1. RTAI Installation on Ubuntu

2. A Hello World Linux system call (arm)

3. Changing default text and font size in Matlab

4. Redirecting X display in Linux

1．RTAI 3.4 Installation with Linux Kernel 2.6.17 on Ubuntu 6.10

1). compile Linux kernel (Ubuntu, gcc version 4.1.2)

Get linux kernel source:

# cd /usr/src

# wget http://www.kernel.org/pub/linux/kernel/v2.6/li nux-2.6.17.3.tar.bz2

# tar -xjvf linux-2.6.17.3.tar.bz2

# ln –s linux-2.6.17.3 linux

Get RTAI 3.4 source (rtai-3.4.tar.bz2) from https://www.rtai.org/RTAI/, copy to /usr/src

# tar –xjvf rtai-3.4.tar.bz2

Patch the Linux kernel

# cd /usr/src/linux

# patch –p1 < /usr/src/rtai3.4/base/arch/i386/patches/hal-linux-2.6.17-i38 6-1.3-08.patch

Configure and compile the kernel

# apt-get install kernel-package libncurses5-dev //download package needed for kernel compilation

# vi /usr/src/linux/Makefile in line 308 add -fno-stack-protector to CFLAGS :=

# make menuconfig //make sure Module versioning support and CONFIG_REGPARM are not set

# make-kpkg clean //under directory /usr/src/linux

# make-kpkg --initrd --append-to-version=-rtai kernel_image kernel_headers

// it takes some time

# cd /usr/src; ls –l // two deb files are generated

# dpkg -i linux-image-2.6.17.3-rtai _2.6.17.3- rtai -10.00.Custom_i386.deb< /p>

# dpkg -i linux-headers-2.6.17.3- rtai _2.6.17.3- rtai -10.00.Custom_i386.deb< /p>

# vi /boot/grub/menu.lst // verify the new kernel is installed

# reboot

2). compile and install RTAI 3.4

# vim /usr/src/rtai-3.4/base/include/rtai_posix.h and remove the declaration of pthread_condattr_setclock and pthread_condattr_getclock

# export LD_LIBRARY_PATH=/usr/realtime/lib:$LD_LIBRARY_PATH

# cd /usr/src/rtai

# make

# make install

3). Test RTAI

# vi /usr/realtime/bin/rtai-load and change #!/bin/sh to #!/bin/bash in the first line

OR link /bin/sh to /bin/bash (it is linked to /usr/dash in Ubuntu 6.10)

# cd /usr/realtime/testsuite/kern/latency/

# ./run

If everything all right, you will get sth. like:

## RTAI latency calibration tool ##

# period = 100000 (ns)

# avrgtime = 1 (s)

# do not use the FPU

# start the timer

# timer_mode is oneshot

RTAI Testsuite - KERNEL latency (all data in nanoseconds)

RTH| lat min| ovl min| lat avg| lat max| ovl max| overruns

RTD| ; -956| ; -956| ; 308| ; 3535| ; 3535| ; 0

RTD| -1037| -1037| ; 299| ; 3462| ; 3535| ; 0

Devices created by following this installation procedure will disappear at each machine rebooting. A short script containing the following can solve the problem:

for n in `seq 0 9`; do

; f=/dev/rtf$n

; if test \! -c $f; then

; mknod -m 666 $f c 150 $n

; fi

done

2．The Hello World System Call in Linux 2.6.11 with Intel XScale Processor (ARM) .

steps in creating a system call.

First of all, one should have the kernel source code.

Below is for creating a system call named "mycall" in arm architecture in

linux 2.6.11.

More details can be found in http://www.linuxjournal.com/article/3326.

1). in /usr/src/linux/arch/arm/kernel/calls.S, add .long sys_mycall

  (not necessarily the same with other architecture. e.g., no need in i386)

2).

Randomly choose a file (I chose arch/arm/kernel/sys_arm.c.) and add

the following

asmlinkage int sys_mycall (int a, int b) {

printk("calling sys_mycall\n");

return(a+b);

}

3).

in /usr/src/linux/include/asm/unistd.h, add a number for the call following

the existing definitions. It must be one bigger than the last one in the file.

In my example, it is

#define __NR_mycall (__NR_SYSCALL_BASE+281)

4).

compile the kernel and restart with the new kernel.

5).write a test file, for example,

#include <errno.h>

#include <linux/unistd.h> /* for _syscallX macros/related stuff */

//#include <linux/kernel.h>

_syscall2(int, mycall, int,a, int,b);

main(){

printf("the sum of 4+3 is %d\n",mycall(4,5));

}

compile using gcc -I /usr/src/linux/include testcall.c -o testcall

3．Changing default axis and tex font sizes in matlab

Create a file named startup.m with the following and put it under matlab\work

% axis and text font size

set(0,'defaultaxesfontsize',20);

set(0,'defaulttextfontsize',20);

set(0,'defaultlinelinewidth',1.5);

set(0,'defaultLineMarkerSize',13);

set(0,'defaultlinelinewidth',1.5);

4．Redirecting X display in Linux

Two machines host1, host2. Host1 is a linux machine; host2 can be a linux machine or a windows machine installed with cygwin Xwindows (started by startxwin.bat)

We intend to run a GUI application in host1 using telnet or ssh, and see its GUI on host2.

1) In host2, type

# xhost +host1 ( or simply xhost + to allow accept redirection from any machines)

2) In host1 type

# ssh host1 (or telnet)

# export DISPLAY=host2:0

Then run any GUI application in host1, such as firefox, and the GUI will be displayed in host2

If both machines (host1 and host2) are installed with fedora core, the step can be omitted