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How to change hostname in Linux

Posted by Unknown

1) Edit file /etc/sysconfig/network using your favourite editor.
vi /etc/sysconfig/network

2) Look for HOSTNAME=xxxxxx

3) Change the xxxx to the name you wish to set for your computer. (ex:HOSTNAME=abc.com)

4) Save the file and restart the network service. (ex: type service network restart in your shell)

Done! You have just changed your hostname in Linux platform

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0

How to remove/uninstall Lilo/Grub?

Posted by Unknown
If you want to remove the Lilo or Grub boot loader from your system (if you are uninstalling linux etc) follow the procedures below:

For Windows 95/98 etc:
Use a dos boot disk and at the command prompt type:
fdisk /mbr

For Windows XP:
Boot off the XP Installation CD and go into rescue mode. From there run the command:
fixmbr
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0

Maximize performace of Oracle and IBM DB2

Posted by Unknown
Commercial databases such as Oracle and IBM DB2 can maximize performance by using raw I/O. One may use the raw command for both IDE and SCSI devices. This will map a raw device to a blocked device for an entire disk partition. To see if your system is using raw I/O issue the command: raw -a

* Configuration file: /etc/sysconfig/rawdevices

Add entries to this file to invoke raw I/O upon system boot.
* Devices: /dev/raw/raw??
* Raw device controller: /dev/rawctl
* Sample use of command: raw /dev/raw/raw1 /dev/hdb5
* One must be of group disk to use the raw device or change permissions:

chmod a+r /dev/rawctl
chmod a+r /dev/hdb5
chmod a+rw /dev/raw/raw1

Note: The above information applies to Red Hat distributions. This info may be different for other distributions. i.e. S.U.S.E. uses /dev/raw1 as a device and /dev/raw as the controller.
You can mimic Red Hat behavior with a symbolic link: ln -s /dev/your_raw_controller /dev/rawctl
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4

Linux Commands to Monitor Memory Usage

Posted by Unknown
Linux Commands to Monitor Memory Usage:

vmstat Monitor virtual memory
free Display amount of free and used memory in the system.
pmap Display/examine memory map and libraries (so). Usage: pmap pid
top Show top processes
sar -B Show statistics on page swapping.
time -v date Show system page size, page faults, etc of a process during execution. Note you must fully qualify the command as "/usr/bin/time" to avoid using the bash shell command "time".
cat /proc/sys/vm/freepages Display virtual memory "free pages".
One may increase/decrease this limit: echo 300 400 500 > /proc/sys/vm/freepages
cat /proc/meminfo Show memory size and usage.
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0

Want to write Linux Kernel?

