Unifi Upgrade – MongoDB does not start

Recently had an issue where upgrading Unifi resulted in MongoDB not starting. Looking to the /var/log/unifi/mongod.log we see:

ERROR: Insufficient free space for journal files
[initandlisten] Please make at least 3379MB available in /usr/lib/unifi/data/db/journal or use --smallfiles
[initandlisten]
[initandlisten] exception in initAndListen: 15926 Insufficient free space for journals, terminating
[initandlisten] dbexit:
[initandlisten] shutdown: going to close listening sockets...
[initandlisten] shutdown: going to flush diaglog...
[initandlisten] shutdown: going to close sockets...
[initandlisten] shutdown: waiting for fs preallocator...
[initandlisten] shutdown: lock for final commit...
[initandlisten] shutdown: final commit...
[initandlisten] shutdown: closing all files...
[initandlisten] closeAllFiles() finished
[initandlisten] journalCleanup...
[initandlisten] removeJournalFiles
[initandlisten] shutdown: removing fs lock...
[initandlisten] dbexit: really exiting now

This is caused by the disk space being too low (under 3.3GB). Taking a look at the filesystem, we can see this is the case:

The type service unifi restart and you should be good to go.

One issue I found from this is that the MongoDB is increasing at a rapid rate. I found an excellent script here which prunes the content in MongoDB for Unifi Controllers.

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