From owner-freebsd-virtualization@freebsd.org Sat Apr 28 11:26:37 2018 Return-Path: Delivered-To: freebsd-virtualization@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id A8635FABA60 for ; Sat, 28 Apr 2018 11:26:37 +0000 (UTC) (envelope-from danny@cs.huji.ac.il) Received: from kabab.cs.huji.ac.il (kabab.cs.huji.ac.il [132.65.116.210]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 3DA5D68C0C for ; Sat, 28 Apr 2018 11:26:36 +0000 (UTC) (envelope-from danny@cs.huji.ac.il) Received: from imac.bk.cs.huji.ac.il ([132.65.179.42]) by kabab.cs.huji.ac.il with esmtp id 1fCNzq-000ONR-TH; Sat, 28 Apr 2018 14:26:30 +0300 Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 11.3 \(3445.6.18\)) Subject: Re: Read-only view of a ZFS filesystem inside a bhyve guest? From: Daniel Braniss In-Reply-To: <20180428113748.72891422@almond.int.arc7.info> Date: Sat, 28 Apr 2018 14:26:30 +0300 Cc: freebsd-virtualization@freebsd.org Content-Transfer-Encoding: quoted-printable Message-Id: References: <20180427174341.03373bc8@almond.int.arc7.info> <20180428113748.72891422@almond.int.arc7.info> To: Mark Raynsford X-Mailer: Apple Mail (2.3445.6.18) X-BeenThere: freebsd-virtualization@freebsd.org X-Mailman-Version: 2.1.25 Precedence: list List-Id: "Discussion of various virtualization techniques FreeBSD supports." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 28 Apr 2018 11:26:37 -0000 > On 28 Apr 2018, at 13:37, Mark Raynsford = wrote: >=20 > On 2018-04-28T09:08:42 +0300 > Daniel Braniss 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 >> newfs /dev/zvol/h/root.ro >> mount /dev/zol/h/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 = =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? that=E2=80=99s why it=E2=80=99s mounted rear-only in the client! 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. updating on the server is possible, but 1- the changes might not be seen by the client 2- opened files will have issues btw, point 2 is also true for NFS. danny >=20 > --=20 > Mark Raynsford | http://www.io7m.com >=20