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Basic Linux & Unix commands

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Basic  Linux & Unix commands 
 
100+ Important LINUX and UNIX Commands 
 
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<li>adduser ::-- Add a new user</li>
<li>arch ::-- Print machine architecture</li>
<li>awk ::-- Find and Replace text within file(s)</li>
<li>bc ::-- An arbitrary precision calculator language</li>
<li>cal ::--Display a calendar</li>
<li>cat ::--Concatenate files and print on the standard output</li>
<li>chdir ::--Change working directory</li>
<li>chgrp ::--Change the group ownership of files</li>
<li>chkconfig ::--Tool for maintaining the /etc/rc[0-6].d directory hierarchy</li>
<li>chmod ::--Change the access permissions of files and directories</li>
<li>chown ::--Change the user and group ownership of files</li>
<li>chroot ::--Change root directory</li>
<li>cksum ::--Print CRC checksum and byte counts</li>
<li>clear ::--Clear terminal screen</li>
<li>cmp ::--Compare two files</li>
<li>comm ::--Compare two sorted files line by line</li>
<li>cp ::--Copy one or more files to another location</li>
<li>cron ::--Daemon to execute scheduled commands</li>
<li>crontab ::--Schedule a command to run at a later time</li>
<li>csplit ::--Split a file into context-determined pieces</li>
<li>cut ::--Divide a file into several parts</li>
<li>date ::--Display or change the date & time</li>
<li>dc ::--Desk Calculator</li>
<li>dd ::--Data Dump - Convert and copy a file</li>
<li>df ::--Display free disk space</li>
<li>diff ::-- Display the differences between two files</li>
<li>diff3 ::--Show differences among three files</li>
<li>dir ::--Briefly list directory contents</li>
<li>dircolors ::-- Colour setup for `ls'</li>
<li>dirname ::--Convert a full pathname to just a path</li>
<li>du ::--Estimate file space usage</li>
<li>echo ::-- Display message on screen</li>
<li>ed ::-- A line-oriented text editor (edlin)</li>
<li>egrep ::--Search file(s) for lines that match an extended expression</li>
<li>eject ::--Eject CD-ROM</li>
<li>env ::-- Display, set, or remove environment variables</li>
<li>expand ::-- Convert tabs to spaces</li>
<li>expr ::-- Evaluate expressions</li>
<li>factor ::-- Print prime factors</li>
<li>false ::-- Do nothing, unsuccessfully</li>
<li>fdformat ::-- Low-level format a floppy disk</li>
<li>fdisk ::-- Partition table manipulator for Linux</li>
<li>fgrep ::-- Search file(s) for lines that match a fixed string</li>
<li>find ::-- Search for files that meet a desired criteria</li>
<li>fmt ::-- Reformat paragraph text</li>
<li>fold ::-- Wrap text to fit a specified width</li>
<li>format ::-- Format disks or tapes</li>
<li>free ::-- Display memory usage</li>
<li>fsck ::-- Filesystem consistency check and repair</li>
<li>gawk ::-- Find and Replace text within file(s)</li>
<li>grep ::-- Search file(s) for lines that match a given pattern</li>
<li>groups ::-- Print group names a user is in</li>
<li>gzip ::-- Compress or decompress named file(s)</li>
<li>head ::-- Output the first part of file(s)</li>
<li>hostname ::-- Print or set system name</li>
<li>id ::-- Print user and group id's</li>
<li>info ::-- Help info</li>
<li>install ::-- Copy files and set attributes</li>
<li>join ::-- Join lines on a common field</li>
<li>kill ::-- Stop a process from running</li>
<li>less ::-- Display output one screen at a time</li>
<li>ln ::-- Make links between files</li>
<li>locate ::-- Find files</li>
<li>logname ::-- Print current login name</li>
<li>lpc ::-- Line printer control program</li>
<li>lpr ::-- Off line print</li>
<li>lprm ::-- Remove jobs from the print queue</li>
<li>ls ::-- List information about file(s)</li>
<li>man ::-- Help manual</li>
<li>mkdir ::-- Create new folder(s)</li>
<li>mkfifo ::-- Make FIFOs (named pipes)</li>
<li>mknod ::-- Make block or character special files</li>
<li>more ::-- Display output one screen at a time</li>
<li>mount ::-- Mount a file system</li>
<li>mv ::-- Move or rename files or directories</li>
<li>nice ::-- Set the priority of a command or job</li>
<li>nl ::-- Number lines and write files</li>
<li>nohup ::-- Run a command immune to hangups</li>
<li>passwd ::-- Modify a user password</li>
<li>paste ::-- Merge lines of files</li>
<li>pathchk ::-- Check file name portability</li>
<li>pr ::-- Convert text files for printing</li>
<li>Printcap ::-- Printer capability database</li>
<li>printenv ::-- Print environment variables</li>
<li>printf ::-- Format and print data</li>
<li>ps ::-- Process status</li>
<li>pwd ::-- Print Working Directory</li>
<li>quota ::-- Display disk usage and limits</li>
<li>quotacheck ::-- Scan a file system for disk usage</li>
<li>quotactl ::-- Set disk quotas</li>
<li>ram ::-- ram disk device</li>
<li>rcp ::-- Copy files between two machines</li>
<li>rm ::-- Remove files</li>
<li>rmdir ::-  Remove folder(s)</li>
<li>rpm ::-- Remote Package Manager</li>
<li>rsync ::-- Remote file copy (Synchronize file trees)</li>
<li>screen ::-- Terminal window manager</li>
<li>sdiff ::-- Merge two files interactively</li>
<li>sed ::-- Stream Editor</li>
<li>select ::-- Accept keyboard input</li>
<li>seq ::-- Print numeric sequences</li>
<li>shutdown ::-- Shutdown or restart linux</li>
<li>sleep ::-- Delay for a specified time</li>
<li>sort ::-- Sort text files</li>
<li>split ::-- Split a file into fixed-size pieces</li>
<li>su ::-- Substitute user identity</li>
<li>sum ::-- Print a checksum for a file</li>
<li>symlink ::-- Make a new name for a file</li>
<li>sync ::-- Synchronize data on disk with memory</li>
<li>tac ::-- Concatenate and write files in reverse</li>
<li>tail ::-- Output the last part of files</li>
<li>tar ::-- Tape Archiver</li>
<li>tee ::-- Redirect output to multiple files</li>
<li>test ::-- Evaluate a conditional expression</li>
<li>time ::-- Measure Program Resource Use</li>
<li>touch ::-- Change file timestamps</li>
<li>top ::-- List processes running on the system</li>
<li>traceroute ::-- Trace Route to Host</li>
<li>tr ::-- Translate, squeeze, and/or delete characters</li>
<li>true ::-- Do nothing, successfully</li>
<li>tsort ::-- Topological sort</li>
<li>tty ::-- Print filename of terminal on stdin</li>
<li>umount ::-- Unmount a device</li>
<li>uname ::-- Print system information</li>
<li>unexpand ::-- Convert spaces to tabs</li>
<li>uniq ::-- Uniquify files</li>
<li>units ::-- Convert units from one scale to another</li>
<li>unshar ::-- Unpack shell archive scripts</li>
<li>useradd ::-- Create new user account</li>
<li>usermod ::-- Modify user account</li>
<li>users ::-- List users currently logged in</li>
<li>uuencode ::-- Encode a binary file</li>
<li>uudecode ::-- Decode a file created by uuencode</li>
<li>vdir ::-- Verbosely list directory contents (`ls -l -b')</li>
<li>watch ::-- Execute/display a program periodically</li>
<li>wc ::-- Print byte, word, and line counts</li>
<li>whereis ::-- Report all known instances of a command</li>
<li>which ::-- Locate a program file in the user's path</li>
<li>who ::-- Print all usernames currently logged in</li>
<li>whoami ::-- Print the current user name</li>
<li>xargs ::-- Execute utility, passing constructed argument list(s)</li>
<li>yes ::-- Print a string until interrupted</li>
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Basic Linux & Unix commands

Basic Linux & Unix commands 100+ Important LINUX and UNIX Commands adduser ::-- Add a new user arch ::-- Print machine architecture awk ::-- Find and Replace text within file(s) bc ::-- An arbitrary precision calculator language cal ::--Display a calendar cat ::--Concatenate files and print on th…

08Sep2014

How to Prevent Yum update of some selected packages in Redhat/Fedora

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 How to Prevent Yum update of some selected packages in Redhat/Redhat</div>
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It is very Simple to exclude some selected packages not to update while using yum update command</div>
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All you need to do is add an exclude line to the end of your [main] section in /etc/yum.conf .</div>
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Your /etc/yum.conf should look something like this:</div>
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[main] cachedir=/var/cache/yum keepcache=0 debuglevel=2 logfile=/var/log/yum.log exactarch=1 obsoletes=1 gpgcheck=1 plugins=1 installonly_limit=3 exclude= hal bash* </div>
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This will prevent upgrades of the hal package as well as bash package while using yum update cmd. The list of apps in the exclude should be space sepeated. Shell wildcards ( * ? ) can also be included.</div>
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From the desk of <a href="http://www.amitmaheshwari.in/" target="_blank">Amit Maheshwari</a></div>
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How to Prevent Yum update of some selected packages in Redhat/Fedora

