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#!/bin/bash

set -e

set -u

ROOT=$(cd $(dirname $0) && pwd)

TARGET=${1:?Specify the target filename}

DIST=${2:-stable}

LOGFILE=${TARGET}.log

>$LOGFILE

exec > >(tee -ia $LOGFILE)

exec 2> >(tee -ia $LOGFILE >&2)

DEBOOTSTRAP_DIR=$(mktemp -d -p . minideb-debootstrap.tmpXXXXXX)

cp -a /usr/share/debootstrap/* $DEBOOTSTRAP_DIR

cp -a $ROOT/debootstrap/* $DEBOOTSTRAP_DIR/scripts

export DEBIAN_FRONTEND=noninteractive

DIRS_TO_TRIM="/usr/share/man

/var/cache/apt

/var/lib/apt/lists

/usr/share/locale

/var/log

/usr/share/info

PACKAGES_TO_EXCLUDE="acl

bsdutils

debconf-i18n

dmsetup

e2fslibs

e2fsprogs

gcc-4.8-base

init

initscripts

insserv

libcap2

libcap2-bin

libcryptsetup4

libdevmapper1.02.1

libkmod2

liblocale-gettext-perl

libmount1

libncursesw5

libprocps3

libsystemd0

libtext-charwidth-perl

libtext-iconv-perl

libtext-wrapi18n-perl

libudev1

mount

ncurses-bin

ncurses-base

procps

startpar

systemd

systemd-sysv

sysv-rc

sysvinit-utils

udev

util-linux

rootfsDir=$(mktemp -d -p . minideb.tmpXXXXXX)

echo "Building base in $rootfsDir"

DEBOOTSTRAP_DIR=$DEBOOTSTRAP_DIR debootstrap --variant container --foreign ${DIST} "$rootfsDir"

chroot "$rootfsDir" bash debootstrap/debootstrap --second-stage

echo -e "deb http://httpredir.debian.org/debian $DIST main" > "$rootfsDir/etc/apt/sources.list"

if [ "$DIST" != "unstable" ]; then

echo "deb http://security.debian.org/ $DIST/updates main" >> "$rootfsDir/etc/apt/sources.list"

chroot "$rootfsDir" apt-get update

chroot "$rootfsDir" apt-get upgrade -y -o Dpkg::Options::="--force-confdef"

chroot "rootfsDir" dpkg -l | tee "$TARGET.manifest"

echo "Applying docker-specific tweaks"

# These are copied from the docker contrib/mkimage/debootstrap script.

# get path to "chroot" in our current PATH

chrootPath="$(type -P chroot)"

rootfs_chroot() {

# "chroot" doesn't set PATH, so we need to set it explicitly to something our new debootstrap chroot can use appropriately!

# set PATH and chroot away!

PATH='/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin' \

"$chrootPath" "$rootfsDir" "$@"

}

# prevent init scripts from running during install/update

echo >&2 "+ echo exit 101 > '$rootfsDir/usr/sbin/policy-rc.d'"

cat > "$rootfsDir/usr/sbin/policy-rc.d" <<-'EOF'

#!/bin/sh

# For most Docker users, "apt-get install" only happens during "docker build",

# where starting services doesn't work and often fails in humorous ways. This

# prevents those failures by stopping the services from attempting to start.

exit 101

EOF

chmod +x "$rootfsDir/usr/sbin/policy-rc.d"

# prevent upstart scripts from running during install/update

(

set -x

rootfs_chroot dpkg-divert --local --rename --add /sbin/initctl

cp -a "$rootfsDir/usr/sbin/policy-rc.d" "$rootfsDir/sbin/initctl"

sed -i 's/^exit.*/exit 0/' "$rootfsDir/sbin/initctl"

)

# shrink a little, since apt makes us cache-fat (wheezy: ~157.5MB vs ~120MB)

( set -x; rootfs_chroot apt-get clean )

# this file is one APT creates to make sure we don't "autoremove" our currently

# in-use kernel, which doesn't really apply to debootstraps/Docker images that

# don't even have kernels installed

rm -f "$rootfsDir/etc/apt/apt.conf.d/01autoremove-kernels"

# Ubuntu 10.04 sucks... :)

if strings "$rootfsDir/usr/bin/dpkg" | grep -q unsafe-io; then

# force dpkg not to call sync() after package extraction (speeding up installs)

echo >&2 "+ echo force-unsafe-io > '$rootfsDir/etc/dpkg/dpkg.cfg.d/docker-apt-speedup'"

cat > "$rootfsDir/etc/dpkg/dpkg.cfg.d/docker-apt-speedup" <<-'EOF'

