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Linux - Embedded & Single-board computer This forum is for the discussion of Linux on both embedded devices and single-board computers (such as the Raspberry Pi, BeagleBoard and PandaBoard). Discussions involving Arduino, plug computers and other micro-controller like devices are also welcome.


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Old 03-03-2014, 12:06 PM   #1
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What would cause an NFS-mounted rootfs to come up read-only?

I'm working on an embedded linux board, and had been running with an NFS mounted ROOTFS. All was good. Then for a while I had switched over to a ramdisk based rootfs, that was fine too. I've since switched back to an NFS-based rootfs and now it always comes up read-only. Something has obviously changed (yea I know, I probably changed it!); but I don't know what. My host machine (from which the NFS mount is achieved) still has an /etc/exports entry similar to :
/full_path_to_my_rootfs *(rw,no_root_squash)
and on my kernel command line:
console=ttymxc0,115200 ip=dhcp root=/dev/nfs nfsroot=${srvrip}:/full_path_to_my_rootfs,v3,tcp

At boot time I see the message:
VFS: Mounted root (nfs filesystem) readonly on device 0:11.

and then other stuff fails because of inability to write.

Any idea what might cause this?

Some more detail (that just makes me more confused)...
The rootfs is created by buildroot, and it is configured to remount rootfs to RW as shown by the line in /inittab:
null::sysinit:/bin/mount -o remount,rw / # REMOUNT_ROOTFS_RW

Last edited by elsutjr; 03-03-2014 at 04:57 PM.
Old 03-04-2014, 01:41 AM   #2
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maybe you are now using a different kernel version?
Add "rw" to your command line and you're done.
I guess the kernel usually mounts the rootfs readonly, as usually the fs is checked whether its clean before writing to it.
1 members found this post helpful.
Old 03-04-2014, 07:53 AM   #3
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That did it!
Didn't need this in the past, but apparently now I do!
Yep, I did change my kernel.
Thanks much,
Old 03-04-2014, 08:40 AM   #4
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I had the same with a diskless nfs client. after kernel update a while ago it would not boot properly.
the rw flag is not a goot idea for hdd machines, but for nfs who cares :-)


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