Why does apt-get install python3 with a trailing hyphen remove a lot of packages? [duplicate]

Solution 1:

This is not a bug; this is documented in the man page. From man apt-get's install section¹ (emphasis mine):

If a hyphen is appended to the package name (with no intervening space), the identified package will be removed if it is installed. Similarly a plus sign can be used to designate a package to install.

So, when you did:

sudo apt-get install python3-

you've removed the python3 package and all the dependent packages (which includes the packages you mentioned).

Fix:

Firstly, you can install the ubuntu-desktop metapackage to get the default desktop environment back:

sudo apt-get install ubuntu-desktop

Now, to re-install the removed packages, go to /var/log/apt/history.log, pick the packages, and run sudo apt-get install on them.

You might also want to peek into /var/log/dpkg.log.

¹ If you have less as the man pager, you can go to the install section of man apt-get directly:

LESS='+/^[[:blank:]]+install' man apt-get

Solution 2:

No, you didn't find a bug. From man apt-get:

If a hyphen is appended to the package name (with no intervening space), the identified package will be removed if it is installed. Similarly a plus sign can be used to designate a package to install. These latter features may be used to override decisions made by apt-get's conflict resolution system.

It's intentional. I'm not sure it's good design, but it is worth reading what changes apt proposes before proceeding.

Combined with globbing it may produce some rather... spectacular results at times.