Why is my debian postinst script not being run?

Question

I have made a .deb of my app using fpm:

fpm -s dir -t deb -n myapp -v 9 -a all -x "*.git" -x "*.bak" -x "*.orig" \
--after-remove debian/postrm  --after-install debian/postinst \
--description "Automated build." -d mysql-client -d python-virtualenv home

Among other things, the postinst script is supposed to create a user for the app:

#!/bin/sh

    set -e

    APP_NAME=myapp

    case "$1" in
        configure)
            virtualenv /home/$APP_NAME/local
            #supervisorctl start $APP_NAME
        ;;

    # http://www.debian.org/doc/manuals/securing-debian-howto/ch9.en.html#s-bpp-lower-privs
       install|upgrade)

       # If the package has default file it could be sourced, so that
       # the local admin can overwrite the defaults

       [ -f "/etc/default/$APP_NAME" ] && . /etc/default/$APP_NAME

       # Sane defaults:

       [ -z "$SERVER_HOME" ] && SERVER_HOME=/home/$APP_NAME
       [ -z "$SERVER_USER" ] && SERVER_USER=$APP_NAME
       [ -z "$SERVER_NAME" ] && SERVER_NAME=""
       [ -z "$SERVER_GROUP" ] && SERVER_GROUP=$APP_NAME

       # Groups that the user will be added to, if undefined, then none.
       ADDGROUP=""

       # create user to avoid running server as root
       # 1. create group if not existing
       if ! getent group | grep -q "^$SERVER_GROUP:" ; then
          echo -n "Adding group $SERVER_GROUP.."
          addgroup --quiet --system $SERVER_GROUP 2>/dev/null ||true
          echo "..done"
       fi
       # 2. create homedir if not existing
       test -d $SERVER_HOME || mkdir $SERVER_HOME
       # 3. create user if not existing
       if ! getent passwd | grep -q "^$SERVER_USER:"; then
         echo -n "Adding system user $SERVER_USER.."
         adduser --quiet \
                 --system \
                 --ingroup $SERVER_GROUP \
                 --no-create-home \
                 --disabled-password \
                 $SERVER_USER 2>/dev/null || true
         echo "..done"
       fi

       # … and a bunch of other stuff.

It seems like the postinst script is being called with configure, but not with install, and I am trying to understand why. In /var/log/dpkg.log, I see the lines I would expect:

2012-06-30 13:28:36 configure myapp 9 9
2012-06-30 13:28:36 status unpacked myapp 9
2012-06-30 13:28:36 status half-configured myapp 9
2012-06-30 13:28:43 status installed myapp 9

I checked that /etc/default/myapp does not exist. The file /var/lib/dpkg/info/myapp.postinst exists, and if I run it manually with install as the first parameter, it works as expected.

Why is the postinst script not being run with install? What can I do to debug this further?

Answer 1

I think the example script you copied is simply wrong. postinst is not supposed to be called with any install or upgrade argument, ever. The authoritative definition of the dpkg format is the Debian Policy Manual. The current version describes postinst in chapter 6 and only lists configure, abort-upgrade, abort-remove, abort-remove, and abort-deconfigure as possible first arguments.

I don't have complete confidence in my answer, because your bad example is still up on debian.org and it's hard to believe such a bug could slip through.