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Trying to create a raid1 on a live system following this article: http://guylabs.ch/2013/09/17/create-a-software-raid1-with-mdadm-on-an-active-ubuntu-13-04-hard-drive/comment-page-1/

uname =a
3.13.0-63-generic #103-Ubuntu SMP Fri Aug 14 21:42:59 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

I created /dev/md0 using /dev/sdb3 and booted off of it fine. When trying to add /dev/sda3 to /dev/md0, it keeps saying Device or resource busy. I have removed dmraid. dmsetup status does list /dev/sda3 being used but I have removed it using dmsetup remove. Any suggestions I can try?

My mdadm.conf file:

DEVICE /dev/sda* /dev/sdb*
ARRAY /dev/md0 metadata=0.90 UUID=dbbbc270:ad7a07d4:989a1506:09fffe2d

dmsetup status:
qwerty--vg-swap_1: 0 7766016 linear

The swap file is mounted as /dev/sda2

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  • # pvs PV VG Fmt Attr PSize PFree /dev/sda3 qwerty-vg lvm2 a-- 697.89g 138.04g – generalya Sep 6 '15 at 18:03
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You have booted off the original disk, /dev/sda, instead of /dev/sdb. For this set of instructions to work, you must reboot from disk sdb, so that disk sda, at the stage at which you are now, appears idle. There is nothing you can do from this session, most likely you made some mistake in configuring GRUB to reboot from sdb. Go back one step, make sure your GRUB is set up to boot from sdb, reboot, then you can proceed.

I understand the instructions above are quite crafty, but I still think it would have been easier to create the RAID configuration from a live system.

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  • True. The disk is busy, either because you booted from it (mostlikely), or because you mounted something on it. In this stage Marius is almost certainly correct, you are still booting from it. Note that this happens quite frequently, e.g. see these posts: superuser.com/questions/514561/… superuser.com/questions/775691/… superuser.com/questions/775691/… – Hennes Sep 6 '15 at 11:01
  • Weird...I followed the instructions and seem to be booting off of /dev/md0 which currently only has /dev/sdb3 as a device. Here is my mount: /dev/md0 on / type ext4 (rw,errors=remount-ro) – generalya Sep 6 '15 at 17:41

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