Date: Fri, 16 Sep 2016 16:18:31 -0500 From: Brandon J. Wandersee <brandon.wandersee@gmail.com> To: Matthew Seaman <matthew@FreeBSD.org> Cc: freebsd-questions@freebsd.org Subject: Re: 10.3 zpool/var canmount = off? Message-ID: <86d1k3tufs.fsf@WorkBox.Home> In-Reply-To: <4bd29396-220a-e198-73b9-0de91b74d096@FreeBSD.org> References: <CA8E95A8-DFBA-488D-9060-1F2694E146EF@gmail.com> <4bd29396-220a-e198-73b9-0de91b74d096@FreeBSD.org>
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Matthew Seaman writes: > The point of having zroot/var (with canmount=off) that just acts as a > placeholder is so that eg. zroot/var/log or zroot/var/tmp (which you'll > see have 'canmount=on') get mounted in the right location in the file > system without becoming part of any boot environment. That means > there's only one copy of those filesystems and it always gets mounted > every time you reboot -- which is really what you want for eg. /var/log > but not correct for boot environments in general. Usually you'll have > several available, but only one of them should be mounted and active. Matthew covered all the big stuff, but the ability to create dataset trees with non-hierarchical mountpoints, or an unmounted dataset as the root of a dataset tree, is actually a very useful administration trick. Boot environments are one example, but it also lets you manage and easily roll back all parts of a system that are related to each other, but the files for which are stored in different parts of the filesystem. You could, for example, create a dataset tree for every component of an Apache or Nginx configuration. I have a tree of filesystems for everything related to ports/packages except distfiles, so I can roll everything back in lock-step if an upgrade goes bad while avoiding having to download everything again. -- :: Brandon J. Wandersee :: brandon.wandersee@gmail.com :: -------------------------------------------------- :: 'The best design is as little design as possible.' :: --- Dieter Rams ----------------------------------
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