This is set of utilities which help to run and mantain GNU/Linux for Raspberry Pi platform. But many of them are of general embedded syetems use or even usable for desktop and server systems.
This is script and configuration tool which allows to switch minimal or full-featured Linux distribution to mode where all root filesystem changes are temporal/hold only in system RAM. This mode is selected by addition init=/sbin/init-overlay parameter to Linux kernel command line. Solution finds and uses available layered filesystem support (aufs, overlay, unionfs).
The documentation can be found in init-overlay.txt file which is intended to be copyed with scripts to the target root filesystem. The install and uninstall overlayctl commands are Raspberry Pi specific for now but rest is portable to any other system.
Some more information can be found in InstallFest 2015 presentation slides.
The Raspberry Pi kernel including Aufs patches and configured to build Aufs and overlayfs support can be cloned from linux-rpi repository.
The cript can setup loopback device for each partition, enables to mount image partitions etc. It requires administrator priviledges and creates local directory with devices and mountpoints according to found DOS MBR style partition table.
For more information consult mount-img-parts script dierctly.
Stephen Warren's U-Boot version is cloned, configured and built by build-u-boot. Example EXTLINUX config to select local boot from SD-card or NFS root is provided as well.