Preemptive Kernel in Redhat?

witnessmenow

I need to build a preemptive kernel for testing some things out, could any one please direct me where i could find out how to do this please?

Thanks!

Khannie

There are loads of guides on building new kernels. Once you've done it once it's actually not that difficult. The main jist of it is that you'll need to install the source (if it's redhat, then with an RPM or yum or whatever). as root: cd /usr/src/linux; make menuconfig

The pre-emptive bits are in the first few options iirc.

Good luck.

witnessmenow

After doing a bit of reading about, is it a patch i need to make the kernel preemptive? I cannot find this patch! Sorry for the nooby questions!

sobriquet

If you've never built a kernel before, start simple: find a guide to building a kernel from source on Redhat, there's more than likely an official one. Get a vanilla kernel building first, then think about changing config options or patching it.

Be clearer though: are you using RHEL or Fedora Core?

Do you know if you need to build a vanilla source (ie from kernel.org) or an RH supplied one? (They might mix in their own patches by default.) If you don't know, the RH one is probably more suitable, like Khannie says it'll be in the RH repositories and installable via yum or whatever. (Not an RH user myself.)

witnessmenow

Ok i did this a few days ago but i thought I'd just let you know what i did(I was using redhat 2.6 kernel). It might prove useful to fellow noobs:

Download your kernel source

move it to

cd /usr/src/

Note: If you have a redhat kernel already and its information is stored at /usr/src/redhat you need to move it(renaming the redhat folder should be fine), when you extract your kernel source it will extract to /usr/src/redhat

extract the kernel source -

gzip -cd kernel source file | tar xvof -

then move to

cd /usr/src/redhat/SOURCES

then type the following (will be diffrent for diffrent kernel versions i guess)

rpmbuild -bb kernel-2.6.spec

then go here (again will be diffrent for diffrent kernels i guess)

/usr/src/redhat/BUILD/kernel-2.6.18/linux-2.6.18.i386

Then type

make menuconfig

This will load up a bit of a GUI:

Go to:
Processor type and features --->

then:
Preemption Model (Preemptible Kernel (Low-Latency Desktop)) --->

and select
Preemptible Kernel (Low-Latency Desktop)

now we're ready to make!

type these in the following order

make clean

make

make install

go to your grub file to make sure its there

vi /boot/grub/grub.conf

Congrats if it is!

Pretty awful guide but you never know, migh help somone!

Naikon

This is my solution under Slackware 12.1:

cd  /usr/src/

You should have your kernel sources installed here, and the kernel
modules package should be installed too.

For example, if you don't have the latest source,
go to http://www.kernel.org/pub/linux/kernel/v2.6/ and download
the sources.

Move the sources to /usr/src/ and perform a gzip and tar decompress.
If the end is .bzip , you will need to use bzip2 with the -d flag prior to the
next step.

tar -xvjf   linux-2.6.25.4.tar.gz

Now, you should have a skeletal directory with all the header files and sources.
Run:

make mrproper

Which will clean up the directory, and prepare for a kernel compile.

Now, run

make menuconfig

Which will give you a ncurses based menu to navigate.
Make sure essential drivers for IDE drives etc, are not loaded
as modules, but compiled into the kernel.

Save your config to a file and exit.
Now run in this order:

make -j(n+1) V=1    // n is the number of cpu's in your setup.
                                            A multi-core system is thus J=3.
                                            V is level of verbose output. 

           make modules  //compile kernel modules


           make modules_install  //install compiled modules 

Now move the System.map to /boot/System.map.
Next, move the finished image in the /arch/x86/boot/
directory(usually called bzImage) to your /boot directory.

Now edit /etc/lilo.conf for the new image.
Add a new entry alongside existing kernel entry.

image = /boot/yourimage
root = /dev/your root partition(sda1 for example)
Label = name presented during boot
read-only /*root partition should be read only*/

Now run /sbin/lilo to append changes.
There should be two entries, your new image,
and the old image incase the new kernel won't boot.

Now take a deep breath and reboot the machine:)
That's all there is to it! (be very careful during the options menu though)