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Techbuddy: Introduction to Linux session

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Ashish Bhatia

This document provides an introduction to Linux concepts including the philosophy, users, files, file handling, and process handling in Linux. It discusses the concept of users and files in Linux, explaining that everything is either a file or a process. It also covers the Linux file hierarchy and permissions system for users and files.

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Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Introduction to Linux by Ashish Bhatia TechBuddy Consulting Pvt. Ltd. 19-21 June 2010 Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Why learn Linux? Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses What is OS? What is OS? 1 BIOS - Boot Loader - OS 2 Hardware - OS - Application Software - User 3 multi-user? 4 multi-tasking? Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses History of GNU/Linux based on ideas from UNIX (originated in 1969 at AT&T) created by Linus Torvalds in 1991 General Public License GPL distribution of source code with binary is must more details later Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Files and Processes A running program is a process it has unique process identifier (PID) Everything else is file even devices like mouse, keyboard etc. every file has a unique inode number in Linux Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses File Hierarchy Unlike windows(except recent versions) where data storage is partitioned into various drives In Linux all (accessible) data is under / Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses File Hierarchy / The ancestor of all directories on the system Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses File Hierarchy / The ancestor of all directories on the system /bin Essential tools and other programs (or binaries) Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses File Hierarchy / The ancestor of all directories on the system /bin Essential tools and other programs (or binaries) /dev Files representing the system’s various hardware devices (eg. /dev/dvd) Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses File Hierarchy / The ancestor of all directories on the system /bin Essential tools and other programs (or binaries) /dev Files representing the system’s various hardware devices (eg. /dev/dvd) /etc Misc system configuration files, startup files (eg. /etc/networking) Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses File Hierarchy / The ancestor of all directories on the system /bin Essential tools and other programs (or binaries) /dev Files representing the system’s various hardware devices (eg. /dev/dvd) /etc Misc system configuration files, startup files (eg. /etc/networking) /home The home dir for all of the system’s users Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses File Hierarchy / The ancestor of all directories on the system /bin Essential tools and other programs (or binaries) /dev Files representing the system’s various hardware devices (eg. /dev/dvd) /etc Misc system configuration files, startup files (eg. /etc/networking) /home The home dir for all of the system’s users /proc Files that give information about current system processes Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses File Hierarchy / The ancestor of all directories on the system /bin Essential tools and other programs (or binaries) /dev Files representing the system’s various hardware devices (eg. /dev/dvd) /etc Misc system configuration files, startup files (eg. /etc/networking) /home The home dir for all of the system’s users /proc Files that give information about current system processes /root superuser’s home directory, whose username is root Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses File Hierarchy / The ancestor of all directories on the system /bin Essential tools and other programs (or binaries) /dev Files representing the system’s various hardware devices (eg. /dev/dvd) /etc Misc system configuration files, startup files (eg. /etc/networking) /home The home dir for all of the system’s users /proc Files that give information about current system processes /root superuser’s home directory, whose username is root /tmp Temp files Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses File Hierarchy / The ancestor of all directories on the system /bin Essential tools and other programs (or binaries) /dev Files representing the system’s various hardware devices (eg. /dev/dvd) /etc Misc system configuration files, startup files (eg. /etc/networking) /home The home dir for all of the system’s users /proc Files that give information about current system processes /root superuser’s home directory, whose username is root /tmp Temp files /usr Subdir with files related to user tools and applications Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Linux Alternative for Windows Internet Explorer = Firefox Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Linux Alternative for Windows Internet Explorer = Firefox Outlook Express = Thunderbird Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Linux Alternative for Windows Internet Explorer = Firefox Outlook Express = Thunderbird Google Talk = Pidgin (and Skype) Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Linux Alternative for Windows Internet Explorer = Firefox Outlook Express = Thunderbird Google Talk = Pidgin (and Skype) media player = amarok Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Linux Alternative for Windows Internet Explorer = Firefox Outlook Express = Thunderbird Google Talk = Pidgin (and Skype) media player = amarok Microsoft Office = Open Office Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Linux Alternative for Windows Internet Explorer = Firefox Outlook Express = Thunderbird Google Talk = Pidgin (and Skype) media player = amarok Microsoft Office = Open Office Notepad = kate,vim Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Linux Alternative for Windows Internet Explorer = Firefox Outlook Express = Thunderbird Google Talk = Pidgin (and Skype) media player = amarok Microsoft Office = Open Office Notepad = kate,vim A more comprehensive list at http://wiki.linuxquestions.org/wiki/ Linux software equivalent to Windows software Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses What is a user A user represents a real-world entity and it has username (and user ID) Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses What is a user A user represents a real-world entity and it has username (and user ID) group (and group ID) Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses What is a user A user represents a real-world entity and it has username (and user ID) group (and group ID) Password Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses What is a user A user represents a real-world entity and it has username (and user ID) group (and group ID) Password Home Dir Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses What is a user A user represents a real-world entity and it has username (and user