Migration from OC 10.6 fails with unhandel exception error

I’m attempting to migrate from OC 10.6 to Nextcloud 21.0.2 and have followed the Upgrade Manually process and got as fare as the “sudo -u www-data php occ upgrade” step and received the following error information:
“An unhandled exception has been thrown:
Error: Interface ‘OCP\Files\External\Config\IBackendProvider’ not found in /var/www/owncloud/apps/files_external/lib/AppInfo/Application.php:40
Stack trace:
#0 /var/www/nextcloud/lib/composer/composer/ClassLoader.php(478): include()
#1 /var/www/nextcloud/lib/composer/composer/ClassLoader.php(346): Composer\Autoload\includeFile()
#2 [internal function]: Composer\Autoload\ClassLoader->loadClass()
#3 [internal function]: spl_autoload_call()
#4 /var/www/nextcloud/lib/private/AppFramework/Bootstrap/Coordinator.php(116): class_exists()
#5 /var/www/nextcloud/lib/private/AppFramework/Bootstrap/Coordinator.php(82): OC\AppFramework\Bootstrap\Coordinator->registerApps()
#6 /var/www/nextcloud/lib/base.php(634): OC\AppFramework\Bootstrap\Coordinator->runInitialRegistration()
#7 /var/www/nextcloud/lib/base.php(1076): OC::init()
#8 /var/www/nextcloud/console.php(49): require_once(’/var/www/nextcl…’)
#9 /var/www/nextcloud/occ(11): require_once(’/var/www/nextcl…’)”

This does not appear to be similar to any of the other posts I have perused, so why am I so special??
Can anyone help??

Hi there, did you try migrating to NC20.0.10? Migrating directly to NC21 isn’t supported, afaik.
See Migrating from ownCloud — Nextcloud latest Administration Manual latest documentation

Ah I see, but that is not clear from that page. It says 20.0.x ( but at least 20.0.5) and I inferred from that, “the higher the better”. I’ll give 20.0.5 a go and report back.
Thanks.

Well, I tried migrating to NC 20.0.10 as suggested, but the error is exactly the same. I can’t help thinking that it has something to do with copying the owncloud config.php file and plonking it into /var/www/nextcloud/config ? I have also left the /var/www/owncloud directory in situ and not deleted it as per the Nextcloud upgrade instructions, as if I delete it, apache2 will not restart due to the directory mentioned in /etc/apache2/sites-available and sites-enabled not being available.

I have created and enabled a nextcloud site in Apache2, reloaded Apache2 and it has made no difference. If I rename the owncloud directory to owncloud.old, I get the following:
“App directory “/var/www/owncloud/apps” not found! Please put the Nextcloud apps folder in the Nextcloud folder or the folder above. You can also configure the location in the config.php file.”

Any ideas… anyone???

OK, I’ve been poking around a bit and it is clear that I am not understanding the “Upgrade Manually” process when used in the context of migrating from Owncloud. I copied the /var/www/owncloud/config/config.php file and placed it in /var/www/nextcloud/config. When I ran the upgrade, I got the above error.
I then modified the config.php to use the nextcloud paths for the apps and apps-external directories and am now getting a different error:
An unhandled exception…
Exception: Environment not properly prepared. in /var/www/nextcloud.lib/private/Console/Application.php:168
Stack trace:
#0 /var/www/nextcloud/console.php(99): OC\Console\Application->loadCommands()
#1 /var/www/nextcloud/occ/(11): require once(‘var/www/nextcl…’)
#2 {main}

I hope this will shed some light on my issue.

Well, I’ve sorted it! The machine is now functioning at Nextcloud 20.0.10. The problem was that although I had “corrected” the environment by adding the apps and apps-external folders, I had not corrected the permissions to make them accessible to www-data.
I had already modified the config.php file to 1.) Change the version from Owncloud 10.6 to 10.5 and 2.) Use the Nextcloud apps and apps-external directories which seems to be a required step in the migration process.