# NFS: exporting a nullfs



## zirias@ (Mar 14, 2021)

Now that my server is running 13.0-RC2 as well, I ran into a problem. I have the following nullfs mounts:

```
/var/jail/builder/src    /usr/src    nullfs    ro,late        0    0
/var/jail/builder/obj    /usr/obj    nullfs    ro,late        0    0
```

I used them for the following exports:

```
/usr/src    -maproot=root    -network=192.168.0.0/16 -ro
/usr/obj    -maproot=root    -network=192.168.0.0/16 -ro
```

This worked fine on any 11.x and 12.x version. It stopped working on 13, with the following error:

```
mountd[13382]: can't change attributes for /usr/src: netcred already exists for given addr/mask
mountd[13382]: bad exports list line '/usr/src   -maproot'
```

As a workaround, I can export /var/jail/builder/src directly, forcing the clients to request this instead of just /usr/src.

Now, is exporting via a nullfs mount expected to work? Did it just work "by accident" previously, or did I actually find a bug in 13?


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## zirias@ (Mar 14, 2021)

As it worked on previous versions, I now just assume this is indeed a bug – a PR will hopefully clarify: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=254282


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