nixCraft

IS Linux kernel is monolithic or compiled and statically linked modular kernel?

I am bit confused on this – Linux is Monolithic kernel or it is a compiled and statically linked traditional UNIX like modular kernel?

How do I find out running Linux kernel is Monolithic or modular kernel?

It will be nice if someone point out to good Linux kernel books, or some other online resources too

__________________
There's no place like 127.0.0.1

It can be compiled as both!

Monolithic kernel
- Single binary file
- All drivers included in kernel itself

Modular kernel
- Multiple files for kernel
- Drivers can be loaded or unloaded into kernel using modprob command, see man page of
lsmod, modprob etc
- Almost all drivers are build and linked against kernel

You can built modular kernel by setting option in kernel configuration option:
Enable loadable module support (CONFIG_MODULES) [Y/n/?]
If you set above option to Y then kernel becomes modular and three possibilities occurs for each and every feature/driver:
m - you can compile driver as module
y - built into kernel itself
n - Don't include feature/driver

Note if you set option to (CONFIG_MODULES) to n (no) then kernel becomes Monolithic and two possibilities occurs for each and every feature/driver:
y - Include feature/driver
n - Don't include feature/driver

See above

You can see kernel configuration file or you can type command (To see CONFIG_MODULES option)
make xconfig
make menuconfig

If the file /etc/modules.conf and modutils (such as lsmod, modprob) are installed then it is safe to assume that you have modular kernel. Most modern disto comes with modular kernel.

Books
Linux Kernel Programming (3rd ed.). Addison Wesley, 2002.
Linux Core Kernel Commentary. The Coriolis Group, LLC, 1999.
IA-64 Linux Kernel: Design and Implementation. Prentice Hall, Inc
Linux Device Drivers (2nd ed.). O'Reilly & Associates, Inc.
Linux IP Stacks Commentary. The Coriolis Group, LLC
WWW Links

www.tldp.org has some docs
www.google.com/linux search you should get tons of info/doc

Some reasons to use Monolithic kernel

Kernel will be faster as less code will be included and no kernel parts will not swapped to virtual memory, modules are slower

More stable as unnecessary drivers/features not included, so attacker cannot take advantage of unused stuff in kernel.

However, many supports modular as best choice because you don't have to recompile the kernel to include support for your new devices ... it is upto you which one satisfies your needs

For server -- Monolithic is good choice
Desktop - Modular is good as we connect pen drives, dig-cam, scanners and so on..

Feel free to search newsgroup using http://groups-beta.google.com/grphp?hl=en&tab=wg for more on this topic