Fink has a special package named passwd that’s responsible for adding users to the system. This is necessary because some packages need users with specific names in order to build, install, or run. For example, when installing the postgresql84 package, there needs to exist a user named ‘postgres’ on the system.
Let’s use the dpkg command to inspect the contents of the passwd package:
$ dpkg -L passwd /. /sw /sw/etc /sw/etc/group-fink /sw/etc/passwd-fink /sw/sbin /sw/sbin/update-passwd
/sw/etc/passwd-fink (group-fink) contains the list of users (resp. groups) that are to be/have been installed on the system, and /sw/sbin/update-passwd is a shell script that effectively adds users and groups based on the aforementioned files.
When the passwd package is being installed (usually because some other package needs a certain user/group) it asks the user whether it should add users and groups to the system. Whilst it is possible to answer negatively, the package that asked for passwd will probably have some problem during building, installing, or running, so users are in general advised to answer positively. If you’ve answered no then you can either add users and groups manually or run
fink reinstall passwd
and answer yes.
Also, if for some reason the users or groups installed by the passwd package are not present on your system any longer, the command above should fix that.