mkrootfs

#!/bin/sh
set -eu
exec 3>&1 >&2 #save stdout for later, diagnostics to stderr

# set defaults
dest=mnt
mirror=http://dl-cdn.alpinelinux.org/alpine
rel=edge
pkg=alpine-baselayout,alpine-keys,apk-tools,musl-utils

while getopts hd:m:r:p:t:ES opt; do
  case $opt in
    d) dest=$OPTARG ;;
    m) mirror=$OPTARG ;;
    r) rel=$OPTARG ;;
    p) pkg=$OPTARG ;;
    t) tzdata=$OPTARG ;;
    S) noout=1 ;;
    *) exec echo "$0 [-d:] [-m:] [-r:] [-p:] [-t:] [-S]" ;;
  esac
done

# ensure the destination exists
mkdir -p "$dest/etc/apk"
cd "$dest"

# set up the repositories file
{ echo "$mirror/$rel/main"
  wget -qO- "$mirror/$rel/community" >&4 2>&4 && echo "$mirror/$rel/community"
  [ "$rel" = edge ] || echo @edge "$mirror/edge/main"
  echo @testing "$mirror/edge/testing"
} > etc/apk/repositories 4>/dev/null

# fetch the container contents
(IFS=,; apk -p . --no-cache --keys-dir /etc/apk/keys add --initdb $pkg)
[ ${tzdata+1} ] && cp "/usr/share/zoneinfo/$tzdata" etc/localtime

# output if requested
[ ${noout+1} ] || tar c * >&3