1. How Do I Load a Kernel Module on System Start-up? ( RHEL5/6)

2. What is the technical differences between a normal SMP kernel and a hugemem kernel?

3. How to specify a ‘default’ boot kernel type for a RHEL?

4. How to update RHEL kernel ?

5. How do I exclude updating the kernel or other packages in RHEL 5/6 while updating system via yum ?

6. How do I boot using an alternate/previous kernel?

7. How do I modify GRUB (grub.conf) to use a new kernel?

8. How to downgrade a kernel?

9. How to set kernel parameters in sysctl.conf file permanently?

10. What is kernel-firmware?

11. How to increase the kernel ring buffer size?

12. How do I blacklist a kernel module to prevent it loading automatically?

13. What is the proper method to remove old kernels from a Red Hat Enterprise Linux system?

14. What are the kernel parameter for inter-process communication?

15. Root cause analysis for kernel panic on RHEL?

16. How can the runtime values of kernel module parameters be displayed in RHEL5?

17. The /boot directory is getting full, how do I remove old kernels?

18. What are the kernel module utilities in Red Hat Enterprise Linux?

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Setting Kernel parameters permanently in Red hat Enterprise Linux

Every time the system boots, the ‘/etc/rc.d/rc.sysinit‘ script is executed by init process. This shell script contains a call to sysctl command and reads the values from /etc/sysctl.conf file as the ones to be set

Therefore, any values added to /etc/sysctl.conf will take effect after the system boot or without downtime using “ sysctl -p ” command

sysctl.conf is a simple file containing sysctl values to be read in and set by sysctl

The syntax is simply as follows:

# comment
; comment

token = value

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Before we discuss about Huge pages, we should revise some of the basic concepts about Operating system memory management.

Operating systems basically deals with two types of memory for its operations one is Physical memory ( actual Physical RAM) and the second is Virtual memory ( combination of Physical and Swap). Virtual Memory is used to store entire program that is currently running and the physical memory is to store only specific part of memory that is important at this moment. And both physical memory and virtual memory will be segmented as pages,  and the process of copying  the pages of the program from to/from the virtual memory to/from the physical memory is called paging.

Operating system manages a page table to map virtual memory pages to physical memory pages. So when ever operating system needs to access memory for some information it will look at the paging table first and then look at the corresponding physical memory, if it doesn’t find information in physical memory then go back to virtual memory to get the required information. Full Story

The internal state of a kernel based on Unix can provide valuable information on current system state. If a user process, or the kernel, is hanging, then the more information that can be gathered at that point, the greater the chance of a good diagnosis.

Under Solaris  ON THE SPARC platform there are well known mechanisms for gathering stack traces, processor states and memory states. Under Linux, this can appear to be more of a black art.

This document sets out to document the information that can be captured, hopefully as early as possible, to improve the chances of a good diagnosis.  Full Story

There are numerous occasions when a crash dump can be a valuable source of information when troubleshooting a system. The most common times are a system hang or a system panic.

Under Solaris[TM] on both SPARC(R) and x86 platforms, the mechanisms for getting a crash dump in these situations are well understood. Under Linux (specifically Red Hat) this situation is less clear.  Full Story