Volumes are disks that can be attached to the jupyter instance. A project could have multiple disks available but only one at the same time will be mounted into the jupyter instance.
Note: The process to attach a disk into docker could be complex because it requires to be mounted first in the VM where docker is running, the into docker. Finally, ermissions and mount point should match. In the case of the mount point, what is important to know, is that Labmachine mount the disk into the /data folder.
About permissions, check your docker image.
Jupctl allows to run different command related to volumes check:
jupctl volumes --help
import and unlink operations only affects metata.
An import operation will add and existing disk to state.json
An unlink operation will remove the disk metadata from state.json but the disk will continue in the cloud provider.