NFS server is exporting the wrong directories

Question

It is a bit embarrassing to admit, but I have problems getting my NFS server exporting the right directories. I am using an up-to-date CentOS 6.2 on both the client and the server.

The server is up and running, the firewall was disabled during the tests.

On the server side I have created this /etc/exports:

/home/user1/documents/   *(ro,sync)

this directory is the root of a volume of a software raid. mount output as follows:

/dev/mapper/lvm--raid-lvol0 on /home/user1/documents type ext4 (rw,nosuid,nodev)

the command showmount -e on the server shows the correct output:

Export list for servername:
/home/user1/documents (everyone)

I try to mount that share from the client and get the following output:

mount.nfs: access denied by server while mounting servername:/home/user1/documents

However when I look afterwards on the server at the file /proc/fs/nfsd/exports I see more than one mountpoint, but not the right one

# Version 1.2
# Path Client(Flags) # IPs
/       *(ro,root_squash,sync,no_wdelay,no_subtree_check,v4root,fsid=0,uuid=696f3ea6:3d7641f3:b6315631:bd63c833)
/home   *(ro,root_squash,sync,no_wdelay,no_subtree_check,v4root,uuid=696f3ea6:3d7641f3:b6315631:bd63c833)
/home/user1     *(ro,root_squash,sync,no_wdelay,no_subtree_check,v4root,uuid=696f3ea6:3d7641f3:b6315631:bd63c833)

Where do these entries come from and why is there no line starting with /home/user1/documents ? I tried mounting /home/user1 instead of /home/user1/documents from the client and this strangely works.

The UIDs of the user are the same on the server and the client. Could it be a problem that the directory to be exported is mounted itself?

Edit

The file /var/lib/nfs/xtab is empty.

Solution 1

I see you are using NFSv4 (the fsid=0 in the /proc/fs/nfsd/exports output gives it away). NFS roots are rquired for NFSv4. You may have better luck with this /etc/exports.

/home                    *(ro,fsid=0)
/home/user1/documents/   *(ro,sync)

You might also need to edit the domain in /etc/idmapd.conf for the server and clients.

On a side note, I highly recommend replacing that asterisk with a subnet if you don't want your data accessable to untrusted systems.

Solution 2

I had a problem with:

/my/dir1 *(rw,sync,fsid=0,crossmnt,no_subtree_check)
/my/dir2 *(rw,sync,fsid=0,crossmnt,no_subtree_check)

and both mount appeared for /my/dir1.

I was trying to use the same default options as given in the Ubuntu 16.04 nfs-kernel-server package /etc/exports example file: https://unix.stackexchange.com/questions/198009/what-provides-etc-exports-and-how-do-i-find-that-out

The solution was to remove fsid=0,crossmnt and use just:

/my/dir1 *(rw,sync,no_subtree_check)
/my/dir2 *(rw,sync,no_subtree_check)

This is also mentioned at: https://forums.opensuse.org/showthread.php/481263-NFS-directs-to-the-wrong-shared-folder/page2?s=ae345ec054b854b5cf036cd1816626f4

I don't really know what all of those do, one day I'll learn NFS. Maybe.

Comments

[Zachw6]

For completeness (if the problem still exists) what does /var/lib/nfs/[ex]tab contain?

[GorillaPatch]

This file is empty (I updated my question). The problem still exists.

[Peter]

Have you tried mounting without the trailing slash? "/home/user1/documents" instead of "/home/user1/documents/". Also I have never used "*" before, so can't validate that; try using the ip address also. Also, try -v when mounting on the client side. And are there any more routers/firewalls involved between the 2 systmes? Is there a NAT in use (a NAT would cause this due to using an unprivileged port, which should show up if you use -v)?

[Zachw6]

@GorillaPatch is /var/lib/nfs/etab also empty ?

[Janne Pikkarainen]

@GorillaPatch: Is this /home/user1/documents/ *(ro,sync) the only content at your /etc/exports?

[GorillaPatch]

yes it is. I am at the moment exporting this directory only.

[GorillaPatch]

@peter no there is no NAT they a attached to the very same switch without any routers on the same subnet.

[GorillaPatch]

Thanks for your help. The asterisk is there for debugging purposes only. Where can I find documentation about NFS roots? This is kind of new to me. I have not seen it in NFSv3.