Re: btrfs raid1 and btrfs raid10 arrays NOT REDUNDANT

Hugo Mills
2014-01-03T23:18:24Z

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On Fri, Jan 03, 2014 at 06:13:25PM -0500, Jim Salter wrote:
> Sorry - where do I put this in GRUB? /boot/grub/grub.cfg is still
> kinda black magic to me, and I don't think I'm supposed to be
> editing it directly at all anymore anyway, if I remember
> correctly...

You don't need to edit grub.cfg -- when you boot, grub has an edit
option, so you can do it at boot time without having to use a rescue
disk.

Regardless, the thing you need to edit is the line starting
"linux", and will look something like this:

linux /vmlinuz-3.11.0-rc2-dirty root=UUID=1b6ec419-211a-445e-b762-ae7da27b6e8a ro single rootflags=subvol=fs-root

If there's a rootflags= option already (as above), add ",degraded"
to the end. If there isn't, add "rootflags=degraded".

Hugo.

> >>HOWEVER - this won't allow a root filesystem to mount. How do you deal
> >>with this if you'd set up a btrfs-raid1 or btrfs-raid10 as your root
> >>filesystem? Few things are scarier than seeing the "cannot find init"
> >>message in GRUB and being faced with a BusyBox prompt... which is
> >>actually how I initially got my scare; I was trying to do a walkthrough
> >>for setting up a raid1 / for an article in a major online magazine and
> >>it wouldn't boot at all after removing a device; I backed off and tested
> >>with a non root filesystem before hitting the list.
> >Add -o degraded to the boot-options in GRUB.
>

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