build.sh

#!/bin/bash

build-kernel() {
    set -x
    vmlinuz_path=$(readlink -f /boot/vmlinuz)
    vmlinuz_filename=$(basename $vmlinuz_path)
    cp "$vmlinuz_path" "$buildddir"
    cd /vagrant/build
    chmod a+r "$vmlinuz_filename"
    ln -sf "$vmlinuz_filename" vmlinuz
    cd -
}

build-initrd() {
    set -x
    #update-initramfs -u
    initrd_path=$(readlink -f /boot/initrd.img)
    initrd_filename=$(basename $initrd_path)
    cp "$initrd_path" "$buildddir"
    cd "$buildddir"
    chmod a+r "$initrd_filename"
    ln -sf "$initrd_filename" initrd.img
    cd -
}

# UGLY CRUTCH HERE
# I coulnd't make mksquashfs exclude all files in some directory, but include the directory itself
# So let's generate list of all files to exclude explicitly
generate-rootfs-excludes() {
    # too much noise
    set +x
    for d in /boot /dev /proc /sys /tmp /var/tmp /run /mnt /home/vagrant /var/cache/apt /var/log /var/lib/apt/lists /usr/share/doc /usr/share/man /var/cache/man /usr/src /var/lib/systemd /var/lib/dhcp/; do
        find $d -mindepth 1 -maxdepth 1 >> "$1"
    done
    # Exclude all files from this packages
    for pkg in virtualbox-guest-utils grub-common grub-gfxpayload-lists grub-pc grub-pc-bin grub2-common; do
        dpkg -L $pkg | while read file; do
            if [ -f "$file" ]; then
                echo "$file" >> "$1"
            fi
        done
    done
    echo /vagrant >> "$1"
}

build-rootfs() {
    set -x
    mv "$buildddir"/rootfs.squashfs "$buildddir"/rootfs.squashfs.bak
    cd /
    generate-rootfs-excludes /tmp/rootfs.exclude_dirs
    echo "Backup /etc/fstab"
    mv /etc/fstab /etc/fstab.bak
    : > /etc/fstab
    mv /etc/localtime /etc/localtime.bak
    ln -fs /run/localtime /etc/localtime

    mksquashfs . /vagrant/build/rootfs.squashfs -no-xattrs -noappend -always-use-fragments -comp xz -ef /tmp/rootfs.exclude_dirs \
    && rm -f "$buildddir"/rootfs.squashfs.bak
    chmod a+r "$buildddir"/rootfs.squashfs

    # Restore interfaces file
    echo "Restore original /etc/fstab"
    # rm -f /etc/network/interfaces
    # mv /etc/network/interfaces.bak /etc/network/interfaces
    mv /etc/fstab.bak /etc/fstab
    rm -f /etc/localtime
    mv /etc/localtime.bak /etc/localtime
    cd -
}

build-home() {
    set -x
    mv "$buildddir"/home.tar.gz "$buildddir"/home.tar.gz.bak
    cd /home/vagrant
    # Don't use default unsecure ssh keys
    tar --exclude="./.ssh" -czf /vagrant/build/home.tar.gz ./ \
    && rm -f "$buildddir"/home.tar.gz.bak
    chmod a+r "$buildddir"/home.tar.gz
    cd -
}

buildddir=/vagrant/build

# should run thos script as root
if [ $(id -u) -ne 0 ]; then
    echo "Should run this scritp as root, trying sudo ..."
    sudo $0 "$@"
    exit $?
fi

case "$1" in
    all)
        build-kernel
        build-initrd
        build-rootfs
        build-home
        ;;
    kernel)
        build-kernel
        ;;
    initrd)
        build-initrd
        ;;
    rootfs)
        build-rootfs
        ;;
    home)
        build-home
        ;;
    *)
        echo "Usage: $0 all|initrd|kernel|rootfs|home"
        exit 1
        ;;
esac