ZFS test rollback doesn't work as expected

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I am confused about how ZFS snapshots and rollback are supposed to work.
I have a zpool containing a couple zvols (each made from partitions of a mirrorvdev). I make a snapshot like this:



~$ sudo zfs snapshot nvme-tank@roll_test


Then I boot a VM located on one of the zvols in the zpool and create a test file



~$ echo "This is a test of the rollback system" > rbtest.txt


Then I shut down the VM and do the rollback. As I understand the concept, the rollback should revert everything in nvme-tank to the state it was when I took the snapshot, before making rbtest.txt.



~$ sudo zfs rollback nvme-tank@roll_test


I then reboot the vm, check for rbtest.txt, and there it is, still there!
enter image description here



The snapshot is there:



~$ zfs list -t all -r nvme-tank
NAME USED AVAIL REFER MOUNTPOINT
nvme-tank 887G 12.1G 24K /media/nvme-tank
nvme-tank@nov82018 0B - 24K -
nvme-tank@roll_test 0B - 24K -
nvme-tank/ext4-zvol 474G 449G 37.8G -
nvme-tank/ntfs-zvol 413G 23.9G 401G -


So, am I misunderstanding what snapshots are supposed to do, using them incorrectly, or is something broken with my zfs?






zfs snapshot zfsonlinux rollback







share|improve this question

























    up vote
    3
    down vote

    favorite












    I am confused about how ZFS snapshots and rollback are supposed to work.
    I have a zpool containing a couple zvols (each made from partitions of a mirrorvdev). I make a snapshot like this:



    ~$ sudo zfs snapshot nvme-tank@roll_test


    Then I boot a VM located on one of the zvols in the zpool and create a test file



    ~$ echo "This is a test of the rollback system" > rbtest.txt


    Then I shut down the VM and do the rollback. As I understand the concept, the rollback should revert everything in nvme-tank to the state it was when I took the snapshot, before making rbtest.txt.



    ~$ sudo zfs rollback nvme-tank@roll_test


    I then reboot the vm, check for rbtest.txt, and there it is, still there!
    enter image description here



    The snapshot is there:



    ~$ zfs list -t all -r nvme-tank
    NAME USED AVAIL REFER MOUNTPOINT
    nvme-tank 887G 12.1G 24K /media/nvme-tank
    nvme-tank@nov82018 0B - 24K -
    nvme-tank@roll_test 0B - 24K -
    nvme-tank/ext4-zvol 474G 449G 37.8G -
    nvme-tank/ntfs-zvol 413G 23.9G 401G -


    So, am I misunderstanding what snapshots are supposed to do, using them incorrectly, or is something broken with my zfs?






    zfs snapshot zfsonlinux rollback







    share|improve this question























      up vote
      3
      down vote

      favorite









      up vote
      3
      down vote

      favorite











      I am confused about how ZFS snapshots and rollback are supposed to work.
      I have a zpool containing a couple zvols (each made from partitions of a mirrorvdev). I make a snapshot like this:



      ~$ sudo zfs snapshot nvme-tank@roll_test


      Then I boot a VM located on one of the zvols in the zpool and create a test file



      ~$ echo "This is a test of the rollback system" > rbtest.txt


      Then I shut down the VM and do the rollback. As I understand the concept, the rollback should revert everything in nvme-tank to the state it was when I took the snapshot, before making rbtest.txt.



      ~$ sudo zfs rollback nvme-tank@roll_test


      I then reboot the vm, check for rbtest.txt, and there it is, still there!
      enter image description here



      The snapshot is there:



      ~$ zfs list -t all -r nvme-tank
      NAME USED AVAIL REFER MOUNTPOINT
      nvme-tank 887G 12.1G 24K /media/nvme-tank
      nvme-tank@nov82018 0B - 24K -
      nvme-tank@roll_test 0B - 24K -
      nvme-tank/ext4-zvol 474G 449G 37.8G -
      nvme-tank/ntfs-zvol 413G 23.9G 401G -


      So, am I misunderstanding what snapshots are supposed to do, using them incorrectly, or is something broken with my zfs?






      zfs snapshot zfsonlinux rollback







      share|improve this question













      I am confused about how ZFS snapshots and rollback are supposed to work.
      I have a zpool containing a couple zvols (each made from partitions of a mirrorvdev). I make a snapshot like this:



      ~$ sudo zfs snapshot nvme-tank@roll_test


      Then I boot a VM located on one of the zvols in the zpool and create a test file



      ~$ echo "This is a test of the rollback system" > rbtest.txt


      Then I shut down the VM and do the rollback. As I understand the concept, the rollback should revert everything in nvme-tank to the state it was when I took the snapshot, before making rbtest.txt.



