How can I export a /dev/mapper mounted filesystem via NFS?

Question

I have a server "pr-cl-n1" that mounts /usr via /dev/mapper like this:

# mount
[...]
/dev/mapper/pr--cl--n1-usr on /usr type ext3 (rw,relatime,errors=continue,barrier=1,data=ordered)

The root of the server is exported via NFS. My /etc/exports looks like this:

/       192.168.1.1(ro,no_root_squash,no_subtree_check)

Now I can mount and read the root / from NFS-client 192.168.1.1 (I use am-utils for auto-mounting), but this client can't access /usr (it's shown empty on the client, but it definitely contains files on the server):

# ls /var/mnt/pr-cl-n1/usr
#

It seems as the "no_subtree_check" is ignored for /dev/mapper mounts. Is there another option I have to use?

Answer 1

unfortunatly / and /usr are different filesystems. You need to export /usr.

/usr  192.168.1.1(ro,no_root_squash,no_subtree_check)

then exportfs -a.