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1126 08-20-2012 12:53 PM

BTRFS, Rollback, Grub2
 
Hello List!

I can't seem to get rollback-support from mkinitcpio-btrfs to work
properly. I've installed ArchLinux more or less like it is shown in the
wiki-article btrfs-on-root:
https://wiki.archlinux.org/index.php/Installing_on_Btrfs_root

I changed it some, because I wanted to install ArchLinux on an
encrypted btrfs-root.

But my root-partition contains a __snapshot folder and an __active
subvolume, but no subvolumes for __home and __usr and such, because I
want to be able to make complete snapshots of my system.

But when I want to create a snapshot, it asks me where I want to do it,
but I can't give __snapshot as target-folder, because it don't exists in
my system... ;)

So: how should my btrfs-root be mounted in order to be able to make full
use of the rollback-feature provided by mkinitcpio-btrfs?

Thanks in advance for your help,

Christian.

C Anthony Risinger 08-20-2012 06:49 PM

BTRFS, Rollback, Grub2
 
On Mon, Aug 20, 2012 at 7:53 AM, 1126
<mailinglists@elfsechsundzwanzig.de> wrote:
> Hello List!
>
> I can't seem to get rollback-support from mkinitcpio-btrfs to work
> properly. I've installed ArchLinux more or less like it is shown in the
> wiki-article btrfs-on-root:
> https://wiki.archlinux.org/index.php/Installing_on_Btrfs_root
>
> I changed it some, because I wanted to install ArchLinux on an
> encrypted btrfs-root.
>
> But my root-partition contains a __snapshot folder and an __active
> subvolume, but no subvolumes for __home and __usr and such, because I
> want to be able to make complete snapshots of my system.
>
> But when I want to create a snapshot, it asks me where I want to do it,
> but I can't give __snapshot as target-folder, because it don't exists in
> my system... ;)
>
> So: how should my btrfs-root be mounted in order to be able to make full
> use of the rollback-feature provided by mkinitcpio-btrfs?
>
> Thanks in advance for your help,

yeah ... someone or something completely botched that page, to where
it neither reflect the original design goals nor improves upon them.
far too much noise and pointlessness (like outbound links to FHS ...
who the @#$% cares?!)

in short, you need something like this in fstab or equiv:

/dev/disk/by-label/btrfs-root /var/lib/btrfs-root btrfs
defaults,noatime,subvolid=0 0 0

... you need to mount `subvolid=0` or `subvolid=5` (same thing)
somewhere, and make snapshots from there. subvolid 5 (for which 0 is
an alias) is hard-coded to the top-level root.

maybe try this:

https://wiki.archlinux.org/index.php?title=Installing_on_Btrfs_root&oldid=185 175

--

C Anthony

1126 08-20-2012 07:36 PM

BTRFS, Rollback, Grub2
 
On Mon, 20. Aug 13:49, C Anthony Risinger wrote:
>
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>
> mvmda: regcomp failed.
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> mvmda: regcomp failed.
>
>
> ---- end of text added by mvmf mail filter ----
>
>
> On Mon, Aug 20, 2012 at 7:53 AM, 1126
> <mailinglists@elfsechsundzwanzig.de> wrote:
> > Hello List!
> >
> > I can't seem to get rollback-support from mkinitcpio-btrfs to work
> > properly. I've installed ArchLinux more or less like it is shown in the
> > wiki-article btrfs-on-root:
> > https://wiki.archlinux.org/index.php/Installing_on_Btrfs_root
> >
> > I changed it some, because I wanted to install ArchLinux on an
> > encrypted btrfs-root.
> >
> > But my root-partition contains a __snapshot folder and an __active
> > subvolume, but no subvolumes for __home and __usr and such, because I
> > want to be able to make complete snapshots of my system.
> >
> > But when I want to create a snapshot, it asks me where I want to do it,
> > but I can't give __snapshot as target-folder, because it don't exists in
> > my system... ;)
> >
> > So: how should my btrfs-root be mounted in order to be able to make full
> > use of the rollback-feature provided by mkinitcpio-btrfs?
> >
> > Thanks in advance for your help,
>
> yeah ... someone or something completely botched that page, to where
> it neither reflect the original design goals nor improves upon them.
> far too much noise and pointlessness (like outbound links to FHS ...
> who the @#$% cares?!)
>
> in short, you need something like this in fstab or equiv:
>
> /dev/disk/by-label/btrfs-root /var/lib/btrfs-root btrfs
> defaults,noatime,subvolid=0 0 0
>
> ... you need to mount `subvolid=0` or `subvolid=5` (same thing)
> somewhere, and make snapshots from there. subvolid 5 (for which 0 is
> an alias) is hard-coded to the top-level root.
>
> maybe try this:
>
> https://wiki.archlinux.org/index.php?title=Installing_on_Btrfs_root&oldid=185 175
>

Hey, thanks! I now can create snapshots in __snapshot
(/var/lib/btrfs-root/__snapshot), but I can't use rollback ... Might
this be due to boot with systemd?

Greetings!

> --
>
> C Anthony

C Anthony Risinger 08-21-2012 01:33 AM

BTRFS, Rollback, Grub2
 
On Mon, Aug 20, 2012 at 2:36 PM, 1126
<mailinglists@elfsechsundzwanzig.de> wrote:
> On Mon, 20. Aug 13:49, C Anthony Risinger wrote:
>>
>> in short, you need something like this in fstab or equiv:
>>
>> /dev/disk/by-label/btrfs-root /var/lib/btrfs-root btrfs
>> defaults,noatime,subvolid=0 0 0
>>
>> ... you need to mount `subvolid=0` or `subvolid=5` (same thing)
>> somewhere, and make snapshots from there. subvolid 5 (for which 0 is
>> an alias) is hard-coded to the top-level root.
>>
>> maybe try this:
>>
>> https://wiki.archlinux.org/index.php?title=Installing_on_Btrfs_root&oldid=185 175
>
> Hey, thanks! I now can create snapshots in __snapshot
> (/var/lib/btrfs-root/__snapshot), but I can't use rollback ... Might
> this be due to boot with systemd?

hmm, i wouldn't think so -- this is pretty low-level and should not be affected.

make sure you have the hook in your mkinitcpio.conf, and make sure
your not trying to rollback after a kernel update ... but you'll need
to elaborate more on what "I can't use rollback" really means (eg.
some output or description or something).

that said, i haven't actually ran the hook for awhile -- i had to ease
off the edge a bit -- and hence am running ext4 currently. but in
light of recent grub2 developments, it sounds like kernel-level
rollbacks will finally be possible so lately i've been trying to
revisit this project.

i'd also like to get the hook -- or some form of it -- included in
Arch proper ...

--

C Anthony


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