Why is the google PPA reenabled after an upgrade to a new release?

PPA's are normally disabled when you upgrade, and must be re-enabled manually. I upgraded to 12.04 about a month ago and I just noticed that while my other PPAs had all been disabled, the Google PPAs were not disabled. Why is this?

Solution 1:

(Credit to Jorge Castro for this answer)

The Google packages install a cron job in /etc/cron.daily/ for custumizing the repository configuration and reenabling the source after a release upgrade.

Each Google package will put its own script (or a link to a script) here. For example: google-musicmanager, google-chrome or google-talkplugin (the latter being a symlink to a script at /opt/google/talkplugin/cron/google-talkplugin).

Here is the description from the google-talkplugin script:

# This script is part of the google-talkplugin package.
#
# It creates the repository configuration file for package updates, and it
# monitors that config to see if it has been disabled by the overly aggressive
# distro upgrade process (e.g.  intrepid -> jaunty). When this situation is
# detected, the respository will be re-enabled. If the respository is disabled
# for any other reason, this won't re-enable it.
#
# This functionality can be controlled by creating the $DEFAULTS_FILE and
# setting "repo_add_once" and/or "repo_reenable_on_distupgrade" to "true" or
# "false" as desired. An empty $DEFAULTS_FILE is the same as setting both values
# to "false".

The script will:

1. # Install the repository signing key
2. # Update the Google repository if it's not set correctly.
3. # Add the Google repository to the apt sources.
4. # Remove our custom sources list file. and
5. # Detect if the repo config was disabled by distro upgrade and enable if necessary.

Here is the portion of the script that detects and reenables the repo config after a release upgrade.

handle_distro_upgrade() {
  if [ ! "$REPOCONFIG" ]; then
    return 0
  fi

  find_apt_sources
  SOURCELIST="$APT_SOURCESDIR/google-talkplugin.list"
  if [ -r "$SOURCELIST" ]; then
    REPOLINE=$(grep -E "^[[:space:]]*#[[:space:]]*$REPOCONFIG[[:space:]]*# disabled on upgrade to .*" "$SOURCELIST")
    if [ $? -eq 0 ]; then
      sed -i -e "s,^[[:space:]]*#[[:space:]]*\($REPOCONFIG\)[[:space:]]*# disabled on upgrade to .*,\1," \
        "$SOURCELIST"
      LOGGER=$(which logger 2> /dev/null)
      if [ "$LOGGER" ]; then
        "$LOGGER" -t "$0" "Reverted repository modification: $REPOLINE."
      fi
    fi
  fi
}

And here is the /etc/apt/sources.list.d/google-talkplugin.list file that is created by the script.

### THIS FILE IS AUTOMATICALLY CONFIGURED ###
# You may comment out this entry, but any other modifications may be lost.
deb http://dl.google.com/linux/talkplugin/deb/ stable main