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dfly handbook suggestion...

From: John Leimon <jleimon@xxxxxxxxxxxxx>
Date: Fri, 14 Oct 2005 16:50:29 -0700 (PDT)

I have modified the Building and Installing a Custom
Kernel page in the dfly to better suit new users.

In specific I added segment within 'Building a Kernel'
that states that buildworld needs to be run after
using cvsup. This is not mentioned explicitly in the
original page and should ease confusion esp. in new
users trying to build a custom kernel after cvsup'ing
in a source tree.

Modified version attached.

 - John
Title: Building and Installing a Custom Kernel

9.3 Building and Installing a Custom Kernel

First, let us take a quick tour of the kernel build directory. All directories mentioned will be relative to the main /usr/src/sys directory, which is also accessible through /sys. There are a number of subdirectories here representing different parts of the kernel, but the most important, for our purposes, are arch/conf, where you will edit your custom kernel configuration, and compile, which is the staging area where your kernel will be built. arch represents either i386 or amd64, at this point in development. Everything inside a particular architecture's directory deals with that architecture only; the rest of the code is common to all platforms to which DragonFly could potentially be ported. Notice the logical organization of the directory structure, with each supported device, file system, and option in its own subdirectory.

Note: If there is not a /usr/src/sys directory on your system, then the kernel source has not been installed. The easiest way to do this is via cvsup.

Next, move to the arch/conf directory and copy the GENERIC configuration file to the name you want to give your kernel. For example:

# cd /usr/src/sys/i386/conf

Traditionally, this name is in all capital letters and, if you are maintaining multiple DragonFly machines with different hardware, it is a good idea to name it after your machine's hostname. We will call it MYKERNEL for the purpose of this example.

Tip: Storing your kernel config file directly under /usr/src can be a bad idea. If you are experiencing problems it can be tempting to just delete /usr/src and start again. Five seconds after you do that you realize that you have deleted your custom kernel config file. Do not edit GENERIC directly, as it may get overwritten the next time you update your source tree, and your kernel modifications will be lost.

You might want to keep your kernel config file elsewhere, and then create a symbolic link to the file in the i386 directory.

For example:

# cd /usr/src/sys/i386/conf
# mkdir /root/kernels
# cp GENERIC /root/kernels/MYKERNEL   
# ln -s /root/kernels/MYKERNEL

Note: You must execute these and all of the following commands under the root account or you will get permission denied errors.

Now, edit MYKERNEL with your favorite text editor. If you are just starting out, the only editor available will probably be vi, which is too complex to explain here, but is covered well in many books in the bibliography. However, DragonFly does offer an easier editor called ee which, if you are a beginner, should be your editor of choice. Feel free to change the comment lines at the top to reflect your configuration or the changes you have made to differentiate it from GENERIC.

If you have built a kernel under SunOS™ or some other BSD operating system, much of this file will be very familiar to you. If you are coming from some other operating system such as DOS, on the other hand, the GENERIC configuration file might seem overwhelming to you, so follow the descriptions in the Configuration File section slowly and carefully.

Note: Be sure to always check the file /usr/src/UPDATING, before you perform any update steps, in the case you sync your source tree with the latest sources of the DragonFly project. In this file all important issues with updating DragonFly are typed out. /usr/src/UPDATING always fits your version of the DragonFly source, and is therefore more accurate for new information than the handbook.

Building a Kernel

  1. Change to the /usr/src directory.

    # cd /usr/src
  2. Compile the kernel.

    # make buildkernel KERNCONF=MYKERNEL
  3. Install the new kernel.

    # make installkernel KERNCONF=MYKERNEL

If you have modified your source tree using CVSup then you will have to use the buildworld, buildkernel sequence as follows:

  1. Change to the /usr/src directory.

    # cd /usr/src
  2. Build userland programs.

    # make buildworld
  3. Compile the kernel.

    # make buildkernel KERNCONF=MYKERNEL
  4. Install the new kernel.

    # make installkernel KERNCONF=MYKERNEL
  5. Install userland files.

    # make installworld

The new kernel will be copied to the root directory as /kernel and the old kernel will be moved to /kernel.old. Now, shutdown the system and reboot to use your new kernel. In case something goes wrong, there are some troubleshooting instructions at the end of this chapter. Be sure to read the section which explains how to recover in case your new kernel does not boot.

Note: If you have added any new devices (such as sound cards), you may have to add some device nodes to your /dev directory before you can use them. For more information, take a look at Making Device Nodes section later on in this chapter.

Contact the Documentation mailing list for comments, suggestions and questions about this document.

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