systemrescue-zfs/airootfs/usr/bin/cowpacman2srm

#!/bin/sh
#
# cowpacman2srm - Create SystemRescueModules (SRM) from pacman packages installed into the COW space
#
# Author: Gerd v. Egidy
# SPDX-License-Identifier: GPL-3.0-or-later
#
# This script is meant to help creating SystemRescueModules (SRM) for SystemRescue.
# More info about SRMs and this script can be found at:
# 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 
# special except provide enough RAM.
# You can also enable any systemd services that are in these packages.
#
# Then call:
# cowpacman2srm [-c compalg] [-l complevel] targetfile.srm
#
# 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
# you are trying to run it with. So it is higly recommended to only use this script on
# the exact version of SystemRescue you plan to use the SRM with.
#

# default paths for temp files
TMP_TARGET=/tmp/srm_content/
PKG_FILELIST=${TMP_TARGET}filelist

# default compression options
COMPRESS=zstd
COMPLEVEL=""

function usage()
{
    echo
    echo "Usage: cowpacman2srm [-c compalg] [-l complevel] targetfile.srm"
    echo
    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:" opt; do
    case "${opt}" in
        c)
            COMPRESS="${OPTARG}"
            ;;
        l)
            COMPLEVEL="-Xcompression-level ${OPTARG}"
            ;;
        *)
            usage
            ;;
    esac
done

shift $((OPTIND-1))
TARGETFILE="$1"

if [ -z "$TARGETFILE" ]; then
    echo "ERROR: no target file specified"
    usage
fi

if [ -e "$TARGETFILE" ]; 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 $PACKAGENAMES | sort >$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}"
    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

echo
echo "Creating squashfs..."

mksquashfs ${TMP_TARGET} $TARGETFILE -info -comp "$COMPRESS" $COMPLEVEL

# clean up
rm -rf ${TMP_TARGET}