The upgrade failed because the USB hard disk’s auto-mount feature automatically mounted the partition we wanted to upgrade.
The temporary solution is to disable the USB auto-mount feature in the settings and perform the upgrade again.
In the meantime we will fix this issue in the next OTA update.
I have already tried this and also closed all apps so that there was no other access by apps.
Switched off news feeds too. The update still fails with same message. Is ther a way to turn off using CLI ?
You can login vis ssh and run lsblk if you found dev/sda3 of /dev/sda5 has mountpoint, then use umount /dev/sda3 or umount /dev/sda5. after that run lsblk, Make sure they are no longer mounted.
Finally you can run update.