On Fri, Apr 8, 2016 at 5:01 AM, Martin Steigerwald <martin@xxxxxxxxxxxx> wrote: > Hello! > > As far as I understood, for differential btrfs send/receive – I didn´t use it > yet – I need to keep a snapshot on the source device to then tell btrfs send > to send the differences between the snapshot and the current state. > > Now the BTRFS filesystems on my SSDs are often quite full, thus I do not keep > any snapshots except for one during rsync or borgbackup script run-time. > > Is it possible to tell btrfs send to use generation number xyz to calculate > the difference? This way, I wouldn´t have to keep a snapshot around, I > believe. > > I bet not, at the time cause -c wants a snapshot. Ah and it wants a snapshot > of the same state on the destination as well. Well on the destination I let > the script make a snapshot after the backup so… what I would need is to > remember the generation number of the source snapshot that the script creates > to backup from and then tell btrfs send that generation number + the > destination snapshots. > > Well, or get larger SSDs or get rid of some data on them. Well if you can't even keep one ro snapshot around, it suggests you need more space. Otherwise the minimal strategy is: Yesterday's source has subvols: root.current root.20160406 So you'd do btrfs sub snap -r root.current root.20160407 btrfs send -p root.20160406 root.20160407 | btrfs receive xxx btrfs sub del root.20160406 Today it's btrfs sub snap -r root.current root.20160408 btrfs send -p root.20160407 root.20160408 | btrfs receive xxx btrfs sub del root.20160407 Tomorrow: btrfs sub snap -r root.current root.20160409 btrfs send -p root.20160408 root.20160409 | btrfs receive xxx btrfs sub del root.20160408 Locally you always have one snapshot to rollback to or make selective reflink copies of files from. -- Chris Murphy -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