ID) group (and group ID) Password Home Dir Default Shell Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses What is a user A user represents a real-world entity and it has username (and user ID) group (and group ID) Password Home Dir Default Shell User Details Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Users and Processes GNU/Linux is a multi-user OS Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Users and Processes GNU/Linux is a multi-user OS Everything is a file or a process Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Users and Processes GNU/Linux is a multi-user OS Everything is a file or a process Each process must specify which user is the owner Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Users and Processes GNU/Linux is a multi-user OS Everything is a file or a process Each process must specify which user is the owner No one except owner has right to access that process* Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Users and Processes GNU/Linux is a multi-user OS Everything is a file or a process Each process must specify which user is the owner No one except owner has right to access that process* what about files? Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Users and Files Each file has three (boolean) permissions Read(r) Write(w) Execute(x) Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Users and Files Each file has three (boolean) permissions Read(r) Write(w) Execute(x) All users can be grouped into Owner(u) Group (members) (g) Others (o) Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Users and Files Each file has three (boolean) permissions Read(r) Write(w) Execute(x) All users can be grouped into Owner(u) Group (members) (g) Others (o) 9 bits r w x r w x r w x Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Users and Files Each file has three (boolean) permissions Read(r) Write(w) Execute(x) All users can be grouped into Owner(u) Group (members) (g) Others (o) 9 bits r w x r w x r w x Super-user bypasses file permissions Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses A few examples chmod 600 file1 Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses A few examples chmod 600 file1 chmod 400 file2 Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses A few examples chmod 600 file1 chmod 400 file2 chmod 711 file3 Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses A few examples chmod 600 file1 chmod 400 file2 chmod 711 file3 chmod 644 file4 Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses A few examples chmod 600 file1 chmod 400 file2 chmod 711 file3 chmod 644 file4 chmod -R 644 dir1 Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Users and Files File Permissions on Dir Execute permission is required for a user to cd into a directory Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Users and Files File Permissions on Dir Execute permission is required for a user to cd into a directory Execute-only permission allows a user to access the files in a directory as long as the user knows the names of the files in the directory(and the user is allowed to read the files) Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Users and Files File Permissions on Dir Execute permission is required for a user to cd into a directory Execute-only permission allows a user to access the files in a directory as long as the user knows the names of the files in the directory(and the user is allowed to read the files) Execute+Read permission is required to view files contained in dir (eg. ls) Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Users and Files File Permissions on Dir Execute permission is required for a user to cd into a directory Execute-only permission allows a user to access the files in a directory as long as the user knows the names of the files in the directory(and the user is allowed to read the files) Execute+Read permission is required to view files contained in dir (eg. ls) Execute+Read+Write permission allows the user to create, delete, or modify any files or subdirectories(even if the file or subdirectory is owned by another user) Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Users and Files Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Users and Files Something More SetUID(u+s) Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Users and Files Something More SetUID(u+s) SetGID(g+s) Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Users and Files Something More SetUID(u+s) SetGID(g+s) Sticky Bit(t) Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Is Linux (really) secure? Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Is Linux (really) secure? Security of system or data? 1 Security by design designed for connectivity and security users do not login into admin account (by default) users do not install packages from unverified sources some distros require admin account even for connecting usb Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Is Linux (really) secure? Security of system or data? 1 Security by design designed for connectivity and security users do not login into admin account (by default) users do not install packages from unverified sources some distros require admin account even for connecting usb 2 intelligent users Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Is Linux (really) secure? Security of system or data? 1 Security by design designed for connectivity and security users do not login into admin account (by default) users do not install packages from unverified sources some distros require admin account even for connecting usb 2 intelligent users 3 Smaller market to target for attackers Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Shell provides the traditional user interface for the Unix operating system and for Unix-like systems Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Shell provides the traditional user interface for the Unix operating system and for Unix-like systems Some popular shells bash ksh csh Unless mentioned all slides assume bash Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Process in Linux Main Attributes uid - user with whose permissions process executes Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Process in Linux Main Attributes uid - user with whose permissions process executes pid - process id Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Process in Linux Main Attributes uid - user with whose permissions process executes pid - process id ppid - parent process id Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Process in Linux Main Attributes uid - user with whose permissions process executes pid - process id ppid - parent process id terminal - to which process is attached Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Standard I/O Every process has access to three (standard) files stdin (usually keyboard) - 0 Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Standard I/O Every process has access to three (standard) files stdin (usually keyboard) - 0 stdout (usually monitor) - 1 Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Standard I/O Every process has access to three (standard) files stdin (usually keyboard) - 0 stdout (usually monitor) - 1 stderr (usually monitor) - 2 Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses I/O Redirection Standard I/O of the process can be redirected to other file(s) cmd >filename redirects output from stdout to filename original contents of file are overwritten use >>to append the output to original content Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses I/O Redirection Standard I/O of the process can be redirected to other file(s) cmd >filename redirects output from stdout to filename original contents of file are overwritten use >>to append the output to original content cmd 2>filename redirects output from stderr to filename original contents of file are overwritten use >>to append the output to original content Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses I/O Redirection Standard I/O of the process can be redirected to other file(s) cmd >filename redirects output from stdout to filename original contents of file are overwritten use >>to append the output to original content cmd 2>filename redirects output from stderr to filename original contents of file are overwritten use >>to append the output to original content cmd <filename redirects input from stdin to filename Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses I/O Redirection Standard I/O of the process can be redirected to other file(s) cmd >filename redirects output from stdout to filename original contents of file are overwritten use >>to append the output to original content cmd 2>filename redirects output from stderr to filename original contents of file are overwritten use >>to append the output to original content cmd <filename redirects input from stdin to filename use /dev/null as output file to discard the output Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Executing multiple processes(sequentially) What are the possible cases? Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Executing multiple processes(sequentially) What are the possible cases? cmd1 ; cmd2 cmd2 is executed after completion of cmd1 Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Executing multiple processes(sequentially) What are the possible cases? cmd1 ; cmd2 cmd2 is executed after completion of cmd1 cmd1 && cmd2 cmd2 is executed after successful completion of cmd1 eg. rm abc && mkdir abc creates directory abc only if abc file is deleted successfully Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Executing multiple processes(sequentially) What are the possible cases? cmd1 ; cmd2 cmd2 is executed after completion of cmd1 cmd1 && cmd2 cmd2 is executed after successful completion of cmd1 eg. rm abc && mkdir abc creates directory abc only if abc file is deleted successfully cmd1 || cmd2 cmd2 is executed on un-successful completion of cmd1 Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Executing multiple processes(sequentially) What are the possible cases? cmd1 ; cmd2 cmd2 is executed after completion of cmd1 cmd1 && cmd2 cmd2 is executed after successful completion of cmd1 eg. rm abc && mkdir abc creates directory abc only if abc file is deleted successfully cmd1 || cmd2 cmd2 is executed on un-successful completion of cmd1 cmd1 | cmd2 cmd2 is executed on successful completion of cmd1 and takes output of cmd1 as its input Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Executing multiple processes(in parallel) what is background mode? Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Executing multiple processes(in parallel) what is background mode? start process in background mode directly using & at the end of command Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Executing multiple processes(in parallel) what is background mode? start process in background mode directly using & at the end of command start process normally (foreground) press ˆz (stops the process) execute bg (to start most recently stopped process in background mode) Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Executing multiple processes(in parallel) Handling processes running in background Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Executing multiple processes(in parallel) Handling processes running in background jobs - print currently pending (running + stopped) jobs Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Executing multiple processes(in parallel) Handling processes running in background jobs - print currently pending (running + stopped) jobs kill %1 - kills job corresponding to number 1 in the jobs output Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Executing multiple processes(in parallel) Handling processes running in background jobs - print currently pending (running + stopped) jobs kill %1 - kills job corresponding to number 1 in the jobs output fg - brings a background process back to foreground Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Executing multiple processes(in parallel) More process handling Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Executing multiple processes(in parallel) More process handling ps [-ely] - see all processes of all users Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Executing multiple processes(in parallel) More process handling ps [-ely] - see all processes of all users pstree - shows processes in tree-like (father-child) relation Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Executing multiple processes(in parallel) More process handling ps [-ely] - see all processes of all users pstree - shows processes in tree-like (father-child) relation top - show list of running processes interactively q - quit k - kill a process signal -9 kill without warning signal -15 kill after warning (allows cleanup) Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Executing multiple processes(in parallel) More process handling ps [-ely] - see all processes of all users pstree - shows processes in tree-like (father-child) relation top - show list of running processes interactively q - quit k - kill a process signal -9 kill without warning signal -15 kill after warning (allows cleanup) kill [signal] process-id kill -9 process-id Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Executing multiple processes(in parallel) More process handling ps [-ely] - see all processes of all users pstree - shows processes in tree-like (father-child) relation top - show list of running processes interactively q - quit k - kill a process signal -9 kill without warning signal -15 kill after warning (allows cleanup) kill [signal] process-id kill -9 process-id killall [signal] process-cmd-name Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Free Software As defined by FSF (1986) 1 run the program (for any purpose) Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Free Software As defined by FSF (1986) 1 run the program (for any purpose) 2 study how the program works (and change it to your needs) Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Free Software As defined by FSF (1986) 1 run the program (for any purpose) 2 study how the program works (and change it to your needs) 3 redistribute copies Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Free