PrawnOS Documentation

Some additional documentation for PrawnOS that wouldn't fit in the README

Useful XFCE4 keybindings and libinput-gestures:

Gestures:

Config file: /etc/libinput-gestures.conf

four finger swipe left: Switch to left workspace
four finger swipe right: Switch to right workspace

Keybindings

Configure under Settings->Window Manager->Keyboard

control+alt+left: move window to left workspace
control+alt+right: move window to right workspace
alt+left: tile widow to the left
alt+right: tile window to the right
alt+up: maximize window
alt+tab: app switcher

Configure under Settings->Keyboard->Application Shortcuts

alt+space : App launcher (spotlight-esque)
control+alt+l: Lock screen
Brightness scripts are also called here and can be remapped here or in ~/.Xmodmap

Configured using xkb

"search" key: function (fn) key
fn + backspace: delete
fn + up: page up
fn + down: page down
fn + left: home
fn + right: end
fn + "brightness up key": increase backlight
fn + "brightness down key": decrease backlight
fn + "volume mute": mute volume
fn + "volume down": decrease volume
fn + "volume up": increase volume

Initramfs and Encryption

PrawnOS uses a custom initramfs, custom init script, and dmcrypt/LUKS to enable full root partition encryption

Because the c201s bootloader, depthcharge, can't be given dynamic cmdline parameters like grub we can't use the "usual" method of setting up an initramfs. Essentially, we can't boot from an initramfs image stored on a /boot partiton

Either the initramfs needs to be built into the part of the kernel image passed to depthcharge using a kernel.its similar to this one by @ifbizo:

/dts-v1/;

/ {
	description = "Linux-libre kernel image with one or more FDT blobs";
	#address-cells = <1>;
	images {
		kernel {
			description = "vmlinuz";
			data = /incbin/("/boot/vmlinuz-SED_KVER");
			type = "kernel_noload";
			arch = "arm";
			os = "linux";
			compression = "none";
			load = <0>;
			entry = <0>;
			hash {
				algo = "sha1";
			};
		};
		fdt {
			description = "dtb";
			data = /incbin/("/boot/rk3288-veyron-speedy.dtb");
			type = "flat_dt";
			arch = "arm";
			compression = "none";
			hash {
				algo = "sha1";
			};
		};
		ramdisk@1{
			description = "initrd.img";
			data = /incbin/("/boot/initrd.img-SED_KVER");
			type = "ramdisk";
			arch = "arm";
			os = "linux";
			compression = "none";
			hash@1{
				algo = "sha1";
			};
		};
	};
	configurations {
		default = "conf";
		conf{
			kernel = "kernel";
			fdt = "fdt";
			ramdisk = "ramdisk@1";
		};
	};
};

Or it needs to be built into the kernel using the kernel config parameter CONFIG_INITRAMFS_SOURCE="PrawnOS-initramfs.cpio.gz"

For PrawnOS I decided to go with building into the kernel to avoid relying on the bootloader, the bootloader may change but the kernel will always support booting an initramfs image.

The script buildInitramFs.sh creates the PrawnOS-initramfs.cpio.gz image that is then used by buildKerenl.sh, copying all of the tools and libraries the initramfs needs from the built filesystem image.

The initramfs is what runs initialy at boot, and allows us to enter a password and decrypt the root partiton

In a normal system, when dmcrypt/LUKS is setup the initramfs image is modified to enable decrypting of the root partiton

Since we have to have a static initramfs image, and can't change it without recompiling the kernel, we detect whether encryption is in use by checking for the tag crypto_LUKS on the root device at boot.

debugging the init script

A rescue debug shell is entered when the init script encounters a problem, or if a device with the partition label RESCUESHELL is present

Label any partition on the system with RESCUESHELL to enter the initramfs rescue shell before mount and root_switch.

You can do this with cgpt add -i 1 -l RESCUESHELL /dev/sda for example to label the first partiton of a usb drive.

This is the suggested method, as then debugging can be enabled/disabled by plugging in/removing the usb device.

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