PPC Linux Kernel Howto

Obtaining source code

• Linuxppc.org keeps a page with links to several sites where source code can be obtained.
• For those of you who prefer the bleeding edge, you can access official PPC trees using Bitkeeper. It seems to be relatively painless to use once you get started, and you can maintain access to developments almost as quickly as they happen. The sacrifice, of course, is stability, but if you don't like the kernel you have today, it will change by tomorrow :)

Compiling the code

• There are a fair amount of web sites devoted to the issue of kernel building, so this howto will be brief on the subject. For more information, try the general Kernel HOWTO. Also, make sure you have read the README files that come with the source.
• If you are using Bitkeeper, make sure you run bk -r edit when you create a new repository in order to check out the code for building and/or editing.
• Generally, you will want to configure and build the kernel by executing something like:

  $ make menuconfig (Or make xconfig for graphical configuration)
  $ make dep
  $ make vmlinux
  
  

  Then copy the new vmlinux and System.map into /boot. You may need to run make clean after make dep.
• If you have problems compiling, check the error messages that the compiler gives you. Sometimes there may be a bug in a source file, in which case you can attempt to find the config option that controls the file and remove it. If you compile without the option, and the kernel runs fine, then your problem is solved. Other problems may be solved by running menuconfig rather than xconfig. In my experience, xconfig doesn't always do the best job of converting old config files and sometimes forgets to set options, causing problems that often aren't detected until the linking stage. Try running menuconfig instead to see what happens.

When configuring the kernel

• If you are creating a kernel that will be used to netboot a machine, you may want to remove as many unnecessary features as possible in order to reduce the size of the file you will be transfering. Necessary items to check for are initial ramddisk support (in Block Devices), ROM file system support, and NFS support. Also, make sure that networking is correctly set up and that you have compiled a kernel without modules.
• For all the rest of the kernels, modules are a useful tool that you should become familiar with. Our work with Myrinet devices requires module support. Make sure if you enable kernel version information support that all modules you compile also enable it. Also, make sure that your modutils are up-to-date. You can find source and binary RPMs at rpmfind.net, or get sources and binaries directly from www.kernel.org.
• Our environment mixes single and dual processor machines. In order to make the software easier to manage, we are running all machines with SMP support enabled, which seems to be working reasonably well.
• Make sure NFS support is enabled on the clients, and that NFS server support is enabled on the server. If you wish to run version 3, check your startup scripts. By default, options to rpc.mountd are set to --no-nfs-version 3. Unless you remove this option, you will be running version 2 even if you have compiled in support for version 3.
• If you want to use more than 1 GB of memory, enable High Memory support in General Setup.
• In order to run DHCPd, you will need to enable Socket Filtering under Networking options on the server.