[Buildroot] readonly rootfs problem

[Ed Sutter <ed.sutter@alcatel-lucent.com>]

On 3/4/2014 1:18 AM, Baruch Siach wrote:
> Hi Ed,
>
> On Mon, Mar 03, 2014 at 05:14:47PM -0500, Ed Sutter wrote:
>> I've been using buildroot to create my rootfs for a few months.
>> I build my kernel directly out of freescale.git.
>> I had been running with my rootfs nfs mounted, and all was well.
>> Recently I had spent some time with a ramdisk-based rootfs because
>> i was working on some kernel stuff.
>> Now I'm going back to running rootfs/nfs and I'm finding that
>> it "insists" on coming up in read-only mode.
>>
>> I was initially using buildroot-2013.08, and recently I
>> updated to buildroot-2013.11; however, I don't think that has
>> anything to do with this.  As far as I can tell I have everything
>> set up properly...
>>
>> ####On NFS host /etc/exports has...
>> /full_path_to_my_rootfs *(rw,no_root_squash)
>>
>> ####On target...
>> /etc/inittab...
>> null::sysinit:/bin/mount -o remount,rw / # REMOUNT_ROOTFS_RW
>>
>> /etc/fstab...
>> # /etc/fstab: static file system information.
>> #
>> # <file system> <mount pt>     <type> <options>         <dump> <pass>
>> /dev/root       /              ext2     rw,noauto         0      1
>> proc            /proc          proc     defaults          0      0
>> devpts          /dev/pts       devpts   defaults,gid=5,mode=620 0      0
>> tmpfs           /dev/shm       tmpfs    mode=0777         0      0
>> tmpfs           /tmp           tmpfs    defaults          0      0
>> sysfs           /sys           sysfs    defaults          0 0
>>
>> Output from mount:
>> # mount
>> rootfs on / type rootfs (rw)
>> 1.2.3.4:/full_path_to_my_rootfs on / type nfs (ro,relatime,vers=3,rsize=4096,wsize=4096,namlen=255,hard,nolock,proto=tcp,timeo=600,retrans=2,sec=sys,mountaddr=1.2.3.4,mountvers=3,mountproto=tcp,local_lock=all,addr=135.222.138.108)
>> devtmpfs on /dev type devtmpfs
>> (rw,relatime,size=110708k,nr_inodes=27677,mode=755)
>> proc on /proc type proc (rw,relatime)
>> devpts on /dev/pts type devpts (rw,relatime,gid=5,mode=620)
>> tmpfs on /dev/shm type tmpfs (rw,relatime,mode=777)
>> tmpfs on /tmp type tmpfs (rw,relatime)
>> sysfs on /sys type sysfs (rw,relatime)
>>
>> I actually think the problem is in the kernel, not the rootfs.
>> I say this because even some of my older rootfs copies (still on my
>> host) are now
>> showing up as read only.  The bootlog always ends up with this message:
>> VFS: Mounted root (nfs filesystem) readonly on device 0:11.
>>
>> Any idea what I might be doing wrong here?
> What happens if you manually run:
>
> 	mount -o remount,rw /
>
> Do you see any error message?
>
> baruch
>
Just got it...
This error started after I updated my kernel, and apparently the new kernel
does not default to a rw nfs-mounted rootfs, so I had to add "rw" to the
kernel command line.
Thanks,
Ed