Background

Maintaining Debian stable systems sometimes requires installation of unofficial versions of packages:

backporting newer versions

This is necessary, when significant new functionality is required on the system but unavailable in the official version found in the current stable release. In this case, the version string usually sorts as newer than the official stable version string. This means that pinning is not necessary, as APT will select such package version by default.

local changes to the official version

Usually these are small changes, so a minor modification of the package version string is sufficient. There are two ways to do this:

Try to invent a version string newer than the current one, but older than the next official one. This way does not require pinning, but is difficult to do reliably. It might turn out, that the next official version string is older than the one invented by you, which would cause the official version to be silently ignored.

The other way is to modify the version string in such way that it sorts as older than the official one. The tilde character is very useful here, because dpkg treats it in a special way: it is sufficient to append any string starting with the tilde, to the version string, e.g. 1.2 → 1.2~sl.1. This requires you to "pin" the package to that version, but it is more reliable, because works regardless of what the next official version number will be.

In both cases, there is one major drawback: APT will not warn you when newer versions of official packages (point releases, security updates) will appear in the stable release. This means you may miss some important change.

apt-forktracer's job let you track newer official versions of locally overridden packages.

Official package version definition

Official package version is a version which is available from a source, whose Release file's Origin header value is equal to the system distributor identifier, as indicated by the lsb_release --id command, or by the DISTRIB_ID field in the /etc/lsb-release file.

Program operation

apt-forktracer analyzes each installed package separately, reporting on the standard output these packages which are in a "non-standard" state. What "non-standard" means depends on the mode of program operation:

default (non-verbose) mode

this state means packages in an incorrect state (e.g. no candidate version) or packages whose candidate version is different than the newest available official version.

verbose mode

this state also includes packages whose installed version is different from the candidate version

In the default mode the program also reads configuration files, which let you ignore some of the "non-standard" packages, as long as they meet certain criteria. If there is no configuration for a given package, then a default configuration is used. More information is available in forktracer.conf(5).

Message format

The program outputs messages such as the following:

    foobar (1.2.3->1.2.4) [Debian: 1.2.3 1.2.4] [Other origin: 1.2.2]

Where:

foobar

package name

1.2.3

installed package version

1.2.4

candidate package version - see apt-cache(8).

Debian

the value of the "Origin" field of one of the package sources. Versions available from this source are listed after a colon.

Other origin

another source origin