Just wanted to throw in that I had a similar issue over this weekend - pulled my rockstor 3 drive and updated a fresh drive to rockstor 4 - had to update to a newer kernel and version of btrfs progs because I had them updated to 5.11 on my rockstor 3 instance, but after all that when I tried to get my rockons working it kept failing with “exit code” in the systemctl info. So I looked at the dockerd:
rockstor1:~ # dockerd
failed to load listeners: can’t create unix socket /var/run/docker.sock: is a directory
Looking at the output of ls -al /var/run/docker.sock and sure enough it is a directory.
rockstor1:~ # ls -al /var/run/docker.sock
total 0
drwxr-xr-x 2 root root 40 Apr 19 10:30 .
drwxr-xr-x 25 root root 840 Apr 19 10:43 …
Removing that folder and a systemctl restart docker.service and I’m back in action!