#!/usr/bin/env bash

set -e
set -u
set -o pipefail

root="${1:?Usage $0 container-root}"
mkdir -p "$root"
mkdir "$root/bin"
cp $(type -P busybox) "$root/bin"

mkdir -p "$root/usr/lib"
touch "$root/usr/lib/os-release"

ln -s busybox "$root/bin/sh"
ln -s busybox "$root/bin/cat"
ln -s busybox "$root/bin/tr"
ln -s busybox "$root/bin/ps"
ln -s busybox "$root/bin/ip"

mkdir -p "$root/sbin"
cat <<'EOF' >"$root/sbin/init"
#!/bin/sh

printf "ps aufx:\n"
ps aufx

printf "/proc/1/cmdline:\n"
printf "%s\n\n" "$(tr '\0' ' ' </proc/1/cmdline)"

printf "/proc/1/environ:\n"
printf "%s\n\n" "$(tr '\0' '\n' </proc/1/environ)"

printf "/proc/1/mountinfo:\n"
cat /proc/self/mountinfo
printf "\n"

printf "/proc/1/cgroup:\n"
printf "%s\n\n" "$(cat /proc/1/cgroup)"

printf "/proc/1/uid_map:\n"
printf "%s\n\n" "$(cat /proc/1/uid_map)"

printf "/proc/1/setgroups:\n"
printf "%s\n\n" "$(cat /proc/1/setgroups)"

printf "/proc/1/gid_map:\n"
printf "%s\n\n" "$(cat /proc/1/gid_map)"

printf "ip link:\n"
ip link
EOF
chmod +x "$root/sbin/init"