Date: Fri, 27 May 2011 16:16:51 +0200 From: Arnaud Houdelette <tzim@tzim.net> To: Andriy Gapon <avg@FreeBSD.org> Cc: freebsd-stable@FreeBSD.org Subject: Re: zfs-root and "safe" atomic updates Message-ID: <a4dc7c5cc5e907c09e1baf8dab0d2156@tzim.net> In-Reply-To: <4DDF8E02.4060108@FreeBSD.org> References: <63454684d7d46c2ef76cfcc979500612@tzim.net> <4DDF8E02.4060108@FreeBSD.org>
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On Fri, 27 May 2011 14:41:54 +0300, Andriy Gapon wrote: > on 27/05/2011 14:08 tzim@tzim.net said the following: >> 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 > > Just for the records, I would like to poin out that kernel.old would > be loaded > from zfs:tank/root. > Yes indeed. (...) >> 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 ? > > I am not aware of any plans to implement nextboot for zfs as it would > require at > least some write support for zpool and there is none (for boot code) > at the moment. > Could'nt the loader use a bit flag in the loader sector ? Nextboot (or something equivalent) missing is the sole thing keeping me from removing ufs boot partition for remote servers. >> What do you think ? How do you address the problem ? > > I have some patches that allow to boot a different loader or a kernel > from a > different (non-bootfs) ZFS dataset: > http://lists.freebsd.org/pipermail/freebsd-fs/2010-July/008976.html > But that still requires access to zfs boot and/or loader command > interface. Interesting though. Thanks. Does the mentionned patch still works with latest 8-stable loader ? And do you still have to change vfs.root.mountfrom once currdev set ?
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