ZFS full system backup hoses the backup host.

[Jan Bramkamp]

On 25/02/16 22:18, Allan Jude wrote:
> On 2016-02-25 15:58, Zaphod Beeblebrox wrote:
>> This violated POLA for me.  I backed up a host using:
>>
>> time zfs send -vRI @backup-1-e zroot at backup-1-f | ssh backuphost "zfs
>> receive -vFud zroot/backup/host"
>>
>>
>> Only to find that the backup host (a week later) failed to reboot?  The
>> problem?  Well... -u on receive marks the filesystem as unmounted only
>> "right now" not "next reboot" and -R on send implies -p (send dataset
>> attributes) and...
>>
>> ... zroot/ROOT/default mountpoint=/ (among others).
>>
>> The only hackish way to fix this I see is to have a list of mountpoints to
>> correct --- which is partially what I'm trying to avoid by using -R --- I
>> just want the whole thing backed up.
>>
>> What have other people done to get around this and/or can we either put in
>> an "ignore properties" on receive flag or a -R on send that doesn't send
>> them?
>
> The sysutils/zxfer script allows you to override properties during
> replication, so I usually set readonly=on and for such a backup would
> set mountpoint=none

Do you know if this is race free or is there a moment on the receiving 
system where it has an (unmounted) dataset with mountpoint=/ which would 
break the system (possibly in interesting ways) after a crash?