Posted by Unknown
  • Title: "Iptables-tutorial"
    Author: Oskar Andreasson.
    URL: http://iptables-tutorial.frozentux.net
    Keywords: iptables, netfilter, firewalls.
    Description: The aim of the iptables-tutorial is to explain iptables in a complete and simple way. It information on all the currently available matches and targets (in kernel), as well as complete example scripts and explanations. It contains a complete section on iptables syntax, as well as other interesting commands such as iptables-save and iptables-restore.
  • Title: "Ipsysctl-tutorial"
    Author: Oskar Andreasson.
    URL: http://ipsysctl-tutorial.frozentux.net
    Keywords: IP sysctl, ipsysctl, firewalls, Interface reference, sysctl/proc basics.
    Description: This document aims at giving more in depth explanations about the different ip sysctl calls available in the Linux kernel.
  • Title: "The Linux Kernel"
    Author: David A. Rusling.
    URL: http://en.tldp.org/LDP/tlk/tlk.html
    Keywords: everything!, book.
    Description: On line, 200 pages book describing most aspects of the Linux Kernel. Probably, the first reference for beginners. Lots of illustrations explaining data structures use and relationships in the purest Richard W. Stevens' style. Contents: "1.-Hardware Basics, 2.-Software Basics, 3.-Memory Management, 4.-Processes, 5.-Interprocess Communication Mechanisms, 6.-PCI, 7.-Interrupts and Interrupt Handling, 8.-Device Drivers, 9.-The File system, 10.-Networks, 11.-Kernel Mechanisms, 12.-Modules, 13.-The Linux Kernel Sources, A.-Linux Data Structures, B.-The Alpha AXP Processor, C.-Useful Web and FTP Sites, D.-The GNU General Public License, Glossary". In short: a must have.
  • Title: "Linux Device Drivers, 2nd Edition"
    Author: Alessandro Rubini and Jonathan Corbet.
    URL: http://www.xml.com/ldd/chapter/book/index.html
    Keywords: device drivers, modules, debugging, memory, hardware, interrupt handling, char drivers, block drivers, kmod, mmap, DMA, buses.
    Description: O'Reilly's popular book, now also on-line under the GNU Free Documentation License.
    Notes: You can also buy it in paper-form from O'Reilly. See below under BOOKS (Not on-line).
  • Title: "Conceptual Architecture of the Linux Kernel"
    Author: Ivan T. Bowman.
    URL: http://plg.uwaterloo.ca/~itbowman/papers/CS746G-a1.html
    Keywords: conceptual software arquitecture, extracted design, reverse engineering, system structure.
    Description: Conceptual software arquitecture of the Linux kernel, automatically extracted from the source code. Very detailed. Good figures. Gives good overall kernel understanding.
  • Title: "Concrete Architecture of the Linux Kernel"
    Author: Ivan T. Bowman, Saheem Siddiqi, and Meyer C. Tanuan.
    URL: http://plg.uwaterloo.ca/~itbowman/papers/CS746G-a2.html
    Keywords: concrete arquitecture, extracted design, reverse engineering, system structure, dependencies.
    Description: Concrete arquitecture of the Linux kernel, automatically extracted from the source code. Very detailed. Good figures. Gives good overall kernel understanding. This papers focus on lower details than its predecessor (files, variables...).
  • Title: "Linux as a Case Study: Its Extracted Software Architecture"
    Author: Ivan T. Bowman, Richard C. Holt and Neil V. Brewster.
    URL: http://plg.uwaterloo.ca/~itbowman/papers/linuxcase.html
    Keywords: software architecture, architecture recovery, redocumentation.
    Description: Paper appeared at ICSE'99, Los Angeles, May 16-22, 1999. A mixture of the previous two documents from the same author.
  • Title: "Overview of the Virtual File System"
    Author: Richard Gooch.
    URL: http://www.atnf.csiro.au/~rgooch/linux/vfs.txt
    Keywords: VFS, File System, mounting filesystems, opening files, dentries, dcache.
    Description: Brief introduction to the Linux Virtual File System. What is it, how it works, operations taken when opening a file or mounting a file system and description of important data structures explaining the purpose of each of their entries.
  • Title: "The Linux RAID-1, 4, 5 Code"
    Author: Ingo Molnar, Gadi Oxman and Miguel de Icaza.
    URL: http://www.linuxjournal.com/article.php?sid=2391
    Keywords: RAID, MD driver.
    Description: Linux Journal Kernel Korner article. Here is it's abstract: "A description of the implementation of the RAID-1, RAID-4 and RAID-5 personalities of the MD device driver in the Linux kernel, providing users with high performance and reliable, secondary-storage capability using software".
  • Title: "Dynamic Kernels: Modularized Device Drivers"
    Author: Alessandro Rubini.
    URL: http://www.linuxjournal.com/article.php?sid=1219
    Keywords: device driver, module, loading/unloading modules, allocating resources.
