Re: [gentoo-user] resizing EFI partition, btrfs context

["Stefan G. Weichinger" <lists@xunil.at>]

Am 2015-10-06 um 14:32 schrieb Rich Freeman:
> On Tue, Oct 6, 2015 at 3:52 AM, Stefan G. Weichinger <lists@xunil.at> wrote:
>> Am 2015-10-06 um 09:45 schrieb Neil Bothwick:
>>> On Tue, 6 Oct 2015 09:35:40 +0200, Stefan G. Weichinger wrote:
>>>
>>>>> How about btrfs send/receive? I've never used them but used
>>>>> the equivalent with ZFS and it was simple to do.
>>>>
>>>> I think "btrfs-replace" is my friend. Will try that later.
>>>
>>> If you want to keep the system live, replace will do the trick, but
>>> when I tried it to replace a drive that was showing SMART errors it
>>> was VERY slow. btrfs send serialises your whole filesystem to a
>>> file so it should be much faster.
>>
>> btrfs send would also have the benefit that I won't lose the
>> source-dev in the process. btrfs-replace would "empty" my hdd, if then
>> things fail I don't have that backup again to start from.
>>
>> I just have to find out how to keep the UUID to keep the copy booting etc
>>
>> I will try that later this day, after some job work.
>>
> 
> I doubt send/receive would preserve the UUID.
> 
> I'd probably use btrfs-replace.
> 
> If you do want to keep the same UUID via any mechanism make sure the
> original drive isn't visible or btrfs may try to use it instead of the
> new one.  That is more of a concern in raid configs, but it might
> apply to single volume.  Btrfs can't tell the difference between the
> active volume you unmounted yesterday and the lvm snapshot of it from
> six months ago, and will potentially try to mix-and-match them
> resulting in carnage.
> 
> Btrfs does support resizing if you just want to shrink the filesystem
> and then dd it over to the new partition.  Just make sure the old one
> isn't attached when you try to mount it.  Just shrink your btrfs
> partition down to a size smaller than where it is going, use dd to
> copy it, then you can run btrfs resize to expand it back to the full
> size.  The syntax is slightly different but it works the same as
> resize2fs, and I believe it works either online or offline.
> 
> However, if you're able to figure out how to use btrfs and migrate it
> from one drive to another, you could probably just edit the UUID in
> your grub config if necessary.  It just takes a text editor, and maybe
> a run of grub2-mkconfig if you're using that.  You'll also want to
> update your fstab, and if you're using dracut you should update that
> as well (as long as it gets a decent UUID from the command line I
> think it will figure things out on its own though - dracut saves a
> copy of your fstab to help find things when you build it but then it
> will remount filesystems using the real fstab before it finishes).

I do a plain rsync into a new btrfs on the ssd now and edited the UUID
within copied gummiboat loader entries .... some GBs left to sync before
I can test booting!

;)

I don't use grub2 anymore, just gummiboot .. and even this might be
replaced by bootctl soon. step by step, you know.