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
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:
• Check whether the system needs to be switched, otherwise do
• Check for dpkg database consistency and otherwise abort.
• Generate and install a regression prevention package, if
requested on the command-line or otherwise on the prompt.
• Get the list of files and alternatives that need to be
• Look for untracked kernel modules files that need to be moved
• Create a shadow hierarchy under /.usrunmess, by creating the
directories symlinks or hardlinking or copying the files as
• Prompt for confirmation before proceeding, if requested on
• 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
• Remove backup symlinks.
• Remove old moved objects, but defer directory removal.
• Remove old deferred directories that are not referenced by
• 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
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
Prompt at the time of no return, so that the debug output or
the shadow hierarchy can be evaluated before proceeding.
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 Protected field set to yes
to protect against accidental removal of the package.
This option enables the dry-run mode, where no destructive
action takes place, only the preparatory part.
Show the usage message and exit.
Show the version and exit.
This page is part of the dpkg (Debian Package Manager) project.
Information about the project can be found at
⟨https://wiki.debian.org/Teams/Dpkg/⟩. If you have a bug report
for this manual page, see
page was obtained from the project's upstream Git repository ⟨git
clone https://git.dpkg.org/git/dpkg/dpkg.git⟩ on 2023-06-23. (At
that time, the date of the most recent commit that was found in
the repository was 2023-05-29.) If you discover any rendering
problems in this HTML version of the page, or you believe there
is a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
1.21.20-209-g3026e 2023-02-07 dpkg-fsys-usrunmess(8)