Re: difficulties replacing a ZFS installer zroot pool with a new zroot pool on a new disk

On 3/29/22 16:16, Russell L. Carter wrote:
> Greetings,
> After many hours, I am stuck trying to replace my spinning rust
> drive with a new SSD.
> 
> Basically I have renamed the old drive pool 'zroot.old' and imported
> it so that it mounts to /mnt/zroot2:
> 
> root@bruno> zfs list | grep zroot.old
> zroot.old                                       89.6G   523G       96K 
> /mnt/zroot2/mnt/zroot.old
> zroot.old/ROOT                                  37.6G   523G       96K  
> none
> zroot.old/ROOT/default                          37.6G   523G     37.6G 
> /mnt/zroot2
> zroot.old/export                                 264K   523G       88K 
> /mnt/zroot2/mnt/zroot.old/export
> zroot.old/export/packages                        176K   523G       88K 
> /mnt/zroot2/mnt/zroot.old/export/packages
> zroot.old/export/packages/stable-amd64-default    88K   523G       88K 
> /mnt/zroot2/mnt/zroot.old/export/packages/stable-amd64-default
> zroot.old/tmp                                    144K   523G      144K 
> /mnt/zroot2/tmp
> zroot.old/usr                                   37.8G   523G       96K 
> /mnt/zroot2/usr
> zroot.old/usr/home                               582M   523G      582M 
> /mnt/zroot2/usr/home
> zroot.old/usr/obj                               6.14G   523G     6.14G 
> /mnt/zroot2/usr/obj
> zroot.old/usr/ports                             27.8G   523G     27.8G 
> /mnt/zroot2/usr/ports
> zroot.old/usr/src                               3.27G   523G     3.27G 
> /mnt/zroot2/usr/src
> zroot.old/var                                   1.89M   523G       96K 
> /mnt/zroot2/var
> zroot.old/var/audit                               96K   523G       96K 
> /mnt/zroot2/var/audit
> zroot.old/var/crash                               96K   523G       96K 
> /mnt/zroot2/var/crash
> zroot.old/var/log                               1.32M   523G     1.32M 
> /mnt/zroot2/var/log
> zroot.old/var/mail                               120K   523G      120K 
> /mnt/zroot2/var/mail
> zroot.old/var/tmp                                176K   523G      176K 
> /mnt/zroot2/var/tmp
> zroot.old/vm                                    14.1G   523G      615M 
> /mnt/zroot2/vm
> zroot.old/vm/debianv9base                       3.79G   523G      120K 
> /mnt/zroot2/vm/debianv9base
> zroot.old/vm/debianv9base/disk0                 3.79G   523G     3.57G  -
> zroot.old/vm/debianv9n2                         9.70G   523G      160K 
> /mnt/zroot2/vm/debianv9n2
> zroot.old/vm/debianv9n2/disk0                   9.70G   523G     11.3G  -
> root@bruno> zfs mount -a
> root@bruno>
> 
> The problem is that /mnt/zroot2/usr/home, /mnt/zroot2/usr, 
> /mnt/zroot2/usr/src are all empty:
> 
> root@bruno> ls /mnt/zroot.old/usr
> root@bruno>
> 
> Even though I can look at the individual datasets and theey're
> still using the same amount data as original.  This is a bit
> unhelpful for migrating over the old configuration.
> 
> The oddball mounting is just the result of several 10s of attempts to
> import and mount so that a) the original zroot pool doesn't clobber the
> new one, and b) attempts to make the datasets visible.
> 
> So can someone enlighten me on the proper way to do this, and possibly
> give a hint how I can get those original datasets visible?   This is
> definitely a new wrinkle for a geezer who has been doing such things
> without (nontrivial) problems for 30 years now.
> 
> Yeah yeah, this is also my backup drive and I should have replicated
> infra over to another system...  I'm a gonna do that next.
> 
> Thanks very much,
> Russell


I recall attempting to install two ZFS FreeBSD OS disks in the same 
machine at the same time, and the results were very confusing.  I 
suggest that you install only one ZFS FreeBSD OS disk at any given time.


If you need to work on the FreeBSD OS disk without booting it, I would 
boot FreeBSD installer media and use the live system/ shell to access 
the ZFS pools and datasets.  I expect that you will want to set the 
"altroot" property when you import any pools.  I am unclear if you will 
need to export the ZFS boot pool ("bootpool") or the ZFS root pool 
("zroot.old"?) if you import them (?).


If the HDD and SSD both have the same interface (e.g. SAS or SATA), if 
the SSD is the same size or larger than the HDD, and if you can revert 
your changes to the HDD so that it is a working FreeBSD instance again, 
you should be able to use a live distribution to clone the HDD to the 
SSD using dd(1), power down, remove the HDD and live media, connect the 
SSD to the interface port the HDD was connected to, and boot the SSD.  I 
would use a Linux live distribution without ZFS support, to ensure that 
the live distribution does not interact with any ZFS content on the HDD 
or SSD before or after the clone.


David