Reset dselect selection before package installation

Question

I was looking through the list of packages with dselect, but pressed Return twice by mistake, thereby making it confirm and quit the [S]elect option.

When I go to the [I]nstall option, it's now suggesting to install a number of new packages that I don't want (and that have nothing to do with what I was looking for in the first place).

Since I haven't proceeded with the installation itself, is there a way to reset the selection to what it was before I selected new packages, without going through the list one by one and pressing - for each package? (It doesn't matter if it's done via dselect or via another related command.)

EDIT: (Adding an example)

I've tried on another machine where dselect is installed. Let's assume that package gnugo isn't installed (that's just an example).

• Launch delect and choose [S]elect to get the list.
• Search for gnugo in this list (using /, if you're not familiar with dselect).
• Select it with +.
• Press Return to validate the suggestions and Return again to validate go back to the main menu (the mistake I made).

• Go to [I]nstall. It will now say:

  Reading package lists... Done
  Building dependency tree       
  Reading state information... Done
  The following NEW packages will be installed
    gnugo:i386 libgpm2:i386 libncurses5:i386 libreadline6:i386 libtinfo5:i386
  0 upgraded, 5 newly installed, 0 to remove and 0 not upgraded.
  Need to get 1,926 kB of archives.
  After this operation, 9,634 kB of additional disk space will be used.
  Do you want to continue [Y/n]? 
  

• Here, choose not to continue (n).

• Quit dselect.
• dpkg --get-selections | grep gnugo yields nothing at all.
• Start dselect again, go straight to [I]nstall again, the packages will still be selected for installation.

Of course, I can go back into the [S]elect list, search for gnugo, press _ to deselect it, but in a more complex case, you may have to go through the new packages list one by one.

[I]nstall in dselect is visibly a front-end to apt-get install, but I'm not sure where it gets its selection from. It appears dpkg --get-selection is not it. As far as dselect is concerned, I'd like to reset it in a state where everything maked with *** stays at it was, but what's now marked with only ** (and not installed yet) goes back to __, without having to go manually through the suggested list from the [I]nstall menu.

EDIT 2:

This is clearly related to the content of /var/lib/dpkg/status, which contains this entry:

Package: gnugo
Status: install ok not-installed
Priority: optional
Section: games

If I change this manually to Status: deinstall ok not-installed, it disappears from the selection in dselect (which makes sense).

What I would like is a general way of turning whatever says Status: install ok not-installed into Status: deinstall ok not-installed (leaving packages saying Status: install ok installed unaffected).

Answer 1

Use the --set-selections* argument to dpkg:

echo "<package-name> purge" | dpkg --set-selections

You can then use apt-get dselect-upgrade to apply your package selection.

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If you need to find the packages that have been selected for install but not yet installed (so you can reverse that selection) use this:

dpkg --get-selections | awk '{ if ($2=="install") print $1}' | grep -vF "$(dpkg -l | awk '/^ii/ {print $2}')"

You can get slightly fancier and pipe that back into --set-selections, thereby automatically deselecting anything that's not already installed:

dpkg --get-selections | awk '{ if ($2=="install") print $1,"deinstall"}' | grep -vF "$(dpkg -l | awk '/^ii/ {print $2}')" | dpkg --set-selections

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*You can also use dpkg --get-selections to list all of the explicit selections. This will also show you the format that --set-selections requires.

Answer 2

It turns out dpkg --get-selections doesn't list what's marked for installation and not yet installed, but dpkg -l '*' does, and starts these lines with in.

As a result, the following line resets these selections:

dpkg -l '*' | grep '^in ' | awk '{ print $2 " deinstall" }' | dpkg --set-selections

Answer 3

Use Aptitude's search capabilities to obtain the list.

aptitude -F '%p' search '~ainstall !~i'

Pass the list to dpkg --set-selections to mark them as to-be-removed.

aptitude -F '%p deinstall' search '~ainstall !~i' | dpkg --set-selections

Aside: welcome to the 21st century, I suggest switching to Aptitude instead of Dselect.