Restore single files from a btrfs snapshot without doing a full copy

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Background



I maintain a series of hourly snapshots on my btrfs filesystem using btrbk. The subvolume and snapshots are stored like this (names shortened to make it easier to follow):



/@vol (subvolume)
/btrbk/@vol.00 (snapshots of /@vol, one per hour)
/btrbk/@vol.01 ...
/home/user/vol (mountpoint for /@vol)


Now I deleted a single file in /home/user/vol which I should not have deleted. No problem, I can easily restore from the latest snapshot:



# cd /home/user/vol
# cp -a --reflink=always /btrbk/@vol.01/all_ipv4_numbers.txt ./
cp: failed to clone './all_ipv4_numbers.txt' from '/btrbk/@vol.01/all_ipv4_numbers.txt': Invalid cross-device link


Seems I can't "reflink" the file. But I don't want to end up with two copies of the file. Ideally I want it to look like nothing happened between the most recent snapshot and the next snapshot that will be taken in the future.



(Yes, I also have actual backups, but restoring from snapshots are more convenient whenever available!)



Question



How do I restore a single file from a btrfs snapshot while keeping all the nice references and magic that makes btrfs know that it is the same data in all the snapshots?






btrfs snapshot






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    down vote

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    Background



    I maintain a series of hourly snapshots on my btrfs filesystem using btrbk. The subvolume and snapshots are stored like this (names shortened to make it easier to follow):



    /@vol (subvolume)
    /btrbk/@vol.00 (snapshots of /@vol, one per hour)
    /btrbk/@vol.01 ...
    /home/user/vol (mountpoint for /@vol)


    Now I deleted a single file in /home/user/vol which I should not have deleted. No problem, I can easily restore from the latest snapshot:



    # cd /home/user/vol
    # cp -a --reflink=always /btrbk/@vol.01/all_ipv4_numbers.txt ./
    cp: failed to clone './all_ipv4_numbers.txt' from '/btrbk/@vol.01/all_ipv4_numbers.txt': Invalid cross-device link


    Seems I can't "reflink" the file. But I don't want to end up with two copies of the file. Ideally I want it to look like nothing happened between the most recent snapshot and the next snapshot that will be taken in the future.



    (Yes, I also have actual backups, but restoring from snapshots are more convenient whenever available!)



    Question



    How do I restore a single file from a btrfs snapshot while keeping all the nice references and magic that makes btrfs know that it is the same data in all the snapshots?






    btrfs snapshot






    share























      up vote
      0
      down vote

      favorite









      up vote
      0
      down vote

      favorite











      Background



      I maintain a series of hourly snapshots on my btrfs filesystem using btrbk. The subvolume and snapshots are stored like this (names shortened to make it easier to follow):



      /@vol (subvolume)
      /btrbk/@vol.00 (snapshots of /@vol, one per hour)
      /btrbk/@vol.01 ...
      /home/user/vol (mountpoint for /@vol)


      Now I deleted a single file in /home/user/vol which I should not have deleted. No problem, I can easily restore from the latest snapshot:



      # cd /home/user/vol
      # cp -a --reflink=always /btrbk/@vol.01/all_ipv4_numbers.txt ./
      cp: failed to clone './all_ipv4_numbers.txt' from '/btrbk/@vol.01/all_ipv4_numbers.txt': Invalid cross-device link


      Seems I can't "reflink" the file. But I don't want to end up with two copies of the file. Ideally I want it to look like nothing happened between the most recent snapshot and the next snapshot that will be taken in the future.



      (Yes, I also have actual backups, but restoring from snapshots are more convenient whenever available!)



      Question



      How do I restore a single file from a btrfs snapshot while keeping all the nice references and magic that makes btrfs know that it is the same data in all the snapshots?






      btrfs snapshot






      share













      Background



      I maintain a series of hourly snapshots on my btrfs filesystem using btrbk. The subvolume and snapshots are stored like this (names shortened to make it easier to follow):



      /@vol (subvolume)
      /btrbk/@vol.00 (snapshots of /@vol, one per hour)
      /btrbk/@vol.01 ...
      /home/user/vol (mountpoint for /@vol)


      Now I deleted a single file in /home/user/vol which I should not have deleted. No problem, I can easily restore from the latest snapshot:



      # cd /home/user/vol
      # cp -a --reflink=always /btrbk/@vol.01/all_ipv4_numbers.txt ./
      cp: failed to clone './all_ipv4_numbers.txt' from '/btrbk/@vol.01/all_ipv4_numbers.txt': Invalid cross-device link


      Seems I can't "reflink" the file. But I don't want to end up with two copies of the file. Ideally I want it to look like nothing happened between the most recent snapshot and the next snapshot that will be taken in the future.



      (Yes, I also have actual backups, but restoring from snapshots are more convenient whenever available!)



      Question



      How do I restore a single file from a btrfs snapshot while keeping all the nice references and magic that makes btrfs know that it is the same data in all the snapshots?






      btrfs snapshot




      btrfs snapshot





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