ubuntu bootstrap for user mode linux: minimal

build-ubuntu-rootfs.sh

#!/bin/sh

# This script creates a user-mode linux machine based on Ubuntu.
# Created by Clay Smith, May 2017
#
# based on: https://gist.github.com/aputs/6247216
# and https://gist.github.com/AVGP/5410903

set -x

control_c()
# run if user hits control-c
{
	echo -en "\n*** Ouch! Exiting ***\n"
	exit $?
}

trap control_c SIGINT

## warning!!!
## sudo access

if [ "`id -u`" != "0" ]; then
  echo "I won't run as user. I need root."
  exit 1
fi

[ ! -e $(which debootstrap 2> /dev/null) ] && echo "error: debootstrap not found" && exit 1

arch=amd64
release=${1:-xenial}
dest_path=$(readlink -f -- "$(dirname $0)")
target_path=$(mktemp --directory)
hostname="$release-$arch"
extra_packages="iproute,net-tools,ca-certificates,apt,apt-utils"

[ ! -e "$target_path" ] && echo "error: error generating temporary directory" && exit 1

sudo rm -fr $target_path
sudo mkdir -p $target_path

root_fs_path=$(mktemp /tmp/root_fs_XXXXXXX)
size=160
echo dd if=/dev/zero of=$root_fs_path count=128 bs=1M
dd if=/dev/zero of=$root_fs_path count=$size bs=1M || f
mkfs.ext4 -T small $root_fs_path
mount -o loop $root_fs_path $target_path

sudo mkdir -p $target_path/etc/apt/apt.conf.d $target_path/etc/dpkg/dpkg.cfg.d

# minimize installation configs
cat << EOF | sudo tee $target_path/etc/apt/apt.conf.d/02compress-indexes
Acquire::GzipIndexes "true";
Acquire::CompressionTypes::Order:: "gz";
EOF

cat << EOF | sudo tee $target_path/etc/apt/apt.conf.d/02nocache
Dir::Cache {
	srcpkgcache "";
	pkgcache "";
}
EOF

cat << EOF | sudo tee $target_path/etc/apt/apt.conf.d/97norecommends
APT
{
	Install-Recommends "false";
};
EOF

cat << EOF | sudo tee $target_path/etc/dpkg/dpkg.cfg.d/01_nodoc
path-exclude /usr/share/doc/*
# we need to keep copyright files for legal reasons
path-include /usr/share/doc/*/copyright
path-exclude /usr/share/man/*
path-exclude /usr/share/groff/*
path-exclude /usr/share/info/*
# lintian stuff is small, but really unnecessary
path-exclude /usr/share/lintian/*
path-exclude /usr/share/linda/*
# lang
path-exclude /usr/share/locale/*
path-include /usr/share/locale/en*
# landscape
path-exclude /usr/share/pyshared/twisted/test*
path-exclude /usr/lib/python*/dist-packages/twisted/test*
path-exclude /usr/share/pyshared/twisted/*/test*
path-exclude /usr/lib/python*/dist-packages/twisted/*/test*
EOF

sudo debootstrap --verbose --arch=$arch --variant=minbase --include=$extra_packages $release $target_path http://archive.ubuntu.com/ubuntu/

#sudo rm -rf $target_path/dev
#sudo mkdir -p $target_path/dev
#sudo mknod -m 0666 $target_path/dev/null c 1 3
#sudo mknod -m 0666 $target_path/dev/zero c 1 5
#sudo mknod -m 0666 $target_path/dev/random c 1 8
#sudo mknod -m 0666 $target_path/dev/urandom c 1 9
#sudo mkdir -m 0755 $target_path/dev/pts
#sudo mkdir -m 1777 $target_path/dev/shm
#sudo mknod -m 0666 $target_path/dev/tty c 5 0
#sudo mknod -m 0666 $target_path/dev/tty0 c 4 0
#sudo mknod -m 0666 $target_path/dev/tty1 c 4 1
#sudo mknod -m 0600 $target_path/dev/console c 5 1
#sudo mknod -m 0666 $target_path/dev/full c 1 7
#sudo mknod -m 0600 $target_path/dev/initctl p
#sudo mknod -m 0666 $target_path/dev/ptmx c 5 2

sudo chroot $target_path /bin/bash -x <<'EOF'
# LC_LANG errors
locale-gen en_US en_US.utf8
touch /etc/resolv.conf

apt-get -y update
apt-get -y upgrade
# cleanup
apt-get -y clean all
apt-get -y autoremove
rm -rf /var/lib/apt/lists/*

find /usr/share/doc -depth -type f ! -name copyright | xargs rm || true
find /usr/share/doc -empty | xargs rmdir || true

rm -rf /usr/share/man /usr/share/groff /usr/share/info /usr/share/lintian /usr/share/linda /var/cache/man
find /usr/share/locale -mindepth 1 -maxdepth 1 ! -name 'en' | xargs rm -r
rm -rf /var/cache/apt/*.bin

# apt-get install fixes
mkdir -p /usr/share/man/man{1,2,3,4,5,6,7,8,9}
EOF

echo "Created filesystem: $root_fs_path"

sudo umount $target_path
#sudo rm -rf $target_path