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I have a strange problem. I am using Ubuntu 14.04 and an NFS home folder, and currently if i try to log in i get thrown back to the loginscreen

I have a NAS, and the home directory is located there. I mount the NAS via NFS at my fstab like this:

157.181.240.65:/dlab    /dlab   nfs defaults    0   0

After that i modified my /etc/passwd file to point the home directory to a folder on my mounted NAS like this:

gerdos:x:1003:1020:Erdos Gabor,,,:/dlab/home/gerdos:/bin/bash

I created every file on the NAS with the same 1003 USERID and 1020 GRPID

Now after a recent update via apt-get i am unable to log into a graphical user interface (gnome flashback compiz).

I think some permissions are bad. I cant really use sudo on files in my home directory, even i clearly have a permission.

A strange one for example:

nano ~/asd # --> No problem, can nano it perfectly,
sudo nano ~/asd # --> Error reading /dlab/home/gerdos/.nano_history: Permission denied

Strange. Permissions on ~/.nano_history:

-rw-------  1 gerdos dlab       39 Feb 23 10:51 .nano_history

It is clear that i have read and write permissions, but sudo does not. I guess the problem might come from somewhere here, that i cant log in.

If i change the permission to 755 sudo still cant read it. On 777 it can. I would like to avoid putting all my files to 777.

How can i solve this problem? How can i "combine" the sudo on the NAS and on my CPU to work together? Is this causing the problem that i can login?

  • Your group do not have any rights or permissions, how come? Can you log on like Guest? – Ken Mollerup Feb 23 '16 at 12:55
  • How did you create the files on the server? What are the permissions of the containing directory (/dlab/home/gerdos)? – steeldriver Feb 23 '16 at 13:35
  • You do NOT place /home on a filesystem other than supported by Linux (ext4 would be the preffered one). – Rinzwind Feb 23 '16 at 19:15
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That's a feature of NFS. Since NFS packets are not authenticated (they just say UID=x,GID=y, trust me), any NFS packets claiming to be from root (UID=0, GID=0) are remapped to nobody, a userid/groupid with NO privileges:

$ grep nobody /etc/passwd
nobody:x:65534:65534:nobody:/nonexistent:/usr/sbin/nologin

The other choice (A Very Bad Idea) is to believe the UID=0 in the NFS packet from Some Other System, and grant it root access to the NFS server/NAS. DO NOT DO THIS.

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