unionfs

[Tim Judd]

I've got an odd problem, and I'm puzzled why it's so puzzling.


At home, my router serves as a basic single-client diskless server.
Been working beautifully with no issues.  Filesystems mount as
expected and operations are as quick as expected as the server who's
servicing it.

The diskless fstab tells to mount the following:
 server:/diskless  /               nfs     ro                      0 0
 md              /var.mfs        mfs     rw,-M,-s=256m           0 0
 /var.mfs        /var            unionfs rw                      0 0

Everything works beautifully, no errors.  Kernel is 7.2R-p2

I copied this exact fstab, to a new hardware firewall and it fails to
accomplish the same task.

/dev/ad0s1a     /               ufs     ro                      0 0
md              /var.mfs        mfs     rw,-M,-s=64m            0 0
/var.mfs        /var            unionfs rw                      0 0

Kernel is standard 7.2R kernel, no changes

Two changes only:
  root is on a hard disk as UFS instead of NFS
  memory filesystem (which mounts) is only 64M

However, when 7.2-RELEASE (unpatched so far) boots, it fails to mount
the unionfs /var.mfs (upper) on top of /var (lower).

The error returned is "mount_unionfs: /var: operation not supported by device"



Any clues?  anything you need?  I'd appreciate any straws to reach for.

--Tim