NFSv4 Mount Directories and Syntax

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SUMMARY

This discussion focuses on configuring NFSv4 exports for multiple directories on a server. The user initially attempted to export two directories, /aaa and /bbb, with the same fsid=0, which is not permitted in NFSv4. The solution involves assigning unique fsid values to each export, specifically fsid=0 for /aaa and fsid=1 for /bbb. The user discovered that unmounting the /aaa filesystem and rebooting resolved a "Stale file handle" error, indicating that proper synchronization is crucial for NFS operations.

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I am trying to export two different directories using nfs v4.

Today I have, on the server /etc/exports
/aaa 192.168.1.0/255.255.255.0(rw,fsid=0,no_root_squash,async)

and in the clients fstab
192.168.1.1:/ /aaa nfs4 rw 0 0

In principle, I want exports to say
Code: 
/aaa        192.168.1.0/255.255.255.0(rw,fsid=0,no_root_squash,async)
/bbb        192.168.1.0/255.255.255.0(ro,fsid=0,no_root_squash,async)

and fstab to say
Code: 
192.168.1.1:/aaa/   /aaa   nfs4    rw   0 0
192.168.1.1:/bbb/   /bbb   nfs4    ro   0 0

This will not work, of course. It says tp exports both of these as the root filesystem (fsid=0). However, I can't see quite what to do - I can't make either aaa or bbb the root, and I sure don't want to export /. While I can't be the first person to have done this, the internet seems not to have an example of someone who has done this successfully.
 
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Trying the HAIL Mary approach and asked chatgpt.

CAVEAT EMPTOR: Please use the response carefully:

To achieve your desired setup, you can use separate exports for each directory (/aaa and /bbb) with unique fsid values. NFSv4 requires that each exported filesystem has a unique fsid. Here's how you can modify your configuration:

On the server in /etc/exports:

bash

/aaa 192.168.1.0/255.255.255.0(rw,no_root_squash,async)
/bbb 192.168.1.0/255.255.255.0(ro,no_root_squash,async)

On the clients in /etc/fstab:

bash

192.168.1.1:/aaa /aaa nfs4 rw 0 0
192.168.1.1:/bbb /bbb nfs4 ro 0 0

With these changes, you are exporting both /aaa and /bbb with appropriate permissions and mounting them separately on the clients. Make sure to run exportfs -ra after modifying /etc/exports to apply the changes.
 
Well, there's a reason why we don't use ChatGPT here...

bbb mounts correctly, but aaa gets a "Stale file handle" message on the client.

This is likely a good example of ChatGPT's failings. It can echo back what most people do, but what I am doing is not what most people are doing.
 
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One additional note. I used chatgpt 3.5 as I'm not yet ready to fork over monthly fees for the newer 4.0.
 
Well, I think the basic flew with ChatGPT is that this is not a good question for it. I am hoping someone who has maybe done something similar can chime in.

I think the problem is the fsid=0. Either there is some simple way to do something else, or there is a trick. For example (and I don't think this is possible) export / as fsid=0, but with no permissions - no read, no write, no nothing. The aaa and bbb can be opened up.

I don't think this trick is possible, but maybe some other trick is.
 
The good news is the problem is solved. The bad news is I don't know why.

My original syntax works, if and only if you unmount the aaa file system and then reboot. Neither one works by itself. (!)
 
A typical export from some of my home systems

host name hp
# /etc/exports: the access control list for filesystems which may be exported
# to NFS clients. See exports(5).
#
# Example for NFSv2 and NFSv3:
# /srv/homes hostname1(rw,sync,no_subtree_check) hostname2(ro,sync,no_subtree_check)
#
# Example for NFSv4:
# /srv/nfs4 gss/krb5i(rw,sync,fsid=0,crossmnt,no_subtree_check)
# /srv/nfs4/homes gss/krb5i(rw,sync,no_subtree_check)
#
/srv/nfs1 10.1.1.0/24(rw,async,no_subtree_check,no_root_squash,fsid=1)
/sdb/nfs1 10.1.1.0/24(rw,async,no_subtree_check,no_root_squash,fsid=2)
/media/disk 10.1.1.0/24(rw,async,no_subtree_check,no_root_squash,fsid=3)

host name hp8
# /srv/homes hostname1(rw,sync,no_subtree_check) hostname2(ro,sync,no_subtree_check)
#
# Example for NFSv4:
# /srv/nfs4 gss/krb5i(rw,sync,fsid=0,crossmnt,no_subtree_check)
# /srv/nfs4/homes gss/krb5i(rw,sync,no_subtree_check)
#
/usbhd 10.1.1.0/24(rw,sync,no_subtree_check,no_root_squash,fsid=1)
/dlna 10.1.1.0/24(rw,sync,no_subtree_check,no_root_squash,fsid=3)
/usbhd/nmusic 10.1.1.0/24(rw,sync,no_subtree_check,no_root_squash,fsid=4)
/sdc/video/hdc1 10.1.1.0/24(rw,sync,no_subtree_check,no_root_squash,fsid=2)


remote mounts from the fstab file on a user machine
hp.sma2.rain.com://media/disk /media/disk nfs bg,soft 0 0
hp8.sma2.rain.com://dlna /dlna nfs bg,soft 0 0
 

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