0003 SOME BASIC COMMANDS OF REDHAT LINUX

2009-05-09T21:19:00.012+05:30

Linux have large command pool. Still here are some linux command useful for beginners with small description. Being this is written for beigners he command listed here may have some more uses than explained in this post, for more information you can get the help of relative commands using man or info commands.

TO CLEAR THE SCREEN

#clear
TO CHECK DIRECTORY LISTINGS OR CONTENTS OF DIRECTORY.
#ls
bin boot dev etc home lib lost+found media mnt opt proc root sbin selinux srv sys tmp usr var

To check long (detailed) directory listings
#ls -l
total 112

drwxr-xr-x 2 root root 4096 2009-05-04 09:26 bin
drwxr-xr-x 5 root root 4096 2009-04-15 11:46 boot
drwxr-xr-x 14 root root 4880 2009-05-09 19:49 dev
drwxr-xr-x 131 root root 12288 2009-05-09 21:10 etc
CREATIN NEW EMPTY FILE.
#touch FILE_NAME

e.g.
#touch my_file.txt

Above command will create a new empty file called "my_file.txt" if it does not exist. If it exists already it will just change the time stamp of the existing file.
CREATING A NEW FILE WITH SOME CONTENT

#cat > FILE_NAME

e.g.
#cat > my_file.txt

after firing the command you have to enter the data in the file. After finishing entering the data in the file you have to press d to save the contents of the file.
READING THE CONTENT OF EXISTING FILE

#cat FILE_NAME

e.g.

#cat my_fiel.txt

After firing this command, contents of the "my_file.txt" will be displayed and controlls will be returned to command prompt. If the contets of the file is too long to read on single screen then you can use command as follws.

#cat my_file.txt | less
or
#less my_file.txt

After firing the above command you can scrolle the output using up/down arrow keys. After finishing reading the file to quit you can press "q" to quit.
CREATING NEW DIRECTORY.

To create the new directory the command is

#mkdir NEW_DIR_NAME

e.g. say you need to create a directory named "data"

#mkdir data

To print a message for each created directory
# mkdir -v data

To create a new directory with user dedined permissions
# mkdir -m=MODE
e.g.
To create a directory say "videos" with user defined permissions "777"
#mkdir -m=777 videos
CHANGING THE DIRECTORY

#cd DIR_NAME

e.g.
To enter in the directory say "videos"
#cd videos

To exit from the directory i.e. to enter in parent directory
#cd ..

To switch to home directory immediately
#cd ~

To switch to previous directory immediately
#cd -
DELETING OR REMOVING EXISTING FILE OR DIRECTORY.

To remove/delete the existing file

#rm FILE_NAME

e.g. to remove a existing file say "my_file.txt"
#rm my_file.txt

To remove/delete existing directory
#rm -rf
e.g. say you want to remove a existing directory "videos"
#rm -rf videos
COPING CONTENTS OF EXISTING FILE/DIRECTORY IN NEW FILE/DIRECTORY.

To copy contents of file "file1" to file "file2"
#cp file1 file2

To copy all the contents of directory "videos" to directory "vsongs"
#cp -Rv videos vsongs
RENAMING A FILE/DIRECTORY.

To change the name of the file "file1" to new name "file1"
#rename file file1

to change th name of the directory "videos" to "video_song"
#mv video video_song
CHANGING THE PERMISSIONS OF FILE/DIRECTORY
#chmod MODE FILE_NAME

e.g. To change the permissions of the file "my_file.txt" to 777
#chmod 777 mt_file.txt

To change permission of a directory named "video" with its all subdirectories and files to new permissions say 446
#chmod -R 446 video
CHANGING THE USER OWNERSHIP OF THE FILE/DIRECTORY.

#chown NEW_OWNER FILE_NAME

e.g. To change owner of a file named "my_file.txt" to new owner (user) say "denis"
#chown dnis my_file.txt

e.g. To change owner of a directory named "video" to new owner (user) say "denis"
#chown dnis video

e.g. To change owner of a directory named "video" with its all subdirectories and files to new owner (user) say "denis"
#chown -R dnis video
CHANGING THE GROUP OWNERSHIP OF THE FILE/DIRECTORY.

