Scripts using debootstrap to build Debian-based VMs

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Build Debian-based VMs with debootstrap

This gist contains two scripts to simple quickly build UEFI-based or BIOS-based Debian/Ubuntu VMs stored as qcow2-files – mainly intended for using those with QEMU/KVM. This is done by relying on the mighty debootstrap and qemu-utils, especially qemu-nbd.

The scripts are basically updated version of K. Trzcinski’s work.

Dependencies

Ensure, that you have the following packages installed:

apt install -y qemu-utils \
               debootstrap \
               grub-pc-bin \
               ovmf # for UEFI-booting 

It is strongly recommended to rely on apt-cacher-ng to build up the build process:

apt install apt-cacher-ng 
# Eventually, check that apt-cacher-ng is running
ss -tln | grep 3142 

Usage

VM_NAME=debian-test
VM_FILE=${VM_NAME}.qcow2
RELEASE=bookworm 
USER=user
PW=pass123

# Create a qcow2
qemu-img create -f qcow2 $VM_FILE 4G

# Build UEFI-based VM 
./build-uefi-based-debian-vm.sh $VM_FILE $VM_NAME $RELEASE $USER $PW

# Run a UEFI-based via qemu
qemu-system-x86_64 -bios /usr/share/ovmf/OVMF.fd -net nic -net user -m 2G -smp cores=1,cpus=1 -drive file=$VM_FILE

Alternatively, build and run a BIOS-based VM like so:

# Build BIOS-based VM 
./build-bios-based-debian-vm.sh $VM_FILE $VM_NAME $RELEASE $USER $PW

# Run a BIOS-based via qemu
qemu-system-x86_64 -net nic -net user -m 2G -smp cores=1,cpus=1 -drive file=$VM_FILE

build-bios-based-debian-vm.sh

#!/bin/bash

clean_debian() {
	[ "$MNT_DIR" != "" ] && chroot $MNT_DIR umount /proc/ /sys/ /dev/ 
	sleep 1s
	[ "$MNT_DIR" != "" ] && umount -l $MNT_DIR
	sleep 1s
	[ "$DISK" != "" ] && qemu-nbd -d $DISK
	sleep 1s
	[ "$MNT_DIR" != "" ] && rm -r $MNT_DIR
}

fail() {
	clean_debian
	echo ""
	echo "FAILED: $1"
	exit 1
}

cancel() {
	fail "CTRL-C detected"
}

if [ $# -lt 5 ]
then
	echo "author: K. Trzcinski updated for EFI by jgru"
	echo "license: GPL"
	echo "usage: $0 <image-file> <hostname> <release> <user> <password> [optional debootstrap args]" 1>&2
	exit 1
fi

FILE=$1
HOSTNAME=$2
RELEASE=$3
USER=$4
PW=$5

shift 5

trap cancel INT

echo "Installing $RELEASE into $FILE..."

MNT_DIR=`mktemp`
rm $MNT_DIR
mkdir $MNT_DIR
DISK=

echo "Looking for nbd device..."

modprobe nbd max_part=16 || fail "failed to load nbd module into kernel"

for i in /dev/nbd*
do
	if qemu-nbd -c $i $FILE
	then
		DISK=$i
		break
	fi
done

[ "$DISK" == "" ] && fail "no nbd device available"

echo "Connected $FILE to $DISK"

echo "Partitioning $DISK..."
parted -s -a optimal -- $DISK \
  mklabel msdos \
  mkpart primary ext4 1MiB 100% \
  set 1 boot on

partprobe $DISK
sleep 2

echo "Creating root partition..."
#mkfs.ext4 -L BOOT ${DISK}p1 || fail "cannot create /boot ext4"
mkfs.ext4 -L ROOT ${DISK}p1 || fail "cannot create / ext4"

echo "Mounting root partition..."
mount ${DISK}p1 $MNT_DIR || fail "cannot mount /"

