diff --git a/airootfs/usr/bin/cowpacman2srm b/airootfs/usr/bin/cowpacman2srm
index d6d4328..d3e0d39 100755
--- a/airootfs/usr/bin/cowpacman2srm
+++ b/airootfs/usr/bin/cowpacman2srm
@@ -2,7 +2,7 @@
 #
 # cowpacman2srm - Create SystemRescueModules (SRM) from pacman packages installed into the COW space
 #
-# Author: Gerd v. Egidy
+# Authors: Gerd v. Egidy and Francois Dupoux
 # SPDX-License-Identifier: GPL-3.0-or-later
 #
 # This script is meant to help creating SystemRescueModules (SRM) for SystemRescue.
@@ -10,14 +10,25 @@
 # https://www.system-rescue.org/Modules/
 #
 # To use first install all packages you want to have in your SRM with pacman.
-# Default COW (Copy-On-Write) space is a ramdisk, so you usually don't have to do anything 
+# Default COW (Copy-On-Write) space is a ramdisk, so you usually don't have to do anything
 # special except provide enough RAM.
 # You can also enable any systemd services that are in these packages.
 #
 # Then call:
-# cowpacman2srm [-c compalg] [-l complevel] [-p] [targetfile.srm]
+# cowpacman2srm [-s subcmd] [-c compalg] [-l complevel] [targetfile.srm]
 #
-# Copy the .srm file to archisobasedir (default: "sysresccd") on your boot disk 
+# This script runs in two stages:
+# 1) During the "prepare" stage all files belonging to pacman packages manually installed
+#    are being copied to a temporary directory
+# 2) During the "create" stage the SRM file (which is a squash file system) is being created
+#    with the contents stored in the temporary directory
+# You can either run both stages in a single run (this is the default) or one stage at a time.
+# If you do not specify any sub-command the script is going to run the two stages in one run.
+# If you want to customize the contents of the SRM module you can run the "prepare" stage first,
+# then make customizations in the temporary directory (for example to add extra files) and then
+# you run the "create" stage to produce the SRM file.
+#
+# Copy the .srm file to archisobasedir (default: "sysresccd") on your boot disk
 # and add the "loadsrm" boot parameter to SystemRescue.
 #
 # There is no mechanism to check if a SRM is compatible with the version of SystemRescue
@@ -32,165 +43,127 @@ PKG_FILELIST=${TMP_TARGET}filelist
 # default options
 COMPRESS=zstd
 COMPLEVEL=""
-PREPARE_MODE=0
+SUBCMD="all"
+OPER_PREPARE=0
+OPER_CREATE=0
 
 function usage()
 {
     echo
-    echo "Usage: cowpacman2srm [-c compalg] [-l complevel] [-p] [targetfile.srm]"
+    echo "Usage: cowpacman2srm [-s subcmd] [-c compalg] [-l complevel] [targetfile.srm]"
     echo
-    echo "compalg is any of the compression algorithms supported by mksquashfs (default: zstd)"
-    echo
-    echo "complevel is the compression level for the given algorithm (if supported with -Xcompression-level)"
-    echo
-    echo "-p: prepare mode. Only prepares a directory with all files that would go into the SRM,"
-    echo "    but does not run mksquashfs. This allows further modifications by the user."
-    echo "    In prepare mode the target file parameter is ignored."
+    echo "options:"
+    echo "- subcmd is a sub-command to execute, it can be any of: prepare, create, all. (default: all)"
+    echo "- compalg is any of the compression algorithms supported by mksquashfs (default: zstd)"
+    echo "- complevel is the compression level for the given algorithm (if supported with -Xcompression-level)"
     echo
     exit 1
 }
 
-while getopts "c:l:p" opt; do
-    case "${opt}" in
-        c)
-            COMPRESS="${OPTARG}"
-            ;;
-        l)
-            COMPLEVEL="-Xcompression-level ${OPTARG}"
-            ;;
-        p)
-            PREPARE_MODE=1
-            ;;
-        *)
-            usage
-            ;;
-    esac
-done
+function prepare()
+{
+    # determine the COW target upperdir, read it out from the mount options of /
+    UPPERDIR=$(findmnt --mountpoint / --noheadings --output FS-OPTIONS | sed -e "s/.*upperdir=\([^,]*\),*.*/\1/")
 
