A script to create a virtual machine

create-vm.sh

#!/bin/bash
echo "Configure a virtual machine!";

NAME=""
HOSTNAME=""
SSH=""
PASSWORD=""
SSH_PWAUTH="true"
ROOT_LOGIN="yes"
NETWORK=""
MEMORY=""
CPU=""
DISK=""
RELEASE=""
NETWORK=""

read -p "Name: " NAME
if [ -z "${NAME}" ]; then
        echo "A vm name is required."
        exit 1
fi

read -p "Hostname: " HOSTNAME
if [ -z "${HOSTNAME}" ]; then
        HOSTNAME="ubuntu"
fi

read -p "SSH Public Key (blank for password auth): " SSH
if [ -z "${SSH}" ]; then
        read -p "Password (blank for random): " PASSWORD
        if [ -z "${PASSWORD}" ]; then
                PASSWORD=$(cat /dev/urandom | tr -dc '[:alpha:]' | fold -w ${1:-20} | head -n 1)
        fi
else
        ssh-keygen -l -f $SSH 2> /dev/null
        RET=$?
        if [ $RET -ne 0 ]; then
                echo "$SSH is not a valid ssh public key"
                exit 1
        fi
        SSH=$(cat $SSH)
        SSH=$(printf "ssh_authorized_keys:\n  - $SSH")
        SSH_PWAUTH="false"
        ROOT_LOGIN="without-password"
        PASSWORD=$(cat /dev/urandom | tr -dc '[:alpha:]' | fold -w ${1:-20} | head -n 1)
fi


read -p "Network Config: " NETWORK_FILE
[ -z "${NETWORK_FILE}" ] || NETWORK=" --network-config=$NETWORK_FILE"

read -p "Bridge: " BRIDGE
[ -z "${BRIDGE}" ] || BRIDGE=" --bridge=$BRIDGE"

while true; do
        read -p "Memory (MB): " MEMORY
        if [ -z "${MEMORY}" ]; then
                echo "Using default memory: 4096MB"
                MEMORY="4096"
        fi
        [[ $MEMORY =~ ^[0-9]+$ ]] || { echo "Enter a valid number"; continue; }
        break
done

while true; do
        read -p "CPU Cores: " CPU
        if [ -z "${CPU}" ]; then
                echo "Using default CPU cores: 2"
                CPU="2"
        fi
        [[ $CPU =~ ^[0-9]+$ ]] || { echo "Enter a valid number"; continue; }
        break
done

while true; do
        read -p "Disk (GB): " DISK
        if [ -z "${DISK}" ]; then
                echo "Using default Disk: 40GB"
                DISK="40"
        fi
        [[ $DISK =~ ^[0-9]+$ ]] || { echo "Enter a valid number"; continue; }
        break
done

echo "
Ubuntu Releases:
1. 16.04        LTS     Xenial Xerus
2. 18.04        LTS     Bionic Beaver
3. 18.10                Cosmic Cuttlefish
4. 19.04                Disco Dingo
5. 19.10                Eoan Ermine
6. 20.04        LTS     Focal Fossa
7. 20.10                Groovy Gorilla
8. 21.04                Hirsute Hippo
9. 21.10                Impish Indri
"

while true; do
        read -p "Release (default 9): " RELEASE
        if [ -z "${RELEASE}" ]; then
                echo "Using default Ubuntu 21.10 Impish Indri"
                RELEASE="9"
        fi

        [[ $RELEASE =~ ^[0-9]+$ ]] || { echo "Please enter a valid version number"; continue; }

        if ((RELEASE == 1)); then
                RELEASE="xenial"
        elif ((RELEASE == 2)); then
                RELEASE="bionic"
        elif ((RELEASE == 3)); then
                RELEASE="cosmic"
        elif ((RELEASE == 4)); then
                RELEASE="disco"
        elif ((RELEASE == 5)); then
                RELEASE="eoan"
        elif ((RELEASE == 6)); then
                RELEASE="focal"
        elif ((RELEASE == 7)); then
                RELEASE="groovy"
        elif ((RELEASE == 8)); then
                RELEASE="hirsute"
        elif ((RELEASE == 9)); then
                RELEASE="impish"
        else
                echo "Version number out of range, 1-9"
                continue
        fi

        break;
done

uvt-simplestreams-libvirt sync --source https://cloud-images.ubuntu.com/minimal/releases/ release=${RELEASE} arch=amd64

