2. What is Linux? • An alternative to Microsoft Windows • Open source • Freely available • Reliable • More use seen in labs/scientific situations, but is seeing more popularity. • Command line based interface
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4. Server Os must be:Stable,Robust,Secure,High Performance.Linux offers all of the above characteristics. So Linux can be used as:
5. -> On stand alone workstation/PC for word processing, graphics, software development, internet, e-mail, chatting, small personal database management system etc.
6. ->In network environment as: * File and Print or Application Server Share the data, Connect the expensive device like printer and share it, e-mail within the LAN/intranet etc are some of the application. Linux Server with different Client Os
7. (B) Linux sever can be connected to Internet, So that PC's on intranet can share the internet/e-mail etc. You can put your web sever that run your web site or transmit the information on the internet. Linux Server can act as Proxy/Mail/WWW/Router Server etc.
26. find: The find command searches through directories for files that match the specified criteria. It can take full pathnames and relative pathnames on the command line. To display the output on screen the –print option must be specified
28. ls: Lists the files in the current directory Some of the available options are: -l gives a long listing -a displays all file{including hidden files
29. Ps: Gives information about all the active processes.
33. umask: Used to specify default permissions while creating files.
34. wc: The wc command can be used to count the number of lines, words and characters in a fine. wc [filename(s)] The available options are: wc –[options] [filename] -1 -w -c
35. who: D isplays information about all the users currently logged onto the system. The user name, terminal number and the date and time that each user logged onto the system. The syntax of the who command is who [options]
51. LINUX DIRECTORIES: < / > The root directory. The starting point of your directory structure. This is where the Linux system begins. Every other file and directory on your system is under the root directory. Usually the root directory contains only subdirectories. < /boot > The place where Linux keeps information that it needs when booting up. < /bin > The /bin directory contains the most important programs that the system needs to operate, such as the shells, ls, grep, and other essential things.
52. < /usr/bin > /usr/bin in turn contains applications for the system's users. < /dev > The devices that are available to a Linux system.In Linux, devices are treated like files and you can read and write devices like they were files. < /etc > The configuration files for the Linux system. Most of these files are text files and can be edited by hand. < /home > This is where users keep their personal files are allowed to write files.
53. < /lib > The shared libraries for programs that are dynamically linked. The shared libraries are similar to DLL's on Winblows. < /mnt > This directory is used for mount points. The different physical storage devices (like the hard disk drives, floppies, CD-ROM's) must be attached to some directory in the file system tree before they can be accessed. This attaching is called mounting, and the directory where the device is attached is called the mount point.
54. < /sbin, /usr/sbin > Most system administration programs are stored in these directories. In many cases you must run these programs as the root user. < /var > This directory contains variable data that changes constantly when the system is running. Some interesting subdirectories: </var/log > A directory that contains system log files. They're updated when the system runs, and checking them out can give you valuable info about the health of your system.
55. </var/mail> Incoming and outgoing mail is stored in this directory. </var/spool> This directory holds files that are queued for some process, like printing. < /tmp > Programs can write their temporary files here.
56. < /usr > This directory contains user applications and a variety of other things for them, like their source codes, and pictures, docs, or config files they use. /usr is the largest directory on a Linux system. </usr/share> Config files and graphics for many user apps. < /usr/local > This is where you install apps and other files for use on the local machine.
58. ed Editor ed is a line-oriented text editor. It is used to create, display, modify and otherwise Manipulate text files. red is a restricted ed: it can only edit files in the current directory and cannot execute shell commands. Syntax: ed [-C] [-p string] [-s] [-] [-x] filename red [-C] [-p string] [-s | - ] [-x] filename
61. ex Editor ex Editor is a line-editor mode of the vi text editor. Syntax: ex [ -| -s ] [ -l ] [ -L ] [ -R ] [ -r [file ] ] [ -t tag ] [ -v ] [ -V ] [ -x ] [ -wn ] [ -C] [+command | -c command ] file
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63. It takes a file as input and prints the result on screen or redirects the output to a specified file. SYNTAX: sed [options] '{command}' [filename] OPTIONS: n do not output the trailing newline e enable interpretation of the backslash-escaped characters listed below v disable interpretation of those sequences in STRINGs
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65. insert. Command mode : letters or sequence of letters interactively command vi. Commands are case sensitive. The ESC key can end a command. Insert mode : Text is inserted. The ESC key ends insert mode and returns you to command mode. One can enter insert mode with the "i" (insert), "a" (insert after), "A" (insert at end of line), "o" (open new line after current line) or "O" (Open line above current line) commands.
66. vim editor Moving cursor around: Exiting from vim : let us now see how to exit from vim editor without saving changes. Vim editor has two modes: * command mode * editing mode
67. Command mode i s the one where we can instruct vim editor to exit to the command line ( shell ). To do that we need press ESC and type : q!. Character Deletion: delete character with x key Inserting Text : Press i or a in command mode and type Saving edited file : In command mode : wq or SHIFT+zz
68. Vim Operators and Motions Deleting Words delete word with dw command Delete to the end of the line delete to the end of the line with d operator and $ motion Motions and count number beginning of the line 0, end of the line $, end of the 2nd word 2e beginning of the 4th word 4w Deleting multiple words to delete 3 words you would use d3w Deleting lines to delete single line dd , delete n lines ndd Vim undo command undo changes with u
89. For example, if a * character appears in the fifth field, then the command mentioned in the line will be executed on all days of the week at the specified time.
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91. If neccessary group of numbers can be specified within a single field seperated by commas.
92. Below are two typical crontab lines. 1. 0 0 * * * backup.sh When executed, the above line runs the backup.sh script at midnight everyday . 2. 00,30 09-17 * * 1-5 mail.sh When execute, the above lines runs the mail.sh script on all weekdays-Monday to Friday every half hour between 9 and 17 hours
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94. every cmd has to be written in a seperate line having the above format in a seperate file.
95. Then it is submitted to crontab command, as shown below, where cmdfile is the name of the file executed periodically. $crontab cmdfile