Software As defined by FSF (1986) 1 run the program (for any purpose) 2 study how the program works (and change it to your needs) 3 redistribute copies 4 improve the program and release your improvements to the public Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Licenses 1 GNU General Purpose License Disclaimer: I am not a legal expert Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Licenses 1 GNU General Purpose License 2 GNU Lesser General Purpose License Disclaimer: I am not a legal expert Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Licenses 1 GNU General Purpose License 2 GNU Lesser General Purpose License 3 Apache License Disclaimer: I am not a legal expert Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Licenses 1 GNU General Purpose License 2 GNU Lesser General Purpose License 3 Apache License 4 BSD License Disclaimer: I am not a legal expert Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Licenses 1 GNU General Purpose License 2 GNU Lesser General Purpose License 3 Apache License 4 BSD License 5 lot of others Disclaimer: I am not a legal expert Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses GNU GPL 1 most popular (and most sophisticated) Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses GNU GPL 1 most popular (and most sophisticated) 2 a work derived from GPL licensed work must be licensed under GPL Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses GNU GPL 1 most popular (and most sophisticated) 2 a work derived from GPL licensed work must be licensed under GPL 3 linking to GPL code? Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses GNU LGPL 1 less restrictive than GPL Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses GNU LGPL 1 less restrictive than GPL 2 LGPL licensed code can be linked by non-(L)GPL code Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses GNU LGPL 1 less restrictive than GPL 2 LGPL licensed code can be linked by non-(L)GPL code 3 derivative work must still release code for personal use (of customer) Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses GNU LGPL 1 less restrictive than GPL 2 LGPL licensed code can be linked by non-(L)GPL code 3 derivative work must still release code for personal use (of customer) 4 LGPL vs GPL? which one to use? Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses BSD 1 Very permissive Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses BSD 1 Very permissive 2 just give credits to the previous contributors Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses BSD 1 Very permissive 2 just give credits to the previous contributors 3 no need to release source-code Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses BSD 1 Very permissive 2 just give credits to the previous contributors 3 no need to release source-code 4 “If you want to give your software away for free, use BSD. If you want to share your software, use the GPL” (Courtesy:OSnews) Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Apache 1 Permissiveness same as BSD but legally more explicit Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Apache 1 Permissiveness same as BSD but legally more explicit 2 handles the problem of software patents Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Apache 1 Permissiveness same as BSD but legally more explicit 2 handles the problem of software patents 3 author of the code (automatically) gives up the right to any of (his/her) patent used in the code Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Case 1 ACME systems internally uses CRM whose codebase is based on a GPL based CRM. Can an employee of the company ask for the source code? Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Case 2 Microspecial Inc. supplies embedded systems to the government, as per the government orders they cannot release the source code to anyone but their codebase is based on GPL based code. What if someone asks for the source code? do they have to give it? Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Case 3 Stickpoint Solutions released Office software 1.0 under GPL and in the next version, they decide to move to BSD license? can they do it? Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Case 4 Tivo used parts of Linux kernel code for its consumer electronics product, so they had to release the source code but they put on the hardware check to avoid customised code from execution. Is this a violation of GPL? Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Case 5 Web Ultimates released source code of CMS(web application) under GPL, Web Peers Inc. used the code to develop their website, do they have to release the source code of their website? Ashish Bhatia Introduction to Linux
Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses References 1 Linux Man Pages 2 The Linux Documentation Project 3 Free Software Foundation (FSF) website Ashish Bhatia Introduction to Linux

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Techbuddy: Introduction to Linux session

  • 1. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Introduction to Linux by Ashish Bhatia TechBuddy Consulting Pvt. Ltd. 19-21 June 2010 Ashish Bhatia Introduction to Linux
  • 2. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Why learn Linux? Ashish Bhatia Introduction to Linux
  • 3. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses What is OS? What is OS? 1 BIOS - Boot Loader - OS 2 Hardware - OS - Application Software - User 3 multi-user? 4 multi-tasking? Ashish Bhatia Introduction to Linux
  • 4. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses History of GNU/Linux based on ideas from UNIX (originated in 1969 at AT&T) created by Linus Torvalds in 1991 General Public License GPL distribution of source code with binary is must more details later Ashish Bhatia Introduction to Linux
  • 5. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Files and Processes A running program is a process it has unique process identifier (PID) Everything else is file even devices like mouse, keyboard etc. every file has a unique inode number in Linux Ashish Bhatia Introduction to Linux
  • 6. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses File Hierarchy Unlike windows(except recent versions) where data storage is partitioned into various drives In Linux all (accessible) data is under / Ashish Bhatia Introduction to Linux
  • 7. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses File Hierarchy / The ancestor of all directories on the system Ashish Bhatia Introduction to Linux
  • 8. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses File Hierarchy / The ancestor of all directories on the system /bin Essential tools and other programs (or binaries) Ashish Bhatia Introduction to Linux
  • 9. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses File Hierarchy / The ancestor of all directories on the system /bin Essential tools and other programs (or binaries) /dev Files representing the system’s various hardware devices (eg. /dev/dvd) Ashish Bhatia Introduction to Linux
  • 10. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses File Hierarchy / The ancestor of all directories on the system /bin Essential tools and other programs (or binaries) /dev Files representing the system’s various hardware devices (eg. /dev/dvd) /etc Misc system configuration files, startup files (eg. /etc/networking) Ashish Bhatia Introduction to Linux
  • 11. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses File Hierarchy / The ancestor of all directories on the system /bin Essential tools and other programs (or binaries) /dev Files representing the system’s various hardware devices (eg. /dev/dvd) /etc Misc system configuration files, startup files (eg. /etc/networking) /home The home dir for all of the system’s users Ashish Bhatia Introduction to Linux
  • 12. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses File Hierarchy / The ancestor of all directories on the system /bin Essential tools and other programs (or binaries) /dev Files representing the system’s various hardware devices (eg. /dev/dvd) /etc Misc system configuration files, startup files (eg. /etc/networking) /home The home dir for all of the system’s users /proc Files that give information about current system processes Ashish Bhatia Introduction to Linux
  • 13. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses File Hierarchy / The ancestor of all directories on the system /bin Essential tools and other programs (or binaries) /dev Files representing the system’s various hardware devices (eg. /dev/dvd) /etc Misc system configuration files, startup files (eg. /etc/networking) /home The home dir for all of the system’s users /proc Files that give information about current system processes /root superuser’s home directory, whose username is root Ashish Bhatia Introduction to Linux
  • 14. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses File Hierarchy / The ancestor of all directories on the system /bin Essential tools and other programs (or binaries) /dev Files representing the system’s various hardware devices (eg. /dev/dvd) /etc Misc system configuration files, startup files (eg. /etc/networking) /home The home dir for all of the system’s users /proc Files that give information about current system processes /root superuser’s home directory, whose username is root /tmp Temp files Ashish Bhatia Introduction to Linux
  • 15. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses File Hierarchy / The ancestor of all directories on the system /bin Essential tools and other programs (or binaries) /dev Files representing the system’s various hardware devices (eg. /dev/dvd) /etc Misc system configuration files, startup files (eg. /etc/networking) /home The home dir for all of the system’s users /proc Files that give information about current system processes /root superuser’s home directory, whose username is root /tmp Temp files /usr Subdir with files related to user tools and applications Ashish Bhatia Introduction to Linux
  • 16. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Linux Alternative for Windows Internet Explorer = Firefox Ashish Bhatia Introduction to Linux
  • 17. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Linux Alternative for Windows Internet Explorer = Firefox Outlook Express = Thunderbird Ashish Bhatia Introduction to Linux
  • 18. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Linux Alternative for Windows Internet Explorer = Firefox Outlook Express = Thunderbird Google Talk = Pidgin (and Skype) Ashish Bhatia Introduction to Linux
  • 19. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Linux Alternative for Windows Internet Explorer = Firefox Outlook Express = Thunderbird Google Talk = Pidgin (and Skype) media player = amarok Ashish Bhatia Introduction to Linux
  • 20. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Linux Alternative for Windows Internet Explorer = Firefox Outlook Express = Thunderbird Google Talk = Pidgin (and Skype) media player = amarok Microsoft Office = Open Office Ashish Bhatia Introduction to Linux
  • 21. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Linux Alternative for Windows Internet Explorer = Firefox Outlook Express = Thunderbird Google Talk = Pidgin (and Skype) media player = amarok Microsoft Office = Open Office Notepad = kate,vim Ashish Bhatia Introduction to Linux
  • 22. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Linux Alternative for Windows Internet Explorer = Firefox Outlook Express = Thunderbird Google Talk = Pidgin (and Skype) media player = amarok Microsoft Office = Open Office Notepad = kate,vim A more comprehensive list at http://wiki.linuxquestions.org/wiki/ Linux software equivalent to Windows software Ashish Bhatia Introduction to Linux
  • 23. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses What is a user A user represents a real-world entity and it has username (and user ID) Ashish Bhatia Introduction to Linux
  • 24. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses What is a user A user represents a real-world entity and it has username (and user ID) group (and group ID) Ashish Bhatia Introduction to Linux
  • 25. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses What is a user A user represents a real-world entity and it has username (and user ID) group (and group ID) Password Ashish Bhatia Introduction to Linux
  • 26. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses What is a user A user represents a real-world entity and it has username (and user ID) group (and group ID) Password Home Dir Ashish Bhatia Introduction to Linux
  • 27. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses What is a user A user represents a real-world entity and it has username (and user ID) group (and group ID) Password Home Dir Default Shell Ashish Bhatia Introduction to Linux
  • 28. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses What is a user A user represents a real-world entity and it has username (and user ID) group (and group ID) Password Home Dir Default Shell User Details Ashish Bhatia Introduction to Linux
  • 29. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Users and Processes GNU/Linux is a multi-user OS Ashish Bhatia Introduction to Linux
  • 30. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Users and Processes GNU/Linux is a multi-user OS Everything is a file or a process Ashish Bhatia Introduction to Linux
  • 31. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Users and Processes GNU/Linux is a multi-user OS Everything is a file or a process Each process must specify which user is the owner Ashish Bhatia Introduction to Linux
  • 32. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Users and Processes GNU/Linux is a multi-user OS Everything is a file or a process Each process must specify which user is the owner No one except owner has right to access that process* Ashish Bhatia Introduction to Linux
  • 33. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Users and Processes GNU/Linux is a multi-user OS Everything is a file or a process Each process must specify which user is the owner No one except owner has right to access that process* what about files? Ashish Bhatia Introduction to Linux
  • 34. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Users and Files Each file has three (boolean) permissions Read(r) Write(w) Execute(x) Ashish Bhatia Introduction to Linux
  • 35. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Users and Files Each file has three (boolean) permissions Read(r) Write(w) Execute(x) All users can be grouped into Owner(u) Group (members) (g) Others (o) Ashish Bhatia Introduction to Linux
  • 36. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Users and Files Each file has three (boolean) permissions Read(r) Write(w) Execute(x) All users can be grouped into Owner(u) Group (members) (g) Others (o) 9 bits r w x r w x r w x Ashish Bhatia Introduction to Linux
  • 37. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Users and Files Each file has three (boolean) permissions Read(r) Write(w) Execute(x) All users can be grouped into Owner(u) Group (members) (g) Others (o) 9 bits r w x r w x r w x Super-user bypasses file permissions Ashish Bhatia Introduction to Linux
  • 38. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses A few examples chmod 600 file1 Ashish Bhatia Introduction to Linux
  • 39. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses A few examples chmod 600 file1 chmod 400 file2 Ashish Bhatia Introduction to Linux
  • 40. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses A few examples chmod 600 file1 chmod 400 file2 chmod 711 file3 Ashish Bhatia Introduction to Linux
  • 41. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses A few examples chmod 600 file1 chmod 400 file2 chmod 711 file3 chmod 644 file4 Ashish Bhatia Introduction to Linux
  • 42. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses A few examples chmod 600 file1 chmod 400 file2 chmod 711 file3 chmod 644 file4 chmod -R 644 dir1 Ashish Bhatia Introduction to Linux
  • 43. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Users and Files File Permissions on Dir Execute permission is required for a user to cd into a directory Ashish Bhatia Introduction to Linux
  • 44. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Users and Files File Permissions on Dir Execute permission is required for a user to cd into a directory Execute-only permission allows a user to access the files in a directory as long as the user knows the names of the files in the directory(and the user is allowed to read the files) Ashish Bhatia Introduction to Linux
  • 45. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Users and Files File Permissions on Dir Execute permission is required for a user to cd into a directory Execute-only permission allows a user to access the files in a directory as long as the user knows the names of the files in the directory(and the user is allowed to read the files) Execute+Read permission is required to view files contained in dir (eg. ls) Ashish Bhatia Introduction to Linux
  • 46. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Users and Files File Permissions on Dir Execute permission is required for a user to cd into a directory Execute-only permission allows a user to access the files in a directory as long as the user knows the names of the files in the directory(and the user is allowed to read the files) Execute+Read permission is required to view files contained in dir (eg. ls) Execute+Read+Write permission allows the user to create, delete, or modify any files or subdirectories(even if the file or subdirectory is owned by another user) Ashish Bhatia Introduction to Linux
  • 47. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Users and Files Ashish Bhatia Introduction to Linux
  • 48. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Users and Files Something More SetUID(u+s) Ashish Bhatia Introduction to Linux
  • 49. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Users and Files Something More SetUID(u+s) SetGID(g+s) Ashish Bhatia Introduction to Linux
  • 50. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Users and Files Something More SetUID(u+s) SetGID(g+s) Sticky Bit(t) Ashish Bhatia Introduction to Linux
  • 51. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Is Linux (really) secure? Ashish Bhatia Introduction to Linux
  • 52. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Is Linux (really) secure? Security of system or data? 1 Security by design designed for connectivity and security users do not login into admin account (by default) users do not install packages from unverified sources some distros require admin account even for connecting usb Ashish Bhatia Introduction to Linux
  • 53. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Is Linux (really) secure? Security of system or data? 1 Security by design designed for connectivity and security users do not login into admin account (by default) users do not install packages from unverified sources some distros require admin account even for connecting usb 2 intelligent users Ashish Bhatia Introduction to Linux
  • 54. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Is Linux (really) secure? Security of system or data? 1 Security by design designed for connectivity and security users do not login into admin account (by default) users do not install packages from unverified sources some distros require admin account even for connecting usb 2 intelligent users 3 Smaller market to target for attackers Ashish Bhatia Introduction to Linux
  • 55. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Shell provides the traditional user interface for the Unix operating system and for Unix-like systems Ashish Bhatia Introduction to Linux
  • 56. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Shell provides the traditional user interface for the Unix operating system and for Unix-like systems Some popular shells bash ksh csh Unless mentioned all slides assume bash Ashish Bhatia Introduction to Linux
  • 57. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Process in Linux Main Attributes uid - user with whose permissions process executes Ashish Bhatia Introduction to Linux
  • 58. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Process in Linux Main Attributes uid - user with whose permissions process executes pid - process id Ashish Bhatia Introduction to Linux
  • 59. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Process in Linux Main Attributes uid - user with whose permissions process executes pid - process id ppid - parent process id Ashish Bhatia Introduction to Linux
  • 60. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Process in Linux Main Attributes uid - user with whose permissions process executes pid - process id ppid - parent process id terminal - to which process is attached Ashish Bhatia Introduction to Linux
  • 61. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Standard I/O Every process has access to three (standard) files stdin (usually keyboard) - 0 Ashish Bhatia Introduction to Linux
  • 62. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Standard I/O Every process has access to three (standard) files stdin (usually keyboard) - 0 stdout (usually monitor) - 1 Ashish Bhatia Introduction to Linux
  • 63. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Standard I/O Every process has access to three (standard) files stdin (usually keyboard) - 0 stdout (usually monitor) - 1 stderr (usually monitor) - 2 Ashish Bhatia Introduction to Linux