echo "Installing Debian $RELEASE..."
debootstrap --verbose --include=sudo,less,openssh-server $* $RELEASE $MNT_DIR http://localhost:3142/ftp2.de.debian.org/debian/  || fail "cannot install $RELEASE into $DISK"

echo "Configuring system..."
UUID=$(blkid ${DISK}p1 | cut -d" " -f2 | sed 's/"//g')
cat <<EOF > $MNT_DIR/etc/fstab
$UUID /                   ext4    errors=remount-ro 0       1
EOF

echo $HOSTNAME > $MNT_DIR/etc/hostname

cat <<EOF > $MNT_DIR/etc/hosts
127.0.0.1       localhost
127.0.1.1 		$HOSTNAME

# The following lines are desirable for IPv6 capable hosts
::1     localhost ip6-localhost ip6-loopback
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
EOF

cat <<EOF > $MNT_DIR/etc/network/interfaces
auto lo
iface lo inet loopback

auto ens3
iface ens3 inet dhcp
EOF

mount --bind /dev/ $MNT_DIR/dev || fail "cannot bind /dev"

chroot $MNT_DIR mount -t proc none /proc || fail "cannot mount /proc"
chroot $MNT_DIR mount -t sysfs none /sys || fail "cannot mount /sys"
# Install kernel and grub
LANG=C DEBIAN_FRONTEND=noninteractive chroot $MNT_DIR apt-get install -y -q linux-image-amd64 grub-pc || fail "cannot install linux-image and grub"

chroot $MNT_DIR grub-install $DISK --no-floppy || fail "cannot install grub"
chroot $MNT_DIR update-grub || fail "cannot update grub"

chroot $MNT_DIR adduser --disabled-password --gecos "" "$USER" || fail "cannot create used in chroot"
chroot $MNT_DIR /sbin/usermod -aG sudo $USER  || fail "cannot add user to sudoers-group in chroot"
chroot $MNT_DIR chpasswd <<< "$USER:$PW" || fail "cannot change password in chroot"

echo "SUCCESS!"
clean_debian
exit 0

build-uefi-based-debian-vm.sh

#!/bin/bash

clean_debian() {
	[ "$MNT_DIR" != "" ] && chroot $MNT_DIR umount /proc/ /sys/ /dev/ #/boot/
	sleep 1s
        [ "$MNT_DIR" != "" ] && umount -l $MNT_DIR/boot/efi
	[ "$MNT_DIR" != "" ] && umount -l $MNT_DIR
	sleep 1s
	[ "$DISK" != "" ] && qemu-nbd -d $DISK
	sleep 1s
	[ "$MNT_DIR" != "" ] && rm -r $MNT_DIR
}

fail() {
	clean_debian
	echo ""
	echo "FAILED: $1"
	exit 1
}

cancel() {
	fail "CTRL-C detected"
}

if [ $# -lt 3 ]
then
	echo "author: K. Trzcinski updated for EFI by jgru"
	echo "license: GPL"
	echo "usage: $0 <image-file> <hostname> <release> <user> <password> [optional debootstrap args]" 1>&2
	exit 1
fi

FILE=$1
HOSTNAME=$2
RELEASE=$3
USER=$4
PW=$5

shift 5


trap cancel INT

echo "Installing $RELEASE into $FILE..."

MNT_DIR=`mktemp`
rm $MNT_DIR
mkdir $MNT_DIR
DISK=

echo "Looking for nbd device..."

