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The specific commands used in this article are appropriate for the OpenSUSE distribution, but do vary from one distribution to another. Check your documentation for the specific commands you will need before trying to recompile your kernel.
Compiling your kernel isn't that difficult, but remember there's a distinct probability of hosing your machine and turning it into a paperweight. (Okay, that may be a bit of an exaggeration. In the worst case, you simply would have to re-install Linux, and you wouldn't lose your data.) In my case, I used the YaST administration tool and installed two kernels, so I could choose either of them at boot time, and if I destroyed one, I could reboot with the other one, re-install the broken kernel and keep trying.
You need some specific packages to do this: kernel-source (the source files for the actual kernel), gcc (the compiler), ncurses (for the menus) and bzip2 (used internally to create boot images). You also need to know a bit about your hardware. Use cat /proc/cpuinfo to see how many CPUs you have and their brands, and cat /proc/meminfo for RAM information (Listing 3).
Listing 3. You will need information about your CPU and RAM before recompiling your kernel.
$ cat /proc/cpuinfo processor : 0 vendor_id : AuthenticAMD cpu family : 6 model : 8 model name : Mobile AMD Athlon(tm) XP 2200+ [...some lines snipped...] $ cat /proc/meminfo MemTotal: 483488 kB MemFree: 11560 kB Buffers: 19888 kB Cached: 323408 kB SwapCached: 2768 kB Active: 166432 kB Inactive: 230396 kB [...more lines snipped...]
Start with a dry run and recompile the kernel without any changes, just to see if everything is set up okay. Working as root, do what's shown in Listing 4.
Listing 4. Do a dry run to ensure that you have everything you need for compiling the kernel.
cd /usr/src/linux make clean make make modules_install make install
The make processes will run for a while, and although they might produce some warnings, there shouldn't be any errors. If everything still is running okay after you reboot, it means you can start experimenting; you already did a kernel build. (If things did go seriously wrong, reboot with the other kernel, re-install the thrashed kernel, fix the problem, and try a dry run again.)
Tweaking the kernel is simply a matter of choosing the appropriate options from a (large) menu. As root, do the following:
cd /usr/src/linux make clean make menuconfig
and you will see a screen (Figure 1) with a menu full of hundreds of options, although luckily, you will have to change only a few of them.
If graphical interfaces are more your style, change the last command to make xconfig for a friendlier way of working (Figure 2).
The following are some of the options to change:
Under General Setup, uncheck Cpuset support.
Under Processor Type and Features, check Tickless System and High Resolution Timer Support. Select the right CPU type under Processor Family, so the compiled kernel code will be optimized for it, and uncheck Generic x86 Support, which is needed only for generic kernels. Choose the amount of RAM you have under High Memory Support. Check Preempt the Big Kernel Lock, and under Preemption Model, choose Preemptible Kernel (Low-Latency Desktop). Note that for a server machine, you should select the No forced preemption option. Under Timer Frequency, choose 1000 (standing for 1000H). Finally, if you have a machine with only one CPU, uncheck Symmetric multi-processing support. If you have two or more CPUs, check that box, and under Maximum number of CPUs, enter the correct number. (All this data comes from doing cat /proc/cpuinfo, as discussed previously.)
Under Block Layer, uncheck everything, unless you have disks larger than 2Tb.
Under Kernel Hacking, uncheck Kernel Debugging, Collect kernel timer statistics, Debug preemptible kernel and Write protect kernel read-only data structures.
After you are done selecting options, exit the configuration program (say “yes” to save the new kernel configuration) and then do the following:
make make modules_install make install
Watch for unexpected error messages; there should be none. You will need to wait, as when you did with the dry run. On my laptop, the complete process requires more than 30 minutes. If you get an error message, either go back to the menu to try to fix whatever was wrong, or reboot with your backup kernel, re-install the broken kernel, and try again. If everything is okay, simply reboot, and try out your new kernel.
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