URI: 

       Title: Detect left over users and groups on OpenBSD
       Author: Solène
       Date: 03 April 2023
       Tags: openbsd
       Description: In this article, I'm sharing a shell script that finds
       users and groups installed by packages but not in use anymore
       
       # Introduction
       
       If you use OpenBSD and administrate machines, you may be aware that
       packages can install new dedicated users and groups, and that if you
       remove a package doing so, the users/groups won't be deleted, instead,
       `pkg_delete` displays instructions about deletion.
       
       In order to keep my OpenBSD systems clean, I wrote a script looking for
       users and groups that have been installed (they start by the character
       `_`), and check if the related package is still installed, if not, it
       outputs instructions that could be run in a shell to cleanup your
       system.
       
       # The code
       
       ```shell
       #!/bin/sh
       
       SYS_USERS=$(mktemp /tmp/system_users.txt.XXXXXXXXXXXXXXX)
       PKG_USERS=$(mktemp /tmp/packages_users.txt.XXXXXXXXXXXXXXX)
       
       awk -F ':' '/^_/ && $3 > 500 { print $1 }' /etc/passwd | sort > "$SYS_USERS"
       find /var/db/pkg/ -name '+CONTENTS' -exec grep -h ^@newuser {} + | sed 's/^@newuser //' | awk -F ':' '{ print $1 }' | sort > "$PKG_USERS"
       
       BOGUS=$(comm -1 -3 "$SYS_USERS" "$PKG_USERS")
       if [ -n "$BOGUS" ]
       then
           echo "Bogus users/groups (missing in /etc/passwd, but a package need them)" >/dev/stderr
           echo "$BOGUS" >/dev/stderr
       fi
       
       EXTRA=$(comm -2 -3 "$SYS_USERS" "$PKG_USERS")
       if [ -n "$EXTRA" ]
       then
           echo "Extra users" >/dev/stderr
       
           for user in $EXTRA
           do
               echo "userdel $user"
               echo "groupdel $user"
           done
       fi
       
       rm "$SYS_USERS" "$PKG_USERS"
       ```
       
       ## How to run
       
       Write the content of the script above in a file, mark it executable,
       and run it from the shell, it should display a list of `userdel` and
       `groupdel` commands for all the extra users and groups.
       
       # Conclusion
       
       With this script and the package `sysclean`, it's quite easy to keep
       your OpenBSD system clean, as if it was just a fresh install.
       
       # Limitations
       
       It's not perfect in its current state because if you deleted an user,
       the according group that is still left won't be reported.