Caproto IOCs for Raspberry Pi

Headless RPi Setup

This documentation builds on official docs for installing an operating system and getting your RPi on a password-protected WiFi network without using a monitor or a keyboard. From there, we can configure it over SSH.

• Download Raspbian Stretch Lite image (no desktop). See Rpi downloads page.

• Use Etcher to "flash" the SD card with this image.

• Mount the boot partition of the SD card.

• To enable ssh, create an empty file named ssh in the root of the boot partition.

• Add a file name wpa_supplicant.conf to that same directory with contents like:

  country=GB
  ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
  update_config=1
  network={
      ssid="YOUR_WIFI_NETWORK_NAME"
      psk="PASSWORD_IN_PLAIN_TEXT"
  }

  For more details, see official docs.

• Unmount and eject the SD card. Load it into the RPi and plug in the RPi. The RPi should automatically boot and join the WiFi network with the hostname raspberrypi.

• Copy ssh key(s). We use an option to avoid adding the host key to ~/.ssh/known_hosts because we are about to change the hostname. Enter yes and the default password, raspberry, when prompted.

  ssh-copy-id -o "UserKnownHostsFile /dev/null" pi@raspberrypi
  ssh -o "UserKnownHostsFile /dev/null" pi@raspberrypi

• Install a proper editor (e.g. sudo apt install vim).

• Set a unique hostname in /etc/hostname and last line of /etc/hosts, such as pizero5.

• Reboot: sudo reboot now.

• After ~20 seconds, verify that you can login: ssh pi@NEW_HOSTNAME. This time, we allow the host key to be added. The RPi should display a security warning because the default password has not been changed. We will address this with Ansible in the next section.

• If you have multiple RPis to configure, get them all to this point before proceeding so that the next step can be done in parallel on all RPis at once.

Security and Software Installation

For this we will use Ansible, which can SSH into one or more RPis in parallel and automate our work.

• Install Ansible.

• Clone this repository.

  git clone https://github.com/danielballan/caproto-rpi
  cd caproto-rpi

• Create an inventory file named hosts by copying hosts.example and adding the hostname(s) of the RPi(s) you want to configure.

  cp hosts.example hosts
  # Now list the hostname of each RPi under the headers [pis].
  

• Apply Ansible playbook initial_setup.yml, which will:

  • Harden SSH.
  • Configure a firewall using uncomplicated firewall (ufw) that is just permissive enough to support SSH and EPICS-related traffic.
  • Get the chip's hardware RNG contributing to system entropy, which is necessary for generating enough entropy to importing certain Python packages.
  • Install git and supervisor.
  • Install Python 3.7 from source. Building Python takes about 60 minutes on a RaspberryPi Zero.
  • Configure pip to look for RPi-compatible wheels on [piwheels.org](https://www.piwheels.org/). This saves a lot of time for packages like scipy that are expensive to compile.

  ansible-playbook initial_setup.yml

• If the RPi will run on battery power, add it to the battery-powered group in hosts and then apply the low_power_usage.yml playbook, which should shave off 10s of mA of power usage.

  ansible-playbook low_power_usage.yml

• After applying one or both of these playbooks, reboot the rpi

  ssh pi@NEW_HOSTNAME
  sudo reboot now

  and give it 20 seconds or so to reboot.

• Finally, run a playbook to install caproto in a virtualenv. No reboot required.

  ansible-playbook caproto.yml