Subject: Re: NFS and Network Driver Question

From: Bob Wirka <[email-masked]>
Date: Thu, 21 Oct 2004 10:09:09 -0500

Here is another wrinkle: The program on my embedded system cannot send 
UDP broadcast messages when NFS mounted. When the system is booted 
without NFS (using the DiskOnChip for root file system) I can send UDP 
broadcasts. When the system is booted with NFS (using my laptop for root 
file system) UDP broadcasts result in "Network unreachable" errors, 
though it CAN send directed UDP messages and TCP messages.

The kernel configuration is identical, except for kernel IP 
autoconfiguration, root over nfs, and compiled-in network driver. The 
NFS configuration on the host has 'no_root_squash', and <<now>> all the 
files on the host root file system are owned by root.

Any ideas?

Thanks,

Bob Wirka
Realtime Control Works

Stephen Hemminger wrote:

> Bob Wirka wrote:
>
>> Ok, now I feel like I'm taking crazy pills...
>>
>> The embedded system boots up and mounts the root file system on my 
>> host laptop. The 'rc.sysinit' startup script executes the command 
>> 'mount -a' which should mount /proc, /dev/pts, and /dev/shm, as 
>> listed in /etc/fstab. When executed, that command returns  "mount: 
>> only root can do that".
>>
>> When I get to the bash prompt, 'whoami' reports that I am, indeed, 
>> root. A 'mount -a' from the command prompt gives the same result; it 
>> doesn't think I'm root for the mount command.
>>
>> I can chown a file owned by root to some other user, and I can create 
>> a file or directory in a directory owned by root; so it doesn't 
>> always think I'm not root.
>>
> Are you getting bit by the nfs uid mapping on the server. Is it 
> mapping your local "root" to "nobody"
> on the server?
>