Initial commit

overlay/usr/bin/system-update

@@ -0,0 +1,135 @@
+#!/bin/sh
+# vim: set sw=4 ts=4 sts=4 et :
+
+cleanup() {
+    cd /
+    if [ -n "${workdir}" ] && [ "${workdir}" != / ]; then
+        rm -rf "${workdir}"
+    fi
+    unset workdir
+}
+
+die() {
+    rc=$?
+    if [ $rc -eq 0 ]; then
+        rc=1
+    fi
+    error "$@"
+    exit $rc
+}
+
+error() {
+    if [ $# -eq 1 ]; then
+        echo "$1" >&2
+    elif [ $# -gt 1 ]; then
+        printf "$@" >&2
+    fi
+}
+
+extract_update() {
+    zstd -dc update.tar.zstd | tar -x \
+        || die 'Could not extract update source'
+    sha256sum -c digests \
+        || die 'Invalid update source: checksum mismatch'
+}
+
+fetch_update() {
+    wget -O update.tar.zstd "$1"
+}
+
+get_root() {
+    set -- $(cat /proc/cmdline)
+    while [ $# -gt 0 ]; do
+        case "$1" in
+            root=*)
+                _root=${1#root=}
+                ;;
+        esac
+        shift
+    done
+    echo $(findfs "${_root}")
+}
+
+get_partlabel() {
+    blkid -o value -s PARTLABEL "$1"
+}
+
+help() {
+    usage
+}
+
+info() {
+    if [ $# -eq 1 ]; then
+        echo "$1" >&2
+    elif [ $# -gt 1 ]; then
+        printf "$@" >&2
+    fi
+}
+
+usage() {
+    printf 'usage: %s source_url\n' "${0##*/}"
+}
+
+while [ $# -gt 0 ]; do
+    case "$1" in
+    --help)
+        help
+        exit 0
+        ;;
+    *)
+        if [ -z "${source_url}" ]; then
+            source_url="$1"
+        else
+            usage >&2
+            exit 2
+        fi
+        ;;
+    esac
+    shift
+done
+
+if [ -z "${source_url}" ]; then
+    usage >&2
+    exit 2
+fi
+
+root=$(get_root)
+partlabel=$(get_partlabel "${root}")
+
+case "${partlabel}" in
+rootfs-a)
+    newpartlabel=rootfs-b
+    ;;
+rootfs-b)
+    newpartlabel=rootfs-a
+    ;;
+*)
+    die \
+        'Unsupported system configuration: invalid rootfs partition label: %s\n' \
+        "${partlabel}" >&2
+esac
+newroot=$(findfs PARTLABEL="${newpartlabel}")
+if [ -z "${newroot}" ]; then
+    die 'Could not find partition with label %s\n' "${partlabel}"
+fi
+info 'Current rootfs: %s (%s)\n' "${partlabel}" "${root}"
+info 'New rootfs: %s (%s)\n' "${newpartlabel}" "${newroot}"
+
+trap cleanup INT TERM QUIT EXIT
+workdir=$(mktemp -d)
+cd "${workdir}"
+
+fetch_update "${source_url}" || die 'Failed to fetch update source'
+extract_update || die 'Failed to extact update source'
+./install "${newroot}" || die 'Error installing system update'
+
+printf 'Do you want to reboot now? [y/N] '
+read confirm
+case "${confirm}" in
+[yY]|[yY][eE][sS])
+    systemctl reboot
+    ;;
+*)
+    info 'A reboot is required to complete the update'
+    ;;
+esac