Please note: You need to a Wi-Fi card or adapter that supports hostapd for these directions to work. Most Atheros-based wifi cards and adapters should work. Check out our networking section for adapters that support hostapd. All of our wifi cards and adapters should list support for hostapd.
You can setup a Hotspot / Access Point / AP / Master Node in GNU/Linux utilizing the graphical user interface through the standard networking tools under most GNU/Linux distributions. Open your network applet's network connections and find the the Wi-Fi tab to locate the Hotspot option.
Here is a basic run down under Linux Mint 20 / Trisquel 10, but this should be the same or similar under most other distributions utilizing the GNOME or Cinnamon desktop environments or some fork thereof (for Ubuntu you may need to search for Advanced Network Configuration):
1. Open Network Connections and click the + button
2. Select Wi-Fi and the Create... button
3. In the Wi-Fi tab select Hotspot under the Mode drop down box
4. Enter an SSID name you would like to utilize for your hotspot in the SSID box
5. In the Wi-Fi Security tab select WPA & WPA2 Personal
6. Enter a password in the password box
7. Click the Save button
8. Make sure you have an active internet connection on this system
That should be it. You should now have an AP setup where you can connect to the internet from another wireless system.