    Description: Linux Journal Kernel Korner article. Here is it's abstract: "This is the first of a series of four articles co-authored by Alessandro Rubini and Georg Zezchwitz which present a practical approach to writing Linux device drivers as kernel loadable modules. This installment presents an introduction to the topic, preparing the reader to understand next month's installment".
  • Title: "Dynamic Kernels: Discovery"
    Author: Alessandro Rubini.
    URL: http://www.linuxjournal.com/article.php?sid=1220
    Keywords: character driver, init_module, clean_up module, autodetection, mayor number, minor number, file operations, open(), close().
    Description: Linux Journal Kernel Korner article. Here is it's abstract: "This article, the second of four, introduces part of the actual code to create custom module implementing a character device driver. It describes the code for module initialization and cleanup, as well as the open() and close() system calls".
  • Title: "The Devil's in the Details"
    Author: Georg v. Zezschwitz and Alessandro Rubini.
    URL: http://www.linuxjournal.com/article.php?sid=1221
    Keywords: read(), write(), select(), ioctl(), blocking/non blocking mode, interrupt handler.
    Description: Linux Journal Kernel Korner article. Here is it's abstract: "This article, the third of four on writing character device drivers, introduces concepts of reading, writing, and using ioctl-calls".
  • Title: "Dissecting Interrupts and Browsing DMA"
    Author: Alessandro Rubini and Georg v. Zezschwitz.
    URL: http://www.linuxjournal.com/article.php?sid=1222
    Keywords: interrupts, irqs, DMA, bottom halves, task queues.
    Description: Linux Journal Kernel Korner article. Here is it's abstract: "This is the fourth in a series of articles about writing character device drivers as loadable kernel modules. This month, we further investigate the field of interrupt handling. Though it is conceptually simple, practical limitations and constraints make this an ``interesting'' part of device driver writing, and several different facilities have been provided for different situations. We also investigate the complex topic of DMA".
  • Title: "Device Drivers Concluded"
    Author: Georg v. Zezschwitz.
    URL: http://www.linuxjournal.com/article.php?sid=1287
    Keywords: address spaces, pages, pagination, page management, demand loading, swapping, memory protection, memory mapping, mmap, virtual memory areas (VMAs), vremap, PCI.
    Description: Finally, the above turned out into a five articles series. This latest one's introduction reads: "This is the last of five articles about character device drivers. In this final section, Georg deals with memory mapping devices, beginning with an overall description of the Linux memory management concepts".
  • Title: "Network Buffers And Memory Management"
    Author: Alan Cox.
    URL: http://www.linuxjournal.com/article.php?sid=1312
    Keywords: sk_buffs, network devices, protocol/link layer variables, network devices flags, transmit, receive, configuration, multicast.
    Description: Linux Journal Kernel Korner. Here is the abstract: "Writing a network device driver for Linux is fundamentally simple---most of the complexity (other than talking to the hardware) involves managing network packets in memory".
  • Title: "The Venus kernel interface"
    Author: Peter J. Braam.
    URL: http://www.coda.cs.cmu.edu/doc/html/kernel-venus-protocol.html
    Keywords: coda, filesystem, venus, cache manager.
    Description: "This document describes the communication between Venus and kernel level file system code needed for the operation of the Coda filesystem. This version document is meant to describe the current interface (version 1.0) as well as improvements we envisage".
  • Title: "Programming PCI-Devices under Linux"
    Author: Claus Schroeter.
    URL: ftp://ftp.llp.fu-berlin.de/pub/linux/LINUX-LAB/whitepapers/pcip.ps.gz
    Keywords: PCI, device, busmastering.
    Description: 6 pages tutorial on PCI programming under Linux. Gives the basic concepts on the architecture of the PCI subsystem, as long as basic functions and macros to read/write the devices and perform busmastering.
  • Title: "Writing Character Device Driver for Linux"
    Author: R. Baruch and C. Schroeter.
    URL: ftp://ftp.llp.fu-berlin.de/pub/linux/LINUX-LAB/whitepapers/drivers.ps.gz
    Keywords: character device drivers, I/O, signals, DMA, accessing ports in user space, kernel environment.
    Description: 68 pages paper on writing character drivers. A little bit old (1.993, 1.994) although still useful.
  • Title: "Design and Implementation of the Second Extended Filesystem"
    Author: Rémy Card, Theodore Ts'o, Stephen Tweedie.
    URL: http://web.mit.edu/tytso/www/linux/ext2intro.html
    Keywords: ext2, linux fs history, inode, directory, link, devices, VFS, physical structure, performance, benchmarks, ext2fs library, ext2fs tools, e2fsck.
