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Update MongoDB for Unifi Network Application 8

I was trying to update MongoDB from 3.6 to 4.4 since the Unifi network app supports it now, and it’ll get rid of those pesky GPG errors from APT.

Make sure you have a backup before starting, especially of /usr/lib/unifi/data/db.

Upgrade Steps

You will need to iterate though each major version of MongoDB, e.g. 3.6 -> 4.0 -> 4.2 -> 4.4.

  1. Edit the APT repo

     nano /etc/apt/sources.list.d/mongodb-org-3.6.list

    Comment out the old one and add the new version, you will probably have to use [allow-insecure=yes] since the certificate has expired and APT doesn’t like that.

     #deb [signed-by=/usr/share/keyrings/mongodb-org-server-3.6-archive-keyring.gpg] https://repo.mongodb.org/apt/ubuntu bionic/mongodb-org/3.6 multiverse

 deb [allow-insecure=yes] https://repo.mongodb.org/apt/ubuntu bionic/mongodb-org/4.0 multiverse

    Remember you will need to iterate though every version, so you will need to change the 4.0 to 4.2, then 4.4, after each upgrade.

  2. Update APT

     apt update
 apt upgrade
 # You will need this for the next step too:
 apt install mongodb-org-shell

  3. Start mongod with the Unifi database

     screen mongod --dbpath /usr/lib/unifi/data/db

    Then detach the screen session so it runs in the background: Ctrl+A, then D

  4. Upgrade the Mongo database

    Open a mongo shell, (using mongo shell) and follow the official upgrade guide.

    For example, I did this for version 4.0:

     db.adminCommand( { getParameter: 1, featureCompatibilityVersion: 1 } )

 db.adminCommand( { setFeatureCompatibilityVersion: "4.0" } ) 

 db.adminCommand( { getParameter: 1, featureCompatibilityVersion: 1 } )

  5. Stop mongod from earlier

     screen -r

    Then type Ctrl+C, to stop it.

  6. Restart from the beginning for the next version, until you get to your desired version.

Final Steps

  1. Fix up the APT repo for version 4.4

    This will get rid of those GPG/verification errors.

     wget -qO- https://www.mongodb.org/static/pgp/server-4.4.asc \
 | gpg --dearmor -o /etc/apt/trusted.gpg.d/mongodb-org-server-4.4-archive-keyring.gpg

 echo "deb [arch=amd64,arm64 signed-by=/etc/apt/trusted.gpg.d/mongodb-org-server-4.4-archive-keyring.gpg] https://repo.mongodb.org/apt/ubuntu focal/mongodb-org/4.4 multiverse" \
 | tee /etc/apt/sources.list.d/mongodb-org-4.4.list

 rm /etc/apt/sources.list.d/mongodb-org-3.6.list

  2. Fix permissions (optional)

    If Unifi isn’t starting, and you are getting permission denied errors in the mongo logs (tail -f /var/log/unifi/mongod.log), you may need to chown back to the unifi user.

    For example:

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

Newer Versions

This guide should still work for newer versions of MongoDB, although there are a few exceptions:

  • Versions 5.0 and newer no longer have major sub-versions, so you can skip some iteration steps e.g. only 4.4 -> 5.0 -> 6.0 -> 7.0 is required.
  • Versions 7.0 and newer have added an additional confirm field to the set version command, so you will need to run db.adminCommand( { setFeatureCompatibilityVersion: "7.0", confirm: true } ) instead.

Thanks for reading!
Steve.

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