[arch-dev-public] Big changes to LVM2 in testing

[Eric Bélanger]

On Wed, Oct 31, 2012 at 9:05 PM, Thomas Bächler <thomas at archlinux.org> wrote:
> I discovered some new awesomeness in LVM2 (okay, not THAT new, but
> still, so far unknown to me).
>
> In our lvm2 package, I enabled lvmetad - this is a metadata caching
> daemon that reacts to events from udev. I completely reorganized our
> systemd and mkinitcpio lvm integration:
>
> * lvm.service and lvm-on-crypt.service are gone.
> * Once you install lvm2, lvmetad.socket and dmeventd.socket are always
> active in systemd.
> * If you need LVM monitoring, you need to enable lvm-monitoring.service
> (recommended if you use LVM, even if you don't know if you need
> monitoring). I didn't enable this by default because it would always
> start lvmetad.service.
> * LVM is fully hotplugged via udev. You don't need to activate anything,
> LVM volumes will just work. LVM no longer requires
> systemd-udev-settle.service and all the race conditions should be gone.
> * LVM in mkinitcpio is also fully hotplugged, lvmwait= is now a no-op.
> However, LVM in mkinitcpio now requires the udev hook.
>
> This requires that the use_lvmetad = 1 option is set in
> /etc/lvm/lvm.conf - this is now the default, but a .pacnew must be
> merged if it exists.
>
> You can restrict the hotplugging of the volume groups with the
> auto_activation_volume_list option in lvm.conf. If you uncomment that,
> only the listed volumes will be enabled. This is commented out by default.
>
> WARNING: If you have any incomplete or clustered volume groups, none of
> this will work yet! However, I doubt any Arch user uses that.
>

If you use both RAID and LVM, make sure that you use the mdadm_udev
hook instead of the mdadm one. I had to do this change to make my
system boot with the lvm2 package in [testing].