If you want to temporarlily change the keyboard layout, you can use the following command:
sudo loadkeys fr
fr should be replaced by the layout you want.
If you want to definitively change the keyboard layout, you have to run:
sudo apt-get install keyboard-configuration
sudo dpkg-reconfigure keyboard-configuration
This may not work on your system: modifications of this documentation are welcome.
System configuration for Raspberry Pi
On a Raspberry Pi system configuration parameters are set in a file called /boot/config.txt (https://www.raspberrypi.org/documentation/configuration/config-txt/).
This file gets overwritten on each Volumio update so user made changes in /boot/config.txt are not preserved. To make them permanent custom settings need to be added to /boot/userconfig.txt instead.
Note: The following options do not work when placed in /boot/userconfig.txt:
gpu_mem gpu_mem_256 gpu_mem_512 gpu_mem_1024 total_mem require_total_mem startx start_x start_debug boot_partition legacy_mapping bootcode_delay force_pvt uart_2ndstage start_file fixup_file