The stalepid utility was developed to facilitate the startup of servers
that write their process ID to a file and refuse to start if that file
exists (e.g. when the process was last terminated by an unclean shutdown,
or simply killed without given the chance to clean up the process ID
file).  The stalepid utility is used to check for and possibly remove
those stale process ID files.  Upon its invocation, stalepid checks for
the following conditions:
-   the file specified by the pidfile argument exists;
-   it contains a single line, and the line contains a single number;
-   there is no process with the process ID specified in the file, or if
    there is one, it is not named processname.

If all those conditions are met, the stalepid utility will remove the
file specified by the pidfile argument, thus allowing the next invocation
of the server to proceed normally.

WWW: https://devel.ringlet.net/sysutils/stalepid/