INTRODUCTION TO LINUX Jacob Chan

GNU/Linux Consists of Linux kernel, GNU utilities, and open source and commercial applications Works like Unix –Multi-user –multi-tasking –Networking –GUI (Fedora, Linux Mint) Stable and robust, but it’s for free (open source) Written by Linus Torvalds

Comparison with Windows Windows is easy to install. BUT it –Is unstable –Performs poorly –Crashes frequently Linux is trickier to install and configure. BUT –Stable –Performs better than Windows –Crashes more rarely than Windows –It is also more flexible than Windows. Linux takes time to master, but it is very powerful

Typing Commands in Linux Format: command -option --argument –Separated by whitespace Commands work on the supplied arguments (much like behaves like a method) Options modify the standard behavior (like the file is readable/writeable/executable)

Creating a User Account How: adduser login_name –Password will be prompted You can log out then log in as the account you created WARNING: Don’t use the system as the super user (root) –If you accidentally delete this, EVERYTHING will be gone (it’s the same as reformatting)

Getting help from online sources How –man command –info command –whereis command –apropos command Try typing ls /usr/man/man1

Files ALL programs, data, hardware devices are considered FILES in the Unix system Each file has a name. They are arranged in directories, which are also files Each file belongs to an owner or a group –The owner, the group, and the rest of the world can either read, write, or execute, provided that they are permitted to do so by the file owner or the super user (root)

File Types Regular Files (-): executables, text files, data files, libraries Directories (d): named references to other files Character device files (c) Block device files (b) Symbolic links (l): file containing a pathname (which may or may not exist) –Hard links: directory entry that exists in same partition

Pathnames Name of a file together with names of directories and subdirectories it is contained Absolute pathname: pathname relative to root (/var/) Relative pathname: pathname relative to the current directory (cs162b/student_profiles)

Root files /bin and /sbin – executables needed at boot time. /boot – contains the Linux kernel and boot data. /dev – contains device files. /etc – contains the system configuration files. /home and /root – home directories of users. /lib and /usr/lib – contains the shared libraries. /proc – contains info about running processes. /tmp and /var/tmp – directory for temporary files. /usr/bin and /usr/sbin – contains executables. /var – contains data files for reading/writing. /opt – contains optional packages.

Create and View (Text) Files -File Creation vi filename ed filename emacs filename -File Viewing cat filename more filename less filename

File Manipulation -Moving files mv old new (rename old to new) mv file folder (move file to folder) -Copying files cp original duplicate (copy original file to duplicate) cp –a folder1 folder2 (copy all contents of folder 1 to folder 2; useful for backing up) -Removing files rm –f file (delete file forcibly) rm –rf directory (recursively delete directory and all contents)

File Statistics wc –lwc file (counts lines, words, characters in file) grep –v pattern file (prints all lines of file that has doesn’t have the pattern) sort –r file (sorts file in increasing/decreasing order) head –n file (prints first n lines of file) tail –n file (prints last n lines of file)

File Statistics cut –cJ-K file (prints all characters in positions J to K of the file cut –dD –fJ-K file (prints all characters in positions J to K with D as the delimiter) cmp file1 file2 (show location of first difference between file1 and file2) diff file1 file2 (show ALL differences between file1 and file2)

Other File Commands ln –s filename linkname (create a symbolic link; NOTE: the file needs not to exist) ln file newfile (create hard links of a file, in which newfile is the alias of the file) touch filename (create empty file or to update file’s date)

Directory Commands pwd (print working directory) cd (home directory will be the working directory) cd dirname (dirname will be the working directory) mkdir dirname (create a new directory dirname) rmdir dirname (remove directory name)

Permissions chmod (change permissions to a file) chmod 777 file (owner, group, world) for each digit: read write executable chown (change owner of file) chown owner.group file chgrp (change group of a file) chgrp grpname file unmask (set file creation mask; what are not allowed in creating directories/files) unmask 022

Next Week Shell Scripting –First lab on shell scripting –More practice on Linux

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