Kernel Compiling 2

Some time ago I wrote a page on compiling the Linux kernel, this is an update to that page and basically a replacement. The latest kernel at the time of this writing is 2.4.5 and can be obtained from kernel.org.

Get the source and place it in a directory in your home directory.
Verify the version of the kernel you have running.
```
   suse:~/kernel # /bin/uname -r
   2.4.3
```

Decompress and untar the source

   suse:~/kernel # tar zxfv linux-2.4.5.tar.gz

Change to the newly created linux directory.

   suse:~/kernel # cd linux
   suse:~/kernel/linux #

Now read the Changes file under the Documentation folder in the kernel source to determine which other programs need to be updated to run the new kernel.
```
   suse:~/kernel/linux # less Documentation/Changes
```
Next you'll have to run one of three setup programs, if you don't have X windows running you best option is to use make menuconfig as it is much more friendly than the prompts of make config.

Command Environment

make config Command line prompts

make menuconfig Command line text menu

make xconfig X Windows GUI
Go through the menus and select the options you want in your kernel, and exit saving the changes to the config file when prompted.
Next run make dep to find the dependencies.
```
   suse:~/kernel/linux # make dep
```
After the dependencies are found run make bzImage (depending on your system speed and kernel options, this can take a long time) to make the new kernel, bzImage is for large kernels and the bz denotes that it is compressed, it gets decompressed automatically when the system boots. The kernel gets saved at {$KERNEL_SOURCE}/arch/i386/boot/bzImage.
```
   suse:~/kernel/linux # make bzImage
```

When the kernel compilation is done it will tell you the size and location of the kernel.

              [ Output clipped ]
   System is 804 kB
   make[1]: Leaving directory `/root/kernel/linux/arch/i386/boot'
   suse:~/kernel/linux #

Next run make modules and make modules_install to configure the kernel modules.
```
   suse:~/kernel/linux # make modules modules_install
```

Next backup your old kernel in case you have a problem with the new one.

Look at your lilo.conf file to see which kernel boots by default, ( as you can see I have four kernels referenced in lilo.conf ) the first in the file is booted by default if not specified in the global section.

   suse:~/kernel/linux # cat /etc/lilo.conf
   boot=/dev/hda
   vga=normal
   read-only
   prompt
   timeout=50
   # End LILO global Section
   #
   image = /boot/vmlinuz.new
     root= /dev/hda5
     label = new

   image = /boot/vmlinuz.old2
     root = /dev/hda5
     label = old2

   image = /boot/vmlinuz
     root = /dev/hda5
     label = linux

   image = /boot/vmlinuz.old
     root = /dev/hda5
     label = original

Backup the old kernel; you need to be root to do this.

   suse:~/kernel/linux # cd /boot
   suse:/boot # cp vmlinuz.new vmlinuz.old2

Copy the new kernel to the /boot directory and rename it to the first entry in lilo.conf (vmlinuz.new).

   suse:/boot # cd /root/kernel/linux/arch/i386/boot
   suse:~/kernel/linux/arch/i386/boot # cp bzImage /boot/vmlinuz.new

If you modified lilo.conf, you need to run the lilo command to update it, the asterisk denotes the default kernel image to boot.
```
   suse:/boot # /sbin/lilo
   Added new *
   Added old2
   Added linux
   Added original
```

Reboot the system.
```
   suse:/boot # /sbin/shutdown -r now
```
At the LILO boot: prompt press [tab] to see all available kernel boot images. You can press enter to boot the first one (new) or the name of any of the other kernels (e.g. original)
```
   LILO boot: [tab]
   new       old2       linux         original
   boot:
```

Next login and verify the kernel version, your login prompt might display it for you.

   Welcome to  (i386) - Kernel 2.4.5 (tty1).

   suse login: root
   Password:
   suse:~ # /bin/uname -r
   2.4.5

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