Difference between revisions of "Linux kernel"

Revision as of 23:49, 16 July 2012

The kernel is the core piece of the Linux operating system.

• Current (stable version): 3.4.5 (2012-07-16)

Resources

The kernel manages the resources of the Linux OS; such as the following:

• File management
• Multitasking
• Memory management
• I/O management
• Process management: /proc/
• Device management: /dev/
• Networking support (including IPv4 and IPv6)
• Virtual memory, shared libraries, demand loading, etc.

The kernel decides who will use these resources, for how long, and when.

Rebuilding kernel from SRPM

Note: some of the paths below include $TOPDIR, which is distribution-dependent and can be further redefined by user. To find out the proper location on your system, issue this command:

rpm --eval "%{_topdir}"

openSUSE 10.2 returns:

/usr/src/packages

Mandriva Linux 2007.1 returns:

/usr/src/rpm

Example kernel update protocol

For this example, I will be using Mandriva Linux and updating/upgrading from kernel kernel-smp-2.6.8.1.12mdk-1-1mdk to kernel-smp-2.6.12.31mdk-1-1mdk.

The first thing you should do before updating your kernel is to backup your /sbin/*25 files (some distributions omit the "-25" at the end of each name) to a floppy disc (handy for quickly restoring them). These would include:

/sbin/depmod-25
/sbin/insmod-25
/sbin/lsmod-25
/sbin/modinfo-25
/sbin/modprobe-25
/sbin/rmmod-25

It wouldn't hurt to also backup your entire /etc directory.

Then, update your old kernel's related rpms:

rpm -Uvh fbgrab-1.0-1mdv2007.0.i586.rpm
rpm -Uvh libgtk-linux-fb-2.0_0-2.4.14-6mdk.i586.rpm
rpm -Uvh bootsplash-3.1.12-0.2.20060mdk.i586.rpm
rpm -Uvh mkinitrd-4.2.17-17.2.20060mdk.i586.rpm
rpm -Uvh module-init-tools-3.2-0.pre8.2.1.20060mdk.i586.rpm
rpm -Uvh aumix-text-2.8-12mdk.i586.rpm
rpm -Uvh sound-scripts-0.35-1mdk.noarch.rpm
rpm -Uvh hotplug-2004_09_23-7mdk.i586.rpm
# Returns clashing dependencies (possible problem source):
#rpm -Uvh udev-068-34mdk.i586.rpm

Now, install (not "upgrade") your new kernel rpm:

# Note: I am NOT using "rpm -Uvh", as I wish to _keep_ the old kernel
# The "smp" RPM is for multi-processor systems
rpm -ivh kernel-smp-2.6.12.31mdk-1-1mdk.i586.rpm

Notes:

# Linux kernel RPM:
# - kernel (/boot/vmlinux-2.X.XX-X);
# - modules (/lib/modules/2.X.XX-X/...);
# - /boot/System.map-2.X.XX-X; and
# - /boot/module-info-2.X.XX-X

Now, create the initrd image:

/sbin/mkinitrd /boot/initrd-2.6.12.31mdksmp.img 2.6.12.31mdk-1-1mdk

Edit /etc/lilo.conf and add new/old kernel boots (you want to keep your old kernel, just in case anything goes wrong you can boot your old, working kernel). For an example,

image=/boot/vmlinuz-2.6.12-31mdksmp
        label="linux-2.6.12-31mdksmp"
        root=/dev/sda1
        initrd=/boot/initrd-2.6.12-31mdksmp.img
        append="acpi=ht resume=/dev/sda5 splash=silent"
        vga=788
        read-only
image=/boot/vmlinuz-2.6.8.1-12mdksmp
        label="linux-2.6.8.1-12mdksmp"
        root=/dev/sda1
        initrd=/boot/initrd-2.6.8.1-12mdksmp.img
        append="acpi=ht resume=/dev/sda5 splash=silent"
        vga=788
        read-only

Now commit the changes to lilo:

lilo -v

Reboot:

shutdown -r now

And that should do it.

Possible problems/fixes

If you have problems with any kernel (old, new, or both), here are some possible troubleshooting steps you can take:

1. Boot in a rescue disk (e.g. Mandrake 10.1 installation CD)
2. Restore your old /sbin/*25 files from the floppy disc (see above)
3. Check to make sure your /etc/lilo.conf is pointing to the correct kernels and images.
4. Then, try rebooting.

Kernel files

Note: These files are found in the /boot directory.

See also

• Linux
• lilo
• grub

External links

• kernel.org
• Mandriva Kernel Update
• How To Install and Update A Redhat Linux Kernel RPM
• Preparing your Mandriva kernel source
• Kernel build — by openvz.org
• KernelNewbies
• The Kernel Boot Process
• How Computers Boot Up