Can't load Webinterface (OMV4)

Hello, my NAS is still running OMV4 Arrakis. Today I tried to change the source of the OMV extras to github via Putty. After that I could no longer log in via the web interface, no error message. Then I cleaned the panel cache with OMV-Firstaid. Now the web interface no longer loads. An error message appears.

Error #0:
OMV\Exception: Failed to read file '/var/cache/openmediavault/cache.omv\controlpanel\login_js.json' (size=0). in /usr/share/php/openmediavault/json/file.inc:207
Stack trace:
#0 /usr/share/php/openmediavault/json/file.inc(223): OMV\Json\File->getContents()
#1 /usr/share/php/openmediavault/controlpanel/controlpanelabstract.inc(173): OMV\Json\File->read()
#2 /var/www/openmediavault/index.php(46): OMV\ControlPanel\ControlPanelAbstract->render()
#3 {main}

What can I do? My plan is to be updated to OMV5->6->7.

Ok, I think I've found the cause. My root drive is full, so the installation of the OMV Extras did not go through. In the folder /admin are further subfolders with always the same structure. The main folder /admin is 41GB in size. Can I simply delete the contents?

Quote from ryecoaaron

/admin in the / directory is not something created by OMV.

hmm, but admin is my web interface login name? If i delete this folder, OMV still working?

Quote from donh

If you have not done so lately run autoremove --purge. It will get rid of old kernels and other no longer needed packages. Should give you enough space to login and do other things.

-bash: autoremove: Kommando nicht gefunden?

Quote from votdev

Don't do that. You need to do 3 Debian upgrades and 4 to 5 are not working anymore because Debian and OMV are EOL and for Debian the package repos have been archived which means their URLs have been changed which has not been updated in OMV4 and OMV5. Therefore, the upgrade process does not work out-of-the-box. Consider doing a new installation from scratch.

Ok, if I completely reinstall OMV, will I lose my raid system, all my data?

Quote from ryecoaaron

admin is the user that you login to the web interface with but it does not have console or ssh login privileges. So, it should not be large. I have no idea what is in the directory but it shouldn't affect OMV if it is deleted. You didn't confirm its absolute path though.

I have checked the admin folders, these were created each time a backup was made, although the backup is actually created on a separate drive.

Now it works, option 10 in omv-firstaid has helped.

I found this in the Backup settings:

admin was entered under additional options