During an upgrade ownCloud from 9.x to 10.x on my FreeBSD 11 system it failed with an error related to webdav: ‘archives of type are not supported‘.
After some investigation it ended up being a conflict between webdav installed by subversion and the ownCloud specific webdav. Adding
<IfModule mod_dav.c> Dav off </IfModule>
to the owncloud section and restarting Apache, as suggested in some posts and the documentation, did not suffice. I disabled svn (by renaming
*.conf.unused) and then restarted Apache again.
After resetting the ‘maintenance‘ flag in owncloud/config/config.php to false again, I was able to run the update procedure. I enabled subversion again, but left the ‘Dav off’ in there for good measure, and it seems to sync my files just fine.
It then failed with an index being too big but that can be resolved by editing
owncloud/core/Migrations/Version20170516100103.php and replacing ‘256’ with ‘255’ in line 53:
$table->addColumn('term', Type::STRING, [ 'notnull' => true, 'length' => 256 ]);
See https://github.com/owncloud/core/issues/27822 for an explanation. Don’t forget to change it back after the upgrade to prevent owncloud from warning you about a code inconsistency.