RET=$?
if [ $RET -ne 0 ]; then
        echo "$RELEASE was not able to be downloaed."
        exit 1
fi


CONFIG=$(cat /dev/urandom | tr -dc '[:alpha:]' | fold -w ${1:-20} | head -n 1).yaml;

cat > ./${CONFIG} << EOF
#cloud-config
hostname: ${HOSTNAME}
ssh_pwauth: ${SSH_PWAUTH}
disable_root: false
package_update: true
package_upgrade: true
chpasswd:
  expire: false
  list:
    - root:${PASSWORD}
${SSH}
runcmd:
  - [ userdel, -r, -f, ubuntu ]
  - [ wget, -O, /tmp/install.sh, https://raw.githubusercontent.com/ohmyzsh/ohmyzsh/master/tools/install.sh ]
  - [ chmod, +x, /tmp/install.sh ]
  - [ runuser, -l, root, -c, '/tmp/install.sh --unattended' ]
  - [ rm, install.sh ]
  - [ usermod, --shell, /bin/zsh, root]
  - [ perl, -i, -pe, 's/#PermitRootLogin .*/PermitRootLogin ${ROOT_LOGIN}/', /etc/ssh/sshd_config ]
  - [ perl, -i, -pe, 's/#TCPKeepAlive .*/TCPKeepAlive yes/', /etc/ssh/sshd_config ]
  - [ perl, -i, -pe, 's/#ClientAliveInterval .*/ClientAliveInterval 60/', /etc/ssh/sshd_config ]
  - [ reboot ]
packages:
  - git
  - vim
  - openssh-server
  - screen
  - ufw
  - iputils-ping
  - zsh
  - zip
  - unzip
  - curl
  - wget
  - perl
EOF

uvt-kvm create --memory=${MEMORY} --disk=${DISK} --cpu=${CPU}${BRIDGE}${NETWORK} --user-data=./${CONFIG} ${NAME} arch="amd64" release=${RELEASE} label="minimal release";

RET=$?
if [ $RET -ne 0 ]; then
        rm ./${CONFIG}
        exit 1
fi

cat > ./${NAME}.configure << EOF
Created Virtual Machine $NAME
To remove or destroy the Virtual Machine type
        uvt-kvm destroy $NAME

--------------------------------------------------------
The login details are:
username: root
password: $PASSWORD
--------------------------------------------------------

# ${CONFIG}
$(cat ./${CONFIG})

# ${NETWORK_FILE:-'no network file specified'})
$(cat ./${NETWORK_FILE:-'/dev/null'})

# command used

uvt-kvm create --memory=${MEMORY} --disk=${DISK} --cpu=${CPU}${BRIDGE}${NETWORK} --user-data=./${CONFIG} ${NAME} arch="amd64" release=${RELEASE} label="minimal release"
EOF

head ./${NAME}.configure
rm ./${CONFIG}

netplan.yaml

version: 2
ethernets:
  enp1s0:
    addresses:
      - 192.168.0.10/29 # ipv4 external
      - 2a01:4f8::3/64  # ipv6 external
    routes:
      - on-link: true     # required for ipv4 external
        to: 0.0.0.0/0
        via: 192.168.0.9  # ip of host on this subnet
      - on-link: true     # required for ipv6 external
        to: ::/0
        via: 2a01:4f8::2  # ip on host with this subnet
    gateway6: 2a01:4f8::2 # required for ipv6 external (ip on host with this subnet)
    nameservers:
      addresses:
        - 1.1.1.1              # required for ipv4 external
        - 2606:4700:4700::1111 # required for ipv6 external
        - 1.0.0.1              # required for ipv4 external
        - 2606:4700:4700::1001 # required for ipv6 external