  • 64. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses I/O Redirection Standard I/O of the process can be redirected to other file(s) cmd >filename redirects output from stdout to filename original contents of file are overwritten use >>to append the output to original content Ashish Bhatia Introduction to Linux
  • 65. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses I/O Redirection Standard I/O of the process can be redirected to other file(s) cmd >filename redirects output from stdout to filename original contents of file are overwritten use >>to append the output to original content cmd 2>filename redirects output from stderr to filename original contents of file are overwritten use >>to append the output to original content Ashish Bhatia Introduction to Linux
  • 66. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses I/O Redirection Standard I/O of the process can be redirected to other file(s) cmd >filename redirects output from stdout to filename original contents of file are overwritten use >>to append the output to original content cmd 2>filename redirects output from stderr to filename original contents of file are overwritten use >>to append the output to original content cmd <filename redirects input from stdin to filename Ashish Bhatia Introduction to Linux
  • 67. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses I/O Redirection Standard I/O of the process can be redirected to other file(s) cmd >filename redirects output from stdout to filename original contents of file are overwritten use >>to append the output to original content cmd 2>filename redirects output from stderr to filename original contents of file are overwritten use >>to append the output to original content cmd <filename redirects input from stdin to filename use /dev/null as output file to discard the output Ashish Bhatia Introduction to Linux
  • 68. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Executing multiple processes(sequentially) What are the possible cases? Ashish Bhatia Introduction to Linux
  • 69. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Executing multiple processes(sequentially) What are the possible cases? cmd1 ; cmd2 cmd2 is executed after completion of cmd1 Ashish Bhatia Introduction to Linux
  • 70. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Executing multiple processes(sequentially) What are the possible cases? cmd1 ; cmd2 cmd2 is executed after completion of cmd1 cmd1 && cmd2 cmd2 is executed after successful completion of cmd1 eg. rm abc && mkdir abc creates directory abc only if abc file is deleted successfully Ashish Bhatia Introduction to Linux
  • 71. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Executing multiple processes(sequentially) What are the possible cases? cmd1 ; cmd2 cmd2 is executed after completion of cmd1 cmd1 && cmd2 cmd2 is executed after successful completion of cmd1 eg. rm abc && mkdir abc creates directory abc only if abc file is deleted successfully cmd1 || cmd2 cmd2 is executed on un-successful completion of cmd1 Ashish Bhatia Introduction to Linux
  • 72. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Executing multiple processes(sequentially) What are the possible cases? cmd1 ; cmd2 cmd2 is executed after completion of cmd1 cmd1 && cmd2 cmd2 is executed after successful completion of cmd1 eg. rm abc && mkdir abc creates directory abc only if abc file is deleted successfully cmd1 || cmd2 cmd2 is executed on un-successful completion of cmd1 cmd1 | cmd2 cmd2 is executed on successful completion of cmd1 and takes output of cmd1 as its input Ashish Bhatia Introduction to Linux
  • 73. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Executing multiple processes(in parallel) what is background mode? Ashish Bhatia Introduction to Linux
  • 74. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Executing multiple processes(in parallel) what is background mode? start process in background mode directly using & at the end of command Ashish Bhatia Introduction to Linux
  • 75. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Executing multiple processes(in parallel) what is background mode? start process in background mode directly using & at the end of command start process normally (foreground) press ˆz (stops the process) execute bg (to start most recently stopped process in background mode) Ashish Bhatia Introduction to Linux
  • 76. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Executing multiple processes(in parallel) Handling processes running in background Ashish Bhatia Introduction to Linux
  • 77. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Executing multiple processes(in parallel) Handling processes running in background jobs - print currently pending (running + stopped) jobs Ashish Bhatia Introduction to Linux
  • 78. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Executing multiple processes(in parallel) Handling processes running in background jobs - print currently pending (running + stopped) jobs kill %1 - kills job corresponding to number 1 in the jobs output Ashish Bhatia Introduction to Linux
  • 79. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Executing multiple processes(in parallel) Handling processes running in background jobs - print currently pending (running + stopped) jobs kill %1 - kills job corresponding to number 1 in the jobs output fg - brings a background process back to foreground Ashish Bhatia Introduction to Linux
  • 80. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Executing multiple processes(in parallel) More process handling Ashish Bhatia Introduction to Linux
  • 81. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Executing multiple processes(in parallel) More process handling ps [-ely] - see all processes of all users Ashish Bhatia Introduction to Linux
  • 82. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Executing multiple processes(in parallel) More process handling ps [-ely] - see all processes of all users pstree - shows processes in tree-like (father-child) relation Ashish Bhatia Introduction to Linux
  • 83. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Executing multiple processes(in parallel) More process handling ps [-ely] - see all processes of all users pstree - shows processes in tree-like (father-child) relation top - show list of running processes interactively q - quit k - kill a process signal -9 kill without warning signal -15 kill after warning (allows cleanup) Ashish Bhatia Introduction to Linux
  • 84. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Executing multiple processes(in parallel) More process handling ps [-ely] - see all processes of all users pstree - shows processes in tree-like (father-child) relation top - show list of running processes interactively q - quit k - kill a process signal -9 kill without warning signal -15 kill after warning (allows cleanup) kill [signal] process-id kill -9 process-id Ashish Bhatia Introduction to Linux