-shift $((OPTIND-1))
-TARGETFILE="$1"
-
-if [ -z "$TARGETFILE" ] && [ "$PREPARE_MODE" -eq 0 ]; then
-    echo "ERROR: no target file specified"
-    usage
-fi
-
-if [ -e "$TARGETFILE" ] && [ "$PREPARE_MODE" -eq 0 ]; then
-    echo "ERROR: target file already existing. Please delete."
-    exit 1
-fi
-
-if [ -e "$TMP_TARGET" ]; then
-    echo "ERROR: temporary directory $TMP_TARGET already existing. Please delete."
-    exit 1
-fi
-
-# determine the COW target upperdir, read it out from the mount options of /
-UPPERDIR=$(findmnt --mountpoint / --noheadings --output FS-OPTIONS | sed -e "s/.*upperdir=\([^,]*\),*.*/\1/")
-
-if [ -z "$UPPERDIR" ] || ! [ -d "$UPPERDIR" ]; then
-    echo "ERROR: can't determine upperdir"
-    exit 2
-fi
-
-if ! [ -d "${UPPERDIR}/var/lib/pacman/local/" ]; then
-    echo "ERROR: no packages installed in the COW space"
-    echo "(${UPPERDIR}/var/lib/pacman/local/ not existing)"
-    exit 3
-fi
-
-# read the names of the packages in the COW space
-# package names are in the desc file in the line after the marker %NAME%
-PACKAGENAMES=$(find ${UPPERDIR}/var/lib/pacman/local/ -name desc -exec grep -A1 --no-filename "%NAME%" \{\} \; | grep -v -E "(--|%NAME%)")
-
-if [ -z "$PACKAGENAMES" ]; then
-    echo "ERROR: no packages installed in the COW space"
-    echo "(${UPPERDIR}/var/lib/pacman/local/ empty)"
-    exit 3
-fi
-
-# create temp dir used to store the package list and later the files to put into the SRM
-mkdir -p $TMP_TARGET
-
-# read all filenames installed by the packages in COW space
-# sort to make sure dir names come before files in the dir
-pacman -Q --list --quiet $PACKAGENAMES | sort -u >$PKG_FILELIST
-
-if cat $PKG_FILELIST | wc -l | grep -q "^0$"; then
-    echo "ERROR: empty file list for the installed packages"
-    
-    # clean up
-    rm -rf ${TMP_TARGET}
-
-    exit 3
-fi
-
-echo -n "Found Packages: "
-echo "$PACKAGENAMES" | wc -w
-echo -n "Found Files: "
-cat $PKG_FILELIST | wc -l
-echo
-echo "Copying to temp dir..."
-
-# newline separator for for loops, necessary for filenames with spaces in them
-IFS_SAVE=$IFS
-IFS=$'\n'
-
-# iterate over all files and dirs installed by the packages
-for FILE in `cat $PKG_FILELIST`; do
-    if [ -d "${FILE}" ] && ! [ -L "${FILE}" ]; then
-        # we have a real dir (not a symlink to a dir)
-        # create it below $TMP_TARGET, copy attributes
-        mkdir -p "${TMP_TARGET}${FILE}"
-        chmod "--reference=${FILE}" "${TMP_TARGET}${FILE}"
-        chown "--reference=${FILE}" "${TMP_TARGET}${FILE}"
-    else
-        # we have a file or symlink, copy it, preserving symlinks as such
-        cp "--target-directory=${TMP_TARGET}" --preserve=all --parents --no-dereference "${FILE}"
+    if [ -z "$UPPERDIR" ] || ! [ -d "$UPPERDIR" ]; then
+        echo "ERROR: can't determine upperdir"
+        exit 2
     fi
-done
 
