docker should look if zfs partition is mounted before starting

[JOduMonT]

• version v1.5.8 from os image rancher/os:v1.5.8
• my RancherOS run in a KVM; the KVM host is Ubuntu 20.04LTS (libvirtd (libvirt) 6.0.0)

To reproduce

1. Install ROS 1.5.8
2. Install ZFS and configure a pool on a second drive (/dev/sdb): https://rancher.com/docs/os/v1.x/en/storage/using-zfs/

sudo docker info|grep "Storage\|Dir"
 Storage Driver: zfs
 Docker Root Dir: /mnt/docker

notes

my zfs is persistently mounting automatically,
after several reboot and at login that result is always the same

sudo zfs list -o mounted
MOUNTED
    yes

but I have to systematically restart docker sudo system-docker restart docker otherwise

sudo docker info
Client:
 Debug Mode: false

Server:
ERROR: Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?
errors pretty printing info

Expected

• docker service start after zfs is mounted

Actual

everything work well until I reboot
than when I reboot, I presume docker try to start before zfs
because after a reboot

• So I was wondering if zfs datasets won't get mounted after reboot #2256 has been really fixed ?

the config

'hostname:': dev007
rancher:
  console: ubuntu
  disable:
  - autologin
  docker:
    graph: /mnt/docker
    storage_driver: zfs
    tls: true
  environment:
    EXTRA_CMDLINE: /init
  network:
    dns:
      nameservers:
      - 1.1.1.1
      - 8.8.8.8
    interfaces:
      eth0:
        address: 172.16.100.7/16
        dhcp: false
        gateway: 172.16.1.254
  services_include:
    kernel-headers-system-docker: true
    qemu-guest-agent: true
    volume-cifs: true
    zfs: true
  state:
    dev: LABEL=RANCHER_STATE
    wait: true
ssh_authorized_keys:
- ssh-***
- ssh-***
- ssh-***
- ssh-***
- ssh-***