Can't boot after upgrade from v1.4.2 to v1.5.1

#1

I upgraded RancherOS via sudo ros os upgrade today.

This is the output log:

Upgrading to rancher/os:v1.5.1
Continue [y/N]: y
Pulling os-upgrade (rancher/os:v1.5.1)...
v1.5.1: Pulling from rancher/os

6c40cc604d8e: Pull complete
805953092b62: Pull complete
ec15c1060150: Pull complete
[more pulls]
Digest: sha256:2a3220b2493d683b353dc68505508c21b471a4bc818c905dafbb7a11aa54b1e7
Status: Downloaded newer image for rancher/os:v1.5.1
os-upgrade_1 | Installing from :v1.5.1
os-upgrade_1 | time="2019-03-13T02:05:34Z" level=error msg="write new (/mnt/new_img/boot/global.cfg) %!s(<nil>)"
Continue with reboot [y/N]: y
INFO[0036] Rebooting

Now my server won’t boot, only showing me this:

I don’t know how to get into recovery mode or how to recover my harddrive (I have backups, but there should be an easier way) EDIT: I can get into the recovery system called grml.

Thanks in advance!

EDIT 2: I can get into the recovery system, mount the disk and chroot into the system. I tried to upgrade using /usr/bin/ros again, but I can’t get the system-docker to start in chroot (and therefore ros waits forever for the systemdocker to start)