pool-content-package` call the `init.d` of the `cdn-server`, I'd like to use triggers. That way it would restart the server only once at the end of an installation run, after all packages were installed. What have I to do to use triggers in my packages with `debhelper` support?

Original source