The Arduino Yún is unusual in that it combines what is effectively a 16MHz Arduino Leonardo microcontroller with an Atheros AR9331, a 400MHz microprocessor running OpenWrt (a version of Linux), so it's a bit like a combination of an Arduino and a Raspberry Pi on one board.
Here's some miscellaneous notes regarding the Yún (which means "cloud" in Mandarin).
Once you've connected the Yún to your network via an ethernet cable (WiFi comes later) you upload the "YunFirstConfig" sketch using the Arduino IDE. Then open the serial console, and you'll be presented with some questions, including your WiFi network name, network password, the name and Linux password for your Yún. Then you can log into the Yún via a web browser and further configure it.
There's also a YunSerialTerminal sketch which permits you to open a console directly to the Yún from the Arduino IDE's serial monitor. There's a single line at the top of the monitor and a "Send" button — not quite a normal terminal experience but it works. Once the Yún is available on your WiFi network you can just remotely connect to it using ssh.
$ ssh root@192.168.1.73 root@192.168.1.73's password: ••••••• BusyBox v1.28.3 () built-in shell (ash) _______ ________ __ | |.-----.-----.-----.| | | |.----.| |_ | - || _ | -__| || | | || _|| _| |_______|| __|_____|__|__||________||__| |____| |__| W I R E L E S S F R E E D O M ----------------------------------------------------- LEDEYun 17.11, r6773+1-8dd3a6e ----------------------------------------------------- root@yun:~#
The Yún comes with Python 2 but I want to use Python 3, so I'll be installing vim, tcsh, Python3, and pip3. The package names on OpenWrt are slightly different than Debian or other Linux flavours, so you might have to use opkg find name to find a software package (or look on the OpenWrt website for clues). You can install either python3 (the full package) or python3-light, which aims to provide most of what people need, and then just install the python3 subpackages as necessary. On a computer as small as a Yún you generally want to save as much space as possible. It wasn't an issue for me because I expanded the Yún's native drive space with a 32GB SD card (this is highly recommended, link below).
Once logged in via ssh here's what I did (abridged version):
# opkg update -y # opkg install vim-full # opkg install python3 # opkg install python3-pip