      ~$ sudo zfs rollback nvme-tank@roll_test


      I then reboot the vm, check for rbtest.txt, and there it is, still there!
      enter image description here



      The snapshot is there:



      ~$ zfs list -t all -r nvme-tank
      NAME USED AVAIL REFER MOUNTPOINT
      nvme-tank 887G 12.1G 24K /media/nvme-tank
      nvme-tank@nov82018 0B - 24K -
      nvme-tank@roll_test 0B - 24K -
      nvme-tank/ext4-zvol 474G 449G 37.8G -
      nvme-tank/ntfs-zvol 413G 23.9G 401G -


      So, am I misunderstanding what snapshots are supposed to do, using them incorrectly, or is something broken with my zfs?






      zfs snapshot zfsonlinux rollback




      zfs snapshot zfsonlinux rollback






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      asked 3 hours ago









      Thoughtcraft

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          You only snapshotted nvme-tank, but you didn't snapshot either of nvme-tank/ext4-zvol or nvme-tank/ntfs-zvol, one of which contains the file you created. So nothing happened because you were snapshotting a different dataset than the one you created the file in.



          If you want snapshots to be recursive to descendent datasets/zvols, you have to explicitly ask for recursive snapshots, with zfs snapshot -r. However, you can only rollback one specific dataset/zvol at a time with zfs rollback.






          share|improve this answer




















          • Additionally, in OpenZFS a new feature channel programs (illumos version of the man page) will allow you to recursively rollback a bunch of datasets at once, but you'll have to write a short Lua script to implement that specific function.
            – Dan
            2 hours ago











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          up vote
          3
          down vote



          accepted










          You only snapshotted nvme-tank, but you didn't snapshot either of nvme-tank/ext4-zvol or nvme-tank/ntfs-zvol, one of which contains the file you created. So nothing happened because you were snapshotting a different dataset than the one you created the file in.



          If you want snapshots to be recursive to descendent datasets/zvols, you have to explicitly ask for recursive snapshots, with zfs snapshot -r. However, you can only rollback one specific dataset/zvol at a time with zfs rollback.






          share|improve this answer




















          • Additionally, in OpenZFS a new feature channel programs (illumos version of the man page) will allow you to recursively rollback a bunch of datasets at once, but you'll have to write a short Lua script to implement that specific function.
            – Dan
            2 hours ago















          up vote
          3
          down vote



          accepted










          You only snapshotted nvme-tank, but you didn't snapshot either of nvme-tank/ext4-zvol or nvme-tank/ntfs-zvol, one of which contains the file you created. So nothing happened because you were snapshotting a different dataset than the one you created the file in.



          If you want snapshots to be recursive to descendent datasets/zvols, you have to explicitly ask for recursive snapshots, with zfs snapshot -r. However, you can only rollback one specific dataset/zvol at a time with zfs rollback.






          share|improve this answer




















          • Additionally, in OpenZFS a new feature channel programs (illumos version of the man page) will allow you to recursively rollback a bunch of datasets at once, but you'll have to write a short Lua script to implement that specific function.
            – Dan
            2 hours ago













          up vote
          3
          down vote



          accepted







          up vote
          3
          down vote



          accepted






          You only snapshotted nvme-tank, but you didn't snapshot either of nvme-tank/ext4-zvol or nvme-tank/ntfs-zvol, one of which contains the file you created. So nothing happened because you were snapshotting a different dataset than the one you created the file in.



          If you want snapshots to be recursive to descendent datasets/zvols, you have to explicitly ask for recursive snapshots, with zfs snapshot -r. However, you can only rollback one specific dataset/zvol at a time with zfs rollback.






          share|improve this answer












          You only snapshotted nvme-tank, but you didn't snapshot either of nvme-tank/ext4-zvol or nvme-tank/ntfs-zvol, one of which contains the file you created. So nothing happened because you were snapshotting a different dataset than the one you created the file in.



          If you want snapshots to be recursive to descendent datasets/zvols, you have to explicitly ask for recursive snapshots, with zfs snapshot -r. However, you can only rollback one specific dataset/zvol at a time with zfs rollback.







          share|improve this answer












          share|improve this answer



          share|improve this answer










          answered 3 hours ago









          Michael Hampton♦

          160k26296604




          160k26296604











          • Additionally, in OpenZFS a new feature channel programs (illumos version of the man page) will allow you to recursively rollback a bunch of datasets at once, but you'll have to write a short Lua script to implement that specific function.
            – Dan
            2 hours ago

















          • Additionally, in OpenZFS a new feature channel programs (illumos version of the man page) will allow you to recursively rollback a bunch of datasets at once, but you'll have to write a short Lua script to implement that specific function.
            – Dan
            2 hours ago
















          Additionally, in OpenZFS a new feature channel programs (illumos version of the man page) will allow you to recursively rollback a bunch of datasets at once, but you'll have to write a short Lua script to implement that specific function.
          – Dan
          2 hours ago





          Additionally, in OpenZFS a new feature channel programs (illumos version of the man page) will allow you to recursively rollback a bunch of datasets at once, but you'll have to write a short Lua script to implement that specific function.
          – Dan
          2 hours ago


















           

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