-# copy the pacman package database too
-
-# first create the directories in the tmp space
-for DIR in `find ${UPPERDIR}/var/lib/pacman/local/ -type d -printf "%P\n"`; do
-    mkdir -p "${TMP_TARGET}var/lib/pacman/local/${DIR}"
-done
-
-# then copy all package database files
-for FILE in `find ${UPPERDIR}/var/lib/pacman/local/ -type f -printf "%P\n"`; do
-    cp --no-dereference "${UPPERDIR}/var/lib/pacman/local/${FILE}" "${TMP_TARGET}var/lib/pacman/local/${FILE}"
-done
-
-# the user may have enabled systemd units provided by the packages in COW space
-# we want to copy these too
-
-# read all systemd symlinks in the cow-dir
-for SYMLINK in `find "${UPPERDIR}/etc/systemd/system/" -type l -printf "%P\n"`; do
-    TARGET=$(readlink "${UPPERDIR}/etc/systemd/system/${SYMLINK}")
-
-    # targets the symlink something that is in our packages?
-    if grep -q "${TARGET}" $PKG_FILELIST; then
-        echo "Copying systemd link /etc/systemd/system/${SYMLINK}"
-        # copy the symlink to our target dir
-        LINKDIR=$(dirname "${TMP_TARGET}/etc/systemd/system/${SYMLINK}")
-        mkdir -p "${LINKDIR}"
-        cp --no-dereference "${UPPERDIR}/etc/systemd/system/${SYMLINK}" "${TMP_TARGET}/etc/systemd/system/${SYMLINK}"
+    if ! [ -d "${UPPERDIR}/var/lib/pacman/local/" ]; then
+        echo "ERROR: no packages installed in the COW space"
+        echo "(${UPPERDIR}/var/lib/pacman/local/ not existing)"
+        exit 3
     fi
-done
 
-# restore line separator
-IFS=$IFS_SAVE
+    # read the names of the packages in the COW space
+    # package names are in the desc file in the line after the marker %NAME%
+    PACKAGENAMES=$(find ${UPPERDIR}/var/lib/pacman/local/ -name desc -exec grep -A1 --no-filename "%NAME%" \{\} \; | grep -v -E "(--|%NAME%)")
 
-rm -f $PKG_FILELIST
+    if [ -z "$PACKAGENAMES" ]; then
+        echo "ERROR: no packages installed in the COW space"
+        echo "(${UPPERDIR}/var/lib/pacman/local/ empty)"
+        exit 3
+    fi
 