How to Prevent Yum update of some selected packages in Redhat/Redhat It is very Simple to exclude some selected packages not to update while using yum update command All you need to do is add an exclude line to the end of your [main] section in /etc/yum.conf . Your /etc/yum.conf should look somet…

01Sep2014

Understanding Booting Process in LINUX

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 Understanding Booting Process in LINUX 
 
The Booting process is the first process that is executed when you start a Linux system.  This process is executed in the following steps:    1. The processor searches for the Basic Input/Output System (BIOS) program in the  memory and executes it. BIOS is a program that provides the lowest level interface to  the devices, such as the hard disk, monitor, and mouse, of the system.     2. BIOS runs the Power-On Self Test (POST) program, which checks the system  hardware by verifying the hardware configuration information. The program does this  to ensure that all the required hardware devices are present and functioning properly.     3. BIOS checks the system memory for errors and searches for a bootable device. The  bootable device may either be the hard disk or other bootable devices, such as a CD- ROM or a diskette drive. The sequence in which BIOS searches for the various  devices for the boot record is called the booting sequence You can specify the booting sequence by editing the booting sequence information in the  BIOS setup program. To enter the BIOS setup program, you need to press the <f1> or  <delete> key on the first boot up screen. The boot sequence can be specified as CD- ROM, C, A, where C represents the hard drive and A represents the diskette drive. In the  preceding boot sequence, BIOS will first search the CD-ROM for the boot record, then  search the hard drive and in the end search the diskette. The following list describes the  sequence in which the boot loader is invoked and loaded:    4. BIOS checks the bootable device for the presence of the Master Boot Record (MBR),  which is the first sector of the bootable device. The MBR is 512 bytes in size and  consists of a boot loader and a partition table. The boot loader contains instructions in  the form of machine code for booting the system. The partition table contains  information about the various partitions of the storage devices, such as the size of the  various partitions and the names of the partitions.     5. BIOS locates and invokes the boot loader by passing the control of the system to the  Initial Program Loader (IPL), also called the first stage of the boot loader, which is  present in the MBR.     6. IPL loads the boot loader in the system memory.   </delete></f1> 
The boot loader takes the control of the system from the IPL when it is loaded into the  
memory of the system. 
 
GRUB Configuration File    The GRUB configuration file specifies the various commands that are used to set the  global preferences of the system. The global preferences are the parameters that are not  specific to any operating system and are applicable to the entire menu interface of GRUB.  These preferences are followed by the commands specific to each operating system listed  on the menu interface.     The default location of grub.conf in the filesystem is /boot/grub/grub.conf. A sample  grub.conf file of a system having RHEL5 is shown below:    default=0  timeout=5  splashimage=(hd0,0)/grub/splash.xpm.gz  hiddenmenu  title Red Hat Enterprise Linux ES (2.6.18-5.EL5)    root (hd0,0)    kernel /vmlinuz-2.6.9-5.EL ro root=LABEL=/ rhgb quiet    initrd /initrd-2.6.18-5.EL5.img    A sample grub.conf file of a system having RHEL5 and Windows XP operating systems  is shown below:  default=0  timeout=5  splashimage=(hd0,0)/grub/splash.xpm.gz  hiddenmenu  title Red Hat Enterprise Linux ES (2.6.18-5.EL5)    root (hd0,0)    kernel /vmlinuz-2.6.18-5.EL5  ro root=LABEL=/ rhgb quiet    initrd /initrd-2.6.18-5.EL5.img  title Windows   rootnoverify (hd0,0)  chainloader +1  
In the preceding grub.conf file the various configuration directives are:    · default: Specifies default operating system to load  · timeout: Specifies the time interval, in seconds, GRUB waits for user to select an  operating system from GRUB menu  · splashimage: Specifies the absolute path of the image shown by GRUB on screen at bootup  · hiddenmenu: Specifies GRUB to hide the menu until user presses a key  · title: Specifies the OS name shown in GRUB menu   · root: Specifies the partition where grub is installed  · kernel: Specifies the absolute path of the kernel file to load and label of root partition  · initrd: Specifies the absolute path of the initial RAM disk 
· rootnoverify: Specifies the root partition to be used by GRUB but does not mount the partition  · chainloader: Specifies GRUB to load the file as a chain loader  Created By <a href="http://www.amitmaheshwari.in/" target="_blank">Amit Maheshwari</a><a href="http://www.amitmaheshwari.in/" target="_blank"> </a> </div>

Understanding Booting Process in LINUX

Understanding Booting Process in LINUX The Booting process is the first process that is executed when you start a Linux system. This process is executed in the following steps: 1. The processor searches for the Basic Input/Output System (BIOS) program in the memory and executes it. BIOS is a pro…

01Sep2014

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Basic Linux & Unix commands

How to Prevent Yum update of some selected packages in Redhat/Fedora

Understanding Booting Process in LINUX

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