Date: Sun, 22 Jan 2012 12:25:54 +0000 From: Johannes Totz <johannes@jo-t.de> To: freebsd-fs@freebsd.org Subject: Re: Booting from zfs snapshot Message-ID: <jfgv8j$82s$1@dough.gmane.org> In-Reply-To: <CAPS9%2BSsyvw=Day%2B1XC8HmzWQG3M=GZE=Nt-qaEQiQTPYME9MrA@mail.gmail.com> References: <CAPS9%2BSsyvw=Day%2B1XC8HmzWQG3M=GZE=Nt-qaEQiQTPYME9MrA@mail.gmail.com>
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On 19/01/2012 16:26, Andreas Nilsson wrote: > Hello, > > I'm trying to wrap my head around the process of booting from a zfs > snapshot. I have hit a few roadblocks, which I hope this is the adequate > list to post to regarding those. > > A short note on what I'm trying to achieve might be in order. In short: a > nanobsd system on zfs only. I want to boot from a snapshot so that when I > push out an upgrade with zfs send, I want the root filesystem to remain > unchanged. > > The problems I've hit so far: > *1 Making the zpool.cache file available > *2 Having / mount via entry in fstab. FWIW, I dont use any fstab for my zfs-only machine. Works perfectly fine with mountpoint property. > *1: The zpool.cache is needed to autoimport a pool as I understand it. Is > there a way to force the kernel to import a pool during bootup even though > no zpool.cache is around? What does this file actually contain? > > I made an experiment and booted a disk with zfs root from machine a in > machine b and that worked. I did partition the disk with gpart using a gpt > scheme, and labeled the partition on which the pool resides as os, and upon > creation of the zpool used gpt/os as device. Does this mean that as long as > gpt/os is available, any machine boot this disk will have the zpool > autoimported? Not quite sure I understand you here. Just a note: booting kernel and mounting root fs are two different things. the *zfsloader will happily load the kernel off a pool and boot it but mounting root might fail later (I guess if no cachefile is present?). > > *2: Having a line like > tank/root/8.2-RELEASE-p5@ro / zfs ro 0 0 > in fstab causes mount to throw an error and leave me in single user mode, > when the system is booted however mount can mount a zfs snapshot just fine. > Setting vfs.root.mountfrom in loader.conf works just fine though. -- Sent from my <insert random gadget here>
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