How to fix a dpkg broken by the Brother MFC-7340 deb driver

You can always (re)install a package using dpkg:

dpkg --install local-file.deb

In order to make a "clean room" installation, you can first purge the package and then install it again:

dpkg --purge brmfc7340lpr
dpkg --install brmfc7340lpr*.deb

You might need to add option --force-depends during purge, if some other package depends on brmfc7340lpr.

Update: Based on the transcript you posted, it seems that the brmfc7340lpr package cannot be (re)installed because its post-removal script is erroring out.

Those files are stored in directory /var/lib/dpkg/info; for each package X, there can be any one of these scripts:

• X.postinst run after the package has been installed, e.g., to start services provided by the package.

• X.prerm run before removing/purging the package, e.g., to ensure that daemons provided by the package are stopped.

• X.postrm run after the package has been removed, e.g., to signal any service optionally using the package that it is no longer available. (For instance, a printer driver package might want to signal cpus/lpr to remove printers depending on that specific driver.)

Now, this brmfc7340lpr package seems to try to (re)start the lpd printer daemon upon removal, which won't work as Ubuntu uses CUPS instead: you should definitely look for a CUPS-compatible printer driver -- see the link in Jorge Castro's answer. (I think this is a bug in the package, as it should not restart the lpd service unconditionally, but just reload it if it's already running.)

The best option to go forward comes from this launchpad answer:

ln -s /etc/init.d/cpus /etc/init.d/lpd

This will effectively (re)start CUPS when the lpd service is instead searched for.

Otherwise, I only see two options, both rather unpleasant:

1. Either edit the /var/lib/dpkg/info/brmfc7340lpr.postrm script, and comment out the line that is invoking /etc/init.d/lpd start (or restart or stop), (e.g., just replace it with /bin/true). Another option is to just place exit 0 as the first non-comment line in the script. This would be my favorite, but requires a bit of confidence with editing shell scripts.

2. Install lpr, purge the brmfc6340lpr package, purge lpr: this requires a bit of attention as lpr conflicts with the default Ubuntu printer spooling system CUPS:

   a. sudo aptitude install lpr (this will remove cups-bsd and ubuntu-desktop as a side effect)

   b. sudo aptitude purge brmfc7340lpr lpr (should work now)

   c. sudo aptitude install cups-bsd ubuntu-desktop (restore system to its original state)

Riccardo's solution should work, I am guessing the problem lies here:

start: Unknown job: lpd

Guess 1: It looks like the deb is trying to restart a service which isn't running and erroring out. Try installing the lpr package from the repositories and then installing the deb and see if that works.

Guess 2: It sounds like you're trying to install a deb from a website for a brother 7340 printer: This page might be a good starting point if you want to split it off into another question.