images/fedora-uncloud-image.sh

#!/bin/sh

# This script generates Fedora images for Uncloud.

# Depends on the following packages (as of Fedora 31):
#   qemu-img util-linux coreutils dnf curl e2fsprogs

# Run locally (without network) with:
#   qemu-system-x86_64 -enable-kvm -m 1G -drive file=$IMAGE,format=qcow2

set -e
set -x

# XXX: Handle command-line arguments?
RELEASE=31
ARCH=x86_64
IMAGE_PATH=fedora-uncloud-$RELEASE-$(date +%+F).img.qcow2
IMAGE_SIZE=10G
NBD_DEVICE=/dev/nbd0

cleanup() {
	# The order here is important.
	umount /mnt/dev/pts 2>/dev/null || true
	umount /mnt/dev/shm 2>/dev/null || true
	umount /mnt/dev 2>/dev/null || true
	umount /mnt/proc 2>/dev/null || true
	umount /mnt/run 2>/dev/null || true
	umount /mnt/sys 2>/dev/null || true
	umount /mnt/boot 2>/dev/null || true
	umount /mnt 2>/dev/null || true
	qemu-nbd --disconnect "$NBD_DEVICE" || true
}

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

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

if [ ! -f '/etc/fedora-release' ]; then
	echo "WARNING: this script has been designed to run on a Fedora system." >&2
	echo "WARNING: Not running Fedora. Giving you 5 seconds to abort." >&2
	sleep 5
fi

# Create base QCOW2 image.
qemu-img create -f qcow2 "$IMAGE_PATH" "$IMAGE_SIZE"
modprobe nbd max_part=16
qemu-nbd --connect="$NBD_DEVICE" "$IMAGE_PATH"

# Don't forget to cleanup, even if the script crash.
trap cleanup EXIT

# Create partition table, format partitions.
sfdisk --no-reread "$NBD_DEVICE" <<EOF
1M,500M,L,*
,,L
EOF

mkfs.ext4 "${NBD_DEVICE}p1"
mkfs.ext4 "${NBD_DEVICE}p2"

# Mount partitions, install base OS.
# Note: we could use the @Core package group but it pulls quite a lot of
# 'unwanted' dependencies. Run `dnf group info Core` for details.

mount "${NBD_DEVICE}p2" /mnt
mkdir /mnt/boot
mount "${NBD_DEVICE}p1" /mnt/boot

dnf -y \
	--releasever=$RELEASE \
	--installroot=/mnt \
	--disablerepo='*' \
	--enablerepo=fedora \
	--enablerepo=updates install \
	--setopt=install_weak_deps=False \
		basesystem systemd systemd-udev passwd dnf fedora-release procps-ng \
		iproute iputils vim-minimal

mount --bind /dev /mnt/dev
mount --bind /dev/pts /mnt/dev/pts
mount --bind /dev/shm /mnt/dev/shm
mount --bind /proc /mnt/proc
mount --bind /run /mnt/run
mount --bind /sys /mnt/sys

# Required to resolve package mirror in chroot.
cp /etc/resolv.conf /mnt/etc/resolv.conf

# Initialize /etc/hosts.
cat > /mnt/etc/hosts << EOF
127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6

EOF

# Use haveged as entropy source.
run_root dnf -y install haveged
run_root systemctl enable haveged

# Accept router advertisements for SLAAC.
run_root sysctl -w net.ipv6.conf.all.accept_ra=1

# Install RDNSSD for DNS discovery from router advertisement. The service is enabled by default.
run_root dnf -y install ndisc6
cat > /mnt/etc/systemd/system/rdnssd.service << EOF
[Unit]
Description=IPv6 Recursive DNS Server discovery Daemon
Documentation=man:rdnssd(8)
Before=network.target
Requires=network.target

[Service]
Type=forking
ExecStartPre=/bin/mkdir -p /var/run/rdnssd
ExecStartPre=/bin/chown nobody /var/run/rdnssd
ExecStartPre=/bin/chmod 0755 /var/run/rdnssd
ExecStart=/sbin/rdnssd -p /var/run/rdnssd.pid -H /etc/rdnssd/merge-hook
PIDFile=/var/run/rdnssd.pid
Restart=on-failure

[Install]
WantedBy=multi-user.target
EOF
run_root systemctl enable rdnssd

# Initialize base services.
run_root systemd-machine-id-setup

run_root ln -sf /usr/share/zoneinfo/UTC /etc/localtime
run_root systemctl enable systemd-timesyncd.service

# Install kernel and bootloader.
# Note: linux-firmware is not required our environment and takes almost 200M
# uncompressed but is a direct dependency of kernel-core...
run_root dnf -y install kernel grub2

# XXX: do we need virtio support for uncloud?
# Add support for virtio block devices at boot time.
cat > /mnt/etc/dracut.conf.d/virtio-blk.conf <<EOF
add_drivers="virtio-blk"
EOF
kernel_version=$(find /mnt/boot -name "vmlinuz-*.$ARCH" | cut -d- -f2-)
run_root dracut --force --kver "$kernel_version"

# Configure grub2.
run_root grub2-install --target=i386-pc "${NBD_DEVICE}"
run_root grub2-mkconfig -o /boot/grub2/grub.cfg

# Install en configure SSH daemon.
run_root dnf -y install openssh-server
run_root systemctl enable sshd

# Generate fstab file.
boot_uuid=$(blkid --match-tag UUID --output value "${NBD_DEVICE}p1")
root_uuid=$(blkid --match-tag UUID --output value "${NBD_DEVICE}p2")
cat >>/mnt/etc/fstab <<EOF
UUID=$boot_uuid /boot ext4 rw,relatime,data=ordered 0 2
UUID=$root_uuid /     ext4 rw,relatime,data=ordered 0 1
EOF

# Reset systemd's environment.
run_root rm -f /etc/machine-id
run_root touch /etc/machine-id
rm -f /var/lib/systemd/random-seed

# Remove temporary files and reclaim freed disk space.
# Note: build logs could be removed as well.
run_root dnf clean all

# Manually install uncloud-init.
uncloud_init_dir=/tmp/uncloud-init
run_root dnf install -y git curl grep make

mkdir -p "$uncloud_init_dir"
run_root git clone https://code.ungleich.ch/uncloud/uncloud-init.git "$uncloud_init_dir"
run_root make -C "$uncloud_init_dir" install
run_root rm -r "$uncloud_init_dir"

run_root systemctl enable uncloud-init

# Remove resolv.conf: will be handled by uncloud-init.
run_root rm /etc/resolv.conf

# Make sure everything is written to disk before exiting.
sync