ZFS: OpenZFS: lost the ability to boot a BE

[Graham Perrin]

On 30/03/2020 19:47, Graham Perrin wrote:
> I lost the ability to boot the environment named 'r357746', I suspect 
> this occurred after I set it to use OpenZFS in lieu of ZFS.
>
> I would like to edit its /boot/loader.conf (revert to zfs_load="YES") 
> but re: https://github.com/openzfs/zfs/issues/4553 I can not think of 
> a way to mount the dataset.
>
> Please, how can I proceed?

Whilst booted from a different environment, I mounted the dataset whilst 
in single user mode, edited /boot/loader.conf … a little tricky, because 
after the mount I could no longer use zfs commands (ZFS library 
initialisation failed, words to that effect). Then beadm to activate the 
BE, and shutdown -r now

Success :-)

With zfs_load="YES" (in lieu of openzfs_load="YES") the BE is usable.

> ----
>
> Re: ZFS: destroying snapshots without compromising boot environments
>
> On 28/03/2020 15:36, Graham Perrin wrote:
>> On 28/03/2020 15:19, Allan Jude wrote:
>>
>> > You can try to destroy the snapshot, if it is the basis of a clone, 
>> then
>> > you will get an error, that you'd need to destroy the BE first, so you
>> > might decide to keep that snapshot. As long as you don't use the -R 
>> flag
>> > to zfs destroy dataset at snapshot, it will not destroy the clones.
>> >
>> > You can also use 'zfs promote' to make the clone into the parent, 
>> making
>> > the original parent into the clone. This allows you to destroy that
>> > original and the snapshot while keeping the clone.
>>
>> Perfect, thank you. I was nervous about destruction without warning.
>>
>> Below, are the differences (in measurement) between beadm and bectl 
>> to be expected?
>>
>> ----
>>
>> root at momh167-gjp4-8570p:~ # beadm list
>> BE       Active Mountpoint  Space Created
>> Waterfox -      -           15.9G 2020-03-10 18:24
>> r357746f -      -            1.3G 2020-03-20 06:19
>> r359249b NR     /           74.7G 2020-03-28 01:19
>> root at momh167-gjp4-8570p:~ # beadm list -aDs
>> BE/Dataset/Snapshot                            Active Mountpoint 
>> Space Created
>>
>> Waterfox
>>   copperbowl/ROOT/Waterfox                     -      - 137.0M 
>> 2020-03-10 18:24
>>     r359249b at 2020-03-17-21:57:17               -      - 59.2G 
>> 2020-03-17 21:57
>>   copperbowl/ROOT/Waterfox at 2020-03-20-06:19:45 -      - 67.0M 
>> 2020-03-20 06:19
>>
>> r357746f
>>   copperbowl/ROOT/r357746f                     -      - 1.2G 
>> 2020-03-20 06:19
>>     Waterfox at 2020-03-20-06:19:45               -      - 59.2G 
>> 2020-03-20 06:19
>>
>> r359249b
>>   copperbowl/ROOT/r359249b at 2020-03-17-21:57:17 -      - 15.7G 
>> 2020-03-17 21:57
>>   copperbowl/ROOT/r359249b                     NR     / 59.0G 
>> 2020-03-28 01:19
>> root at momh167-gjp4-8570p:~ # bectl list
>> BE       Active Mountpoint Space Created
>> Waterfox -      -          204M  2020-03-10 18:24
>> r357746f -      -          1.21G 2020-03-20 06:19
>> r359249b NR     /          74.7G 2020-03-28 01:19
>> root at momh167-gjp4-8570p:~ # bectl list -aDs
>> BE/Dataset/Snapshot                              Active Mountpoint 
>> Space Created
>>
>> Waterfox
>>   copperbowl/ROOT/Waterfox                       -      - 204M 
>> 2020-03-10 18:24
>>   Waterfox at 2020-03-20-06:19:45                   -      - 67.0M 
>> 2020-03-20 06:19
>>
>> r357746f
>>   copperbowl/ROOT/r357746f                       -      - 1.21G 
>> 2020-03-20 06:19
>>
>> r359249b
>>   copperbowl/ROOT/r359249b                       NR     / 74.7G 
>> 2020-03-28 01:19
>>   r359249b at 2020-03-17-21:57:17                   -      - 15.7G 
>> 2020-03-17 21:57
>> root at momh167-gjp4-8570p:~ # zfs list -t snapshot
>> NAME                                                     USED AVAIL  
>> REFER  MOUNTPOINT
>> copperbowl/ROOT/Waterfox at 2020-03-20-06:19:45            67.0M - 59.2G  -
>> copperbowl/ROOT/r359249b at 2020-03-17-21:57:17            15.7G - 59.2G  -
>> copperbowl/iocage/releases/12.0-RELEASE/root at jbrowsers     8K - 1.24G  -
>> copperbowl/poudriere/jails/head at clean                    328K - 1.89G  -
>> root at momh167-gjp4-8570p:~ # zfs destroy 
>> copperbowl/ROOT/r359249b at 2020-03-17-21:57:17
>> cannot destroy 'copperbowl/ROOT/r359249b at 2020-03-17-21:57:17': 
>> snapshot has dependent clones
>> use '-R' to destroy the following datasets:
>> copperbowl/ROOT/r357746f
>> copperbowl/ROOT/Waterfox at 2020-03-20-06:19:45
>> copperbowl/ROOT/Waterfox
>> root at momh167-gjp4-8570p:~ # date ; uname -v
>> Sat Mar 28 15:30:57 GMT 2020
>> FreeBSD 13.0-CURRENT #1 r359249: Tue Mar 24 00:12:27 GMT 2020 
>> root at momh167-gjp4-8570p:/usr/obj/usr/src/amd64.amd64/sys/GENERIC-NODEBUG
>> root at momh167-gjp4-8570p:~ #
>>