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Linux Software RAID – Failed to RUN_ARRAY /dev/md0 invalid argument Error and Solution

When I run the following command at shell prompt on Debian or Ubuntu Linux

mdadm -Ac partitions /dev/md0 -m dev

I'm getting the message/warning that read as follows:

Failed to RUN_ARRAY /dev/md0 invalid argument.

How do I fix this issue? How do I rebuild array again on Linux operating system using mdadm command?

This error indicate that the RAID metadata is lost or is no longer consistent. However, sometime following command can fix the issue if other two driver are known to be good. /proc/mdstat file will provide RAID status and make sure RAID is active. Type the following command at a shell prompt to fix this issue:
mdadm -A /dev/md0 -f --update=summaries /dev/sda1 /dev/sdb1

For more information, check out the manual page for mdadm:
$ man mdadm

{ 3 comments… add one }

  • John September 2, 2009, 4:29 pm

    Grosooooo. This solve my problem, thanks!

  • Pieter March 22, 2012, 3:06 pm

    this partially solved my problems: at least I can start the raid device and mount it now, but it doesn’t update fstab, mtab or storage.conf.
    And after a reboot I have to start all over again. So how can I make this consistent across reboots?

  • Ben November 22, 2013, 11:04 pm


    mdadm --examine --scan --config=mdadm.conf  > /etc/mdadm.conf

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