Failed to fetch subvolume detail for snapshot_dir

[alexeiroz]

Hello

I'm a new btrfs and btrbk user.
I'm trying to backup my laptop SSD to external USB HDD with btrbk.
Both internal and external drives are btrfs.
But unfortunately I unable to pass even the dry ran stage.
I'm keep getting the following error:

>sudo btrbk -l debug -c /home/nc/btrbk/btrbk-msi-laptop-2.conf -v -n run
btrbk command line client, version 0.32.6  (Sat Dec 23 17:54:29 2023)
Using configuration: /home/nc/btrbk/btrbk-msi-laptop-2.conf
WARNING: Skipping subvolume "/mnt/btr_pool/@": Failed to fetch subvolume detail for snapshot_dir
WARNING: ... Command execution failed (exitcode=1)
WARNING: ... sh: readlink -v -e '/mnt/btr_pool/btrbk_snapshots'
WARNING: ... readlink: /mnt/btr_pool/btrbk_snapshots: No such file or directory
Completed within: 0s  (Sat Dec 23 17:54:29 2023)
--------------------------------------------------------------------------------
Backup Summary (btrbk command line client, version 0.32.6)

    Date:   Sat Dec 23 17:54:29 2023
    Config: /home/nc/btrbk/btrbk-msi-laptop-2.conf
    Dryrun: YES

Legend:
    ===  up-to-date subvolume (source snapshot)
    +++  created subvolume (source snapshot)
    ---  deleted subvolume
    ***  received subvolume (non-incremental)
    >>>  received subvolume (incremental)
--------------------------------------------------------------------------------
/mnt/btr_pool/@
!!! Aborted: Failed to fetch subvolume detail for snapshot_dir

NOTE: Some errors occurred, which may result in missing backups!
Please check warning and error messages above.

NOTE: Dryrun was active, none of the operations above were actually executed!

Below some information about my system configuration:

>cat /etc/os-release 
NAME="openSUSE Tumbleweed-Slowroll"
# VERSION="20231219"
ID="opensuse-tumbleweed"
ID_LIKE="opensuse suse"
VERSION_ID="20231219"
PRETTY_NAME="openSUSE Tumbleweed-Slowroll"
ANSI_COLOR="0;32"
CPE_NAME="cpe:/o:opensuse:tumbleweed:20231219"
BUG_REPORT_URL="https://bugzilla.opensuse.org"
SUPPORT_URL="https://bugs.opensuse.org"
HOME_URL="https://www.opensuse.org"
DOCUMENTATION_URL="https://en.opensuse.org/openSUSE:Slowroll"
LOGO="distributor-logo-Tumbleweed"

> btrbk --version
btrbk command line client, version 0.32.6

at /home/nc/btrbk/btrbk-msi-laptop-2.conf 
snapshot_preserve_min   2d
snapshot_preserve       14d
target_preserve_min     no
target_preserve         20d 10w *m

target         /mnt/usb-backup/btrbk-msi-laptop

volume          /mnt/btr_pool/
 snapshot_dir    btrbk_snapshots
 subvolume      @
 #subvolume      @/home
 #subvolume     /@/var
 #subvolume     /@/usr/local
 #subvolume     /@/srv
 #subvolume     /@/root
 #subvolume     /@/opt
 #subvolume     /@/boot/grub2/x86_64-efi
 #subvolume     /@/boot/grub2/i386-pc

> cat /etc/fstab 
UUID=b16700d9-c4bb-427f-b7e0-e9f03e1aac03  /                       btrfs  defaults                      0  0
UUID=b16700d9-c4bb-427f-b7e0-e9f03e1aac03  /var                    btrfs  subvol=/@/var                 0  0
UUID=b16700d9-c4bb-427f-b7e0-e9f03e1aac03  /usr/local              btrfs  subvol=/@/usr/local           0  0
UUID=b16700d9-c4bb-427f-b7e0-e9f03e1aac03  /srv                    btrfs  subvol=/@/srv                 0  0
UUID=b16700d9-c4bb-427f-b7e0-e9f03e1aac03  /root                   btrfs  subvol=/@/root                0  0
UUID=b16700d9-c4bb-427f-b7e0-e9f03e1aac03  /opt                    btrfs  subvol=/@/opt                 0  0
UUID=b16700d9-c4bb-427f-b7e0-e9f03e1aac03  /home                   btrfs  subvol=/@/home                0  0
UUID=b16700d9-c4bb-427f-b7e0-e9f03e1aac03  /boot/grub2/x86_64-efi  btrfs  subvol=/@/boot/grub2/x86_64-efi  0  0
UUID=b16700d9-c4bb-427f-b7e0-e9f03e1aac03  /boot/grub2/i386-pc     btrfs  subvol=/@/boot/grub2/i386-pc  0  0
UUID=8159fe0a-742d-4fbd-becf-fb31cd93a64f  swap                    swap   defaults                      0  0
UUID=b16700d9-c4bb-427f-b7e0-e9f03e1aac03  /.snapshots             btrfs  subvol=/@/.snapshots          0  0

/dev/sda2  /mnt/btr_pool  btrfs  subvolid=5,noatime  0 0

> sudo btrfs subvolume list /
ID 256 gen 30 top level 5 path @
ID 257 gen 2089 top level 256 path @/var
ID 258 gen 1389 top level 256 path @/usr/local
ID 259 gen 1389 top level 256 path @/srv
ID 260 gen 1694 top level 256 path @/root
ID 261 gen 1390 top level 256 path @/opt
ID 262 gen 1997 top level 256 path @/home
ID 263 gen 25 top level 256 path @/boot/grub2/x86_64-efi
ID 264 gen 1213 top level 256 path @/boot/grub2/i386-pc
ID 265 gen 2027 top level 256 path @/.snapshots
ID 266 gen 2082 top level 265 path @/.snapshots/1/snapshot
ID 267 gen 76 top level 265 path @/.snapshots/2/snapshot
ID 268 gen 128 top level 265 path @/.snapshots/3/snapshot
ID 269 gen 378 top level 265 path @/.snapshots/4/snapshot
...

> sudo btrfs subvolume list /mnt/btr_pool 
ID 256 gen 30 top level 5 path @
ID 257 gen 2092 top level 256 path @/var
ID 258 gen 1389 top level 256 path @/usr/local
ID 259 gen 1389 top level 256 path @/srv
ID 260 gen 1694 top level 256 path @/root
ID 261 gen 1390 top level 256 path @/opt
ID 262 gen 1997 top level 256 path @/home
ID 263 gen 25 top level 256 path @/boot/grub2/x86_64-efi
ID 264 gen 1213 top level 256 path @/boot/grub2/i386-pc
ID 265 gen 2027 top level 256 path @/.snapshots
ID 266 gen 2082 top level 265 path @/.snapshots/1/snapshot
ID 267 gen 76 top level 265 path @/.snapshots/2/snapshot
...

[denisalevi]

Either your btrfs top volume is not mounted at /mnt/btr_pool and/or you didn't create the snapshot directory btrbk_snapshots (it is not created by btrbk, you need to create it, see docs)

1. Make sure your root is mounted at /mnt/btr_pool:

   sudo mount /dev/to/your/btrfs/top/volume /mnt/btr_pool
   

2. Create the missing snapshot_dir:

   sudo mkdir /mnt/btr_pool/btrbk_snapshots