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Unix Daemon Server Programming

                Unix processes works either in foreground or background. A process running in foreground interacts with the user in front of the terminal (makes I/O), whereas a background process runs by itself. The user can check its status but he doesn't (need to) know what it is doing. The term 'daemon' is used for processes that performs service in background. A server is a process that begins execution at startup (not neccessarily), runs forever, usually do not die or get restarted, operates in background, waits for requests to arrive and respond to them and frequently spawn other processes to handle these requests.

Howto: build Linux kernel module against installed kernel w/o full kernel source tree

 

Recently I received a question via email:

How do I build Linux kernel module against installed or running Linux kernel? Do I need to install new kernel source tree from kernel.org?

To be frank you do not need a new full source tree in order to just compile or build module against the running kernel i.e an exploded source tree is not required to build kernel driver or module. The instruction outlined below will benefit immensely to a developers/power users.

This is essential because if you just want to compile and install driver for new hardware such as Wireless card or SCSI device etc. With following method, you will save the time, as you are not going to compile entire Linux kernel.

 

How to: Compile Linux kernel 2.6

 

                Compiling custom kernel has its own advantages and disadvantages. However, new Linux user / admin find it difficult to compile Linux kernel. Compiling kernel needs to understand few things and then just type couple of commands. This step by step howto covers compiling Linux kernel version 2.6.xx under Debian GNU Linux. However, instructions remains the same for any other distribution except for apt-get command.

HowTo Upgrade To The 2.6 Kernel

 

                Anyone who's been following Linux kernel development for the past several months has heard about one exciting feature after another being merged into the still un-released 2.6 kernel. New features that noticeably affect user experience include Robert Love's  preemptible kernel work , Ingo Molnar's O(1) Scheduler, Rik Van Riel's  reverse mapping VM , Nick Piggins'  Anticipatory I/O scheduler , and much, much more...

                Having some spare time a few nights ago, I decided to give the latest kernel, 2.6.0-test4, a trial run on my aging 550Mhz PIII desktop computer, and the result was nothing short of spectacular. As the final 2.6.0 release approaches, it is important that an increasing number of users (aka testers) give this kernel a try, especially as currently it's still a sexy task for developers to track down kernel bugs and stabalize their work. Once work starts on the 2.7 development tree, inevitably much talent will again be focusing on new features.

                The purpose of this document is to provide some helpful tips to readers that currently compile their own 2.4 kernels, but haven't yet made the leap to 2.6. This is still a development kernel, so you may run into problems, but overall stability and performance is quite impressive and I can't recommend enough that you try it today.

 

Kernel space: Ticket spinlocks

 

                Spinlocks are the lowest-level mutual exclusion mechanism in the Linux kernel. As such, they have a great deal of influence over the safety and performance of the kernel, so it is not surprising that a great deal of optimization effort has gone into the various (architecture-specific) spinlock implementations. That does not mean that all of the work has been done, though; a patch merged for 2.6.25 shows that there is always more which can be done.