Development:Configuring FEX

Configuration via GUI

The FEXConfig tool provides a graphical user interface to edit FEX configuration. On first use, it will load default settings and save them to .fex-emu/Config.json.

Setup Rootfs

The General tab in FEXConfig contains the rootfs configuration.

• Named RootFS folders option shows RootFS installed in $HOME/.fex-emu/RootFS/
  • sqsh files and folders are selectable here
• Selecting an option in the Named RootFS option will set the name in RootFS
  • If your x86 RootFS is in an absolute folder elsewhere, you can place the absolute path in the RootFS option

Manual Configuration

The FEX main configuration file lives at $HOME/.fex-emu/Config.json

• or $XDG_CONFIG_HOME/.fex-emu/Config.json if you use XDG).

This is a JSON file that holds all of our settings. The basic structure is as follows:

 {
     "Config": {
           "Threads": "0",
           "MaxInst": "500",
           "RootFS": "Ubuntu_21_10"
     }
 }

There are a fair number of configuration options to tinker with. You can see a full suite of configuration option in the FEX man pages.

• man FEX - To see the options
  • Under the ENVIRONMENT section there is each option's ENVIRONMENT override
  • Additionally each option has a "JSON key" name that shows the Key inside of the Config.json file
  • Every option is a string inside of the config and will be reinterpreted to their programmatic type at load