clarification of snapshots

[tessus]

Ok, I think the disconnect is coming to an end.

Snapshots are not traditional snapshots but "streams". As soon as you switch to a stream (which is named snapshot) it starts from the point it was created and starts persisting data from that point forward. There is no going back to that point ever again. <-- This is the important part, which separates this concept from traditional snapshots.

To answer my previous querstions:

when will a snapshot in OPNsense start to persist data? When I make it active for the first time?

Yes, it starts persisting data as soon as it is made active (after the reboot).

this means I cannot use (rollback to) a snapshot more than once.

Yes, this is correct.

how do I rollback to Sept. 2025 when the "default" snapshot was created?

You can't, it is not possible.

[OPNenthu]

You got it.

Since I already typed this out while you were posting...

This is exactly what makes no sense. If I create a snapshot and then do a firmware update, it is an operation. Installing kernel, packages, and whatnot.
So how can I rollback or switch to a point where the new firmware was not installed, if the operations are persisted.

Just 1) activate the snapshot you took before you installed the updates and 2) reboot.  Done.

Everything you did after you took the snapshot will get reverted because those changes exist only in the snapshot that was active at the time (i.e. 'default'), not in the snapshot you took manually.

After you boot into the snapshot you activated manually, it will retain its name.  You can then delete the old 'default' and rename the current one as 'default' if you wish.  Then you're effectively back to where you started.

--

BTW, they appear to be datasets, but the one listed as default is also a snapshot (don't quite understand that).

Code Select Expand

root@firewall:~ # zfs list -t snapshot
NAME                                       USED  AVAIL  REFER  MOUNTPOINT
zroot/ROOT/default@2026-01-15-21:20:50-0   564M      -  1.63G  -

root@firewall:~ # zfs list
NAME                                USED  AVAIL  REFER  MOUNTPOINT
zroot                              2.45G   215G    96K  /zroot
zroot/ROOT                         2.19G   215G    96K  none
zroot/ROOT/20260115212044-25.7.10     8K   215G  1.63G  /   <-- this is a manual "snapshot" I took before upgrade to 25.7.11
zroot/ROOT/default                 2.19G   215G  1.64G  / <-- this is 25.7.11_1


[tessus]

After you boot into the snapshot you activated manually, it will retain its name.  You can then delete the old 'default' and rename the current one as 'default' if you wish.

This is clear to me. Thanks. What I had issues with was that snapshots were not traditional snapshots I could rollback to multiple times.

Your previous post was partly responsible for my understanding of OPNsense snapshots. It finally made click. Thank you!

[passeri]

So how can I rollback or switch to a point where the new firmware was not installed, if the operations are persisted

This is, in terms of my explanation, a configuration change. It is not part of the snapshot, so you can still roll back to the prior configuration.