To have a volume mounted automatically, you list it in a table. Here is how to read an entry and match it against the volume.
fstab is the filesystem table: what to mount, where and how. The system one lives in /etc/fstab: the system mounts its volumes at boot, and sudo mount -a does it on demand. The lesson uses a separate table, /srv/storage-lab/fstab, which plays no part in booting the machine.
One line describes one filesystem in six space-separated fields:
| Field | What it holds |
|---|---|
| source | what to mount: UUID=…, a device, or an image file with the loop option |
| mount point | where to mount it |
| type | the filesystem: ext4, xfs |
| options | defaults is the usual set, ro means read-only |
| two numbers | 0: no dump backup; 2: check after the root filesystem |
The source is usually given as a UUID, an identifier the filesystem receives when it is created. A name like /dev/loop0 or /dev/vdb depends on the order devices appear in and may go to another volume after a reboot, while the UUID stays with the filesystem. blkid prints it. mount looks the UUID up among attached devices, which is why the exercises attach the image as a loop device beforehand.
Data volumes get the nofail option: if such a volume is missing at boot, the system boots without it instead of stopping in emergency mode.
In the exercise the table already exists, but the volume will not mount from it.
Check the line against the volume
Read the training table /srv/storage-lab/fstab and compare its line with what blkid knows about the volume /srv/storage-lab/disk.img. Change nothing.