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13. Copyright Considerations With LKMsA perennial question about LKMs is whether the terms of GPL apply to one, considering that the Linux kernel is distributed under GPL. For example, is it OK to ship an LKM in binary only form? This section covers the copyright issues surrounding LKMs, which are as interesting as they are complex. Fair warning: we don't reach a conclusion. The law is unsettled a

Next Previous Contents 8. Linux Networking 8.1 How Linux networking is managed? There exists a device driver for each kind of NIC. Inside it, Linux will ALWAYS call a standard high level routing: "netif_rx [net/core/dev.c]", which will controls what 3 level protocol the frame belong to, and it will call the right 3 level function (so we'll use a pointer to the function to determine which is right)

Returns true if... -efile exists -afile exists This is identical in effect to -e. It has been "deprecated," [1] and its use is discouraged. -ffile is a regular file (not a directory or device file) -sfile is not zero size -dfile is a directory -bfile is a block device -cfile is a character device device0="/dev/sda2" # / (root directory) if [ -b "$device0" ] then echo "$device0 is a block device."

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David S. Lawyer mailto:[email protected] v1.43 March 2013 This document was originally written for real text terminals which were like monitors (with keyboards), but could only display text with a command line interface (no pictures). They were widely used to access mainframe computers in the late 1970's and 1980's but use of them declined in the 1990's and they are seldom used anymore. However much o

This document describes the TCP keepalive implementation in the linux kernel, introduces the overall concept and points to both system configuration and software development. Table of Contents1. Introduction1.1. Copyright and License1.2. Disclaimer1.3. Credits / Contributors1.4. Feedback1.5. Translations2. TCP keepalive overview2.1. What is TCP keepalive?2.2. Why use TCP keepalive?2.3. Checking fo

Builtin variables:variables affecting bash script behavior $BASHThe path to the Bash binary itself $BASH_ENVAn environmental variable pointing to a Bash startup file to be read when a script is invoked $BASH_SUBSHELLA variable indicating the subshell level. This is a new addition to Bash, version 3. See Example 21-1 for usage. $BASHPIDProcess ID of the current instance of Bash. This is not the sam

This document outlines the set of requirements and guidelines for file and directory placement under the Linux operating system according to those of the FSSTND v2.3 final (January 29, 2004) and also its actual implementation on an arbitrary system. It is meant to be accessible to all members of the Linux community, be distribution independent and is intended to discuss the impact of the FSSTND an

This document describes the working basics of PC-class computers, Unix-like operating systems, and the Internet in non-technical language. Table of Contents1. Introduction1.1. Purpose of this document1.2. New versions of this document1.3. Feedback and corrections1.4. Related resources2. Basic anatomy of your computer3. What happens when you switch on a computer?4. What happens when you log in?5. W

2. TCP keepalive overview In order to understand what TCP keepalive (which we will just call keepalive) does, you need do nothing more than read the name: keep TCP alive. This means that you will be able to check your connected socket (also known as TCP sockets), and determine whether the connection is still up and running or if it has broken. 2.1. What is TCP keepalive? The keepalive concept is v

This document describes the TCP keepalive implementation in the linux kernel, introduces the overall concept and points to both system configuration and software development. Table of Contents1. Introduction1.1. Copyright and License1.2. Disclaimer1.3. Credits / Contributors1.4. Feedback1.5. Translations2. TCP keepalive overview2.1. What is TCP keepalive?2.2. Why use TCP keepalive?2.3. Checking fo

Add references to HFSC, alter author email addresses

7.1.1. GeneralAt times you need to specify different courses of action to be taken in a shell script, depending on the success or failure of a command. The if construction allows you to specify such conditions. The most compact syntax of the if command is: if TEST-COMMANDS; then CONSEQUENT-COMMANDS; fi The TEST-COMMAND list is executed, and if its return status is zero, the CONSEQUENT-COMMANDS lis

3.1.1.1. GeneralA simple description of the UNIX system, also applicable to Linux, is this: "On a UNIX system, everything is a file; if something is not a file, it is a process." This statement is true because there are special files that are more than just files (named pipes and sockets, for instance), but to keep things simple, saying that everything is a file is an acceptable generalization. A

Appendix B. Reference CardsThe following reference cards provide a useful summary of certain scripting concepts. The foregoing text treats these matters in more depth, as well as giving usage examples.

2.3.1. Debugging on the entire scriptWhen things don't go according to plan, you need to determine what exactly causes the script to fail. Bash provides extensive debugging features. The most common is to start up the subshell with the -x option, which will run the entire script in debug mode. Traces of each command plus its arguments are printed to standard output after the commands have been exp

Table E-1. Reserved Exit Codes Exit Code NumberMeaningExampleComments

Next Previous Contents 4. Examples for different shells Below we provide an set of examples for some of the more common shells. We start with zsh as it provides several facilities that make our job much easier. We will then progress through increasingly difficult examples. In all the examples we test the environment variable $TERM to make sure we only apply the escapes to xterms. We test for $TERM

7.3. Other Comparison OperatorsA binary comparison operator compares two variables or quantities. Note that integer and string comparison use a different set of operators. integer comparison -eqis equal to if [ "$a" -eq "$b" ] -neis not equal to if [ "$a" -ne "$b" ] -gtis greater than if [ "$a" -gt "$b" ] -geis greater than or equal to if [ "$a" -ge "$b" ] -ltis less than if [ "$a" -lt "$b" ] -lei

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Appendix N. Converting DOS Batch Files to Shell Scripts Quite a number of programmers learned scripting on a PC running DOS. Even the crippled DOS batch file language allowed writing some fairly powerful scripts and applications, though they often required extensive kludges and workarounds. Occasionally, the need still arises to convert an old DOS batch file to a UNIX shell script. This is general

Abstract The goal of the Linux IPv6 HOWTO is to answer both basic and advanced questions about IPv6 on the Linux operating system. This HOWTO will provide the reader with enough information to install, configure, and use IPv6 applications on Linux machines. Intermediate releases of this HOWTO are available at mirrors.bieringer.de or mirrors.deepspace6.net. See also revision history for changes.

29.1. /devThe /dev directory contains entries for the physical devices that may or may not be present in the hardware. [1] Appropriately enough, these are called device files. As an example, the hard drive partitions containing the mounted filesystem(s) have entries in /dev, as df shows. bash$ df Filesystem 1k-blocks Used Available Use% Mounted on /dev/hda6 495876 222748 247527 48% / /dev/hda1 507

It's no longer necessary to provide RPMS or debs at project level. The packaging infrastructure has gotten good at that. New caveats about configuration and autotools. AsciiDOC is now a viable alternative for documentation masters.

There are always three default files [1] open, stdin (the keyboard), stdout (the screen), and stderr (error messages output to the screen). These, and any other open files, can be redirected. Redirection simply means capturing output from a file, command, program, script, or even code block within a script (see Example 3-1 and Example 3-2) and sending it as input to another file, command, program,

Next Previous Contents 5. Delete and Backspace Getting Delete and Backspace to work just right is nontrivial, especially in a mixed environment, where you talk to console, to X, to bash, to emacs, login remotely, etc. You may have to edit several configuration files to tell all of the programs involved precisely what you want. On the one hand, there is the matter of which keys generate which codes