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I have three Raspberry Pis running Raspbian. One is serving as an NFS NAS, the other two are load-balanced web servers running NGINX. The configuration is like this:

On the NAS (10.34.0.40):

root@nas:~# cat /etc/exports /drupal 10.34.0.10(rw,sync,no_root_squash,no_subtree_check) 10.34.0.20(rw,sync,no_root_squash,no_subtree_check,fsid=0) /wordpress 10.34.0.10(rw,sync,no_root_squash,no_subtree_check) 10.34.0.20(rw,sync,no_root_squash,no_subtree_check,fsid=0)

On the WEB1 (10.34.0.10) server:

root@web1:~# cat /etc/fstab proc /proc proc defaults 0 0 /dev/mmcblk0p1 /boot vfat defaults 0 2 /dev/mmcblk0p2 / ext4 defaults,noatime 0 1 nas:/drupal /usr/share/nginx/html/drupal nfs hard,intr 0 0 nas:/wordpress /usr/share/nginx/html/wordpress nfs hard,intr 0 0

On the WEB2 (10.34.0.20) server:

root@web2:~# cat /etc/fstab proc /proc proc defaults 0 0 /dev/mmcblk0p1 /boot vfat defaults 0 2 /dev/mmcblk0p2 / ext4 defaults,noatime 0 1 nas:/drupal /usr/share/nginx/html/drupal nfs hard,intr 0 0 nas:/wordpress /usr/share/nginx/html/wordpress nfs hard,intr 0 0

The two fstabs are identical (in fact,the two web servers have identical configurations provisioned with ansible). However, while WEB1 mounts the two mountpoints correctly, WEB2 mounts the nas:/drupal directory to both /usr/share/nginx/html/drupal and /usr/share/nginx/html/wordpress. In other words, when I do an ls /usr/share/nginx/html/wordpress, I get the contents on nas:/drupal, not nas:/wordpress.

If I do a df on both systems I get:

WEB1:

root@web1:~# df -h Filesystem Size Used Avail Use% Mounted on /dev/root 30G 4.8G 24G 18% / devtmpfs 459M 0 459M 0% /dev tmpfs 463M 0 463M 0% /dev/shm tmpfs 463M 6.3M 457M 2% /run tmpfs 5.0M 4.0K 5.0M 1% /run/lock tmpfs 463M 0 463M 0% /sys/fs/cgroup /dev/mmcblk0p1 60M 21M 40M 35% /boot nas:/drupal 15G 3.8G 11G 28% /usr/share/nginx/html/drupal nas:/wordpress 15G 3.8G 11G 28% /usr/share/nginx/html/wordpress tmpfs 93M 0 93M 0% /run/user/1001

WEB2:

root@web2:~# df -h Filesystem Size Used Avail Use% Mounted on /dev/root 30G 3.2G 25G 12% / devtmpfs 459M 0 459M 0% /dev tmpfs 463M 0 463M 0% /dev/shm tmpfs 463M 6.3M 457M 2% /run tmpfs 5.0M 4.0K 5.0M 1% /run/lock tmpfs 463M 0 463M 0% /sys/fs/cgroup /dev/mmcblk0p1 60M 21M 40M 35% /boot nas:/drupal 15G 3.8G 11G 28% /usr/share/nginx/html/drupal tmpfs 93M 0 93M 0% /run/user/1001

So it looks like WEB2 is not mounting the nas:/wordpress share.

I should note that both nas:/drupal and nas:/wordpress have exactly the same permissions.

Can anyone tell me what is going on here?

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  • nfsstat -m on WEB2 gives the following result: <snip> /usr/share/nginx/html/wordpress from nas:/drupal Flags: rw,relatime,vers=3,rsize=131072,wsize=131072,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,mountaddr=10.34.0.40,mountvers=3,mountport=34053,mountproto=udp,local_lock=none,addr=10.34.0.40 </snip> Commented Aug 24, 2016 at 15:48
  • What's the output of ls -ld /usr/share/nginx/html/wordpress on web2 ? Is it a symlink? Commented Aug 24, 2016 at 15:49
  • It is not a symlink. ls -ld /usr/share/nginx/html/wordpress/ drwxr-xr-x 2 root root 4096 Aug 24 08:56 /usr/share/nginx/html/wordpress/ Commented Aug 24, 2016 at 15:50
  • You have set the same fsid=0 in the exports for both filesystems only for web2, but they are probably different filesystems. Commented Aug 24, 2016 at 16:04
  • Yup, I had just noticed that and made the change, and lo and behold everything is fine now. But that does not explain why the two systems treated the mount differently. I would have expected WEB1 to exhibit the same behavior as WEB2. If it had I probably would have figured out the fsid issue sooner. Commented Aug 24, 2016 at 16:10

1 Answer 1

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The problem is your fsid=0 value.

If we look at the exports entries we can split them into the two hosts:

10.34.0.10(rw,sync,no_root_squash,no_subtree_check) 10.34.0.20(rw,sync,no_root_squash,no_subtree_check,fsid=0)

So for the .10 client the exports will have different FSIDs, but on the .20 client, both shares will appear to have the same FSID.

Thus the .10 client will see both exports correctly, but the .20 will be confused.

Remove the ,fsid=0 value and things should work correctly for both clients.

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