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RancherOS ZFS setup

This RancherOS system service bootstraps a single ZFS pool and import it on system start.

Getting started

Install ZFS

sudo ros service enable zfs
sudo ros service up zfs
# It might take some time (10 to 20 minutes)
# You can follow the progress of the build, in another session, via:
sudo ros service logs --follow zfs
# Check ZFS is enabled
lsmod | grep zfs

Install & run the service

sudo ros config set rancher.repositories.zfs-setup.url https://raw.githubusercontent.com/Evaneos/rancher-os-zfs-setup/v0.1.0
sudo ros service enable zfs-setup
sudo ros service up zfs-setup
# You can follow the progress of the setup, in another session, via:
sudo ros service logs --follow zfs-setup

Use case

This service has been created for docker-machine in order to use ZFS and its snapshot and versioning capabilities on a local machine.

Why?

The official documentation about using ZFS on RancherOS is cumbersome and quite incomplete.

Furthermore, the specific needs of a local docker-machine are not covered:

• creating a ZFS pool from a file (since we cannot use a block device)
• making the ZFS pool persistent across restarts

Note that, however, docker-machine is in maintenance mode.

Workflow

This service has 2 flows: the setup and the import/start.

The setup is run the first time to create the ZFS pool.

The import/start is run every time the machine starts in order to import and mount the ZFS pool.

Configuration

You can customize a few element used by the service.

Note the Setup only column: if yes, the configuration element will only be used when setting up the ZFS pool.

Path	Type	Default	Setup only
rancher.zfs_setup.pool_size	numfmt compliant value eg. 25Gi	Left space - 2Gi	yes

Disclaimer

This service is solely thought for docker-machine and does not aim to fit other needs for now.

Troubleshooting

Unable to verify the Docker daemon is listening

# [...]
Detecting the provisioner...
Unable to verify the Docker daemon is listening: Maximum number of retries (10) exceeded

In general, you just have to wait a bit (30 seconds to 1 minute) and the docker daemon will then start.

Per RancherOS and its ZFS design, importing the ZFS pool and starting the docker service can take some time. As a matter of fact, if docker-machine allowed 1 or 2 more retries, this would not be an issue.

References

• Using ZFS [official docs]
• System services [official docs]
• Rancher OS core services [github]
• Conflict between ZFS storage & overlay driver [github issue]