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I am trying to setup a diskless client which will mount over nfs to the server. When I try to boot the client I get the following error message:

VFS: Cannot open root device "nfs" or unknown-block(0,255) Please append a correct "root=" boot option Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,255)

I've set up my kernel parameters as follows:

kernel=, <-- tftpboot parameters....(which works)

Linux PPC load: root=/dev/nfs rw nfsroot= ip=dhcp

The kernel is found via tftpboot, so I know the 'kernel' parameter above works. The kernel is loaded and start executing, but hits the above error eventually.

The mount point is properly exported from the server, as I can mount it manually from other machines.

I've read several threads about this topic (at least very similar), but none, as far as I've seen so far, has addressed mounting a nfs drive. I've only seen topics talking about local hard drives.

Any ideas,guidance is very appreciated...thanks...

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Is there more than one nic? If so, does the primary nic change? Does your dhcp server show an address being assigned? – ramruma Jan 9 '14 at 6:30
@ramruma My server is assigning ip-address to client. i am providing client's mac-address in /etc/dhcp/dhcpd.conf to get ip-address . i am placing kernel in /tftpboot directory. my boot arguments are in default file. The default file is DEFAULT openwrt LABEL openwrt KERNEL openwrt-x86-generic-vmlinuz append boot=nfs root=/dev/sda3 root=server-ip:/media/_openwrt ip=dhcp rw I want to mount rootfilesystem which is present in /media/_openwrt while booting only. But i am getting the above error ...... – khaleel Jan 9 '14 at 7:12
check that the kernel included nfs client – kofemann Jan 9 '14 at 7:56
@tigran i didn't get you . can you please elaborate – khaleel Jan 9 '14 at 8:20
it's not obvious that kernel which recieved over netfork supports nfs, IOW, is nfs support enebled when kernel is compiles – kofemann Jan 9 '14 at 10:26

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