1. What we need:

- any varaint of Olimex A20-OLinuXino-LIME2;
- 5V DC power supply compatible with the board's power jack;
- Empty micro SD card at least 8GB of size, recommended speed 10 or higher (for downloading and booting the Linux gnuhealth image);
- Card reader-writer to download the image to the card;
- HDMI display and cable;
- USB keyboard and USB mouse; 
- Internet connection for the LIME2 board.

2. Download image:

https://www.gnuhealth.org/downloads/embedded/olimex/lime2/

gnuhealth-3.6.4-lime2-a20-SD-armbian-20.05-xfce.img.gz

Extract it and download to the card. For download to the card I'd recommend the free version of Etcher.

Important! In this image you have everything required installed, no need to install PostgreSQL, GNU Health HMIS, display manager or to run any services.

3. Insert the SD card in LIME2 board, connect the display to the HDMI connector, connect the keyboard to the USB, power the board using the power jack and 5V DC, when you get asked about login, login with user:

root

and password:

freedom

4. It is imperative to perform update and upgrade, notice that it is slow and might take a lot of time to update and upgrade - up to an hour, run these commands:

apt update -y

and after that 

apt upgrade -y

after both are complete run them again to ensure there is nothing left to update and upgade;

ignore messages for errors and if prompted agree to proceed

5. Start the graphic environment with startx - it is good to be 720p for better mouse support but can be tested at 1080p.

6. Start terminal from applications -> terminal emulator

7. Install at-spi2-core (else we would have error on GUI launch), write in the terminal:

sudo apt install at-spi2-core

8. Login as gnu health in terminal and navigate to directory HOME:

su - gnuhealth
cd $HOME

9. Start GUI of GNU health from terminal with:

gnuhealth-client

10. There is login prompt and we loging with these:

Server: federation.gnuhealth.org
Database: health36
User name: admin
Password: gnusolidario

11. Voila 

For further reading check the links below:

https://en.wikibooks.org/wiki/GNU_Health/Embedded
https://en.wikibooks.org/wiki/GNU_Health/Installation
https://en.wikibooks.org/wiki/GNU_Health/The_Demo_database
https://en.wikibooks.org/wiki/GNU_Health/Operating_System-Specific_Notes