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Storage / Stage 7 of 11

LVM snapshots and rollback

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Step 7 of 7 · summary · 2 min

Summary

  • A snapshot keeps the old versions of changed blocks and reads the rest from the origin; if the device fails, it is lost along with the volume.
  • A snapshot's space is used by every change to the origin; at a Data% of 100 the snapshot becomes invalid.
  • A merge returns the whole volume to the snapshot moment and runs with the origin unmounted; a single file comes from the snapshot mounted read-only.
  • The 64 MiB snapshot at the start of the lesson showed the whole 128 MiB volume: it kept only the blocks the update changed and read the rest from the origin.

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Reference for this lesson

Articles

  • cp — copy files and directories — The cp command copies files and directories, with overwrite prompts, preserved permissions and times, recursively.
  • Mounting and fstab — Mounting filesystems: the mount command, persistent mounts in /etc/fstab, UUIDs and options.
  • LVM logical volumes — A logical volume management system allocating physical volume capacity through volume groups.
  • Filesystems: ext4, xfs, fsck — Filesystems: creating one with mkfs, labels and UUIDs, fsck checks, choosing between ext4 and xfs.
Ubuntu 24.04
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