some additions with initram and pysh

INITRAM/VERSION

@@ -0,0 +1 @@
+39.2

INITRAM/bin

@@ -0,0 +1 @@
+usr/bin

INITRAM/buildconfig

@@ -0,0 +1,4 @@
+MODULES=(btrfs)
+BINARIES=(/usr/bin/btrfs)
+FILES=()
+HOOKS=(base udev autodetect keyboard keymap modconf block filesystems fsck)

INITRAM/config

@@ -0,0 +1,6 @@
+MODULES="btrfs"
+EARLYHOOKS="udev"
+HOOKS="udev keymap"
+LATEHOOKS=""
+CLEANUPHOOKS="udev"
+EMERGENCYHOOKS=""

INITRAM/early_cpio

@@ -0,0 +1 @@
+1

INITRAM/etc/initrd-release

@@ -0,0 +1 @@
+../usr/lib/os-release

INITRAM/etc/mtab

@@ -0,0 +1 @@
+../proc/self/mounts

INITRAM/etc/os-release

@@ -0,0 +1 @@
+../usr/lib/os-release

INITRAM/hooks/keymap

@@ -0,0 +1,23 @@
+#!/usr/bin/ash
+# SPDX-License-Identifier: GPL-2.0-only
+
+run_hook() {
+    local mode ctrl
+
+    if [ -e /keymap.bin ]; then
+        msg -n ':: Loading keymap...'
+        if [ -f /keymap.utf8 ]; then
+            mode='-u'
+            ctrl='G'
+        else
+            mode='-a'
+            ctrl='@'
+        fi
+        kbd_mode "$mode" -C /dev/console
+        printf "\033%%$ctrl" >>/dev/console
+        loadkmap </keymap.bin
+        msg 'done.'
+    fi
+}
+
+# vim: set ft=sh ts=4 sw=4 et:

INITRAM/hooks/udev

@@ -0,0 +1,30 @@
+#!/usr/bin/ash
+
+run_earlyhook() {
+    local quiet
+    kmod static-nodes --format=tmpfiles --output=/run/tmpfiles.d/kmod.conf
+    systemd-tmpfiles --prefix=/dev --create --boot
+    quiet="$(getarg quiet)"
+    if [ "${quiet}" = "y" ]; then
+        /usr/lib/systemd/systemd-udevd --daemon --resolve-names=never >/dev/null 2>&1
+    else
+        /usr/lib/systemd/systemd-udevd --daemon --resolve-names=never
+    fi
+    # used externally by poll_device()
+    # shellcheck disable=SC2034
+    udevd_running=1
+}
+
+run_hook() {
+    msg ":: Triggering uevents..."
+    udevadm trigger --action=add --type=subsystems
+    udevadm trigger --action=add --type=devices
+    udevadm settle
+}
+
+run_cleanuphook() {
+    udevadm control --exit
+    udevadm info --cleanup-db
+}
+
+# vim: set ft=sh ts=4 sw=4 et:

INITRAM/init

@@ -0,0 +1,112 @@
+#!/usr/bin/ash
+# SPDX-License-Identifier: GPL-2.0-only
+
+export PATH='/usr/local/sbin:/usr/local/bin:/usr/bin'
+
+udevd_running=0
+mount_handler=default_mount_handler
+init=/boot/init
+rd_logmask=0
+
+. /init_functions
+
+mount_setup
+
+# parse the kernel command line
+parse_cmdline </proc/cmdline
+
+# setup logging as early as possible
+rdlogger_start
+
+disablehooks="$(getarg disablehooks)"
+# busybox ash supports string replacements
+# shellcheck disable=SC3060
+for d in ${disablehooks//,/ }; do
+    [ -e "/hooks/$d" ] && chmod 644 "/hooks/$d"
+done
+
+# shellcheck disable=SC1091
+. /config
+
+# We rely on word splitting
+# shellcheck disable=SC2086
+run_hookfunctions 'run_earlyhook' 'early hook' $EARLYHOOKS
+
+if [ -n "$earlymodules$MODULES" ]; then
+    # busybox ash supports string replacements
+    # shellcheck disable=SC3060,SC2086
+    modprobe -qab ${earlymodules//,/ } $MODULES
+fi
+
+# We rely on word splitting
+# shellcheck disable=SC2086
+run_hookfunctions 'run_hook' 'hook' $HOOKS
+
+# honor the old behavior of break=y as a synonym for break=premount
+break="$(getarg break)"
+if [ "${break}" = "y" ] || [ "${break}" = "premount" ]; then
+    # shellcheck disable=SC2086
+    run_hookfunctions 'run_emergencyhook' 'emergency hook' $EMERGENCYHOOKS
+    echo ":: Pre-mount break requested, type 'exit' to resume operation"
+    launch_interactive_shell
+fi
+
+if rootdev="$(resolve_device "$root")"; then
+    # If the tag is supported by util-linux mount, pass it as is.
+    # Otherwise, use the resolved device path.
+    case "$root" in
+        'UUID='* | 'LABEL='* | 'PARTUUID='* | 'PARTLABEL='*) : ;;
+        *) root="$rootdev" ;;
+    esac
+fi
+unset rootdev
+
+fsck_root
+
+# Mount root at /new_root
+"$mount_handler" /new_root
+
+# We rely on word splitting
+# shellcheck disable=SC2086
+run_hookfunctions 'run_latehook' 'late hook' $LATEHOOKS
+
+# We rely on word splitting
+# shellcheck disable=SC2086
+run_hookfunctions 'run_cleanuphook' 'cleanup hook' $CLEANUPHOOKS
+
+if [ "$(stat -c %D /)" = "$(stat -c %D /new_root)" ]; then
+    # Nothing got mounted on /new_root. This is the end, we don't know what to do anymore
+    # We fall back into a shell, but the shell has now PID 1
+    # This way, manual recovery is still possible.
+    # shellcheck disable=SC2086
+    run_hookfunctions 'run_emergencyhook' 'emergency hook' $EMERGENCYHOOKS
+    err "Failed to mount the real root device."
+    echo "Bailing out, you are on your own. Good luck."
+    echo
+    launch_interactive_shell --exec
+elif [ ! -x "/new_root${init}" ]; then
+    # Successfully mounted /new_root, but ${init} is missing
+    # The same logic as above applies
+    # shellcheck disable=SC2086
+    run_hookfunctions 'run_emergencyhook' 'emergency hook' $EMERGENCYHOOKS
+    err "Root device mounted successfully, but ${init} does not exist."
+    echo "Bailing out, you are on your own. Good luck."
+    echo
+    launch_interactive_shell --exec
+fi
+
+if [ "${break}" = "postmount" ]; then
+    # shellcheck disable=SC2086
+    run_hookfunctions 'run_emergencyhook' 'emergency hook' $EMERGENCYHOOKS
+    echo ":: Post-mount break requested, type 'exit' to resume operation"
+    launch_interactive_shell
+fi
+
+# this should always be the last thing we do before the switch_root.
+rdlogger_stop
+
+exec env -i \
+    "TERM=$TERM" \
+    /usr/bin/switch_root /new_root "$init" "$@"
+
+# vim: set ft=sh ts=4 sw=4 et: