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

Question

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.

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.

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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?

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).

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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.

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Read the docs for more information.

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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.

Comments

[pLumo]

Why do you think that you "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. You can restore from a live usb.

[Admin]

@RoVo - I was asking whether that's the case. I had heard about restoring from a live usb but I don't understand how that works, I haven't found details.

[Admin]

Great. I only need a "perfect" saved form of my system that I could restore later, I don't need constant snapshots because I don't need the last form of my system but an initial one. In this respect snapshots are similar to saved partitions without the difficulties. - Your answer clarifies the most important aspects, but my question was intended for a more general comparison between images and snapshots. For example: given that snapshots have the aforementioned advantages: are there any theoretical pros of saving system partition images instead of system snapshots?

[pLumo]

I will expand my answer.

[Admin]

one advantage of iso images is that they can be easily saved on any support, while snapshots require certain file-systems. I have a lot of external drives all ntfs-formatted, none are suited as such for timeshift. on the other hand iso images of partitions are more difficult to create and especially to restore, and they require the deletion of the previous system, whether that's what I want or not