Build small operating system in binary format.

build-image

# https://github.com/solo-io/unik/blob/master/containers/compilers/firecracker/build-image
#!/bin/bash

# run this container like so
# docker run --rm --privileged -v /path/to/code:/go/src/gopath/to/code firecracker-builder

set -ex


dd if=/dev/zero of=/tmp/rootfs bs=1M count=50
mkfs.ext4 /tmp/rootfs

mkdir /tmp/tmp
# mknod /dev/loop0 b 7 0 
mount /tmp/rootfs /tmp/tmp -o loop

tar xzf /tmp/alpine-minirootfs-3.8.1-x86_64.tar.gz -C /tmp/tmp

CODEDIR=${CODEDIR:-/opt/code}

cp -r  /tmp/overlay/* /tmp/tmp/

cd $CODEDIR
go get -d -v ./...
CGO_ENABLED=0 go build -o /tmp/tmp/usr/local/bin/program

# not using gopath.. so no need for: cp /go/bin/* /tmp/tmp/usr/local/bin/program

cat > /tmp/tmp/prepare.sh <<EOF
passwd root -d root
apk add -u openrc ca-certificates
exit 
EOF

chroot /tmp/tmp/ /bin/sh /prepare.sh

rm /tmp/tmp/prepare.sh 

umount /tmp/tmp

OUTDIR=${OUTDIR:-$CODEDIR}

mkdir -p $OUTDIR || :

cp /tmp/rootfs $OUTDIR