linux-kernel - Re: Failover root devices

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Message-ID: <55FAA6BB.3060008@odi.ch>
Date:	Thu, 17 Sep 2015 13:40:43 +0200
From:	Ortwin Glück <odi@....ch>
To:	Drew DeVault <sir@...wn.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Failover root devices

 > I would like to see Linux support multiple root devices

You can do that completely in user space from an initramfs.

 From your init script you can do what you want. You may even parse /proc/cmdline and use the root= 
parameter as you propose. Then mount whatever root device you want by whatever method you like and 
finally
  exec switch_root /mnt/root /sbin/init "$@"

See here for example scripts for initramfs:
http://www.linuxfromscratch.org/blfs/view/svn/postlfs/initramfs.html

Above script actually makes it easy by supporting disk labels: root=LABEL=ROOT will boot the first 
available partition that is labelled ROOT. It is independent of the device name and works nice when 
you switch hardware vs. virtual machines for instance.

Ortwin

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