    Description: Paper written by three of the top ext2 hackers. Covers Linux filesystems history, ext2 motivation, ext2 features, design, physical structure on disk, performance, benchmarks, e2fsck's passes description... A must read!
    Notes: This paper was first published in the Proceedings of the First Dutch International Symposium on Linux, ISBN 90-367-0385-9.
  • Title: "Journaling the Linux ext2fs Filesystem"
    Author: Stephen C. Tweedie.
    URL: ftp://ftp.uk.linux.org/pub/linux/sct/fs/jfs/journal-design.ps.gz
    Keywords: ext3, journaling.
    Description: Excellent 8-pages paper explaining the journaling capabilities added to ext2 by the author, showing different problems faced and the alternatives chosen.
  • Title: "Linux Kernel Module Programming Guide"
    Author: Peter Jay Salzman, Michael Burian, Ori Pomerantz.
    URL: http://tldp.org/LDP/lkmpg/2.6/html/
    Keywords: modules, /proc, ioctls, system calls, interrupt handlers .
    Description: Very nice 73 pages free book on the topic of modules programming. Lots of examples. Updated to 2.6 kernels.
  • Title: "Device File System (devfs) Overview"
    Author: Richard Gooch.
    URL: http://www.atnf.csiro.au/~rgooch/linux/docs/devfs.txt
    Keywords: filesystem, /dev, devfs, dynamic devices, major/minor allocation, device management.
    Description: Document describing Richard Gooch's controversial devfs, which allows for dynamic devices, only shows present devices in /dev, gets rid of major/minor numbers allocation problems, and allows for hundreds of identical devices (which some USB systems might demand soon).
  • Title: "I/O Event Handling Under Linux"
    Author: Richard Gooch.
    URL: http://www.atnf.csiro.au/~rgooch/linux/docs/io-events.html
    Keywords: IO, I/O, select(2), poll(2), FDs, aio_read(2), readiness event queues.
    Description: From the Introduction: "I/O Event handling is about how your Operating System allows you to manage a large number of open files (file descriptors in UNIX/POSIX, or FDs) in your application. You want the OS to notify you when FDs become active (have data ready to be read or are ready for writing). Ideally you want a mechanism that is scalable. This means a large number of inactive FDs cost very little in memory and CPU time to manage".
  • Title: "Kernel Hacking HOWTO"
    Author: Andrew Ebling.
    URL: http://www.kernelhacking.org/docs/kernelhacking-HOWTO/
    Keywords: HOWTO, kernel hacking, getting started, source navigation, kernel debugging, profiling, benchmarking.
    Description: Another kernel hacking howto. More recent than the now lost Rusty's one.
  • Title: "ALSA 0.5.0 Developer documentation"
    Author: Stephan 'Jumpy' Bartels .
    URL: http://www.math.TU-Berlin.de/~sbartels/alsa/
    Keywords: ALSA, sound, soundcard, driver, lowlevel, hardware.
    Description: Advanced Linux Sound Architecture for developers, both at kernel and user-level sides. Work in progress. ALSA is supposed to be Linux's next generation sound architecture.
  • Title: "Programming Guide for Linux USB Device Drivers"
    Author: Detlef Fliegl.
    URL: http://usb.in.tum.de/usbdoc/
    Keywords: USB, universal serial bus.
    Description: A must-read. From the Preface: "This document should give detailed information about the current state of the USB subsystem and its API for USB device drivers. The first section will deal with the basics of USB devices. You will learn about different types of devices and their properties. Going into detail you will see how USB devices communicate on the bus. The second section gives an overview of the Linux USB subsystem [2] and the device driver framework. Then the API and its data structures will be explained step by step. The last section of this document contains a reference of all API calls and their return codes".
    Notes: Beware: the main page states: "This document may not be published, printed or used in excerpts without explicit permission of the author". Fortunately, it may still be read...
  • Title: "Linux Kernel Mailing List Glossary"
    Author: John Levon.
    URL: http://www.movement.uklinux.net/glossary.html
    Keywords: glossary, terms, linux-kernel.
    Description: From the introduction: "This glossary is intended as a brief description of some of the acronyms and terms you may hear during discussion of the Linux kernel".
  • Title: "Linux Kernel Locking HOWTO"
    Author: Various Talented People, and Rusty.
    URL: http://netfilter.kernelnotes.org/unreliable-guides/kernel-locking-HOWTO.html
    Keywords: locks, locking, spinlock, semaphore, atomic, race condition, bottom halves, tasklets, softirqs.
    Description: The title says it all: document describing the locking system in the Linux Kernel either in uniprocessor or SMP systems.
