Ubuntu – What are the main differences between a system snapshots (Timeshift) and partition images (saved as iso)

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Following comments under this answer of mine I became interested in the question whether the best option for me in order to back-up a system is a partition back-up as described at the linked answer or a snapshot as created by Timeshift (which I have not yet used).

So, I know what a partition image is and how it can be created and restored, but I would like to know whether snapshots are a better option or not. I have some info about snapshots but I want to know more details on the differences between snapshots and partition isos as far as restoration is concerned.

I see that there are differences between the two types of snapshots created by Timeshift as they are clearly listed once the program starts.

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As my system is on an ext4 partition (and I find preferable to save the snapshot on an external drive), the option that I will use for now is RSYNC. But I am interested about BTRFS, which I plan to use in the future.

The clarifications I need regard mainly the following aspects:

Do I have to run the very system that I have backed-up with Timeshift in order to restore the snapshot?

It seems to me that's the case, contrary to a partition saved as iso. In that case the system that I have just backed-up has to be functional and Timeshift installed in it in order to restore the back-up. But then what is the point of that back-up? Normally I want a back-up in case I lose the backed-up system. If the OS is lost, how can the snapshot be restored?

My idea of a back-up is to save a healthy well customized system that I could restore later when the running system has become bloated or unusable.

It seems to me that the purpose of a snapshot is to constantly make back-ups of the actual running system in its present state. But if the system is not in good health are these back-ups efficient? Or are the snapshots images of various stages/moments of the system that are ALL saved, including an initial, healthy and well-customized one? Even so, how is that to be restored if the running system is lost?

Or maybe I'm wrong and Snapshot can restore a system B onto a system A, thus replacing it?

Best Answer

Do I have to run the very system that I have backed-up with Timeshift in order to restore the snapshot?

That is clearly not the case:

● Snapshots can be restored either from the running system (online restore) or from a live CD (offline restore).

If the OS is lost, how can the snapshot be restored?

● An offline restore is when you restore a system other than the one that you are currently running. If you have a multi-boot setup, then you can boot into one installed OS and then restore another OS that may be installed on another disk. You can also boot from a Linux Live CD or USB, install Timeshift and then restore the installed system. An offline restore using a Live CD/USB may be required if your installed system is not bootable.

● The snapshots to be restored can be of any Linux distribution. [...] Timeshift will take care of things like reinstalling the bootloader and other details.

Read the docs for more information.

Benefits of using Timeshift (rsync) compared to cloning your disk:

  • Only first backup is a full backup, the following backups are incremental.

    • saves a lot of disk space
    • backing up is much faster
    • You can restore your system to any point in time you have backups for

  • Thimeshift will not backup unused space.

  • On restore, you can choose whether to restore the bootlader or not.
  • On restore, you can choose which files to keep and which files to restore.

Benefits of cloning your disk compared to Timeshift (rsync):

  • Doesn't need to be stored on a Linux File System.
  • Use standard Linux tool to restore.

Benefits of using Timeshift (BTRFS):

  • Backup happens on File System level using file system features only.
  • Initial backup is fast and doesn't use any space
  • Backup on the same disk, no additional disks needed

but ...

  • Needs BTRFS with special layout on the system
  • Backup on the same disk means data loss if disk is broken.
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