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# dpkg manual page - dpkg-fsys-usrunmess(8)
#
# Copyright © 2020-2021 Guillem Jover <guillem@debian.org>
#
# This is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <https://www.gnu.org/licenses/>.
=encoding utf8
=head1 NAME
dpkg-fsys-usrunmess - undoes the merged-/usr-via-aliased-dirs mess
=head1 SYNOPSIS
B<dpkg-fsys-usrunmess> [B<option>...]
=head1 DESCRIPTION
B<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 B<not> supported by dpkg. See the dpkg FAQ.
B<Note>: In Debian its tech-ctte has decreed that on the release after
bookworm the non-usrmerged layout is not going to be supported, and thus
some of its maintainers might not fix issues or intentionally remove
non-usrmerged support, so you will need decide and pick your poison.
The program will perform the following overall actions:
=over
=item *
Check whether the system needs to be switched, otherwise do nothing,
=item *
Check for dpkg database consistency and otherwise abort.
=item *
Generate and install a regression prevention package, if requested on the
command-line or otherwise on the prompt.
=item *
Get the list of files and alternatives that need to be restored.
=item *
Look for untracked kernel modules files that need to be moved too.
=item *
Create a shadow hierarchy under F</.usrunmess>, by creating the directories
symlinks or hardlinking or copying the files as needed.
=item *
Prompt for confirmation before proceeding, if requested on the command-line.
=item *
Lock the dpkg database.
=item *
Mark all packages as half-configured to force running maintainer scripts
that might need to recreate files.
=item *
Replace the aliased directories with the shadow ones, by creating a backup
of the old symlinked directories and renaming the shadow ones over.
=item *
Relabel MAC information for directories and symlinks if necessary.
=item *
Remove backup symlinks.
=item *
Remove old moved objects, but defer directory removal.
=item *
Remove old deferred directories that are not referenced by dpkg-query.
=item *
Remove shadow root directory.
=item *
Register a B<policy-rc.d> to disallow service actions, which means that
services might need to be restarted afterwards, ideally via a reboot.
=item *
Reconfigure all packages.
=item *
Unregister the B<policy-rc.d> and restore the alternatives state.
=back
B<Note>: When running the program from some shells such as L<bash(1)> or
L<zsh(1)>, after executing it, you might need to request the shell to
forget all remembered executable locations with for example C<hash -r>.
B<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.
B<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.
=head1 OPTIONS
=over
=item B<-p>, B<--prompt>
Prompt at the time of no return, so that the debug output or the shadow
hierarchy can be evaluated before proceeding.
=item B<--prevention>
=item B<--no-prevention>
Enables or disables generating and installing a regression prevention package
into the system.
If no option has been specified, the action to take will be prompted.
The generated package contains the B<Protected> field set to B<yes> to
protect against accidental removal of the package.
=item B<-n>, B<--no-act>
=item B<--dry-run>
This option enables the dry-run mode, where no destructive action takes place,
only the preparatory part.
=item B<-?>, B<--help>
Show the usage message and exit.
=item B<--version>
Show the version and exit.
=back
=head1 ENVIRONMENT
=over
=item B<DPKG_USRUNMESS_NOACT>
This setting defines whether to enable dry-run mode.
=back
=head1 SEE ALSO
L<https://wiki.debian.org/Teams/Dpkg/FAQ#broken-usrmerge>.
|
