initramfs: lvm sysroot

Only activate the Clear Linux OS rootfs volume.

Add lvm conf file to allow pvscan, but prevent starting the
lvmetad service. Otherwise, if non-root lvms exist, all lvms
are active and the Host OS will hang when starting lvmetad service.

Add new lvm2-mount-sysroot.service to only activate the rootfs
which is identified by the CLR_ROOT logical volume name.

Signed-off-by: Mark D Horn <mark.d.horn@intel.com>

initramfs/etc/lvm/lvm.conf

@@ -0,0 +1,78 @@
+# Configuration section devices.
+# How LVM uses block devices.
+devices {
+	# Configuration option devices/obtain_device_list_from_udev.
+	# Obtain the list of available devices from udev.
+	# This avoids opening or using any inapplicable non-block devices or
+	# subdirectories found in the udev directory. Any device node or
+	# symlink not managed by udev in the udev directory is ignored. This
+	# setting applies only to the udev-managed device directory; other
+	# directories will be scanned fully. LVM needs to be compiled with
+	# udev support for this setting to apply.
+	obtain_device_list_from_udev = 1
+
+	# Configuration option devices/filter.
+	# Limit the block devices that are used by LVM commands.
+	# Run vgscan after changing the filter to regenerate the cache.
+	# See the use_lvmetad comment for a special case regarding filters.
+	#
+	# Example
+	# Accept every block device:
+	# filter = [ "a|.*/|" ]
+	# Reject the cdrom drive:
+	# filter = [ "r|/dev/cdrom|" ]
+	# Work with just loopback devices, e.g. for testing:
+	# filter = [ "a|loop|", "r|.*|" ]
+	# Accept all loop devices and ide drives except hdc:
+	# filter = [ "a|loop|", "r|/dev/hdc|", "a|/dev/ide|", "r|.*|" ]
+	# Use anchors to be very specific:
+	# filter = [ "a|^/dev/hda8$|", "r|.*/|" ]
+	#
+	# This configuration option has an automatic default value.
+	# filter = [ "a|.*/|" ]
+
+	# Configuration option devices/global_filter.
+	# Limit the block devices that are used by LVM system components.
+	# Because devices/filter may be overridden from the command line, it is
+	# not suitable for system-wide device filtering, e.g. udev and lvmetad.
+	# Use global_filter to hide devices from these LVM system components.
+	# The syntax is the same as devices/filter. Devices rejected by
+	# global_filter are not opened by LVM.
+	# This configuration option has an automatic default value.
+	# global_filter = [ "a|.*/|" ]
+
+#	global_filter = [ "a|.*CLR_ROOT.*|", "r|.*|" ]
+}
+
+# Configuration section global.
+# Miscellaneous global LVM settings.
+global {
+	# Configuration option global/use_lvmetad.
+	# Use lvmetad to cache metadata and reduce disk scanning.
+	# When enabled (and running), lvmetad provides LVM commands with VG
+	# metadata and PV state. LVM commands then avoid reading this
+	# information from disks which can be slow. When disabled (or not
+	# running), LVM commands fall back to scanning disks to obtain VG
+	# metadata. lvmetad is kept updated via udev rules which must be set
+	# up for LVM to work correctly. (The udev rules should be installed
+	# by default.) Without a proper udev setup, changes in the system's
+	# block device configuration will be unknown to LVM, and ignored
+	# until a manual 'pvscan --cache' is run. If lvmetad was running
+	# while use_lvmetad was disabled, it must be stopped, use_lvmetad
+	# enabled, and then started. When using lvmetad, LV activation is
+	# switched to an automatic, event-based mode. In this mode, LVs are
+	# activated based on incoming udev events that inform lvmetad when
+	# PVs appear on the system. When a VG is complete (all PVs present),
+	# it is auto-activated. The auto_activation_volume_list setting
+	# controls which LVs are auto-activated (all by default.)
+	# When lvmetad is updated (automatically by udev events, or directly
+	# by pvscan --cache), devices/filter is ignored and all devices are
+	# scanned by default. lvmetad always keeps unfiltered information
+	# which is provided to LVM commands. Each LVM command then filters
+	# based on devices/filter. This does not apply to other, non-regexp,
+	# filtering settings: component filters such as multipath and MD
+	# are checked during pvscan --cache. To filter a device and prevent
+	# scanning from the LVM system entirely, including lvmetad, use
+	# devices/global_filter.
+	use_lvmetad = 0
+}

initramfs/usr/lib/systemd/system/initrd-root-device.target.wants/lvm2-mount-sysroot.service

@@ -0,0 +1 @@
+../lvm2-mount-sysroot.service

initramfs/usr/lib/systemd/system/lvm2-mount-sysroot.service

@@ -0,0 +1,12 @@
+[Unit]
+Description=LVM2 mount sysroot before switching to rootfs
+DefaultDependencies=no
+Before=initrd-root-device.target
+
+[Service]
+Type=oneshot
+ExecStart=-/bin/lvm lvchange --select lv_name=~CLR_ROOT -a y
+TimeoutStartSec=0
+
+[Install]
+WantedBy=initrd-root-device.target