Stumped on NFS usernames

I know there's a lot of discussions out there about usernames with
NFS, but I'm having a mental block trying to understand what's going
on. I want to mount NFS shares between two linux systems. I've got the
shares working fine, and I'm able to connect with mount -t nfs, but
when I create files in the share on the client computer, the owner is
something like nfsuser or something.

I'd like to be able to specify the username when I mount the share. Is
this possible? I've found a lot of references to username mapping for
NFS, but everything I've found seems to be between linux and windows
or linux and mac.

Thanks greatly,
-Brian

On 2008-01-10, bmearns <(E-Mail Removed)> wrote:
> I know there's a lot of discussions out there about usernames with
> NFS, but I'm having a mental block trying to understand what's going
> on. I want to mount NFS shares between two linux systems. I've got the
> shares working fine, and I'm able to connect with mount -t nfs, but
> when I create files in the share on the client computer, the owner is
> something like nfsuser or something.

Your numeric ids likely don't match.

> I'd like to be able to specify the username when I mount the share. Is
> this possible? I've found a lot of references to username mapping for
> NFS, but everything I've found seems to be between linux and windows
> or linux and mac.

I don't know what references you've found; perhaps you should show some
of them. It's not possible to specify a user when you mount NFS,
because NFS assumes that the numeric UID the client presents is the
numeric UID that the server should use. If that uid doesn't exist, it
will go to nfsuser.

What you need to do is look at the /etc/passwd files and make sure that
any user which will be writing from an NFS client to the server has the
same numeric UID on all systems. If they don't, then you will need to
change the numeric UID so that they're all the same. You'll need to do
this both in /etc/passwd and for any files owned by the old numeric UID.
(There was a thread about how to change a user's numeric UID in one of
the linux newsgroups a few weeks back.)

It's important to stress that NFS itself only deals with the numeric
UID. So, if on the NFS server you have

nobody:x:99:99:Nobody:/:/sbin/nologin

and on a client you have

myuser:x:99:99:Me:/:/sbin/nologin

then a file on the server

-rwxr-xr-x 1 nobody whatever 6188 Nov 13 2006 myFile

will look like

-rwxr-xr-x 1 myuser whatever 6188 Nov 13 2006 myFile

on the client. NFS never passes the name around.

--keith

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(try just my userid to email me)
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Great, thanks for the feedback. I guess I'll need to do some more
reading to find out the nitty-gritty of groups and what not, but I'm
able to access shares with the correct UID, and it shows up as the
correct username on both sides.

Thanks!
-Brian

On Jan 10, 10:56 pm, bmearns <bmea...@coe.neu.edu> wrote:
> I know there's a lot of discussions out there about usernames with
> NFS, but I'm having a mental block trying to understand what's going
> on. I want to mount NFS shares between two linux systems. I've got the
> shares working fine, and I'm able to connect with mount -t nfs, but
> when I create files in the share on the client computer, the owner is
> something like nfsuser or something.
>
> I'd like to be able to specify the username when I mount the share. Is
> this possible? I've found a lot of references to username mapping for
> NFS, but everything I've found seems to be between linux and windows
> or linux and mac.
>
> Thanks greatly,
> -Brian

Hi Brian,

Yes, the thing is that nfs by default use a username called nobody,and
it is there on the /etc/passwd file.So that's why you are getting up
this.
In oder to avoid this you need to use the special permissions like
sticky bit ( so only the owner can delete up the file) or change up
the directory permission.

Thank You

Melbin Mathew

Hi,


> It's important to stress that NFS itself only deals with the numeric
> UID.

This changed in NFS4. Here NFS uses username@nfs4-domain and
groupname@nfs4-domain in transport.
But the problems of inconsistent name/id mapping remains nearly the same.

Regards,

Michael

On 2008-01-16, Michael Weis <(E-Mail Removed)> wrote:
>
>> It's important to stress that NFS itself only deals with the numeric
>> UID.
>
> This changed in NFS4. Here NFS uses username@nfs4-domain and
> groupname@nfs4-domain in transport.

Ooh, didn't know that, thanks! From what I can tell, NFSv4 in the linux
kernel is relatively new, so my hunch is the OP is not using it. But
it's still good to keep in mind.

> But the problems of inconsistent name/id mapping remains nearly the same.

True. At least what I wrote earlier was mostly accurate.

--keith

--
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(try just my userid to email me)
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