linux/Documentation/ABI/testing/sysfs-firmware-initrd

What:		/sys/firmware/initrd
Date:		December 2023
Contact:	Alexander Graf <[email protected]>
Description:
		When the kernel was booted with an initrd and the
		"retain_initrd" option is set on the kernel command
		line, /sys/firmware/initrd contains the contents of the
		initrd that the kernel was booted with.