One of our servers running MongoDB crashed today and we encountered the typical

old lock file: /var/lib/mongodb/mongod.lock. probably means unclean shutdown recommend removing file and running –repair see: http://dochub.mongodb.org/core/repair for more information

As the docs do not seem to have much of an alternative to running –repair I looked for a way to automate it from upstart. Mongo creates a mongod.lock file in the data directory with the processes PID in and on a safe shutdown removes the PID, leaving the file there.

This upstart scripts includes a pre-start script that checks if the lock file exists, reads it, makes sure there is a PID there, makes sure no mongod processes exist with that PID then performs the repair as the mongodb user.