Cloud-init config to set up my Ubuntu dev machine.

cloud-init.cfg

## template: jinja
#cloud-config

{% if v1.distro_release == 'focal' %}

users:
    - name: berkant
      shell: /usr/bin/bash
      ssh_import_id: gh:berkant
      sudo: ALL=(ALL:ALL) NOPASSWD:ALL

chpasswd:
    expire: false

apt_upgrade: true
apt:
    sources:
        caddy:
            source: deb [trusted=yes] https://dl.cloudsmith.io/public/caddy/stable/deb/ubuntu focal main
        neovim:
            source: ppa:neovim-ppa/stable
        hashicorp:
            source: deb [trusted=yes] https://apt.releases.hashicorp.com focal main
        speedtest:
            source: deb [trusted=yes] https://packagecloud.io/ookla/speedtest-cli/ubuntu focal main
        tailscale:
            source: deb [trusted=yes] https://pkgs.tailscale.com/stable/ubuntu focal main

packages:
    - python-is-python3
    - build-essential
    - python3-pip
    - p7zip-full
    - traceroute
    - mediainfo
    - speedtest
    - tailscale
    - neofetch
    - mlocate
    - ffmpeg
    - iperf3
    - neovim
    - screen
    - vnstat
    - aria2
    - caddy
    - iftop
    - unzip
    - whois
    - curl
    - file
    - htop
    - tree
    - wget
    - cbm
    - git
    - mtr
    - jq

runcmd:
    - tailscale up -authkey='<% EDIT_THIS_FIELD_YourNodeAuthKey %>'

    - ufw --force reset
    - ufw allow in on tailscale0 to any
    - ufw --force enable

    - sed -i '1i PermitRootLogin no' /etc/ssh/sshd_config
    - sed -i '1i PasswordAuthentication no' /etc/ssh/sshd_config
    - sed -i '1i ClientAliveInterval 5' /etc/ssh/sshd_config
    - systemctl --no-block restart sshd

    - pip3 install youtube-dl httpie nyx

    - wget -O /tmp/rclone.deb https://github.com/rclone/rclone/releases/download/v1.55.1/rclone-v1.55.1-linux-amd64.deb
    - dpkg -i /tmp/rclone.deb

    - wget -O /tmp/bat.deb https://github.com/sharkdp/bat/releases/download/v0.18.0/bat_0.18.0_amd64.deb
    - dpkg -i /tmp/bat.deb

    - mkdir -p /opt/nvm
    - wget -qO- https://raw.githubusercontent.com/nvm-sh/nvm/v0.38.0/install.sh | NVM_DIR=/opt/nvm bash
    - printf '\nexport NVM_DIR="/opt/nvm"\n[ -s "$NVM_DIR/nvm.sh" ] && . "$NVM_DIR/nvm.sh"\n' >> /etc/bash.bashrc

    - wget -O /tmp/bento4.zip http://zebulon.bok.net/Bento4/binaries/Bento4-SDK-1-6-0-637.x86_64-unknown-linux.zip
    - unzip /tmp/bento4.zip -d /opt
    - printf '\nexport PATH="$PATH:/opt/Bento4-SDK-1-6-0-637.x86_64-unknown-linux/bin"\n' >> /etc/bash.bashrc

{% endif %}

for your interest about runcmd parameter:

• runcmd only has code to "shellify" your strings or array of strings (i.e: turns them into a shell script)
• runcmd will only write a shell script into the file /var/lib/cloud/instance/scripts/runcmd
• runcmd is part of the cloud_config_modules boot stage
• You need to execute that runcmd shell script using the scripts-user module
• scripts-user is part of the cloud_final_modules boot stage

example for runcmd command with executing while running cloud-init

cloud_config_modules:
  - runcmd

cloud_final_modules:
  - scripts-user

runcmd:
  - [ touch, /tmp/myfile ]