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up vote 4 down vote favorite
1

If I had a running debian system, the following command could be issued to get list of installed packages: 

dpkg --get-selections > packages.lst

But now I have only a full backup of root partition (complete system backup) of the working system and nothing more. How can I generate list of installed packages from these files?

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Only the root partition - not the complete system? Which directories are on this partition? –  Thomas Weinbrenner 11 hours ago
    
I meant "complete system backup", edited question accordingly. –  ceremcem 10 hours ago

3 Answers 3

up vote 6 down vote accepted

chroot into it, and run dpkg would be the easiest thing. See http://superuser.com/a/417004/20798 for how to get a working /proc, /sys, and /dev inside the chroot.

Since you have a working debian system outside the backup, you could probably just use

dpkg --admindir=dir --get-selections

The dir defaults to /var/lib/dpkg, so put the path to your backup's /var/lib/dpkg.

Don't forget that dpkg --get-selections doesn't show which packages were manually installed, and which were only installed to satisfy dependencies (and thus should be auto-removed when no longer needed because newer versions of the packages you actually want have different deps, or because you purge a manually installed package.)

I use aptitude, which makes it easy to mark everything as auto-installed, then go through and mark some packages as manually installed until nothing you want to keep is getting auto-removed. Start with big meta-packages, like build-essential, the Debian equivalents of ubuntu-standard and ubuntu-desktop, and stuff like that. In aptitude, hit r to see the reverse-depends of a package (pkgs that depend on it).

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You can use apt-mark or (far more convenient but not installed by default) apt-clone to clone a set of installed packages including the automatic/manual flag. –  Gilles 8 hours ago
up vote 3 down vote

Peter's approach is better but you could also just parse /var/lib/dpkg/status which doesn't require a chroot:

 $ perl -00ne 'if(/: install/){/Package:\s*(\S+)/ && print "$1\n"}' /var/lib/dpkg/status

On my machine, that returned the same list of packages as dpkg --get selections | awk '$NF=="install"{print $1}' (the awk is needed to make it show only installed packages).

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up vote 0 down vote

You can have a listing using of you packages using :

awk '/Package:/ {print $2}' /var/lib/dpkg/status

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That will not only show installed packages. –  terdon♦ 10 hours ago

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