modprobe nbd max_part=16 || fail "failed to load nbd module into kernel"

for i in /dev/nbd*
do
	if qemu-nbd -c $i $FILE
	then
		DISK=$i
		break
	fi
done

[ "$DISK" == "" ] && fail "no nbd device available"

echo "Connected $FILE to $DISK"

echo "Partitioning $DISK..."
parted -s -a optimal -- $DISK \
  mklabel gpt \
  mkpart primary fat32 1MiB 270MiB \
  mkpart primary ext4 1GiB -0 \
  name 1 uefi \
  name 2 root \
  set 1 msftdata on || fail "failed to partition"


partprobe $DISK
sleep 2

echo "Creating partitions..."
mkfs -t fat -F 32 -n EFI ${DISK}p1 || fail "cannot create / efi"
mkfs -t ext4 -L root ${DISK}p2 || fail "cannot create / ext4"

echo "Mounting root partition..."
mount ${DISK}p2 $MNT_DIR || fail "cannot mount /"

echo "Installing Debian $RELEASE..."
debootstrap --verbose --include=sudo,less,,openssh-server $* $RELEASE $MNT_DIR http://localhost:3142/ftp2.de.debian.org/debian/  || fail "cannot install $RELEASE into $DISK"

echo "Configuring system..."
EFI_UUID=$(blkid ${DISK}p1 | cut -d" " -f2 | sed 's/"//g')
ROOT_UUID=$(blkid ${DISK}p2 | cut -d" " -f2 | sed 's/"//g')
cat <<EOF > $MNT_DIR/etc/fstab
$ROOT_UUID /                   ext4    errors=remount-ro 0       1
EOF
#$EFI_UUID /boot/efi            vfat    defaults 0 1

echo $HOSTNAME > $MNT_DIR/etc/hostname

cat <<EOF > $MNT_DIR/etc/hosts
127.0.0.1       localhost
127.0.1.1 		$HOSTNAME

# The following lines are desirable for IPv6 capable hosts
::1     localhost ip6-localhost ip6-loopback
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
EOF

cat <<EOF > $MNT_DIR/etc/network/interfaces
auto lo
iface lo inet loopback

auto eth0
iface eth0 inet dhcp
EOF

mount --bind /dev/ $MNT_DIR/dev || fail "cannot bind /dev"

[[ -d $MNT_DIR/boot/efi ]] || mkdir $MNT_DIR/boot/efi || fail "cannot create /boot/efi in chroot"
mount -t vfat ${DISK}p1 $MNT_DIR/boot/efi || fail "cannot /boot/efi-part"

chroot $MNT_DIR mount -t proc none /proc || fail "cannot mount /proc"
chroot $MNT_DIR mount -t sysfs none /sys || fail "cannot mount /sys"

# Install kernel and grub
LANG=C DEBIAN_FRONTEND=noninteractive chroot $MNT_DIR apt-get install -y -q linux-image-amd64 grub-efi-amd64 || fail "cannot install linux-image and grub"
chroot $MNT_DIR debconf-set-selections <<< "grub-efi-amd64 grub2/update_nvram boolean false" || fail "cannot update debconf"

chroot $MNT_DIR sed -i -e 's/^\\(GRUB_CMDLINE_LINUX="[^"]*\\)"$/\\1 console=ttyS0"/' /etc/default/grub || fail "cannot customize grub cmdline"
# Tell GRUB to use the serial console
chroot $MNT_DIR cat - >>/etc/default/grub <<EOF || fail "cannot modify /etc/default/grub"
GRUB_TERMINAL="serial"
GRUB_SERIAL_COMMAND="serial --unit=0 --speed=9600 --stop=1"
EOF
chroot $MNT_DIR grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=debian --recheck --no-nvram --removable || fail "cannot install grub"
chroot $MNT_DIR update-grub || fail "cannot update grub"
chroot $MNT_DIR systemctl enable [email protected] || fail "cannot activate serial via systemd"

chroot $MNT_DIR adduser --disabled-password --gecos "" "$USER" || fail "cannot create used in chroot"
chroot $MNT_DIR /sbin/usermod -aG sudo $USER  || fail "cannot add user to sudoers-group in chroot"
chroot $MNT_DIR chpasswd <<< "$USER:$PW" || fail "cannot change password in chroot"

echo "Finishing grub installation..." # Needed to function correctly 
grub-install $DISK --target=x86_64-efi  --root-directory=$MNT_DIR || fail "cannot reinstall grub" 

echo "SUCCESS!"
clean_debian
exit 0