    Notes: "It was originally written for the later (>2.3.47) 2.3 kernels, but most of it applies to 2.2 too; 2.0 is slightly different". Freely redistributable under the conditions of the GNU General Public License.
  • Title: "Global spinlock list and usage"
    Author: Rick Lindsley.
    URL: http://lse.sourceforge.net/lockhier/global-spin-lock
    Keywords: spinlock.
    Description: This is an attempt to document both the existence and usage of the spinlocks in the Linux 2.4.5 kernel. Comprehensive list of spinlocks showing when they are used, which functions access them, how each lock is acquired, under what conditions it is held, whether interrupts can occur or not while it is held...
  • Title: "Porting Linux 2.0 Drivers To Linux 2.2: Changes and New Features "
    Author: Alan Cox.
    URL: http://www.linux-mag.com/1999-05/gear_01.html
    Keywords: ports, porting.
    Description: Article from Linux Magazine on porting from 2.0 to 2.2 kernels.
  • Title: "How To Make Sure Your Driver Will Work On The Power Macintosh"
    Author: Paul Mackerras.
    URL: http://www.linux-mag.com/1999-07/gear_01.html
    Keywords: Mac, Power Macintosh, porting, drivers, compatibility.
    Description: The title says it all.
  • Title: "Video4linux Drivers, Part 1: Video-Capture Device"
    Author: Alan Cox.
    URL: http://www.linux-mag.com/2000-01/gear_01.html
    Keywords: video4linux, driver, video capture, capture devices, camera driver.
    Description: The title says it all.
  • Title: "Video4linux Drivers, Part 2: Video-capture Devices"
    Author: Alan Cox.
    URL: http://www.linux-mag.com/2000-02/gear_01.html
    Keywords: video4linux, driver, video capture, capture devices, camera driver, control, query capabilities, capability, facility.
    Description: The title says it all.
  • Title: "Linux 2.4 Kernel Internals"
    Author: Tigran Aivazian and Christoph Hellwig.
    URL: http://www.moses.uklinux.net/patches/lki.html
    Keywords: Linux, kernel, booting, SMB boot, VFS, page cache.
    Description: A little book used for a short training course. Covers building the kernel image, booting (including SMP bootup), process management, VFS and more.
  • Title: "Linux IP Networking. A Guide to the Implementation and Modification of the Linux Protocol Stack."
    Author: Glenn Herrin.
    URL: http://www.cs.unh.edu/cnrg/gherrin
    Keywords: network, networking, protocol, IP, UDP, TCP, connection, socket, receiving, transmitting, forwarding, routing, packets, modules, /proc, sk_buff, FIB, tags.
    Description: Excellent paper devoted to the Linux IP Networking, explaining anything from the kernel's to the user space configuration tools' code. Very good to get a general overview of the kernel networking implementation and understand all steps packets follow from the time they are received at the network device till they are delivered to applications. The studied kernel code is from 2.2.14 version. Provides code for a working packet dropper example.
  • Title: "Linux PCMCIA Programmer's Guide"
    Author: David Hinds.
    URL: http://pcmcia-cs.sourceforge.net/ftp/doc/PCMCIA-PROG.html
    Keywords: PCMCIA.
    Description: "This document describes how to write kernel device drivers for the Linux PCMCIA Card Services interface. It also describes how to write user-mode utilities for communicating with Card Services.
  • Title: "(nearly) Complete Linux Loadable Kernel Modules. The definitive guide for hackers, virus coders and system administrators."
    Author: pragmatic/THC.
    URL: http://packetstormsecurity.org/docs/hack/LKM_HACKING.html
    Keywords: syscalls, intercept, hide, abuse, symbol table.
    Description: Interesting paper on how to abuse the Linux kernel in order to intercept and modify syscalls, make files/directories/processes invisible, become root, hijack ttys, write kernel modules based virus... and solutions for admins to avoid all those abuses.
    Notes: For 2.0.x kernels. Gives guidances to port it to 2.2.x kernels.
  • Title: "Linux Kernel Threads in Device Drivers"
    Author: Martin Frey.
    URL: http://www.scs.ch/~frey/linux/kernelthreads.html
    Keywords: threads, creation, stopping, initialization.
    Description: How to start and stop kernel threads in a loadable module.
  • Title: "The Linux Kernel Hackers' Guide"
    Author: Michael K.Johnson and others.
    URL: http://en.tldp.org/LDP/khg/HyperNews/get/khg.html
    Keywords: everything!
    Description: Probably, too old to be useful... Many people have contributed. The interface is similar to web available mailing lists archives. You can find some articles and then some mails asking questions about them and/or complementing previous contributions. A little bit anarchic in this aspect, but with some valuable information in some cases.
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