sd-debug

#!/bin/bash

build() {
    declare -F add_busybox >/dev/null || . /usr/lib/initcpio/functions.d/systemd-extras

    add_busybox || return $?

    add_binary /usr/bin/agetty
    add_binary /usr/bin/login
    add_binary /usr/lib/security/pam_unix.so
    add_binary /usr/bin/unix_chkpwd
    chmod 6755 "$BUILDROOT/usr/bin/unix_chkpwd"

    local service=(
        "[Unit]"
        "Description=initramfs debugging"
        "DefaultDependencies=no"
	"Before=sysinit.target"
        ""
        "[Service]"
        "Type=idle"
	"StandardInput=tty-force"
        "StandardOutput=tty"
        "TTYPath=/dev/${SD_DEBUG_TTY:-tty2}"
        "ExecStart=/usr/bin/agetty --noreset --noclear --autologin root - linux"
    )
    printf "%s\n" "${service[@]}" > "${BUILDROOT}/usr/lib/systemd/system/init-debug.service"

    add_symlink /etc/systemd/system/sysinit.target.wants/init-debug.service /usr/lib/systemd/system/init-debug.service

    local pam_conf=(
        "login   auth       required     pam_unix.so shadow"
        "login   account    required     pam_unix.so"
        "login   password   required     pam_unix.so shadow"
        "login   session    required     pam_unix.so"
    )
    printf "%s\n" "${pam_conf[@]}" > "${BUILDROOT}/etc/pam.conf"

}

help() {
    cat <<__EOF_HELP__
Starts a root shell (busybox dash) on \$SD_DEBUG_TTY (default tty2).  No login
password required.

CAUTION:

This install hook opens your system wide open to anybody with physical access.
It is for debugging purposes only. Use it only temporarily for sorting out
problems with your initramfs environment.
__EOF_HELP__
}