Linux Notes¶

These notes apply to the Ubuntu and Raspbian distros.

Update OS¶

Update Raspbian to the latest and greatest bits with:

sudo apt-get update
sudo apt-get upgrade
sudo apt-get dist-upgrade
sudo apt-get autoremove
sudo apt-get autoclean
sudo reboot now

Remove unnecessary bits with:

sudo apt-get remove --purge wolfram-engine
sudo apt-get remove --purge libreoffice*
sudo apt-get clean
sudo apt-get autoremove
# To find other things to remove
apt list --installed

Change hostname¶

Multiple Raspis on your network cannot share the same hostname. Change your hostname with:

sudo nano /etc/hostname
sudo reboot now

Enable Wi-Fi¶

Detailed instructions are here

Alternative directions are here.

Discover what SIDs are available with: sudo iwlist wlan0 scan

Add this to /etc/network/interfaces:

auto wlan0
allow-hotplug wlan0
iface wlan0 inet dhcp
wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf

Add a network entry to /etc/wpa_supplicant/wpa_supplicant.conf for each SID with which the Raspi will need to connect:

sudo nano /etc/wpa_supplicant/wpa_supplicant.conf

The network entries should look like:

country=US
ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1

network={
    ssid="MyWiFiNetwork1"
    psk="the_password1"
    key_mgmt=WPA-PSK
}

network={
    ssid="MyWiFiNetwork2"
    psk="the_password2"
    key_mgmt=WPA-PSK
}

Stop wlan0 with: sudo ifdown wlan0

Start wlan0 with: sudo ifup wlan0

Restart networking with: sudo /etc/init.d/networking restart

Look at the log with: systemctl status networking.service

Determine your IP address with: ifconfig

Get wlan0 status with: iwconfig

Determine wlan0 channels with: iwlist wlan0 channel

Installing MDNS and Chrome¶

Install MDNS (enabling hostname.local usage) with:

sudo apt-get install avahi-daemon avahi-discover libnss-mdns

Install Chrome with:

sudo apt install chromium-browser

If chromium-browser is not found, add the universe repository with:

sudo apt-add-repository universe

Set up ssh to not ask for a password¶

Run ssh-keygen on the Mac, and hit return when asked for file in which to save the key and the passphrase. This will generate a public and private keys stored in ~/.ssh/id_rsa and ~/.ssh/id_rsa.pub.

ssh-keygen

Add the contents of ~/.ssh/id_rsa.pub on the Mac (using copy and paste) into ~/.ssh/authorized_keys on the Raspi.

sudo nano ~/.ssh/authorized_keys

Set the proper permissions for ~/.ssh/authorized_keys with: chmod 600 ~/.ssh/authorized_keys

You should now be able to ssh to the Raspi without a password.

Simplify ssh logins¶

To log into a Raspi with ssh raspi instead of ssh pi@raspi.local, add this to your ~/.ssh/config file:

Host raspi, raspi.local
  HostName raspi.local
  User pi
  StrictHostKeyChecking no
  UserKnownHostsFile /dev/null

Ensure that ~/.ssh/config is visible only to you by setting the permissions with:

sudo chmod 400 ~/.ssh/config

The StrictHostKeyChecking no option will prevent authenticity prompts from appearing during ssh logins and when doing git pushes with git push raspi master. You will no longer see prompts like this:

The authenticity of host 'raspi.local (fe84::d84b:3c2:9ba9:afa7%en0)' can't be established.
ECDSA key fingerprint is SHA256:g+fFiMPfdWH8Lwi6eKjAOWgYoTfDAPh00GnsLLE88fk.
Are you sure you want to continue connecting (yes/no)?

The UserKnownHostsFile /dev/null option will prevent ssh from writing to .ssh/known_hosts and then later failing when host keys change. In general, this is not a good security practice, but it is acceptable when working with local Raspis since you are on a private LAN and not likely dealing with malicious hosts.

Details are here.

Enable file sharing with: sudo apt-get install netatalk

Enable VNC¶

Enable VNC with raspi-config. Choose the Interfacing Options and then the VNC option. Tab to and then reboot.

Start the VNC server with:

vncserver :1 -geometry 1024x728 -depth 24

Use -geometry 2048x1456 for a larger display.

Download a VNCViewer app from here.

Start the VNCViewer app on the Mac and connect to the Raspi at raspberrypi:1.

Install Python¶

Install Python 2 with: sudo apt-get install python python-pip python-dev

Install Python 3 with: sudo apt-get install python3 python3-pip python3-dev

Vim Setup¶

Install vim with: sudo apt-get install vim

Create a .vimrc file containing this:

set ts=4 showmatch
set ruler laststatus=2 title hlsearch
syntax on
let python_highlight_all = 1

Serial Notes¶

To view data on a Raspi connected to an Arduin via serial use:

screen /dev/ttyACM0 115200

To exit screen use: Crtl-a d

Misc useful commands¶

Downgrade from rpi-update with:

sudo apt-get install --reinstall raspberrypi-bootloader raspberrypi-kernel

Install ncdu with:

sudo apt-get install ncdu