|EECE-4029||Operating Systems||Fall 2016|
Install Linux On Something, Compile a Kernel Module
due: Sep 2 - nothing to submit to blackboard
|Teaching theory is fine but it is more useful in the long run if it is accompanied by practical experience. We will use the linux OS as a testbed for ideas and to get a feel for controlling a computer at a low level. This experience will be desirable to numerous employers. Linux is used because it is open and is a testbed for most new OS concepts, making it ideal for this class.|
|The instructions below are not fool-proof. See the instructor if you have problems|
|Install linux on either 1) a USB flash drive of 32 GB, 16 GB, 8 GB, or, if desperate, 4 GB; 2) an old, disused computer; 3) a windows computer by repartitioning the hard drive to allow for dual booting (could be dangerous); or 4) as a virtual machine on any computer with spare capacity (safe but slow and be really sure to assign more than one processor to the virtual machine). Instructions for installing linux on a USB drive, from an ISO image, or from the network are given in installinux.html. Or use the instructions provided in the full ubuntu linux installation guide. For option 4) (virtualization) see How to Install Ubuntu on VirtualBox. Another virtualization guide is here or get a ready made Ubuntu 14.04.4 vdi image (watch it - I know nothing about this), but expect no support or guarantees from the instructor who has minimal experience with Windows.|
|Kernel Header Installation Options:|
Once you have a working linux system, kernel header files and a
compiler must be installed in order to compile kernel modules. To get
the headers and compilers use apt-get as directed
below or you can download the latest kernel directly from kernel.org.
Note: if you download and use the USB image mentioned above and in installlinux.html, you will already have the headers and compilers installed.
Note: you must also have pre-compiled kernel modules in /lib/modules/3.13.0-XX-generic where 3.13.0-XX-generic is the same as the header subdirectory in /usr/src/, after linux-headers-. This should have been done automatically when the kernel is installed but is mentioned here because it has been a source of problems in the past as /lib/modules/3.13.0-XX-generic/build is a link to /usr/src/linux-headers-3.13.0-XX-generic that is traversed when compiling kernel code. If the proper kernel headers are not there, the build link is dangling.
|C/C++ Compiler Installation:|
If you installed using the DVD install disk mentioned above, the C compiler
should already be installed and you should be able to being compiling kernel
modules. If not, to install the compilers do this as root:
prompt> apt-get install build-essential fakeroot libxml-parser-perl gcc g++
|Compiling, Loading, and Unloading a Kernel Module:|
The following assumes you installed ubuntu with account name student
with password student.
You will have to become super user (a.k.a. root) in order to load and unload kernel modules. Installing Ubuntu Linux as above allows access to root as follows:
prompt> sudo su password for student: studentYou should only have to type the password once per session per time-period per shell as ubuntu is set to remember the password on a shell for some time-period or until the session is terminated.
Note: although you need to operate as super user to load and unload kernel modules, you should never compile anything as super user!!! You will be really sorry in the long run if you do. There is no doubt you will feel better compiling as root because it is easy to do so and then load a module but you will certainly regret it if you do as you will eventually be in the instructor's office asking for help to repair your system and the instructor is going to remember this visit at the end of the semester.
Next try to compile a kernel module and observe what happens when it is loaded and unloaded. Create a test directory and download source code and a Makefile for a simple module as user student (not as super user) as follows:
prompt> mkdir Test prompt> cd Test prompt> wget http://gauss.ececs.uc.edu/Courses/c4029/labs/tester_1.c --2014-08-24 14:23:41-- http://gauss.ececs.uc.edu/Courses/c4029/labs/tester_1.c Resolving gauss.ececs.uc.edu (gauss.ececs.uc.edu)... 126.96.36.199 Connecting to gauss.ececs.uc.edu (gauss.ececs.uc.edu)|188.8.131.52|:80... connected. HTTP request sent, awaiting response... 200 OK Length: 345 [text/x-c] Saving to: 'tester_1.c' 100%[========================================>] 345 --.-K/s in 0.007s 2014-08-24 14:23:41 (47.0 KB/s) - 'tester_1.c' saved [345/345] prompt> wget http://gauss.ececs.uc.edu/Courses/c4029/labs/Makefile --2014-08-24 14:23:55-- http://gauss.ececs.uc.edu/Courses/c4029/labs/Makefile Resolving gauss.ececs.uc.edu (gauss.ececs.uc.edu)... 184.108.40.206 Connecting to gauss.ececs.uc.edu (gauss.ececs.uc.edu)|220.127.116.11|:80... connected. HTTP request sent, awaiting response... 200 OK Length: 534 [text/plain] Saving to: 'Makefile' 100%[========================================>] 534 --.-K/s in 0.001s 2014-08-24 14:23:55 (691 KB/s) - 'Makefile' saved [534/534]Now compile the kernel module like this:
prompt> make make -C /lib/modules/3.9.9-302.fc19.i686/build M=/home/franco/Downloads modules make: Entering directory `/usr/src/kernels/3.9.9-302.fc19.i686' CC [M] /home/franco/Downloads/tester_1.o Building modules, stage 2. MODPOST 1 modules CC /home/franco/Downloads/tester_1.mod.o LD [M] /home/franco/Downloads/tester_1.ko make: Leaving directory `/usr/src/kernels/3.9.9-302.fc19.i686'To see the file that is the kernel module do this:
prompt> ls -a Makefile tester_1.c .tester_1.mod.o.cmd tester_1.mod.o Module.symvers ./ tester_1.mod.c .tester_1.o.cmd tester_1.o .tmp_versions/ ../ .tester_1.ko.cmd tester_1.ko modules.orderThe kernel module is tester_1.ko and is shown above in green with a lot of auxilliary files that were created during compilation. Load the module like this (assuming you already ran "sudo su" once successfully):
prompt> sudo su prompt# insmod tester_1.ko prompt# exitCheck to see whether the module loaded like this:
prompt> lsmod | grep tester tester_1 12394 0Observe that the module is running like this:
prompt> dmesg ... [21045.273404] tester 1: Module loaded successfullyUnload the module like this:
prompt> sudo su prompt# rmmod tester_1 prompt# exitObserve the result of unloading like this:
prompt> dmesg ... [21045.273404] tester 1: Module loaded successfully [21062.871344] tester 1: Module unloaded successfullyIf you get a result that looks something similar to the above, you are able to compile modules and check whether they are loaded, running, or unloaded.