A little background: I would like to try ownCloud version 9.0, mostly because of the file tagging feature. However, I can’t just jump to version 9.0 as this is not a supported procedure. From the ownCloud 8.0 Server Administration Manual:

It is best to keep your ownCloud server upgraded regularly, and to install all point releases and major releases without skipping any of them, as skipping releases increases the risk of errors. Major releases are 8.0, 8.1, 8.2, and 9.0. Point releases are intermediate releases for each major release. For example, 8.0.9 and 8.1.3 are point releases. Skipping major releases is not supported.

This is sound advice in general when it comes to upgrades, but at least now I have no excuse as I have been officially warned.

The problem

The first step was updating from version 8.0.5. I used the Web updater method but I immediately stumbled upon a fatal issue during the installation:

PHP Fatal error: Class 'OC_FileProxy' not found in /var/www/html/owncloud/apps/files_sharing/appinfo/app.php on line 28

I did disable all of my ownCloud apps before starting the update, as recommended in the upgrade documentation, so this looked weird.

The solution

Apparently the files_sharing app cannot be disabled from the Web interface, so I had to do it manually:

sudo -u www-data php occ <a href="http://app:disable" target="_blank">app:disable</a> files_sharing
sudo -u www-data php occ upgrade
sudo -u www-data php occ maintenance:mode --off

Remember to replace www-data with your web server user.

After doing this, I was able to bring ownCloud back up. Just a little quirk so far, now I’ll move on with the next upgrades in line.