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5.3 Linux Support 25
5.3.9 mmcinitrd.u-boot
The mmcinitrd.u-boot userland Makefile target has a lot of parts, but its’
goal is simple
Provide an application developer a means of staying focused on
development without the possibility of trashing a flash.
It presumes the existence of an SD card formatted with the VFAT filesys-
tem, and a cramfs image on the SD card (in the root as cramfs.img). The
mmcinitrd.u-boot file is also typically loaded on the SD card, but that isn’t
strictly necessary, as long as it is available and handed to the Linux kernel.
Through a series of steps, it links the /bin, /lib, /usr, /var, /sbin,
and /share directories from within cramfs.img, leaving the root of the
filesystem read-write (and volatile), with /mmc referring to the root of the
SD card.
Furthermore, it presumes the existence of a script or executable named
linux init in the root directory of the SD card.
This is done both as an example and as a useful way of nailing down the
static pieces of a package (in the cramfs.img file) and allowing read-write
access to the filesystem during application development.
The linux init script on the SD card may be modified to start an app
directly, without any risk of b oot failure.
Look at the file /etc/init.d/rcS for the details of how this is accom-
plished.
5.3.10 Javascript stuff
Refer to the Boundary Devices’ Javascript Manual for details of the Bound-
ary Devices scripting application.
5.3.11 Login and SSHD support
By default, the Userland build tool creates a password file /etc/passwd
with a root password of BoundaryDevices.
This is only needed when connecting over sshd.
Use the menuconfig make target to change this.
December 28, 2005 Revision 2.8