File /dev/video3 disappears !!!

Hi all.
I'm Diep.I have got a frienlyARM tiny 210v2 KIT.I have installed Qtopia in
zImage.When it's done,I connect Webcam usb to KIT.I run Camera usb 
application in Friendly Tab.It's working :D.On PC installed Ubuntu 11.10,I
use Gftp to KIT.I find to Path /dev/video3  (on KIT).I want to copy video3
file but i cannot.
I think this file is using.I edit file .rcS (int /etc/init.d..).I did
disable line Load Qtopia by add ' # ".Save it.
After I reboot KIT.On PC I use Gftp to KIT.I again find to /dev/video3.
But amazing,video3 file disappeared.I'm very worry,and edit again .rcS file
permit Load Qtopia and reboot....
Login KIT.I find /dev/video3 but it is realy disappear!
Can you help me fix this problem! Why does video3 disappear?

Only going on some old mini2440 experience but shows us your rcS file.

Is /etc bound to /tmp?

It's my .rcS when i edit deny Load Qtopia
[code]
#! /bin/sh

PATH=/sbin:/bin:/usr/sbin:/usr/bin:/usr/local/bin:
runlevel=S
prevlevel=N
umask 022
export PATH runlevel prevlevel

#
#  Trap CTRL-C &c only in this shell so we can interrupt subprocesses.
#
trap ":" INT QUIT TSTP
/bin/hostname FriendlyARM

[ -e /proc/1 ]    || /bin/mount -n -t proc  none /proc
[ -e /sys/class ] || /bin/mount -n -t sysfs none /sys
[ -e /dev/tty ]   || /bin/mount    -t ramfs none /dev
/bin/mount -n -t usbfs none /proc/bus/usb

echo /sbin/mdev > /proc/sys/kernel/hotplug
/sbin/mdev -s
/bin/hotplug
# mounting file system specified in /etc/fstab
mkdir -p /dev/pts
mkdir -p /dev/shm
/bin/mount -n -t devpts none /dev/pts -o mode=0622
/bin/mount -n -t tmpfs tmpfs /dev/shm
/bin/mount -n -t ramfs none /tmp
/bin/mount -n -t ramfs none /var
mkdir -p /var/empty
mkdir -p /var/log
mkdir -p /var/lock
mkdir -p /var/run
mkdir -p /var/tmp

/sbin/hwclock -s

syslogd
/etc/rc.d/init.d/netd start
echo "                        " > /dev/tty1
echo "Starting networking..." > /dev/tty1
sleep 1
/etc/rc.d/init.d/httpd start
echo "                        " > /dev/tty1
echo "Starting web server..." > /dev/tty1
sleep 1
#/etc/rc.d/init.d/leds start
#echo "                        " > /dev/tty1
#echo "Starting leds service..." > /dev/tty1
#echo "                        "
#sleep 1

echo "                        " > /dev/tty1
/etc/rc.d/init.d/alsaconf start
echo "Loading sound card config..." > /dev/tty1
echo "                        "

# install additional modules
modprobe ft5x06_ts 2>/dev/null
modprobe goodix_touch 2>/dev/null
modprobe ov9650 2>/dev/null
modprobe tvp5150_tiny210 2>/dev/null
modprobe rtl8192cu 2>/dev/null

/sbin/ifconfig lo 127.0.0.1
/etc/init.d/ifconfig-eth0
fa-network-service
hdmi-service autostart

# /opt/360box/apktools-service
# /opt/360box/run.sh &

#/bin/qtopia &
echo "                                  " > /dev/tty1
echo "Starting Qtopia or MyApp, please waiting..." > /dev/tty1
sleep 1


[/code]

# mounting file system specified in /etc/fstab

OK, now the contents of the above file.

/etc/fstab

No such file.No folder of file has name is ' fstab'

OK.

In an early mini2440 rcS /etc was bound to /tmpfs so that it was volatile. 
IE, it did not retain any changes made to it.  

Are you using a SD card?  You might have to do a sync after making changes
in case you try to shut the processor down BEFORE the changes are written
to SD card.

Maybe, try just putting a test.txt file into /etc, save it, shut the
machine down, re-boot and see if it has disappeared.

I have just installed Qtopia for KIT.I check /etc/fstab file.But i cannot
find it.It's not exist :(

Yes,I use a sd card to boot.
I have just created a test.txt anh copied it to /etc/ on KIT.Then reboot
machine.On PC I use Gftp to KIT.I also see test.txt file :) .But I dont
also see /etc/tstab :(

Now i need to edit .rcS file
[code]
/bin/mount -n -t devpts none /dev/pts -o mode=0622
/bin/mount -n -t tmpfs tmpfs /dev/shm
/bin/mount -n -t ramfs none /tmp
/bin/mount -n -t ramfs none /var
[/code]

Help me,please!