1 files changed, 119 insertions, 0 deletions
diff --git a/modules.d/90dmsquash-live-autooverlay/create-overlay.sh b/modules.d/90dmsquash-live-autooverlay/create-overlay.sh
new file mode 100755
index 0000000..10e8ea5
--- /dev/null
+++ b/modules.d/90dmsquash-live-autooverlay/create-overlay.sh
@@ -0,0 +1,119 @@
+#!/bin/sh
+
+type getarg > /dev/null 2>&1 || . /lib/dracut-lib.sh
+
+if getargbool 0 rd.live.debug -n -y rdlivedebug; then
+    exec > /tmp/create-overlay.$$.out
+    exec 2>> /tmp/create-overlay.$$.out
+    set -x
+fi
+
+gatherData() {
+    overlay=$(getarg rd.live.overlay)
+    if [ -z "$overlay" ]; then
+        info "Skipping overlay creation: kernel command line parameter 'rd.live.overlay' is not set"
+        exit 0
+    fi
+    # shellcheck disable=SC2086
+    if ! str_starts ${overlay} LABEL=; then
+        die "Overlay creation failed: the partition must be set by LABEL in the 'rd.live.overlay' kernel parameter"
+    fi
+
+    overlayLabel=${overlay#LABEL=}
+    # shellcheck disable=SC2086
+    if [ -b /dev/disk/by-label/${overlayLabel} ]; then
+        info "Skipping overlay creation: overlay already exists"
+        exit 0
+    fi
+
+    filesystem=$(getarg rd.live.overlay.cowfs)
+    [ -z "$filesystem" ] && filesystem="ext4"
+    if [ "$filesystem" != "ext4" ] && [ "$filesystem" != "xfs" ] && [ "$filesystem" != "btrfs" ]; then
+        die "Overlay creation failed: only ext4, xfs, and btrfs are supported in the 'rd.live.overlay.cowfs' kernel parameter"
+    fi
+
+    live_dir=$(getarg rd.live.dir)
+    [ -z "$live_dir" ] && live_dir="LiveOS"
+
+    [ -z "$1" ] && exit 1
+    rootDevice=$1
+
+    # The kernel command line's 'root=' parameter was parsed into the $root variable by the dmsquash-live module.
+    # $root contains the path to a symlink within /dev/disk/by-label, which points to a partition.
+    # This script needs that partition's parent block device.
+    # shellcheck disable=SC2046
+    # shellcheck disable=SC2086
+    rootDeviceAbsolutePath=$(readlink -f ${rootDevice})
+    rootDeviceSysfsPath=/sys/class/block/${rootDeviceAbsolutePath##*/}
+    if [ -f "${rootDeviceSysfsPath}/partition" ]; then
+        # shellcheck disable=SC2086
+        read -r partition < ${rootDeviceSysfsPath}/partition
+    else
+        partition=0
+    fi
+    # shellcheck disable=SC2086
+    read -r readonly < ${rootDeviceSysfsPath}/ro
+    # shellcheck disable=SC2086
+    if [ "$partition" != "1" ] || [ "$readonly" != "0" ]; then
+        info "Skipping overlay creation: unpartitioned or read-only media detected"
+        exit 0
+    fi
+    # shellcheck disable=SC2046
+    # shellcheck disable=SC2086
+    fullDriveSysfsPath=$(readlink -f ${rootDeviceSysfsPath}/..)
+    blockDevice=/dev/${fullDriveSysfsPath##*/}
+    currentPartitionCount=$(grep --count -E "${blockDevice#/dev/}[0-9]+" /proc/partitions)
+
+    # shellcheck disable=SC2086
+    freeSpaceStart=$(parted --script ${blockDevice} unit % print free \
+        | awk -v x=${currentPartitionCount} '$1 == x {getline; print $1}')
+    if [ -z "$freeSpaceStart" ]; then
+        info "Skipping overlay creation: there is no free space after the last partition"
+        exit 0
+    fi
+    partitionStart=$((${freeSpaceStart%.*} + 1))
+    if [ $partitionStart -eq 100 ]; then
+        info "Skipping overlay creation: there is not enough free space after the last partition"
+        exit 0
+    fi
+
+    overlayPartition=${blockDevice}$((currentPartitionCount + 1))
+
+    label=$(blkid --match-tag LABEL --output value "$rootDevice")
+    uuid=$(blkid --match-tag UUID --output value "$rootDevice")
+    if [ -z "$label" ] || [ -z "$uuid" ]; then
+        die "Overlay creation failed: failed to look up root device label and UUID"
+    fi
+}
+
+createPartition() {
+    # shellcheck disable=SC2086
+    parted --script --align optimal ${blockDevice} mkpart primary ${partitionStart}% 100%
+}
+
+createFilesystem() {
+    # shellcheck disable=SC2086
+    mkfs.${filesystem} -L ${overlayLabel} ${overlayPartition}
+
+    baseDir=/run/initramfs/create-overlayfs
+    mkdir -p ${baseDir}
+    # shellcheck disable=SC2086
+    mount -t ${filesystem} ${overlayPartition} ${baseDir}
+
+    mkdir -p ${baseDir}/${live_dir}/ovlwork
+    # shellcheck disable=SC2086
+    mkdir ${baseDir}/${live_dir}/overlay-${label}-${uuid}
+
+    umount ${baseDir}
+    rm -r ${baseDir}
+}
+
+main() {
+    gatherData "$1"
+    createPartition
+    udevsettle
+    createFilesystem
+    udevsettle
+}
+
+main "$1"