Ubiquiti Unifi Controller MongoDB Issues

After upgrading Unifi on a Debian server running a Ubiquiti Unifi controller, I ran into an issue where the web interface would not load. After poking through the logs I found that the issue appeared to be with MongoDB.

In the server log file located at /var/log/unifi/server.log for my install I found the following messages:

[2018-04-01 18:58:40,167] <db-server> INFO  db     - DbServer stopped
[2018-04-01 18:58:44,188] <db-server> ERROR system - [exec] error, rc=2

Database Repair

The first thing I suspected was corruption for the MongoDB data – the server had previously did not have a clean shutdown (the filesystem became read only). To repair the MongoDB database for Unifi you can execute MongoDB like this:

mongod --dbpath /usr/lib/unifi/data/db --port 27117 --repair

After the repair, the permissions on the MongoDB database files should be updated to make sure they are owned by the Unifi user:

chown -R unifi. /usr/lib/unifi/data/db

After the repair, MongoDB was still failing to start.

Debugging MongoDB startup

For my install of Unifi, when MongoDB starts up it executes MongoDB like this:

/usr/lib/unifi/bin/mongod --dbpath /usr/lib/unifi/data/db --port 27117 --unixSocketPrefix /usr/lib/unifi/run --logappend --logpath /usr/lib/unifi/logs/mongod.log --nohttpinterface --bind_ip

/usr/lib/unifi/bin/mongod is a symlink to /usr/bin/mongod.

To get the startup options I replaced the /usr/lib/unifi/bin/mongod file with the following script:

echo $* > /tmp/mongod_startup
exec /usr/bin/mongod $*

After replacing the file make sure it is executable with chmod +x /usr/lib/unifi/bin/mongod. Make sure the controller is running, it should then execute the script and you can review the startup options in the file /tmp/mongod_startup.

The problem

Once I had the startup command for MongoDB I attempted to run it to see what was happening. It turns out the --nohttpinterface flag was causing the problem – MongoDB was throwing an error like this:

Error parsing command line: unrecognised option '--nohttpinterface'

The fix

To fix it I replaced the MongoDB symlink that the controller executes so that the option that does not work is removed. Since the default file is a symlink its safe to remove it (to restore you can just create the symlink again):

rm -f /usr/lib/unifi/bin/mongod

You can then create the file /usr/lib/unifi/bin/mongod with the following content:

exec /usr/bin/mongod ${*//--nohttpinterface/}

After creating the file, make sure it is executable (chmod +x /usr/lib/unifi/bin/mongod). Start the controller service again if it is not running already and it should now be working.

One thought on “Ubiquiti Unifi Controller MongoDB Issues

  1. since macOS is bsd inside can these be run as is?

    mongod is using nearly 100% constantly and have MILLIONS of log entries

    /bin/hostapd exited with code 256 and restarted by inittab

    deleting the logs seems like a great idea weekly

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