From owner-freebsd-stable@freebsd.org Wed May 18 09:51:58 2016 Return-Path: Delivered-To: freebsd-stable@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 8668FB3E0F5 for ; Wed, 18 May 2016 09:51:58 +0000 (UTC) (envelope-from hausen@punkt.de) Received: from kagate.punkt.de (kagate.punkt.de [217.29.33.131]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 2A690188B for ; Wed, 18 May 2016 09:51:57 +0000 (UTC) (envelope-from hausen@punkt.de) Received: from hugo10.ka.punkt.de (hugo10.ka.punkt.de [217.29.44.10]) by gate2.intern.punkt.de with ESMTP id u4I9RwmI071487 for ; Wed, 18 May 2016 11:27:58 +0200 (CEST) Received: from [217.29.44.117] ([217.29.44.117]) by hugo10.ka.punkt.de (8.14.2/8.14.2) with ESMTP id u4I9RwUZ008595 for ; Wed, 18 May 2016 11:27:58 +0200 (CEST) (envelope-from hausen@punkt.de) From: "Patrick M. Hausen" Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Subject: State of unionfs? Message-Id: Date: Wed, 18 May 2016 11:27:59 +0200 To: freebsd-stable Mime-Version: 1.0 (Mac OS X Mail 9.3 \(3124\)) X-Mailer: Apple Mail (2.3124) X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.22 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 18 May 2016 09:51:58 -0000 Hi, all, we were looking for a way to get overlay/copy-on-write mounts for ZFS datasets to ease jail management. Google turned up this old thread: = https://lists.freebsd.org/pipermail/freebsd-fs/2010-September/009221.html So, clearly in September 2010 mount_unionfs(8) was not supported for ZFS datasets. A quick check on a current RELENG-10.3 system showed that this has changed .Union-mounting one dataset on top of another does indeed work at a superficial glance. Yet the manpage for mount_unionfs(8) still contains this disturbing note: BUGS THIS FILE SYSTEM TYPE IS NOT YET FULLY SUPPORTED (READ: IT DOESN'T = WORK) AND USING IT MAY, IN FACT, DESTROY DATA ON YOUR SYSTEM. USE AT = YOUR OWN RISK. BEWARE OF DOG. SLIPPERY WHEN WET. BATTERIES NOT INCLUDED. Is this still the case? Are there alternatives to our approach. What we would like to implement is e.g. a standard pre-populated /etc = for each jail with only modified files being written to a separate per-jail = dataset. Much like NanoBSD does when populating the /etc mfs at boot. While we can create a clone from a central snapshot for each jail, the problem with this way is that we cannot exchange the base snapshot = later, e.g. after a major system update for the jail in question. Which is = precisely the intention in the first place ;-) Thanks for any hints Patrick --=20 punkt.de GmbH * Kaiserallee 13a * 76133 Karlsruhe Tel. 0721 9109 0 * Fax 0721 9109 100 info@punkt.de http://www.punkt.de Gf: J=C3=BCrgen Egeling AG Mannheim 108285