# For most Docker users, package installs happen during "docker build", which

# doesn't survive power loss and gets restarted clean afterwards anyhow, so

# this minor tweak gives us a nice speedup (much nicer on spinning disks,

# obviously).

force-unsafe-io

EOF

if [ -d "$rootfsDir/etc/apt/apt.conf.d" ]; then

# _keep_ us lean by effectively running "apt-get clean" after every install

aptGetClean='"rm -f /var/cache/apt/archives/*.deb /var/cache/apt/archives/partial/*.deb /var/cache/apt/*.bin || true";'

echo >&2 "+ cat > '$rootfsDir/etc/apt/apt.conf.d/docker-clean'"

cat > "$rootfsDir/etc/apt/apt.conf.d/docker-clean" <<-EOF

# Since for most Docker users, package installs happen in "docker build" steps,

# they essentially become individual layers due to the way Docker handles

# layering, especially using CoW filesystems. What this means for us is that

# the caches that APT keeps end up just wasting space in those layers, making

# our layers unnecessarily large (especially since we'll normally never use

# these caches again and will instead just "docker build" again and make a brand

# new image).

# Ideally, these would just be invoking "apt-get clean", but in our testing,

# that ended up being cyclic and we got stuck on APT's lock, so we get this fun

# creation that's essentially just "apt-get clean".

DPkg::Post-Invoke { ${aptGetClean} };

APT::Update::Post-Invoke { ${aptGetClean} };

Dir::Cache::pkgcache "";

Dir::Cache::srcpkgcache "";

# Note that we do realize this isn't the ideal way to do this, and are always

# open to better suggestions (https://github.com/docker/docker/issues).

EOF

# remove apt-cache translations for fast "apt-get update"

echo >&2 "+ echo Acquire::Languages 'none' > '$rootfsDir/etc/apt/apt.conf.d/docker-no-languages'"

cat > "$rootfsDir/etc/apt/apt.conf.d/docker-no-languages" <<-'EOF'

# In Docker, we don't often need the "Translations" files, so we're just wasting

# time and space by downloading them, and this inhibits that. For users that do

# need them, it's a simple matter to delete this file and "apt-get update". :)

Acquire::Languages "none";

EOF

echo >&2 "+ echo Acquire::GzipIndexes 'true' > '$rootfsDir/etc/apt/apt.conf.d/docker-gzip-indexes'"

cat > "$rootfsDir/etc/apt/apt.conf.d/docker-gzip-indexes" <<-'EOF'

# Since Docker users using "RUN apt-get update && apt-get install -y ..." in

# their Dockerfiles don't go delete the lists files afterwards, we want them to

# be as small as possible on-disk, so we explicitly request "gz" versions and

# tell Apt to keep them gzipped on-disk.

# For comparison, an "apt-get update" layer without this on a pristine

# "debian:wheezy" base image was "29.88 MB", where with this it was only

# "8.273 MB".

Acquire::GzipIndexes "true";

Acquire::CompressionTypes::Order:: "gz";

EOF

# update "autoremove" configuration to be aggressive about removing suggests deps that weren't manually installed

echo >&2 "+ echo Apt::AutoRemove::SuggestsImportant 'false' > '$rootfsDir/etc/apt/apt.conf.d/docker-autoremove-suggests'"

cat > "$rootfsDir/etc/apt/apt.conf.d/docker-autoremove-suggests" <<-'EOF'

# Since Docker users are looking for the smallest possible final images, the

# following emerges as a very common pattern:

# RUN apt-get update \

# && apt-get install -y <packages> \

# && <do some compilation work> \

# && apt-get purge -y --auto-remove <packages>

# By default, APT will actually _keep_ packages installed via Recommends or

# Depends if another package Suggests them, even and including if the package

# that originally caused them to be installed is removed. Setting this to

# "false" ensures that APT is appropriately aggressive about removing the

# packages it added.

# https://aptitude.alioth.debian.org/doc/en/ch02s05s05.html#configApt-AutoRemove-SuggestsImportant

Apt::AutoRemove::SuggestsImportant "false";

EOF

cat > "$rootfsDir/usr/sbin/install_packages" <<-'EOF'

#!/bin/sh

set -e

set -u

export DEBIAN_FRONTEND=noninteractive

apt-get update -qq

apt-get install -y "$@"

rm -r /var/lib/apt/lists /var/cache/apt/archives

EOF

chmod 0755 "$rootfsDir/usr/sbin/install_packages"

echo "Trimming down"

chroot "$rootfsDir" dpkg --force-all -P $PACKAGES_TO_EXCLUDE

for DIR in $DIRS_TO_TRIM; do

rm -r "$rootfsDir/$DIR"/*

done

find "$rootfsDir/usr/share/doc" -mindepth 1 -not -name copyright -not -type d -delete

find "$rootfsDir/usr/share/doc" -mindepth 1 -type d -empty -delete

echo "Total size"

du -skh "$rootfsDir"

echo "Package sizes"

chroot "$rootfsDir" dpkg-query -W -f '${Package} ${Installed-Size}\n'

echo "Largest dirs"

du "$rootfsDir" | sort -n | tail -n 20

echo "Built in $rootfsDir"

tar cf "$TARGET" -C "$rootfsDir" .

rm -r "$rootfsDir"

rm -r "$DEBOOTSTRAP_DIR"

echo "Image built at ${TARGET}"

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