ungleich-tools/alpine-rebuild-initramfs.sh

#!/bin/sh

set -e
set -x

MAJOR_VERSION=3.11
MINOR_VERSION=2
IMAGE=alpine-minirootfs-$MAJOR_VERSION.$MINOR_VERSION-x86_64.tar.gz
SSH_KEYS=$(cat ~/.ssh/id_rsa.pub)
RESOLVCONF=/etc/resolv.conf

working_directory=$(pwd -P)
rootfs_tmpdir=$(mktemp -d)
rootfs_url="http://dl-cdn.alpinelinux.org/alpine/v$MAJOR_VERSION/releases/x86_64/$IMAGE"

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

if [ "$(whoami)" != 'root' ]; then
    echo "This script must be run as root." >&2
    exit 1
fi

# Download, extract inital rootfs.
curl "$rootfs_url" -o "$working_directory/$IMAGE"
tar xf $IMAGE -C $rootfs_tmpdir

# Add SSH keys
run_root mkdir -p root/.ssh
echo $SSH_KEYS > $rootfs_tmpdir/root/.ssh/authorized_keys
run_root chmod 0600 root/.ssh/authorized_keys
run_root chmod 0700 root/.ssh

# Import local resolv.conf.
cat "$RESOLVCONF" > $rootfs_tmpdir/etc/resolv.conf

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

# Servers have static addresses, disable the standard
# alpine setting of using tempaddr = 2
cat > "$rootfs_tmpdir/etc/sysctl.d/99-ipv6.conf" <<EOF
net.ipv6.conf.default.use_tempaddr = 0
net.ipv6.conf.all.use_tempaddr = 0

net.ipv6.conf.all.accept_ra = 1
EOF

cat > "$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
    post-up ip addr show dev eth0 | grep inet6 >> /etc/issue
    post-up echo post post up >> /etc/issue
EOF

cat > "$rootfs_tmpdir/etc/hostname" <<EOF
alpine-unconfigured
EOF

echo ipv6 >> "$rootfs_tmpdir/etc/modules"

# Layer atop base rootfs.
run_root apk update
run_root apk upgrade
run_root apk add openssh linux-vanilla openrc udev
run_root rc-update add udev
run_root rc-update add udev-trigger
run_root rc-update add sshd
run_root rc-update add networking
run_root rc-update add hostname

# FIXME: add / install rdnssd / ndisc6 / start it on boot
# ndisc6 is only @testing

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

# Cleanup.
#rm -r "$rootfs_tmpdir"

# Upload to netboot server. - needs to be done outside sudo
echo "Use alpine-initramfs.gz alpine-kernel from $working_directory"!