Date: Sun, 27 Jul 2014 15:25:57 +0100 From: Mike Clarke <jmc-freebsd2@milibyte.co.uk> To: freebsd-questions@freebsd.org Subject: Re: Backing up zfs system to external disk Message-ID: <1855317.BxjNgUaonN@curlew.lan> In-Reply-To: <1947386.pOQVzt1YdP@curlew.lan> References: <1947386.pOQVzt1YdP@curlew.lan>
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On Saturday 26 July 2014 13:14:16 Mike Clarke wrote: > The script imports the backup pool with the -N option to avoid > mounting filesystems on top of the running system, updates the > backup pool to the latest snapshot with zfs send | zfs receive and > then exports the backup pool. > > This normally works fine except in the rare cases when the system > is shut down or crashes while the backup pool is still imported. > If this happens then problems arise on the next reboot because > filesystems will be mounted from both the system and backup pools > using identical mountpoints. After further study of the manpages and some experiments I now see the cause of my problem. I should have used "zpool import -N -o cachefile=none". This creates a temporary pool which is not cached so will not be available for mounting next time the system is booted. This now leads me to wonder why the -N option doesn't follow the design of "-R /some_mountpoint" and "-o altroot=/some_mountpoint", both of which default to set cachefile to none. Is there some subtle reason for the -N option not doing the same or is this a bug in the system? I can't imagine any situation where anyone would want to import a pool without mounting it and require it to be automatically mounted after rebooting. -- Mike Clarke
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