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Re: booting a clone from a /dev/md0 disk as single ext4 disk

From: John Griessen
Subject: Re: booting a clone from a /dev/md0 disk as single ext4 disk
Date: Thu, 27 Oct 2016 10:36:54 -0500
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Icedove/45.4.0

On 10/23/2016 12:03 PM, Andrei Borzenkov wrote:
Sorry, I could not parse this sentence. What I'd do,

1. create target devices (presumably, Linux MD)
2. copy from source to target
3. adjust /etc/fstab, /etc/mdadm.conf and whatever else is appropriate
(which may include recreating initrd)
4. chroot and run grub-install and grub-mkconfig or your distro command
that calls them

Note that in case of Linux MD grub2 grub-install only supports
installation on MBR. You also need to install grub2 individually on each
disk that belongs to MD array holding /boot/grub if you want resiliency
against individual disk failures.

Also note that in relation to grub2 "Linux MD" is really relevant only
if grub2 itself (i.e. /boot/grub directory) is on MD array.

5. configure your distro to use new bootloader location(s) as default.
So next time you update grub2 package it runs grub-install with correct
parameters. In case of Debina-based distro this actually means running

I found my main problem was a wrong rsync copy.  I had been doing rsync -acHv
and I noticed my scripts had become  rsync -aCHv which is filtering out many 
files needed
to run.   I decided that MD raid was not so helpful in my workstation use
as having really good robust backups incrementally happening with rsync,
and easy to restore by just booting a different disk and occasionally removing 
a disk,
putting it on shelf for hacker safe backup.  I don't seem to need a chroot to 
a rsync copy of a running drive to boot OK.  I just stop networking and 
and firefox and run rsync until there are just a few log files difference and 
that a good bootable backup.

I have my debian grub-pc package pinned at 2.02~beta2-22+deb8u1 for now.  Grub2 
working well with a GPT partitioned disk now.  Everything seems high 

Thanks for the help.

John Griessen

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