lvm merge

gistfile1.txt

#!/bin/bash

#
# How to prepare:
# - ensure that the lvm thin pool is big enough
# - backup any (most likely /boot and /boot/efi) device with:
#  # mkdir /restoredev
#  # dev=<device>; dd if="$dev" of=/restoredev/$(systemd-escape -p "$dev")
# - make a thin snapshot
# - remove /restoredev
#
# If the thin snapshot is tagged with the <tag> specified with rd.lvm.mergetags=<tag>
# dracut will
# - make a copy of the snapshot
# - merge it back to the original
# - rename the copy back to the name of the snapshot
# - if /restordev appears in the root, then it will restore the images found in
#   that directory. This can be used to restore /boot and /boot/efi
#

type getarg >/dev/null 2>&1 || . /lib/dracut-lib.sh

do_merge() {
    local _conffix
    for tag in $(getargs rd.lvm.mergetags); do
        lvm vgs --noheadings -o vg_name | \
            while read -r vg || [[ -n $vg ]]; do
                unset LVS
                declare -a LVS
                lvs=$(lvm lvs --noheadings -o lv_name "$vg")
                for lv in $lvs; do
                    tags=$(trim "$(lvm lvs --noheadings -o lv_tags "$vg/$lv")")
                    strstr ",${tags}," ",${tag}," || continue
                    if [[ -z $_conffix ]]; then
                        sed -i -e 's/\(^[[:space:]]*\)locking_type[[:space:]]*=[[:space:]]*[[:digit:]]/\1locking_type = 1/' \
                            /etc/lvm/lvm.conf
                        _conffix=1
                    fi

                    info "Creating backup ${lv}_dracutsnap of $vg/$lv"
                    lvm lvcreate -pr -s "$vg/$lv" --name "${lv}_dracutsnap"
                    info "Merging back $vg/$lv to the original LV"
                    lvm lvconvert --merge "$vg/$lv"
                    LVS+=($lv)
                done
                udevadm settle
                lvm vgchange -an "$vg"
                udevadm settle
                lvm vgchange -ay "$vg"
                udevadm settle
                for lv in "${LVS[@]}"; do
                    info "Renaming ${lv}_dracutsnap backup to $vg/$lv"
                    lvm lvrename "$vg" "${lv}_dracutsnap" "${lv}"
                done
            done
    done
    systemctl start sysroot.mount

    if [[ -d /sysroot/restoredev ]]; then
        (
            if cd /sysroot/restoredev; then
                for i in *; do
                    target=$(systemd-escape -pu "$i")
                    if ! [[ -b $target ]]; then
                        warn "Not restoring $target, as the device does not exist"
                        continue
                    fi

                    if ! umount "$target" &> /dev/null; then
                        error "umount '$target' failed"
                        continue
                    fi

                    info "Restoring $target"
                    dd if="$i" of="$target" |& vinfo
                done
            fi
        )
    fi
    systemctl stop sysroot.mount
    info "Rebooting"
    reboot
}

if getarg rd.lvm.mergetags; then
    do_merge
fi