> On May 28, 2019, at 12:44 PM, Trond Myklebust <trondmy@xxxxxxxxxxxxxxx> wrote: > > On Tue, 2019-05-28 at 11:25 -0400, Steve Dickson wrote: >> >> On 5/21/19 3:58 PM, Trond Myklebust wrote: >>> On Tue, 2019-05-21 at 15:06 -0400, Chuck Lever wrote: >>>>> On May 21, 2019, at 2:17 PM, Trond Myklebust < >>>>> trondmy@xxxxxxxxxxxxxxx> wrote: >>>>> >>>>> On Tue, 2019-05-21 at 13:40 -0400, Chuck Lever wrote: >>>>>> Hi Trond - >>>>>> >>>>>>> On May 21, 2019, at 8:46 AM, Trond Myklebust < >>>>>>> trondmy@xxxxxxxxx >>>>>>> wrote: >>>>>>> >>>>>>> The following patchset adds support for the 'root_dir' >>>>>>> configuration >>>>>>> option for nfsd in nfs.conf. If a user sets this option to >>>>>>> a >>>>>>> valid >>>>>>> directory path, then nfsd will act as if it is confined to >>>>>>> a >>>>>>> chroot >>>>>>> jail based on that directory. All paths in /etc/exporfs and >>>>>>> from >>>>>>> exportfs are then resolved relative to that directory. >>>>>> >>>>>> What about files under /proc that mountd might access? I >>>>>> assume >>>>>> these >>>>>> pathnames are not affected. >>>>>> >>>>> That's why we have 2 threads. One thread is root jailed using >>>>> chroot, >>>>> and is used to talk to knfsd. The other thread is not root >>>>> jailed >>>>> (or >>>>> at least not by root_dir) and so has full access to /etc, >>>>> /proc, >>>>> /var, >>>>> ... >>>>> >>>>>> Aren't there also one or two other files that maintain export >>>>>> state >>>>>> like /var/lib/nfs/rmtab? Are those affected? >>>>> >>>>> See above. They are not affected. >>>>> >>>>>> IMHO it could be less confusing to administrators to make >>>>>> root_dir an >>>>>> [exportfs] option instead of a [mountd] option, if this is >>>>>> not a >>>>>> true >>>>>> chroot of mountd. >>>>> >>>>> It is neither. I made in a [nfsd] option, since it governs the >>>>> way >>>>> that >>>>> both exportfs and mountd talk to nfsd. >>>> >>>> My point is not about implementation, it's about how this >>>> functionality >>>> is presented to administrators. >>>> >>>> In nfs.conf, [nfsd] looks like it controls what options are >>>> passed >>>> via >>>> rpc.nfsd. That still seems like a confusing admin interface. >>>> >>>> IMO admins won't care about who is talking to whom. They will >>>> care >>>> about >>>> how the export pathnames are interpreted. That seems like it >>>> belongs >>>> squarely with the exportfs interface. >>>> >>> >>> With the exportfs interface, yes. However it is not specific to the >>> exportfs utility, so to me [exportfs] is more confusing than what >>> exists now. >>> >>> OK, so what if we put it in [general] instead, and perhaps rename >>> it >>> "export_rootdir"? >>> >> I'm just catching up... my apologies tartness... >> >> So setting root_dir effects *all* exports in /etc/exports? >> If that is the case, that one variable can change hundreds >> of export... is that what we really want? >> >> Wouldn't be better to have a little more granularity? > > Can you explain what you mean? The intention here is that if you have > all your exported filesystems set up in a subtree under > /mnt/my/exports, then you can remove that unnecessary prefix. > > So, for instance, if I'm trying to export /mnt/my/exports/foo and > /mnt/my/exports/bar, then I can make those two filesystems appear as > /foo, and /bar to the remote clients. > > If an admin wants to rearrange all the paths in /etc/exports, and make > a custom namespace, then that is possible using bind mounts: just > create a directory /my_exports, and use mount --bind to attach the > necessary mountpoints into the right spots in /my_exports, then use > export_rootdir to remove the /my_exports prefix. Just to be clear, do you expect that each mount namespace on a Linux NFS server would have its own /etc/exports and /etc/nfs.conf ? Maybe you stated that before, and I missed it. >> As for where root_dir should go, I think it makes senses >> to create a new [exportfs] section and have mountd read it >> from there. I think that would be more straightforward if >> we continue with the big hammer approach where any and all >> exports are effected. >> > > Fair enough, I can add the [exports] section if you all agree that is > an appropriate place. > > -- > Trond Myklebust > Linux NFS client maintainer, Hammerspace > trond.myklebust@xxxxxxxxxxxxxxx -- Chuck Lever chucklever@xxxxxxxxx
