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0a8267f69b
On Linux >= 6.10, the first rootfs is an extra ghost rootfs of 336K, that has a corrupted CPIO. To overcome this issue, do not fail on `cpio --extract`.
106 lines
3.2 KiB
Bash
Executable File
106 lines
3.2 KiB
Bash
Executable File
#!/bin/bash
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# Does as it says on the tin.
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#
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# Example: extract-initramfs-from-vmlinuz /boot/flatcar/vmlinuz-a out-dir
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#
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# This will create one or more out-dir/rootfs-N directories that contain the contents of the initramfs.
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set -euo pipefail
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# check for unzstd. Will abort the script with an error message if the tool is not present.
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unzstd -V >/dev/null
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fail() {
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echo "${*}" >&2
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exit 1
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}
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# Stolen from extract-vmlinux and modified.
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try_decompress() {
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local header="${1}"
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local no_idea="${2}"
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local tool="${3}"
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local image="${4}"
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local tmp="${5}"
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local output_basename="${6}"
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local pos
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local tool_filename=$(echo "${tool}" | cut -f1 -d' ')
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# The obscure use of the "tr" filter is to work around older versions of
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# "grep" that report the byte offset of the line instead of the pattern.
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# Try to find the header and decompress from here.
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for pos in $(tr "${header}\n${no_idea}" "\n${no_idea}=" < "${image}" |
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grep --text --byte-offset --only-matching "^${no_idea}")
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do
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pos=${pos%%:*}
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# Disable error handling, because we will be potentially
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# giving the tool garbage or a valid archive with some garbage
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# appended to it. So let the tool extract the valid archive
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# and then complain about the garbage at the end, but don't
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# fail the script because of it.
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set +e; tail "-c+${pos}" "${image}" | "${tool}" >"${tmp}/out" 2>/dev/null; set -e;
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if [ -s "${tmp}/out" ]; then
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mv "${tmp}/out" "${output_basename}-${tool_filename}-at-${pos}"
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else
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rm -f "${tmp}/out"
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fi
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done
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}
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try_unzstd_decompress() {
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local image="${1}"
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local tmp="${2}"
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local output_basename="${3}"
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try_decompress '(\265/\375' xxx unzstd "${image}" "${tmp}" "${output_basename}"
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}
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me="${0##*/}"
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if [[ $# -ne 2 ]]; then
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fail "Usage: ${me} <vmlinuz> <output_directory>"
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fi
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image="${1}"
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out="${2}"
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if [[ ! -s "${image}" ]]; then
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fail "The image file '${image}' either does not exist or is empty"
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fi
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mkdir -p "${out}"
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tmp=$(mktemp --directory /tmp/eifv-XXXXXX)
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trap "rm -rf ${tmp}" EXIT
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tmp_dec="${tmp}/decompress"
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mkdir "${tmp_dec}"
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fr_prefix="${tmp}/first-round"
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ROOTFS_IDX=0
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perform_round() {
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local image="${1}"
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local tmp_dec="${2}"
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local round_prefix="${3}"
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try_unzstd_decompress "${image}" "${tmp_dec}" "${round_prefix}"
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for rnd in "${round_prefix}"*; do
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if [[ $(file --brief "${rnd}") =~ 'cpio archive' ]]; then
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mkdir -p "${out}/rootfs-${ROOTFS_IDX}"
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# On Linux 6.10, the first rootfs is an extra ghost rootfs of 336K, that has a corrupted CPIO
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cpio --quiet --extract --make-directories --directory="${out}/rootfs-${ROOTFS_IDX}" --nonmatching 'dev/*' < $rnd || true
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ROOTFS_IDX=$(( ROOTFS_IDX + 1 ))
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fi
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done
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}
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shopt -s nullglob
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perform_round "${image}" "${tmp_dec}" "${fr_prefix}"
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for fr in "${fr_prefix}"*; do
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fr_files="${fr}-files"
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fr_dec="${fr_files}/decompress"
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mkdir -p "${fr_dec}"
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sr_prefix="${fr_files}/second-round"
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perform_round "${fr}" "${fr_dec}" "${sr_prefix}"
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done
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if [[ ${ROOTFS_IDX} -eq 0 ]]; then
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fail "no initramfs found in ${image}"
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fi
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echo "done, found ${ROOTFS_IDX} rootfs(es)"
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