Historical

Have you ever tried to undo an upgrade that went wrong in Debian? For individual packages, this can easily be done by specifying the desired version for the downgrade next to the package name, as in

sudo apt install foo=0.98.2

However, if you are updating a large number of packages, you then end up with constructs like the one shown in Listing 1.

$ awk '$1 == "2022-08-25" && $3 == "upgrade" {print $4"="$5}' /var/log/dpkg.log

Nala offers you a history function borrowed from Fedora's DNF package manager. It not only shows you what happened during the update, but it can also roll back the results completely. Currently, the history function is still under development and only works for individual packages and their dependencies. The output from

sudo nala history

shows the most recent actions, whether this be a single package installation, a removed package, or a system upgrade with 300 packages.

Especially for system upgrades where a bug has crept in, the history function will be immensely helpful once it is fully implemented. There are good reasons for more and more distributions to use snapshots and atomic upgrades in the form of images. However, because these modern techniques are still a long way off in Debian, Nala's history function offers a passable alternative option that requires hardly any effort.

The line-by-line output of history starts on the left with an ID, which plays a crucial role for rolling back (Figure 7). This is followed by the apt command, with Nala still partly confusing update with upgrade as parameters. But because this is only about information, it does not have any real implications. Once you have found the action to undo, use the ID of the line in

sudo nala history undo <ID>

Figure 7: Nala's history function will support rolling back complete upgrades in the future, which is very helpful should something go wrong during an update.

After doing so, everything reverts to the way it was before. If you do change your mind,

sudo nala history redo <ID>

will reverse the process and reinstall the upgrade.

Conclusions

Nala adds some important features to Debian's package management: The output is attractively colorful and informative. Clutter is avoided, with the tool highlighting everything that is important. Parallel downloads speed up updates and upgrades, while the fetch function additionally lets you choose the fastest mirror servers. But the real highlight is Nala's history function, which will beam Debian to a position close to snapshot-supported distributions in the future. The developer intends to port Nala from Python to Rust in the near future to increase download speed. He will then look to integrate the extended history function.

I have been using Nala daily for six months without any serious complications. In rare cases, the upgrade hangs for some unknown reason, but continues to run normally after pressing the Enter key. Nala extends apt in a way that makes it especially interesting for users of Debian Testing, Unstable, and their offshoots. However, thanks to Nala, updates are also more fun on Ubuntu and other Debian derivatives.