Date: Sat, 28 Apr 2018 14:28:22 +0300 From: Daniel Braniss <danny@cs.huji.ac.il> To: Mark Raynsford <list+org.freebsd.virtualization@io7m.com> Cc: freebsd-virtualization@freebsd.org Subject: Re: Read-only view of a ZFS filesystem inside a bhyve guest? Message-ID: <E3C490E4-F797-473C-BB6B-4C2397353CAD@cs.huji.ac.il> In-Reply-To: <E3FEEF2F-2AFA-4ED1-8342-A0FEEF1A0EFF@cs.huji.ac.il> References: <20180427174341.03373bc8@almond.int.arc7.info> <FCEED1DB-80FA-4407-9017-9B17F6E155B9@cs.huji.ac.il> <20180428113748.72891422@almond.int.arc7.info> <E3FEEF2F-2AFA-4ED1-8342-A0FEEF1A0EFF@cs.huji.ac.il>
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> On 28 Apr 2018, at 14:26, Daniel Braniss <danny@cs.huji.ac.il> wrote: >=20 >=20 >=20 >> On 28 Apr 2018, at 13:37, Mark Raynsford = <list+org.freebsd.virtualization@io7m.com> wrote: >>=20 >> On 2018-04-28T09:08:42 +0300 >> Daniel Braniss <danny@cs.huji.ac.il> wrote: >>=20 >>> since the clients and the server are sharing the zfs volume, >>> I=E2=80=99m doing the following: >>> on the server I did: >>> zfs create -sV 4G h/root.ro <http://root.ro/>; >>> newfs /dev/zvol/h/root.ro <http://root.ro/>; >>> mount /dev/zol/h/root.ro <http://root.ro/>; /mnt >>> copy a working root image to it. >>> umount /mnt >>> the clients then mount it as ro, >>> the vm conflg file has: >>> disk0_type=3Dvirtio-blk=E2=80=9D >>> disk0_name=3D=E2=80=9C/dev/zvol/h/root.ro = <http://root.ro/>=E2=80=9D >>> disk0_dev=3D=E2=80=9Ccustom=E2=80=9D >>>=20 >>> one solution to the fact that the root is read-only is to use = unionfs (probably nullfs will do too) >>>=20 >>> the only problem I have is updating the image. >>=20 >> Wow, didn't know this was possible. Is this safe? Two essentially >> independent operating system instances being able to write to the = same >> zvol? >=20 > that=E2=80=99s why it=E2=80=99s mounted rear-only in the client! grr, hate spell checkers, s/rear/read/ :-) > each client can get another vol for writing, ie /var > if you want to have =E2=80=98permanent=E2=80=99 changes that will = survive reboots. >=20 > updating on the server is possible, but > 1- the changes might not be seen by the client > 2- opened files will have issues >=20 > btw, point 2 is also true for NFS. >=20 > danny >=20 >>=20 >> --=20 >> Mark Raynsford | http://www.io7m.com >>=20 >=20
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