quick-vm

#!/usr/bin/bash
#
# Use libguestfs and libvirt to create a qemu-based Debian 12 VM. The first
# argument to this script will be used as the domain name for libvirt. The
# resulting VM can be managed through any libvirt compatible tool like "virsh".
#
# After first boot, the VM will have an SSH server up and running. A user can
# connect to it as the "root" user by using the SSH key stored in the file
# <name>-root-key. The VM also supports mDNS so if the host and network are
# configured properly, a user can login with:
#
# ssh -i <generated-root-key> root@<name>.local
#
# Some error checking is included.
#

if [[ -z $1 ]]
then
    echo "Usage: $0 <VM-name>"
    exit 1
fi

NAME=$1
IMAGE=$NAME.img
KEY=$NAME-root-key

if virsh domid $NAME > /dev/null
then
    echo "A VM named \"$NAME\" exists. Abort."
    exit 2
fi

if [[ -f $KEY && -f $KEY.pub ]]
then
    echo "SSH key pair for $NAME exists. Re-use existing key."
else
    # Remove in case one of the 2 files was present.
    rm -f $KEY $KEY.pub
    ssh-keygen -f $KEY -C root -P ""
fi

if [[ -f $IMAGE && $IMAGE -nt $KEY ]]
then
    echo "Image file $IMAGE exists and is newer that $KEY. Skip image creation."
else
    virt-builder debian-12              \
        --size 6G                       \
        --memsize 1024                  \
        --format raw                    \
        --hostname $NAME                \
        --output $IMAGE                 \
        --root-password password:toor   \
        --install network-manager,avahi-daemon  \
        --upload $KEY.pub:/root/key     \
        --firstboot firstboot.sh
fi

virt-install                            \
    --name $NAME                        \
    --ram 1024                          \
    --vcpus 2                           \
    --disk path=$IMAGE                  \
    --osinfo debian12                   \
    --console pty,target_type=serial    \
    --network type=bridge,source=virbr0 \
    --graphics none                     \
    --import                            \
    --noautoconsole