Setting up a Raspberry Pi with Python 3.7+ using Ansible¶
Here’s a set of files to automatically setup bricknil on a Raspberry Pi. These Ansible playbooks will help you take a clean Raspbian image and compile Python 3.7+ along with all the Bricknil required libraries. You just need a Raspberry Pi; these instructions do not require you to plug in a monitor and works over Wifi. This compilation of Python is necessary because the raspbian distro does not ship with the latest version of Python at the time of this writing. And it took me a little bit of effort to figure out how to compile Python with the SSL libraries (so pip works), so I hope this might be of use to some folks.
The steps required are listed below in order, and you can find the Ansible yaml playbooks in the Bricknil source under pi_setup.
Steps¶
Download a Raspbian image and burn it to a SD card¶
Download the Raspbian Stretch Lite image
Burn it to a suitable SD card. On OS X, Balena Etcher is a good tool to do this.
On the newly imaged SD card’s /boot folder:
Make an empty file called ssh to enable SSH access.
Make wpa_supplicant.conf file to supply your wifi credentials:
country=US ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev update_config=1 network={ ssid="NETWORK_NAME psk="WIFI PASSWORD" }
Now, you should be able to use this SD card to boot your raspberry pi. After giving it a few minutes to boot, you can login in by doing the following on your local machine:
ssh pi@raspberrypi.local <enter 'raspberry' as the default password
Install Ansbile on your local machine¶
You can just type pip install ansible
Change the default password on the Pi¶
You may need to modify the hosts file in pi_setup directory to put in your own IP address for the Pi.
You will need to install the python library passlib by running pip install passlib on your local machine (not the Pi)
Use the change_password.yml playbook to test your ansible install and change the default password on the pi (use raspberry for the ssh password when prompted, and then enter your new password):
ansible-playbook -i hosts change_password.yml --ask-pass
The playbook being run is simply:
- hosts: all
remote_user: pi
become_method: sudo
vars_prompt:
- name: new_password
prompt: "Enter the password you would like to use for the user pi"
confirm: yes
tasks:
- name: backup shadow file
copy:
remote_src: yes
src: /etc/shadow
dest: /tmp/shadow
become: yes
- name: generate hash pass
delegate_to: localhost
command: python -c "from passlib.hash import md5_crypt; import getpass; print (md5_crypt.hash('{{new_password}}'))"
register: hash
- debug:
var: hash.stdout
- name: update password
user:
name: pi
password: '{{hash.stdout}}'
become: yes
Run the setup playbook¶
The final step is to just run the the install playbook. This will install all the packages, download Python 3.7, compile it, and set up a virtualenv to run bricknil from. The actual playbook is in tasks.yml, shown below and included in the source, and the command to execute it on your local machine is:
ansible-playbook -i hosts tasks.yml --ask-pass
The install will take around two hours, so please be patient. Most of the time is spent compiling and installing Python from source. Here’s the playbook being executed:
- hosts: all remote_user: pi become_method: sudo vars: PYTHON: "3.7.2" OPEN_SSL: openssl-1.0.2g build_path: "{{ansible_env.HOME}}/build" HOME: "{{ansible_env.HOME}}" tasks: - name: Update APT package cache apt: update_cache=yes become: yes - name: Update packages apt: upgrade=dist become: yes - name: Install build-essential package: name="build-essential" state=present become: yes - name: Install build packages apt: state: present name: - tk-dev - libncurses5-dev - libncursesw5-dev - libreadline6-dev - libdb5.3-dev - libgdbm-dev - libsqlite3-dev - libssl-dev - libbz2-dev - libexpat1-dev - liblzma-dev - zlib1g-dev - libffi-dev - uuid-dev - vim - git - python-pip - screen become: yes - name: Ensure build directory exists file: path: "{{ build_path }}" state: directory recurse: yes - name: Download openssl get_url: url: "https://www.openssl.org/source/{{ OPEN_SSL }}.tar.gz" dest: "{{ build_path }}/{{ OPEN_SSL }}.tar.gz" mode: "755" register: openssl_download - name: Untar openssl unarchive: remote_src: yes src: "{{ build_path }}/{{ OPEN_SSL }}.tar.gz" dest: "{{ build_path }}" when: openssl_download.changed - name: configure openssl command: ./config shared --prefix=/usr/local args: chdir: "{{ build_path }}/{{ OPEN_SSL }}" when: openssl_download.changed - name: make openssl command: make -j 4 args: chdir: "{{ build_path }}/{{ OPEN_SSL }}" register: make_openssl when: openssl_download.changed - name: install openssl command: make install args: chdir: "{{ build_path }}/{{ OPEN_SSL }}" become: yes when: make_openssl.changed - name: set /etc/ld.so.conf.d to add /usr/local/ lineinfile: path: /etc/ld.so.conf.d/openssl.conf create: yes line: "/usr/local/lib" become: yes - name: run ldconfig to update dynamic link lib path to use /usr/local/lib command: ldconfig become: yes - name: Download python 3.7 get_url: url: "https://www.python.org/ftp/python/{{PYTHON}}/Python-{{PYTHON}}.tgz" dest: "{{ build_path }}/Python-{{ PYTHON }}.tgz" mode: "755" register: python_download - name: Untar python unarchive: remote_src: yes src: "{{ build_path }}/Python-{{ PYTHON }}.tgz" dest: "{{ build_path }}" when: python_download.changed - name: Uncomment SSL blockinfile: path: "{{ build_path}}/Python-{{ PYTHON }}/Modules/Setup.dist" insertbefore: "#SSL=/usr/local/ssl" block: | SSL=/usr/local _ssl _ssl.c \ -DUSE_SSL -I$(SSL)/include -I$(SSL)/include/openssl \ -L$(SSL)/lib -lssl -lcrypto - name: configure python command: ./configure --enable-optimizations --with-openssl=/usr/local --prefix=/usr/local args: chdir: "{{ build_path }}/Python-{{ PYTHON }}" when: python_download.changed register: python_configure - name: make python shell: 'make -j 4' args: chdir: "{{ build_path }}/Python-{{ PYTHON }}" register: make_python when: python_configure.changed - name: install python shell: 'make altinstall' args: chdir: "{{ build_path }}/Python-{{ PYTHON }}" become: yes when: python_configure.changed - name: Setup .bashrc blockinfile: path: "{{ HOME }}/.bashrc" block: | export VIRTUALENVWRAPPER_PYTHON="/usr/local/bin/python3.7" source /usr/local/bin/virtualenvwrapper.sh - name: Install pip virtualenv pip: executable: /usr/local/bin/pip3.7 name: - virtualenv - virtualenvwrapper become: yes - name: pip install bricknil pip: name: - bricknil virtualenv: "{{ HOME }}/.virtualenvs/bricknil" virtualenv_python: python3.7 - name: git clone bricknil git: repo: 'https://github.com/virantha/bricknil.git' dest: '{{ HOME }}/bricknil' clone: yes
And that’s it! Your raspberry pi should be ready to go as a networked appliance to run your Lego controller scripts from.
Running Bricknil examples on the Pi¶
The script installs a virtualenv called bricknil, so you can activate it in the normal way to get access to Python 3.7+ and the python dependencies for running bricknil.
The script also installed the bricknil source from github, so all the examples should be ready to go. Just ssh into the Pi and:
cd bricknil
On linux, you need to run as sudo to access the bluetooth libraries; after you login to the Pi over ssh you can do the following to run the virtualenv installed Python as sudo:
sudo ~/.virtualenvs/bricknil/bin/python examples/train_all.py