bugGNU GRUB - Bugs: bug #45902, BTRFS subvolume - don't resolve...


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bug #45902: BTRFS subvolume - don't resolve symlinks

Submitted by:  Florian <ikcalb>
Submitted on:  Wed 09 Sep 2015 10:37:19 AM UTC  
Category:  Filesystem Severity:  Major
Priority:  3 - Low Item Group:  Feature Request
Status:  None Privacy:  Public
Assigned to:  None Originator Name:  Florian Kerle
Open/Closed:  Open Release: 
Release:  other Reproducibility:  Every Time
Planned Release:  2.03+

Wed 09 Sep 2015 10:39:01 AM UTC, comment #1: 

release: 2.0.2~beta2-22
on debian jessie

Florian <ikcalb>
Wed 09 Sep 2015 10:37:19 AM UTC, original submission:  

BTRFS subvolumes are a convenient way of making backups - especially for the currently used root filesystem, as they are COW.

Using one physical BTRFS partition:
- mounted on `/mnt`
- using folders to group snapshots for logical partitions
  (i.e. snapshots for `home` stored in `home@`)
- symlink for the currently used subvolume for each logical partition

 |-home  --> ./home@/current
 |-root  --> ./root@/current

CURRENT BEHAVIOR (steps to reproduce)
1) when booted to subvolume `root` in the above configuration, issue `update-grub`
2) check `/boot/grub/grub.cfg`
   it will resolve the `root` symlink on `/mnt` to `root@/current`

To ease recovery / switching between snapshots, editing one symlink is more elegant than
- to move the current subvolume (`root`) away and the backup in place
  (not only paths for kernel/initrd when booting had to be updated, but also fstab - if not replacing the subvolume one way or another)

Unfortunately idk how to determine with which parameters a BTRFS volume was mounted. (i.e. using the symlink, or the subvolume path directely)
btrfs-tools seem to report the resolved subvolume name only.

Florian <ikcalb>


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    Follow 4 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2016-10-11 phcoder Priority5 - Normal => 3 - Low
    2016-03-02 phcoder Planned ReleaseNone => 2.03+
    2015-09-09 ikcalb Carbon-CopyRemoved ikcalb => -
    2015-09-09 ikcalb Carbon-Copy- => Added ikcalb

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