I lost count of the number of times someone told me I was nuts for wanting to compile a new kernel Why not get a new different distro of Linux that works on a specific machine? What is wrong with the kernel that comes with the distro? In many cases, the default kernel works just fine. Conversely, there are reasons for compiling a new kernel.
» Continue reading “Why Compile a New Kernel?”
The courseware for my Linux Kernel Fundamentals course is now available from ITcourseware at http://bit.ly/bf82sN.
After hours of searching the Web, I have found nothing that really sheds a whole lot of light on the subject of tuning CFS. Most of the pages on the Web refer to CFS as it was in version 2.6.23 of the Linux kernel. Most web pages do not provide accurate information. I really wonder about the system administrator who could not understand why he was unable create a directory or file in the /proc directory. While I do not know the the best set of values for the tuneable parameters, I can, hopefully, shed some light on the subject. » Continue reading “Tuning the Linux Kernel’s Completely Fair Scheduler”
The Linux Kernel manages all hardware through device drivers. Furthermore, the kernel operates in its own protected memory space, which is not accessible from user memory space. Hardware device communicate to the Kernel via interrupts and exceptions. User applications communicate to the Kernel via system calls, which actually trigger a CPU exception that interrupts the Kernel. The question becomes, how can we access what the Kernel knows about the hardware from a user space application? What user applications allow us to view this information? » Continue reading “Hardware Management and Linux”
Do you know how many pixels there are to an em? How about an en? What is wrong with pixels? And the big question is, who should dictate the font and font size, the web page designer or the browser user? While there are different opinions regarding these questions, I am going argue for ems and user control.
This is by no means a new topic, it is just an often ignored topic. It is so easy to fall in the trap of assuming that everybody sees the world exactly as we see it. We tend to forget about the blind and visually impaired, when we design our Web. In so doing, we ignore an important audience.
» Continue reading “Web Accessibility – A Starting Point”
The common misconception is that the shell always searches the PATH variable to find a command. The truth is that the shell may never get to the PATH variable before it has a name match. Before confusing the issue, let’s look at a simple example. If there is an alias that reads which=’whence -a’, and you enter which pwd, the which command is never executed. The shell first finds the alias, and then subsitutes the alias for the command, and starts the search all over. From this, we know that an alias has precedence over the PATH variable. So what is the order of precedence for finding the command?
» Continue reading “Command Order of Precedence”
There are man pages with typographical errors, but that is not the issue of this post. Assuming you are using ksh or bash, how do you answer these questions:
If you answered yes to both questions, you are wrong, but for different reasons. » Continue reading “The man Command Lies (Sometimes)”
Bash and KornShell offer features that are more powerful, and often, more efficient than Bourne Shell. Yet, I constantly see back tics (accent graves), instead of the easier to read format of $(…). I see the use of the expr command for math calculations in stead of (( … )). Even higher on the list of common sins is the use of [ ... ], instead of [[ ... ]]. It is my contention that the blame lies on introductory books and courses, which change the title to Bash Shell Programming, or KornShell Programming, but are nothing more than warmed-over Bourne Shell courses. So whey not use Bourne Shell syntax? After all, isn’t Bourne Shell the standard UNIX shell?
» Continue reading “Trapped in Bourne Shell”
There are a number of myths surrounding KornShell that give it a bad rap. A history that few know about just adds to the confusion. Can you answer the following questions:
If you know the answers to these questions, you are a KornShell guru, who does not perpetuate the myths. If not, you need to read on so that you know the truth about KornShell.
» Continue reading “KornShell’s Bad Rap”
