Commit a637bdb8 authored by Gerardo Exequiel Pozzi's avatar Gerardo Exequiel Pozzi
Browse files

[archiso] Add optional OverlayFS support

This is the first attemp to test overlayfs in archiso.
The current dm-snapshot mode is keep and is enabled by default,
while the new mode is enabled via "-s sfs" to mkarchiso.
No new boot parameters are added, since archiso hooks detects
if the .sfs file is for dm-snapshot (airootfs.img inside)
or for overlayfs.
Persistence is supported in overlayfs mode using the same options
(cowlabel or cowdevice), but warning while in dm-snapshot mode,
only one file is used (airootfs.cow), in overlayfs mode internal
files for workdir/ and upperdir/ are allocated, so you can not use

To test this, you need to enable [testing] in pacman.conf from
releng profile and edit then add "-s sfs" in make_prepare()

Look at:
    setarch ${arch} mkarchiso ${verbose} -w "${work_dir}" -D "${install_dir}" prepare
Replace with:
    setarch ${arch} mkarchiso ${verbose} -w "${work_dir}" -s sfs -D "${install_dir}" prepare

The build requires just half of space that the build for dm-snapshot,
since there is no ext4 img ;)

Just to remember: there is no space gain in .sfs (just about 2M)

There is at least one thing during boot with machine-id service:
Dec 24 03:31:39 archiso systemd-machine-id-commit[183]: Failed to unmount transient /etc/machine-id file in our private namespace: Invalid argument

Signed-off-by: default avatarGerardo Exequiel Pozzi <>
parent fe29d5f3
# args: source, newroot, mountpoint
_mnt_fs() {
_mnt_dmsnapshot() {
local img="${1}"
local newroot="${2}"
local mnt="${3}"
......@@ -37,6 +37,16 @@ _mnt_fs() {
echo $(readlink -f /dev/mapper/${dm_snap_name}) >> /run/archiso/used_block_devices
# args: source, newroot, mountpoint
_mnt_overlayfs() {
local src="${1}"
local newroot="${2}"
local mnt="${3}"
mkdir -p /run/archiso/cowspace/${cow_directory}/upperdir /run/archiso/cowspace/${cow_directory}/workdir
mount -t overlay -o lowerdir=${src},upperdir=/run/archiso/cowspace/${cow_directory}/upperdir,workdir=/run/archiso/cowspace/${cow_directory}/workdir airootfs "${newroot}${mnt}"
# args: /path/to/image_file, mountpoint
_mnt_sfs() {
local img="${1}"
......@@ -165,7 +175,11 @@ archiso_mount_handler() {
mkdir -p "/run/archiso/cowspace/${cow_directory}"
_mnt_sfs "/run/archiso/bootmnt/${archisobasedir}/${arch}/airootfs.sfs" "/run/archiso/sfs/airootfs"
_mnt_fs "/run/archiso/sfs/airootfs/airootfs.img" "${newroot}" "/"
if [[ -f "/run/archiso/sfs/airootfs/airootfs.img" ]]; then
_mnt_dmsnapshot "/run/archiso/sfs/airootfs/airootfs.img" "${newroot}" "/"
_mnt_overlayfs "/run/archiso/sfs/airootfs" "${newroot}" "/"
if [[ "${copytoram}" == "y" ]]; then
umount /run/archiso/bootmnt
......@@ -4,6 +4,7 @@ build() {
add_module "cdrom"
add_module "loop"
add_module "dm-snapshot"
add_module "overlay"
......@@ -16,6 +16,7 @@ iso_application="Arch Linux Live/Rescue CD"
# Show an INFO message
......@@ -87,6 +88,10 @@ _usage ()
echo " Default: '${work_dir}'"
echo " -o <out_dir> Set the output directory"
echo " Default: '${out_dir}'"
echo " -s <sfs_mode> Set SquashFS image mode (img or sfs)"
echo " img: prepare airootfs.sfs for dm-snapshot usage"
echo " sfs: prepare airootfs.sfs for overlayfs usage"
echo " Default: ${sfs_mode}"
echo " -c <comp_type> Set SquashFS compression type (gzip, lzma, lzo, xz)"
echo " Default: '${sfs_comp}'"
echo " -v Enable verbose output"
......@@ -193,8 +198,8 @@ _cleanup () {
_msg_info "Done!"
# Makes a filesystem from a source directory.
_mkairootfs () {
# Makes a ext4 filesystem inside a SquashFS from a source directory.
_mkairootfs_img () {
if [[ ! -e "${work_dir}/airootfs" ]]; then
_msg_error "The path '${work_dir}/airootfs' does not exist" 1
......@@ -224,6 +229,22 @@ _mkairootfs () {
rm ${work_dir}/airootfs.img
# Makes a SquashFS filesystem from a source directory.
_mkairootfs_sfs () {
if [[ ! -e "${work_dir}/airootfs" ]]; then
_msg_error "The path '${work_dir}/airootfs' does not exist" 1
mkdir -p "${work_dir}/iso/${install_dir}/${arch}"
_msg_info "Creating SquashFS image, this may take some time..."
if [[ "${quiet}" = "y" ]]; then
mksquashfs "${work_dir}/airootfs" "${work_dir}/iso/${install_dir}/${arch}/airootfs.sfs" -noappend -comp "${sfs_comp}" -no-progress &> /dev/null
mksquashfs "${work_dir}/airootfs" "${work_dir}/iso/${install_dir}/${arch}/airootfs.sfs" -noappend -comp "${sfs_comp}" -no-progress
_msg_info "Done!"
_mkchecksum () {
_msg_info "Creating checksum file for self-test..."
cd "${work_dir}/iso/${install_dir}/${arch}"
......@@ -292,7 +313,11 @@ command_prepare () {
_show_config prepare
if [[ ${sfs_mode} == "sfs" ]]; then
......@@ -330,7 +355,7 @@ if [[ ${EUID} -ne 0 ]]; then
_msg_error "This script must be run as root." 1
while getopts 'p:r:C:L:P:A:D:w:o:c:vh' arg; do
while getopts 'p:r:C:L:P:A:D:w:o:s:c:vh' arg; do
case "${arg}" in
p) pkg_list="${pkg_list} ${OPTARG}" ;;
r) run_cmd="${OPTARG}" ;;
......@@ -341,6 +366,7 @@ while getopts 'p:r:C:L:P:A:D:w:o:c:vh' arg; do
D) install_dir="${OPTARG}" ;;
w) work_dir="${OPTARG}" ;;
o) out_dir="${OPTARG}" ;;
s) sfs_mode="${OPTARG}" ;;
c) sfs_comp="${OPTARG}" ;;
v) quiet="n" ;;
h|?) _usage 0 ;;
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