NAME

       dpkg-fsys-usrunmess - undoes the merged-/usr-via-aliased-dirs mess

SYNOPSIS

       dpkg-fsys-usrunmess [option...]

DESCRIPTION

       dpkg-fsys-usrunmess is a tool to fix up filesystems that have been installed anew with
       recent installers with unfortunate defaults or migrated to the broken merged /usr via
       aliased directories layout, which is not supported by dpkg. See the dpkg FAQ.

       The program will perform the following overall actions:

       ·   Check whether the system needs to be switched, otherwise do nothing,

       ·   Check for dpkg database consistency and otherwise abort.

       ·   Generate and install a regression prevention package.

       ·   Get the list of files and alternatives that need to be restored.

       ·   Create a shadow hierarchy under /.usrunmess, by creating the directories symlinks or
           hardlinking or copying the files as needed.

       ·   Prompt for confirmation before proceeding, if requested on the command-line.

       ·   Lock the dpkg database.

       ·   Mark all packages as half-configured to force running maintainer scripts that might
           need to recreate files.

       ·   Replace the aliased directories with the shadow ones, by creating a backup of the old
           symlinked directories and renaming the shadow ones over.

       ·   Relabel MAC information for directories and symlinks if necessary.

       ·   Remove backup symlinks.

       ·   Remove old moved objects, but defer directory removal.

       ·   Remove old deferred directories that are not referenced by dpkg-query.

       ·   Remove shadow root directory.

       ·   Register a policy-rc.d to disallow service actions, which means that services might
           need to be restarted afterwards, ideally via a reboot.

       ·   Reconfigure all packages.

       ·   Unregister the policy-rc.d and restore the alternatives state.

       Note: When running the program from some shells such as bash(1) or zsh(1), after executing
       it, you might need to request the shell to forget all remembered executable locations with
       for example "hash -r".

       Note: Some directories might linger after the migration in case they contain untracked
       files. A list is printed once the script has finished for further investigation.

       Warning: Note that this operation has the potential to render the system unusable or
       broken in case of a sudden crash or reboot, unexpected state of the system, or possible
       bugs in the script. Be prepared with recovery media and consider doing backups beforehand.

OPTIONS

       -p, --prompt
           Prompt at the time of no return, so that the debug output or the shadow hierarchy can
           be evaluated before proceeding.

       -n, --no-act
       --dry-run
           This option enables the dry-run mode, where no destructive action takes place, only
           the preparatory part.

       -?, --help
           Show the usage message and exit.

       --version
           Show the version and exit.

ENVIRONMENT

       DPKG_USRUNMESS_NOACT
           This setting defines whether to enable dry-run mode.

SEE ALSO

       <https://wiki.debian.org/Teams/Dpkg/FAQ#Q:_Does_dpkg_support_merged-.2Fusr-via-aliased-dirs.3F>.