How do I replicate installed package selections from one Debian system to another? (Debian Wheezy)

To clone a Debian installation, use the apt-clone utility. It's available (as a separate package, not part of the default installation) in Debian since wheezy and in Ubuntu since 12.04. On the existing machine, run

apt-clone clone foo

This creates a file foo.apt-clone.tar.gz. Copy it to the destination machine, and run

apt-get install apt-clone
apt-clone restore foo.apt-clone.tar.gz

If you're working with an old system where apt-clone isn't available, or if you just want to replicate the list of installed packages but not any configuration file, here are the manual steps.

• On the source machine:

  cat /etc/apt/sources.list /etc/apt/sources.list.d >sources.list
  dpkg --get-selections >selections.list
  apt-mark showauto >auto.list
  

• On the target machine:

  cp sources.list /etc/apt/
  apt-get update
  /usr/lib/dpkg/methods/apt/update /var/lib/dpkg/
  dpkg --set-selections <selections.list
  apt-get dselect-upgrade
  xargs apt-mark auto <auto.list
  

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I believe that you're affected by an incompatible change in dpkg that first made it into wheezy. See bug #703092 for background.

The short story is that dpkg --set-selections now only accepts package names that are present in the file /var/lib/dpkg/status or /var/lib/dpkg/available. If you only use APT to manage packages, like most people, then /var/lib/dpkg/available is not kept up-to-date.

After running apt-get update and before running dpkg --set-selections and apt-get -u dselect-upgrade, run the following command:

apt-cache dumpavail >/tmp/apt.avail
dpkg --merge-avail /tmp/apt.avail

From jessie onwards, you can simplify this to

apt-cache dumpavail | dpkg --merge-avail

Alternatively, run

/usr/lib/dpkg/methods/apt/update /var/lib/dpkg/

or even simpler

apt-get install dctrl-tools
sync-available

Another simple method that doesn't require installing an additional package but will download the package lists again is

dselect update

See the dpkg FAQ for more information. (This is mentioned in the dpkg man page, but more in a way that would remind you of the issue if you were already aware, not in a way that explains how to solve the problem!)

Note that cloning a package installation with dpkg --set-selections doesn't restore the automatic/manual mark in APT. See Restoring all data and dependencies from dpkg --set-selections '*' for more details. You can save the marks on the source system with

apt-mark showauto >auto.list

and restore them on the target system with

xargs apt-mark auto <auto.list