Downgrading 13.1 to 12.4 for fun?

decuser

decuser

I'm not sure it's fun, but I didn't think it'd be painful. However, when I went to import my zpool, I got:

Code: 
zpool import
   pool: zfs
     id: 1387220501496143749
  state: UNAVAIL
status: The pool can only be accessed in read-only mode on this system. It
    cannot be accessed in read-write mode because it uses the following
    feature(s) not supported on this system:
    org.zfsonlinux:userobj_accounting (User/Group object accounting.)
    org.zfsonlinux:project_quota (space/object accounting based on project ID.)
    com.delphix:log_spacemap (Log metaslab changes on a single spacemap and flush them periodically.)
action: The pool cannot be imported in read-write mode. Import the pool with
    "-o readonly=on", access the pool on a system that supports the
    required feature(s), or recreate the pool from backup.
 config:

    zfs           UNAVAIL  unsupported feature(s)
      mirror-0    ONLINE
        ada1      ONLINE
        ada2      ONLINE
      indirect-1  ONLINE
root@loki:~ # zpool import zfs
This pool uses the following feature(s) not supported by this system:
    org.zfsonlinux:userobj_accounting (User/Group object accounting.)
    org.zfsonlinux:project_quota (space/object accounting based on project ID.)
    com.delphix:log_spacemap (Log metaslab changes on a single spacemap and flush them periodically.)
All unsupported features are only required for writing to the pool.
The pool can be imported using '-o readonly=on'.
cannot import 'zfs': unsupported version or feature

I'm a guessing here, but it is probably a version mismatch between the zfs in 13 and 12. I recall having this kind of issue once before when migrating between linux and freebsd.

The solution, if I recall properly was to basically mount the pool read only and export it to a new pool. Does this sound correct? It's not a humongous dataset.

What's the easiest way to restore it that's safe?

Currently I have the zroot pool with 900 gigs free and the unmounted mirrored 1000G pool (with about 16 gigs of data on it).

Thanks!
 
13.x is using OpenZFS, 12.x is using "ZFS from FreeBSD/IllumOS". If the pool was created under 13.x it's as if you did zpool upgrade to an incompatible version.
 
By accident i upgraded my zpool to newer features. But i had it fixed by upgrading only /boot directory in order to mount it.
My /boot/boot* is from 14. But my kernel is 13.
 
Sure. I know downgrades aren't 'supported'. I kind of implied it in the question, but maybe I misled unintentionally. Here's how I got here:

1. I had a 13.1 system with two pools - zfsroot (stripe) and zfs (mirrored pool)
2. I exported zfs pool
3. I installed a fresh 12.4 system on the ada0 device (becoming a new zfsroot)

Now I'm wanting to create a new mirrored zfs pool in 12.4 from the data that's on the current 13.1 pool which is mountable read only zpool import -o readonly=on zfs and the data seems fine.

I don't see any real reason why I can't do it, knowing full well that 13.1 is more modern, cooler, maybe even better.
 
Ah. I found my notes. Once I complete the restore, I'll post the solution. Straightforward, but who knows if they'll be useful to anyone else :).
 
Easy as they come - I did a bunch of stuff to ensure that the restore was byte identical, but it boiled down to:

Mount the pool readonly:
Code: 
zpool import -o readonly=on zfs

Use rsync to backup the files (just for comparison really):
Code: 
rsync -vaz /zfs/{fossils,scm} .
diff -r fossils /zfs/fossils
diff -r scm /zfs/scm

Use zfs to send the data to a file (the real work):
Code: 
zfs send zfs/fossils > t/fossils-backup
zfs send zfs/scm > t/scm-backup

Use dd to create some empty files to hold the temporarily restored mounts:
Code: 
dd if=/dev/zero of=/temp-scm bs=1M count=20000
dd if=/dev/zero of=/temp-fossils bs=1M count=5000

Use zpool to create the temporary pools:
Code: 
zpool create t-fossils /temp-fossils
zpool create t-scm /temp-scm

Use zfs to recv the backups into the temp pools and compare the files:
Code: 
zfs recv -F t-fossils < t/fossils-backup
zfs recv -F t-fossils < t/scm-backup
diff -r /t-fossils /zfs/fossils
diff -r /t-scm /zfs/scm

Remove the existing 13.1 pool and its cruft:
Code: 
zpool destroy -r zfs
zpool labelclear -f ada1
zpool labelclear -f ada2
gpart destroy -F ada1

Create the new mirror and its mounts:
Code: 
zpool create zfs mirror ada1 ada2
zfs create -o compression=off zfs/fossils
zfs create -o compression=off zfs/scm

Create a snapshot on the first temp pool, restore it into the new mount, and clean up after:
Code: 
zfs snapshot t-fossils@snap1
zfs send t-fossils@snap1 | zfs recv -Fd zfs/fossils
zfs list -t snapshot
zfs destroy t-fossils@snap1
zfs destroy zfs/fossils@snap1

Compare it:
Code: 
diff -r /zfs/fossils scm-bak/fossils

Create a snapshot on the second temp pool, restore it into the new mount, and clean up after:
Code: 
zfs snapshot t-scm@snap1
zfs send t-scm@snap1 | zfs recv -Fd zfs/scm
zfs list -t snapshot
zfs destroy t-scm@snap1
zfs destroy zfs/scm@snap1

Compare it:
Code: 
diff -r /zfs/scm scm-bak/scm

Clean up the remaining cruft and see what love hath wrought:
Code: 
zpool destroy t-fossils
zpool destroy t-scm
rm -fr /root/scm-bak
zpool status

So bottom line. No problems at all, just a bit of patience and a lot of free disk space.
 
I heart FreeBSD (and ZFS) - where else can you swap out major versions (completely unsupported, of course) so easily and not screw stuff up royally?

Code: 
uname -a

FreeBSD loki.sentech.home 12.4-RELEASE FreeBSD 12.4-RELEASE r372781 GENERIC  amd64


zpool status

  pool: zfs

 state: ONLINE

  scan: none requested

config:


    NAME        STATE     READ WRITE CKSUM

    zfs         ONLINE       0     0     0

      mirror-0  ONLINE       0     0     0

        ada1    ONLINE       0     0     0

        ada2    ONLINE       0     0     0
 
decuser said:
gpart destroy -F ada1
Click to expand...
Did you forget ada2 by any chance?
Sorry, this nitpicking comes with the job :/

Otherwise, good job on this. I would not have thought of this way. And another fossil user. I like it.
 
Crivens said:
Did you forget ada2 by any chance?
Sorry, this nitpicking comes with the job :/

Otherwise, good job on this. I would not have thought of this way. And another fossil user. I like it.
Click to expand...

Well, that was interesting. I actually did do ada2, but it didn't have a partition to destroy, so I left it out of the note... maybe something to do with the way zfs mirrors?

I heart fossil, made the switch from git to fossil for the bulk of my repos about a year ago. Other than the learning curve, it was smooth and the repos are much, much easier to manage and host... at least for my uses. Somebody hosting a repo for bunches of users might feel differently.
 
You must log in or register to reply here.
Back
Top