Command Line – debfoster

Debian was one of the first distributions to have a modern package system. Over the decades, a whole ecosystem of related commands has grown up around it, including front ends like apt-get and, more recently, apt for the basic package manager dpkg, and then utilities ranging from apt-file for searching files inside packages to apt-cache for searching packages. In fact, a search on "apt" in the Stable repository for Debian 10 returns 54 hits, while a search on "deb" returns 68. One of the lesser-known but handier members of this ecosystem is debfoster [1], whose main purpose is to weed out unnecessary packages. However, like apt, debfoster actually combines several other functions, displaying information on currently installed packages, and serving as a replacement for apt-get.

You can start to use debfoster by running the command without options or targets to create a database of packages that you want to keep installed. This first session takes at least 20 minutes on an average system, since every installed package is queried. However, once the database is populated, later sessions generally only refer to a handful of packages. If you find that you have accidentally kept a package – which is easy to do the first time as your responses become automatic – you can exit and try again.

Once the database is created, debfoster can be run in two ways: by running it after packages have been installed or removed or as an alternative means to install and remove packages. To install a package, use the structure alongside another command with debfoster PACKAGE(S). To remove packages, add a minus sign (-) before the list of packages.

Either way, debfoster concludes by detecting orphans: packages that were installed as a dependency, but are no longer needed because of changes to the system. apt-get and apt, of course, perform the same function, but only give the choice of using the autoremove sub-command to delete them. By contrast, debfoster gives a wider variety of choices (Table 1). For one thing, the default is to keep the package (Figure 1), while apt-get and apt simply keep repeating their message about orphans each time they start. For another, you can choose to delete only the package (n) or its dependences as well (p) or view package information (i) before a decision is made. Similarly, you can exit debfoster instead of answering, committing the changes already indicated or without saving any of them. More importantly, many packages have no dependencies and are not detected by the basic package manager as orphans, and these may linger long after they are no longer wanted. All in all, debfoster offers a more hands-on, less accident-prone approach to package management that advanced users may appreciate.

Figure 1: debfoster provides options (Table 1) to display information useful for package management.

Command Options

debfoster's options begin with a number of queries about installed packages. --show-keeper (-a) lists files to be kept (Figure 2), --show-orphans (-s) lists dependencies that are no longer needed (Figure 3), --show-depends PACKAGE (-d) or --show-related PACKAGE (-r) lists the packages that the specified package depends on (Figure 4), and --show-providers PACKAGE (-p) lists the package for which the specified package is installed only as a dependency – something that rarely happens in recent releases. More likely, --show-providers may return a message of Installed Package or Not a Dependency, which limits its usefulness. The other query options, though, are useful for knowing what packages to keep. The number of orphans can be particularly surprising, especially if you install packages from outside the official repositories.

Figure 2: debfoster creates a database of keepers – files not to remove.

Figure 3: Orphans are packages that were dependencies of a removed package.

Figure 4: debfoster can list a package's dependencies.

Other options affect how debfoster runs. To guard against mistakes, --mark-only (-m) does a dry run so you can see the results of your answers before anything is deleted. If you decide the results contain no surprises, then you can run debfoster with the --force (-f) option to have all deletions made. You can also run it with --quiet (-q) to assume that all answers are Yes, in order to update the keepers list. Should you be transferring files from one machine to another, you may want to use --config FILE (-c) to create a clean configuration file (see below) or --keeperfile FILE (-k) to create a clean database and then replace the transferred files with the newly-created ones. In addition, the usual --verbose (-v) option can sometimes give you a more detailed look at what is happening.

In its role as an apt-get or apt replacement, debfoster can also take --upgrade (-u), with or without packages specified.

Configuring debfoster

The default configuration file for debfoster is /etc/debfoster.conf. All fields in the file are case-insensitive, and the most commonly used fields (Table 2) are first in the file. If desired, an alternate configuration file can be specified using the option --config FILE (-c). Half a dozen fields are the commands for which debfoster is a front end. For the most part, these fields do not need to be changed, although if you are in the habit of using apt, you probably want to change InstallCmd's value to apt install.

Other fields can affect how debfoster operates. Some fields, like MaxPriority or UseHold are based on package settings, while others like Verbose or Quiet set options for debfoster command. Fields in /etc/debfoster.conf can be overwritten by command-line options, particularly --ignore-default-rules (-i), which suppresses the settings for the UseHold, UseEssential, MaxPriority, KeepSections, and NokeepSections fields.

A Convenient Arrangement

debfoster adds nothing new to the Debian package manager. Its functions are spread over a number of different commands. Rather, its strength lies in its convenient rearrangement of functions in a single command. Moreover, aside from the number of possible answers to questions, it is quick to learn, with options that most command-line users will have seen in other commands. As a result of these advantages, using it can tell you things about your packages that you could find elsewhere, but probably won't, because to do so is inconvenient. If you care about running as lean a system as possible, debfoster quickly justifies the few minutes needed to learn its basic workings.