Re: Mount multiple-device-filesystem by UUID

[Duncan <1i5t5.duncan@cox.net>]

Hugo Mills posted on Sat, 27 Jul 2013 20:44:48 +0100 as excerpted:

> On Sat, Jul 27, 2013 at 08:52:50PM +0200, Hendrik Friedel wrote:
>> As stated in the wiki, multiple-device filesystems (e.g. raid 1) will
>> only mount after a btfs device scan, or if all devices are passed with
>> the mount options.
>> 
>> I remember, that for Ubuntu 12.04 I changed the initrd. But after a
>> re-install, I have to do this again, and I don't remember how I did it.
> 
>    With Ubuntu, just install the btrfs-tools package. It should modify
> the initrd correctly.
> 
>> So, the other option would be passing the devices in the fstab. But
>> here, I'd prefer UUIDs rather than device names, as they can change.
> 
>    This is why we don't recommend using device= mount flags.
> 
>> Is this possible? What is the syntax?
> 
>    I don't believe it is possible. Finding filesystems by UUID is (I
> think) a userspace-based thing, so you'd have to have an initrd anyway.

btrfs raid1 root here, was initr*less until I switched to btrfs which is 
broken with direct-kernel-root-mount rootflags=device=whatever syntax.

UUIDs are indeed userspace -- udev/systemd.  However, if your initr* 
includes udev, at least here, it "just works".

I use root=LABEL=whatever here on the kernel commandline for root, and 
LABEL=whatever for non-root in fstab, but as long as udev has the 
directory in /dev/disk/*, mount should work with it, so root=UUID=whatever 
at the kernel commandline should work, as should UUID=whatever in fstab 
as the first field.

-- 
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"Every nonfree program has a lord, a master --
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