-if [ "$PREPARE_MODE" -eq 1 ]; then
+    # create temp dir used to store the package list and later the files to put into the SRM
+    mkdir -p $TMP_TARGET
+
+    # read all filenames installed by the packages in COW space
+    # sort to make sure dir names come before files in the dir
+    pacman -Q --list --quiet $PACKAGENAMES | sort -u >$PKG_FILELIST
+
+    if cat $PKG_FILELIST | wc -l | grep -q "^0$"; then
+        echo "ERROR: empty file list for the installed packages"
+
+        # clean up
+        rm -rf ${TMP_TARGET}
+
+        exit 3
+    fi
+
+    echo -n "Found Packages: "
+    echo "$PACKAGENAMES" | wc -w
+    echo -n "Found Files: "
+    cat $PKG_FILELIST | wc -l
     echo
-    echo "SRM content prepared in ${TMP_TARGET}"
-    echo
-    echo "Do any wanted modifications and then run:"
-    echo "mksquashfs ${TMP_TARGET} targetfile.srm -info -comp $COMPRESS $COMPLEVEL"
-else
+    echo "Copying to temp dir..."
+
+    # newline separator for for loops, necessary for filenames with spaces in them
+    IFS_SAVE=$IFS
+    IFS=$'\n'
+
+    # iterate over all files and dirs installed by the packages
+    for FILE in `cat $PKG_FILELIST`; do
+        if [ -d "${FILE}" ] && ! [ -L "${FILE}" ]; then
+            # we have a real dir (not a symlink to a dir)
+            # create it below $TMP_TARGET, copy attributes
+            mkdir -p "${TMP_TARGET}${FILE}"
+            chmod "--reference=${FILE}" "${TMP_TARGET}${FILE}"
+            chown "--reference=${FILE}" "${TMP_TARGET}${FILE}"
+        else
+            # we have a file or symlink, copy it, preserving symlinks as such
+            cp "--target-directory=${TMP_TARGET}" --preserve=all --parents --no-dereference "${FILE}"
+        fi
+    done
+
+    # copy the pacman package database too
+
+    # first create the directories in the tmp space
+    for DIR in `find ${UPPERDIR}/var/lib/pacman/local/ -type d -printf "%P\n"`; do
+        mkdir -p "${TMP_TARGET}var/lib/pacman/local/${DIR}"
+    done
+
+    # then copy all package database files
+    for FILE in `find ${UPPERDIR}/var/lib/pacman/local/ -type f -printf "%P\n"`; do
+        cp --no-dereference "${UPPERDIR}/var/lib/pacman/local/${FILE}" "${TMP_TARGET}var/lib/pacman/local/${FILE}"
+    done
+
+    # the user may have enabled systemd units provided by the packages in COW space
+    # we want to copy these too
+
+    # read all systemd symlinks in the cow-dir
+    for SYMLINK in `find "${UPPERDIR}/etc/systemd/system/" -type l -printf "%P\n"`; do
+        TARGET=$(readlink "${UPPERDIR}/etc/systemd/system/${SYMLINK}")
+
+        # targets the symlink something that is in our packages?
+        if grep -q "${TARGET}" $PKG_FILELIST; then
+            echo "Copying systemd link /etc/systemd/system/${SYMLINK}"
+            # copy the symlink to our target dir
+            LINKDIR=$(dirname "${TMP_TARGET}/etc/systemd/system/${SYMLINK}")
+            mkdir -p "${LINKDIR}"
+            cp --no-dereference "${UPPERDIR}/etc/systemd/system/${SYMLINK}" "${TMP_TARGET}/etc/systemd/system/${SYMLINK}"
+        fi
+    done
+
+    # restore line separator
+    IFS=$IFS_SAVE
+
+    rm -f $PKG_FILELIST
+}
+
+function create()
+{
     echo
     echo "Creating squashfs..."
 
@@ -198,4 +171,69 @@ else
 
     # clean up
     rm -rf ${TMP_TARGET}
+}
+
+while getopts "s:c:l:" opt; do
+    case "${opt}" in
+        s)
+            SUBCMD="${OPTARG}"
+            ;;
+        c)
+            COMPRESS="${OPTARG}"
+            ;;
+        l)
+            COMPLEVEL="-Xcompression-level ${OPTARG}"
+            ;;
+        *)
+            usage
+            ;;
+    esac
+done
+
+case "${SUBCMD}" in
+    prepare)
+        OPER_PREPARE=1
+        ;;
+    create)
+        OPER_CREATE=1
+        ;;
+    all)
+        OPER_PREPARE=1
+        OPER_CREATE=1
+        ;;
+    *)
+        echo "ERROR: invalid sub-command: '${SUBCMD}'"
+        usage
+        ;;
+esac
+
+shift $((OPTIND-1))
+TARGETFILE="$1"
+
+if [ "$OPER_CREATE" -eq 1 ] && [ -z "$TARGETFILE" ]; then
+    echo "ERROR: no target file specified"
+    usage
+fi
+
+if [ "$OPER_CREATE" -eq 1 ] && [ -e "$TARGETFILE" ]; then
+    echo "ERROR: target file already exists. Please delete it."
+    exit 1
+fi
+
+if [ "$OPER_PREPARE" -eq 1 ] && [ -e "$TMP_TARGET" ]; then
+    echo "ERROR: temporary directory $TMP_TARGET already exists. Please delete it."
+    exit 1
+fi
+
+if [ "$OPER_PREPARE" -eq 0 ] && [ ! -d "$TMP_TARGET" ]; then
+    echo "ERROR: temporary directory $TMP_TARGET does not exist. Please make sure you run the 'prepare' sub-command before 'create'."
+    exit 1
+fi
+
+if [ "$OPER_PREPARE" -eq 1 ]; then
+    prepare
+fi
+
+if [ "$OPER_CREATE" -eq 1 ]; then
+    create
 fi