Date: Fri, 27 May 2011 13:08:53 +0200 From: tzim@tzim.net To: <freebsd-stable@freebsd.org> Subject: zfs-root and "safe" atomic updates Message-ID: <63454684d7d46c2ef76cfcc979500612@tzim.net>
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I use zfs on / for quite some time now on 8-stable. Each time I want to update base, I use those steps : - zfs snapshot tank/root@old - zfs clone tank/root@old tank/root.old - csup / Rebuild world and kernel - install world & kernel - reboot - (mergemaster and all usual post-update stuff) This way, if I unfortunately can't boot, I can revert to old userland & kernel by : - dropping into loader prompt - setting vfs.root.mountfrom to zfs:tank/root.old - booting kernel.old - then rollback tank/root to pre-update snapshot and reboot (again) I see 2 drawbacks to my method : - This wont work if the update screws the loader. - I must be able to access the loader prompt (can't do it on a remote server). Also, world is updated "in place". I think it should be possible to do the installworld & installkernel on a root clone then boot into it (changing tank bootfs property), but then : how to revert to previous state in case of failure ? Is there a "nextboot" thing planed for zfs ? What do you think ? How do you address the problem ?
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