Re: using snapshot for backup: best practise?

[Mark Harmstone <mark@harmstone.com>]

On 26/06/2025 12.43 pm, Ulli Horlacher wrote:
> 
> I am using fsfreeze when running a backup to ensure a consistent filesystem.
> 
> While the backup is running writes to the filesystem are suspended and the
> whole system is unresponsive, e.g. logins are not possible.
> On certain errors the unfreeze will not happen and the system is locked
> forever.
> 
> Using snapshots seems a better idea for backups :-)
> 
> But snapshots do not include subvolumes.

Omar Sandoval had patches to add recursive snapshotting to btrfs-progs, but
they never made it in, for reasons I can't remember.

> For example the / filesystem has the subvolumes:
> /home
> /home/tux/test
> /var/spool
> 
> When I run the command:
> 
> btrfs subvolume snapshot / /.snapshot/_
> 
> the snapshot will contain only the root subvolume.
> 
> I have to manually add:
> 
> rmdir /.snapshot/_/home
> btrfs subvolume snapshot /home /.snapshot/_/home
> rmdir /.snapshot/_/home/tux/test
> btrfs subvolume snapshot /home/tux/test /.snapshot/_/home/tux/test
> rmdir /.snapshot/_/var/spool
> btrfs subvolume snapshot /var/spool /.snapshot/_/var/spool
> 
> Then run the backup on /.snapshot/_ und afterwards:
> 
> btrfs subvolume del /.snapshot/_/var/spool
> btrfs subvolume del /.snapshot/_/home/tux/test
> btrfs subvolume del /.snapshot/_/home
> btrfs subvolume del /.snapshot/_
> 
> But this will work only for this special example!
> And I have hundreds of systems to backup with different filesystem layout!
> 
> Is there a best practise "Using snapshots for making backup"?
> I need automatic detecting, creating and removing of nested snapshots.
>