Retrieve list of packages from unbootable Ubuntu 15.04 installation

Question

How can I get a list of packages installed (excluding dependencies) on an Ubuntu installation that I cannot boot into?

Something like this answer aptitude search '~i!~M' but reading packages from an external HDD on which Ubuntu 15.04 is installed.

Answer 1

The answer provided by knudfl in 2010 on http://www.linuxquestions.org/questions/debian-26/getting-list-of-installed-packages-from-a-dead-system-811288/ can still help you:

1. mount the disk of the dead system (e.g. on /media/disk )

2. grab the list of installed programs:

   ls /media/disk/var/lib/dpkg/info/ | grep list