Rpi4 Boot problem: Kernel panic message after attaching an external hard disk


I’ve installed nextcloud on my raspberry pi 4. Moved my root to an SSD and after this the system booted succesfully.

Then I mounted an external harddisk. But when i reboot the system i get the error:

end Kernel panic - not syncing: no working init found. Try passing init= option to kernal. See linux Documentation/admin-guide/init.rst for gidance

The strange thing is that if i perform a reboot without attaching the external harddisk the system boots like it should do.

What can i do about this? I’ve searched the internet but nothing seems to fix this problem…