This is tested on a TX53-8030 which came with
version Ka-Ro 2010-01-06 - built 09:51:04, Feb  8 2012.

First, repartition the NAND:
fis init -f
fis create -s 0 -l 0x00400000 -b 0x70108000 -r 0x70108000 -e 0x70108000 linux
fis create -s 0 -l 0x07b20000 -b 0x70100000 rootfs

Then, configure RedBoot:
fconfig
Run script at boot: true
Boot script: 
fis load linux
exec -w 1 -c "ubi.mtd=2 root=ubi0:rootfs rootfstype=ubifs rw console=ttymxc0,115200 consoleblank=0 logo.nologo tx53_base=stkv3 video=VGA-1:640x480MR-32@60 panic=1"
>> 
Boot script timeout (10ms resolution): 1
Use BOOTP for network configuration: true
Default server IP address: 192.168.1.111  <-- your tftp server's IP address
Console baud rate: 115200
Set FEC network hardware address [MAC]: true
FEC network hardware address [MAC]: [press enter]
GDB connection port: 9000
Force console for special debug messages: false
Network debug at boot time: false
automatic boot partition selection: false
Update RedBoot non-volatile configuration - continue (y/n)? y
reset
CTRL-C

Now, and whenever you receive an update, flash the kernel and rootfs:
load -r -b 0x70100000 zImage
fis create linux
load -r -b 0x70100000 rootfs.ubi
fis create rootfs
reset


##########################################
# building the rootfs image with imagetool
##########################################

Extract custom-tx53-java.tar.bz2 >>> custom-tx53-java
Put tx53.conf and gpe-demo-extended.conf in ~/.mucross/
Start imagetool.
File->open, select tx53-accutime-java.prj
Make sure that Target Device is "tx53"
and Image Type "is gpe-demo-extended".
Go to the "Custom" tab. Make sure "Include Customisation Directory" is ticked.
Select custom-tx53-java as the custom directory.
Create Filesystem.