ungleich-tools/alpine-rebuild-initramfs.sh

#!/bin/sh

if [ $# -ne 1 ]; then
    echo "$0 ssh-keyfile"
    echo "   ssh-keyfile: ssh keys to add into the image"
    exit 1
fi

set -e
set -x

SSH_KEYS=$1; shift

MAJOR_VERSION=3.12
MINOR_VERSION=0
IMAGE=alpine-minirootfs-$MAJOR_VERSION.$MINOR_VERSION-x86_64.tar.gz

RESOLVCONF=/etc/resolv.conf

working_directory=$(pwd -P)
rootfs_tmpdir=$(mktemp -d)
#rootfs_tmpdir=alpine_${MAJOR_VERSION}-${MINOR_VERSION}-rootfs

mkdir -p ${rootfs_tmpdir}

rootfs_url="http://dl-cdn.alpinelinux.org/alpine/v$MAJOR_VERSION/releases/x86_64/$IMAGE"

run_root () {
    sudo chroot $rootfs_tmpdir /usr/bin/env \
        PATH=/bin:/sbin \
        /bin/sh -c "$*"
}

wget -c "$rootfs_url" -O "$IMAGE"

# keep right permissions, use sudo
sudo tar xf $IMAGE -C $rootfs_tmpdir

# Add SSH keys
run_root mkdir -p root/.ssh
sudo cp $SSH_KEYS $rootfs_tmpdir/root/.ssh/authorized_keys
run_root chown root:root root/.ssh/authorized_keys
run_root chmod 0600 root/.ssh/authorized_keys
run_root chmod 0700 root/.ssh

# Import local resolv.conf.
sudo cp "$RESOLVCONF" $rootfs_tmpdir/etc/resolv.conf

# Make sure init is found by the kernel.
run_root ln -sf /sbin/init /init

run_root apk update
run_root apk add linux-lts openrc udev openssh
# rdnssd
run_root rc-update add udev
run_root rc-update add udev-trigger
run_root rc-update add sshd
# run_root rc-update add rdnssd
run_root rc-update add networking
run_root rc-update add hostname

sudo tee "$rootfs_tmpdir/etc/network/interfaces" <<EOF
auto lo
iface lo inet loopback

auto eth0
iface eth0 inet6 manual
    pre-up ip link set eth0 up
    pre-up echo 1 > /proc/sys/net/ipv6/conf/eth0/accept_ra
EOF

sudo tee "$rootfs_tmpdir/etc/hostname" <<EOF
alpine-unconfigured
EOF

# Generate iniramfs image
(cd $rootfs_tmpdir; sudo find . | sudo cpio -H newc -o | gzip -9 > "$working_directory/alpine-initramfs.gz")
cp "$rootfs_tmpdir/boot/vmlinuz-lts" "$working_directory/alpine-kernel"

echo rm -rf "$rootfs_tmpdir"

echo "Use alpine-initramfs.gz alpine-kernel from $working_directory"!

exit 0