Answer by Stephen Harris for Method to test if disks in system are formatted

The logic I would use may appear to be a little convoluted, but I think it should catch the failure mode.

Basically the steps are

1. mke2fs
2. mount the filesystem
3. Create a file called "format.complete" in the filesystem
4. unmount the filesystem

So we need to put some tests before this. The logic would be:

1. Attempt to mount the filesystem at $tmpmount forcing ext2
2. If mount returned error code ==> Goto NOT FORMATTED
3. If $tmpmount/lost+found does not exist then an odd filesystem mounted; should not happen but... umount. Goto NOT FORMATTED
4. If $tmpmount/format.complete does not exist then format was interrupted; umount. Goto NOT FORMATTED
5. umount ==> FORMATTED, skip to next disk.

The "NOT FORMATTED" would be the original 4 steps.

We can add those structures together. The result would be that disks would only be formatted if they don't have a format.complete file on them.

Once all disks have been formatted you can optionally then remount each one and delete the format.complete file.

Essentially we maintain a small amount of state on each disk and use that to determine if formatting was successful.