mickg wrote:

Neil Brown wrote:

quoted

On Thursday October 5, mickg@mickg.net wrote:

quoted

Neil Brown wrote:

quoted

On Wednesday October 4, mickg@mickg.net wrote:

quoted

I have been trying to run: mdadm --grow /dev/md0 --raid-devices=6 
--backup-file /backup_raid_grow
I get:
mdadm: Need to backup 1280K of critical section..
mdadm: /dev/md0: Cannot get array details from sysfs

It shouldn't do that.... Can you   strace -o /tmp/trace -s 300 
mdadm --grow .....

...

quoted

open("/sys/block/md0/md/component_size", O_RDONLY) = -1 ENOENT (No 
such file or directory)

So it couldn't open .../component_size.  That was added prior to the
release of 2.6.16, and you are running 2.6.17.13 so the kernel
certainly supports it.  Most likely explanation is that /sys isn't 
mounted.
Do you have a "/sys"?
Is it mounted?
Can you "ls -l /sys/block/md0/md" ??

Maybe you need to
  mkdir /sys
  mount -t sysfs sysfs /sys

and try again.

Worked like a charm!

Thank you!

There is a
  sysfs   /sys    sysfs   noauto 0 0
line in /etc/fstab
I am assuming noauto is the culprit?

Should it be made to automount ?

mickg 

I will belatedly add that experience shows that /proc and /sys are 
optional (and can in theory be mounted other places), in practice a lot 
of software depends on them being present and in the usual place.

-- 
bill davidsen [off-list ref]
  CTO TMR Associates, Inc
  Doing interesting things with small computers since 1979