Error message - cannot receive incremental stream: most recent snapshot of rpoolbak/data does not match incremental source

[sandreas]

System information

Type	Version/Name
Distribution Name	Debian
Distribution Version	12
Kernel Version	6.5.11-7
Architecture	x64
OpenZFS Version	2.2.2

Describe the problem you're observing

I use the following command to sync an encrypted zfs pool rpool to an external drive rpoolbak:

zfs send --raw -RI "rpool@backup-2025-03-31" "rpool@backup-2025-04-06" | pv | zfs recv -Fdu "rpoolbak"

Which basically translates to clone the sending side 1:1 to the receiving side:

• Destroy snapshots that do not exist on the sending side (-F)
• Replace rpool@with rpoolbak@ / discard the sending sides filesystem name (-d)
• Receiving filesystem is not mounted (-u

This works as expected until I start deleting any older snapshots on the source rpool. As soon as I delete an older snapshot on the SOURCE (! - the destination pool rpoolbak does NOT get modified in any way), I get this message during the backup:

cannot receive incremental stream: most recent snapshot of rpoolbak/data does not match incremental source

It still does "something" (send / receive), but it's not clear, if the resulting copy on rpoolbak is corrupt - it does seem to work though.

In my opinion this should either:

• Show an error and do nothing without -f
• Proceed and don't show an error

Describe how to reproduce the problem

Assuming you have a pool rpool with the following structure and the tool pv installed to watch progress / transfer speed:

rpool
rpool/ROOT
rpool/ROOT/debian
rpool/data
rpool/var-lib-vz

# create backup pool on external drive
zpool create rpoolbak /dev/sdb

# in case you have zfs-auto-snapshot running
zfs set com.sun:auto-snapshot=false rpoolbak

zfs snapshot -r "rpool@backup-2025-03-30"

# full backup
zfs send --raw -R "rpool@backup-2025-03-30" | pv | zfs recv -Fdu rpoolbak

# change some files

# create a "newer" snapshot
zfs snapshot -r "rpool@backup-2025-03-31"

# incremental backup
zfs send --raw -RI "rpool@backup-2025-03-30" "rpool@backup-2025-03-31" | pv | zfs recv -Fdu "rpoolbak"

# change some files

# destroy old snapshot (e.g. to gain space)
zfs destroy rpool@backup-2025-03-30

# create snapshot
zfs snapshot -r "rpool@backup-2025-04-01"

# incremental backup after destroying old snapshot
zfs send --raw -RI "rpool@backup-2025-03-31" "rpool@backup-2025-04-01" | pv | zfs recv -Fdu "rpoolbak"
# error: 
# cannot receive incremental stream: most recent snapshot of rpoolbak/data does not match incremental source