  • 85. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Executing multiple processes(in parallel) More process handling ps [-ely] - see all processes of all users pstree - shows processes in tree-like (father-child) relation top - show list of running processes interactively q - quit k - kill a process signal -9 kill without warning signal -15 kill after warning (allows cleanup) kill [signal] process-id kill -9 process-id killall [signal] process-cmd-name Ashish Bhatia Introduction to Linux
  • 86. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Free Software As defined by FSF (1986) 1 run the program (for any purpose) Ashish Bhatia Introduction to Linux
  • 87. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Free Software As defined by FSF (1986) 1 run the program (for any purpose) 2 study how the program works (and change it to your needs) Ashish Bhatia Introduction to Linux
  • 88. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Free Software As defined by FSF (1986) 1 run the program (for any purpose) 2 study how the program works (and change it to your needs) 3 redistribute copies Ashish Bhatia Introduction to Linux
  • 89. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Free Software As defined by FSF (1986) 1 run the program (for any purpose) 2 study how the program works (and change it to your needs) 3 redistribute copies 4 improve the program and release your improvements to the public Ashish Bhatia Introduction to Linux
  • 90. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Licenses 1 GNU General Purpose License Disclaimer: I am not a legal expert Ashish Bhatia Introduction to Linux
  • 91. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Licenses 1 GNU General Purpose License 2 GNU Lesser General Purpose License Disclaimer: I am not a legal expert Ashish Bhatia Introduction to Linux
  • 92. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Licenses 1 GNU General Purpose License 2 GNU Lesser General Purpose License 3 Apache License Disclaimer: I am not a legal expert Ashish Bhatia Introduction to Linux
  • 93. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Licenses 1 GNU General Purpose License 2 GNU Lesser General Purpose License 3 Apache License 4 BSD License Disclaimer: I am not a legal expert Ashish Bhatia Introduction to Linux
  • 94. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Licenses 1 GNU General Purpose License 2 GNU Lesser General Purpose License 3 Apache License 4 BSD License 5 lot of others Disclaimer: I am not a legal expert Ashish Bhatia Introduction to Linux
  • 95. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses GNU GPL 1 most popular (and most sophisticated) Ashish Bhatia Introduction to Linux
  • 96. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses GNU GPL 1 most popular (and most sophisticated) 2 a work derived from GPL licensed work must be licensed under GPL Ashish Bhatia Introduction to Linux
  • 97. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses GNU GPL 1 most popular (and most sophisticated) 2 a work derived from GPL licensed work must be licensed under GPL 3 linking to GPL code? Ashish Bhatia Introduction to Linux
  • 98. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses GNU LGPL 1 less restrictive than GPL Ashish Bhatia Introduction to Linux
  • 99. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses GNU LGPL 1 less restrictive than GPL 2 LGPL licensed code can be linked by non-(L)GPL code Ashish Bhatia Introduction to Linux
  • 100. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses GNU LGPL 1 less restrictive than GPL 2 LGPL licensed code can be linked by non-(L)GPL code 3 derivative work must still release code for personal use (of customer) Ashish Bhatia Introduction to Linux
  • 101. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses GNU LGPL 1 less restrictive than GPL 2 LGPL licensed code can be linked by non-(L)GPL code 3 derivative work must still release code for personal use (of customer) 4 LGPL vs GPL? which one to use? Ashish Bhatia Introduction to Linux
  • 102. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses BSD 1 Very permissive Ashish Bhatia Introduction to Linux
  • 103. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses BSD 1 Very permissive 2 just give credits to the previous contributors Ashish Bhatia Introduction to Linux
  • 104. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses BSD 1 Very permissive 2 just give credits to the previous contributors 3 no need to release source-code Ashish Bhatia Introduction to Linux
  • 105. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses BSD 1 Very permissive 2 just give credits to the previous contributors 3 no need to release source-code 4 “If you want to give your software away for free, use BSD. If you want to share your software, use the GPL” (Courtesy:OSnews) Ashish Bhatia Introduction to Linux
  • 106. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Apache 1 Permissiveness same as BSD but legally more explicit Ashish Bhatia Introduction to Linux
  • 107. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Apache 1 Permissiveness same as BSD but legally more explicit 2 handles the problem of software patents Ashish Bhatia Introduction to Linux
  • 108. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Apache 1 Permissiveness same as BSD but legally more explicit 2 handles the problem of software patents 3 author of the code (automatically) gives up the right to any of (his/her) patent used in the code Ashish Bhatia Introduction to Linux
  • 109. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Case 1 ACME systems internally uses CRM whose codebase is based on a GPL based CRM. Can an employee of the company ask for the source code? Ashish Bhatia Introduction to Linux
  • 110. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Case 2 Microspecial Inc. supplies embedded systems to the government, as per the government orders they cannot release the source code to anyone but their codebase is based on GPL based code. What if someone asks for the source code? do they have to give it? Ashish Bhatia Introduction to Linux
  • 111. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Case 3 Stickpoint Solutions released Office software 1.0 under GPL and in the next version, they decide to move to BSD license? can they do it? Ashish Bhatia Introduction to Linux
  • 112. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Case 4 Tivo used parts of Linux kernel code for its consumer electronics product, so they had to release the source code but they put on the hardware check to avoid customised code from execution. Is this a violation of GPL? Ashish Bhatia Introduction to Linux
  • 113. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses Case 5 Web Ultimates released source code of CMS(web application) under GPL, Web Peers Inc. used the code to develop their website, do they have to release the source code of their website? Ashish Bhatia Introduction to Linux
  • 114. Philosophy Concept of Users File Handling in Linux Process Handling in Linux Licenses References 1 Linux Man Pages 2 The Linux Documentation Project 3 Free Software Foundation (FSF) website Ashish Bhatia Introduction to Linux