Date: Wed, 24 Jul 2013 21:55:24 +0800 From: Julian Elischer <julian@freebsd.org> To: Andriy Gapon <avg@FreeBSD.org> Cc: freebsd-fs@FreeBSD.org, freebsd-rc@FreeBSD.org Subject: Re: rc.d support for zfs boot environments Message-ID: <51EFDCCC.4040205@freebsd.org> In-Reply-To: <51EFB254.8070807@FreeBSD.org> References: <51EFB254.8070807@FreeBSD.org>
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On 7/24/13 6:54 PM, Andriy Gapon wrote:
> I would like to add another rc.d script or extend the current rc.d/zfs script
> for enhanced support of ZFS boot environments.
isn't this what PC-BSD are working on?
>
> To be short, a ZFS boot environment is a filesystem that typically has loader,
> kernel and can be mounted as a root filesystem. By having multiple filesystems
> of this kind a user can easily select which one to boot to. This allows for
> things like having known good configurations, easily recovering from failed
> upgrades, experimenting with new code, etc.
>
> One of the features of boot environments is support for subordinate filesystems.
> For example:
> NAME MOUNTPOINT CANMOUNT
> pond/ROOT/20130331 /pond/ROOT/20130331 noauto
> pond/ROOT/20130331/usr /usr off
> pond/ROOT/20130331/usr/local /usr/local noauto
> pond/ROOT/20130331/usr/local/etc /usr/local/etc noauto
> pond/ROOT/kms /pond/ROOT/kms noauto
> pond/ROOT/kms/usr /usr off
> pond/ROOT/kms/usr/local /usr/local noauto
> pond/ROOT/kms/usr/local/etc /usr/local/etc noauto
>
> 20130331 and kms are two boot environments here.
> .../usr, .../usr/local, .../usr/local/etc are their subordinate datasets /
> filesystems.
> The idea is that one can have filesystems that are tied to a boot environment.
> These filesystems hold files that must be in the boot environment but they are
> better to be stored in a different filesystem than the main one. There can be
> different reasons for this like a need for different ZFS properties or
> convenience of separate management (snapshots, cloning, etc).
>
> Because these filesystems should not be automatically mounted during boot they
> are configured with canmount=noauto. The root filesystem is mounted
> automatically by the kernel. But the subordinate filesystems are not mounted by
> rc.d/zfs -> zfs mount -a because of the canmount property. So they need to be
> mounted explicitly.
>
> Below is a patch that I have for this case.
> I would like to ask both fs@ and rc@ communities to review the patch for
> correctness, soundness and style. I will appreciate any suggestions and comments.
> If you are already using boot environments and think that you may need to use
> subordinate datasets, then testing is most welcome too.
>
> commit df1df94f75a13f611a8234b01bfb9d6b43172c45
> Author: Andriy Gapon <avg@icyb.net.ua>
> Date: Sun Jul 7 21:01:27 2013 +0300
>
> rc.d/zfsbe: a new script designed for boot environment support
>
> currently it ensures that subordinate datasets are mounted at the
> right points.
>
> diff --git a/etc/rc.d/zfs b/etc/rc.d/zfs
> index 598723a..3c40043 100755
> --- a/etc/rc.d/zfs
> +++ b/etc/rc.d/zfs
> @@ -4,7 +4,7 @@
> #
>
> # PROVIDE: zfs
> -# REQUIRE: mountcritlocal
> +# REQUIRE: zfsbe
>
> . /etc/rc.subr
>
> diff --git a/etc/rc.d/zfsbe b/etc/rc.d/zfsbe
> new file mode 100755
> index 0000000..9e4c50e
> --- /dev/null
> +++ b/etc/rc.d/zfsbe
> @@ -0,0 +1,70 @@
> +#!/bin/sh
> +#
> +# $FreeBSD$
> +#
> +
> +# PROVIDE: zfsbe
> +# REQUIRE: mountcritlocal
> +
> +# Handle boot environment subordinate filesystems
> +# that may have canmount property set to noauto.
> +# For these filesystems mountpoint relative to /
> +# must be the same as their dataset name relative
> +# to BE root dataset.
> +
> +. /etc/rc.subr
> +
> +name="zfsbe"
> +rcvar="zfs_enable"
> +start_cmd="be_start"
> +stop_cmd="be_stop"
> +required_modules="zfs"
> +
> +mount_subordinate()
> +{
> + local _be
> +
> + _be=$1
> + zfs list -rH -o mountpoint,name,canmount -s mountpoint -t filesystem $_be | \
> + while read _mp _name _canmount ; do
> + [ "$_canmount" = "off" ] && continue
> + case "$_mp" in
> + "")
> + ;;
> + "legacy")
> + ;;
> + "/")
> + ;;
> + "/$_be")
> + ;;
> + "/$_be/"*)
> + mount -t zfs $_name ${_mp#/$_be}
> + ;;
> + *)
> + zfs mount $_name
> + ;;
> + esac
> + done
> +}
> +
> +be_start()
> +{
> + if [ `$SYSCTL_N security.jail.jailed` -eq 1 ]; then
> + :
> + else
> + mount -p | while read _dev _mp _type _rest; do
> + [ $_mp = "/" ] || continue
> + if [ $_type = "zfs" ] ; then
> + mount_subordinate $_dev
> + fi
> + break
> + done
> + fi
> +}
> +
> +be_stop()
> +{
> +}
> +
> +load_rc_config $name
> +run_rc_command "$1"
>
>
>
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