Für den Fall, dass die neue SD Card nicht erkannt wird

1) overwrite the first blocks of the SD card, while the card is inserted to your laptop/PC (replace $DEVICE with your correct device, otherwise you may erase important data on your PC!):  dd if=/dev/zero of=$DEVICE bs=1M count=10

2) shut down the CK and insert the SD card

3) boot the CK (this time it worked for me)

4) ssh root@localip

5) cat /proc/partitions   (if mmcblk1p1 exists, the sdcard has been automatically formatted by the CK)

6) mount /dev/mmcblk1p1 /data

7) (re)login to the cloud key and activate auto backup (https://help.ubnt.com/hc/en-us/articles/226218448-UniFi-How-to-Configure-Auto-Backup)

8) reboot the CK (in my setup the CK still worked)

Formatierungsschema: ext4