f22 fedup with btrfs snapshot?

[Chris Murphy]

On Tue, Jun 2, 2015 at 11:52 AM, Neal Becker <ndbecker2 at gmail.com> wrote:

> I think this may be all I need:
>
> sudo mount /dev/sda3 /mnt
> [nbecker at nbecker2 ~]$ ls -l /mnt
> total 0
> drwxr-xr-x. 1 root root  14 Jun  1 18:46 home
> dr-xr-xr-x. 1 root root 172 Jun  2 09:39 root
>
> [nbecker at nbecker2 ~]$ sudo btrfs sub snap /mnt/root /mnt/root-f21
> Create a snapshot of '/mnt/root' in '/mnt/root-f21'
> [nbecker at nbecker2 ~]$ ls -l /mnt
> total 0
> drwxr-xr-x. 1 root root  14 Jun  1 18:46 home
> dr-xr-xr-x. 1 root root 172 Jun  2 09:39 root
> dr-xr-xr-x. 1 root root 172 Jun  2 09:39 root-f21
>
> So now I have a snap of f21 root in in root-f21 subvol, and I should be able
> to rollback by editing grub.cfg and /etc/fstab to point to root-f21 subvol
> instead of root subvol, correct?



Correct. One small problem is the fstab in root-f21/etc/fstab still
has mount option subvol=root. So you'd maybe want to change that or
you get boot failure.

Another problem is a good chance that F21 kernels get removed
(eventually) from the ext4 /boot and then you can't use a Fedora 22
kernel menu entry since root-f21 lib/modules doesn't have those
kernels. So you'll want to make sure you have both /etc/yum.conf and
/etc/dnf/dnf.conf set to preserve more than 3 kernels to make sure
neither one starts deleting kernels you might need.

Of course, then the problem is ext4 /boot can become full which is why
we really need /boot on Btrfs support from grubby. :-P

Only 22 days later...


-- 
Chris Murphy