#chgrp NEW_GROUP FILE_NAME

e.g. To change group group of a file named "my_file.txt" to new group say "denis"
# chgrp dnis my_file.txt

e.g. To change group of a directory named "video" to new group say "denis"
#chgrp dnis video

e.g. To change group of a directory named "video" with its all subdirectories and files to new group say "denis"
#chgrp -R dnis video
CHECKING FILE SYSTEMS DISK USES
# df -h
GETTING REPORT OF DISK USES.
#du -h
GETTING CURRENT WORKING DIRECTORY.
#pwd
CREATING A SYMBOLIC LINK
To creates a symbolic link named symlink that points to the file test

#ln -s FILE_NAME SYMBOLIC_LINK_NAME

e.g
#ln -s test symlink

Typing "ls -i test symlink" will show the two files are different with different inodes. Typing "ls -l test symlink" will show that.
GETTING WHICH USEERS ARE LOGGED IN.
#who
LOCATING BINARIES AND MANUAL PAGES FOR COMMANDS

To locate binaries and manual pages for the "ls" command.

#locate ls
SHUTTING DOWN THE COMPUTER

To shuts the system down to halt immediately.
#shutdown -h now

To shut the system down immediately and the system reboots.
#shutdown -r now

To reboot the system in 10 minutes and send the message to all users.
#shutdown -r +10 "Rebooting in 10 minutes"

To shut the system down and do a reboot at 1:00 in the afternoon.
#shutdown -r 13:00
LOGGING OUT FROM THE TERMINAL

#logout

or press CTRL+D
CHECKING/SETTING DATE AND TIME

To check date and time of the system
#date

list the time and date in the below format:
DATE: 02/08/01
TIME:16:44:55
#date '+DATE: %m/%d/%y%nTIME:%H:%M:%S'

To sate date and time of the systm
#date -s "11/20/2003 12:48:00"
SETTING ALIASES

Alias allows you to have a small more familiar command or name to execute a long string of commans.

#alias ALIAS_NAME 'LONG_COMMAND'

e.g. The follofing command will create a alias named "shutt" to command "shutdown -r now".

#alias shutt 'shutdown -r now'
TO DISPLAY THE ARCHITECTURE OF THE PROCESSOR

#arch
CHECKING CALENDER ON COMMAND LINE

To check calendar for the current month and the year.
#cal

To check calendar for the specific month and the year say December of 2000.
#cal 12 2000

To display prev/current/next month calender.
#cal -3

To display a calendar for the current year.
#cal -y
DNS LOOKUP

To get IP of the hostname
#dig www.gooogle.com

To get hostname of the IP addresses
#dig -x 192.168.1.1

0002 GETTING HELP FOR LINUX COMMANDS.

2009-05-09T20:16:00.003+05:30

In vast command world of linux, no one can know all the commands., or no one can remember all the options/switches available for all commands. So it is very important to learn how to get help for the commands available.
Their are different ways of getting help in linux machines.

Getting short and fast help (for intermediate users) is adding "-h" or "--help" with command as follows

#vim -h

#ls --help

Detailed information about any command is using a manual pages or info pages.

Say if you want help of "ls" command

#man ls

#info ls

#pinfo ls

0001 Well come in the world of open source operating system.....

2008-05-10T14:28:00.006+05:30

Hi friends....
This is NISHANT CHAWRE. I'm working on this blog to power up the open source movement. Soon you'll start finding blogs on this blog site for preparation of RHCE exam. But being this is a huge task I'll need your help also to improve this blog site. I'm requesting you to contribute in this movement by sending articles useful for RHCE certification , as well as latest trends and technologies in open source OS.
You people can send me your articles on nishant.chawre@gmail.com with SUB as " Post for rhce-exam.blogspot.com". I'll defiantly put your articles on this blog with your name and information.

0000 Something about exam

2008-05-05T20:42:00.001+05:30

RHCE exam have three sections.
Section 1 : Qualifying section.
In this section you have to solve 4 compulsory question. In addition to 4 compulsory question you have to solve 6 questions. You must score at least 80/100 to be eligible for next phase in the exam that is RHCT and RHCE.
Section 2: RHCT section.
In this section you have to sole 10 questions to be RHCT. You have to score
at least 70/100
Section 3: RHCE section
In this section you have to sole 10 questions to be RHCT. You have to score at least 70/100

RHCE Exam

0003 SOME BASIC COMMANDS OF REDHAT LINUX

0002 GETTING HELP FOR LINUX COMMANDS.

0001 Well come in the world of open source operating system.....

0000 Something about exam