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List of some commands used in Linux
If you want to get more information about any of the following command, use man page or info pages as
Syntax:
man {command-name}
Example:
$ man cat
Syntax:
info {command-name}
Example: $ info date
Even some command like mv, ls give command help on command line by typing command as follows
Syntax:
{command-name} --help
Example:
$ mv --help
$ ls --help | more
To see help or options related with ls command; here you can get screen-by-screen help, since help of ls command is quite
big that can't fit on single screen.
NOTE that following commands are for new users or for Beginners only. The purpose is if you use this command you will
be more familiar with your shell and secondly, you need some of these command in your Shell script.
cat
To display text file.
Syntax
cat {file name}
Examples
$cat foo
cfdisk*
To create/modify/delete partition table interactively.
Syntax
cfdisk
cd
To change current directory.
Syntax
cd {directory name}
Options
- (minus) Change to previous directory location.
Examples
$ cd /usr/local/apache
$ pwd
/usr/local/apache
$ cd /var/log
$ pwd
/var/log
$ cd –
$ pwd
/usr/local/apache
$ cd (Change to home directory)
NOTE: Linux’s $OLDPWD variable holds your last directory setting, if you type $ cd $OLDPWD, it is same as $
cd -. What happen if you type $ cd – as soon as you login into Linux?
chfn
Change the finger information of user.
Syntax
chfn [user-name]
Examples
$ chfn vivek
$ chfn # change the currently log on users finger information
chgrp
Change the group owner of a file.
Syntax
chgrp {group name} {file/directory name}
Options
-R Recursively change group owner of files/directory
Examples
chgrp oracle /usr/database
chgrp msc /home/cstudents
chmod
Change the file/directory permission directory.
Syntax
chmod permission-options file/directory name.
Options
(a)permission-options -
rwx rwx rwx
| | |
1 2 3
1 – owner
2 – group
3 – others
For r,w,x octal value is 4,2,1 respectively.
So if you want to give r,w,x permission to owner, for group r,x, and for w,x to others. Then,
rwx rwx rwx
421 401 021
For owner add this number as 4+2+1 = 7
For group add this number as 4+0+1 = 5
For others add this number as 0+2+1 = 3
So command will be $ chmod 753 filename
Examples
$chmod 755 first.sh
(b)permission-options -
chmod {u|g|o|a} {+|-} {r|w|x} {filename}
u - User who owns the file
g - Group file owner
o - User classified as other
a - All other system user
+ Set permission
- Remove permission
r - Read permission
w - Write permission
x - Execute permission
Examples
$ chmod u+x,g+wx,o+x myscript
Above command set permission for file called 'myscript' as User (Person who creates that file or directory) has execute
permission (u+x) Group of file owner can write to this file as well as execute this file (g+wx) Others can only execute file
but can not modify it, Since we have not given w (write permission) to them. (o+x).
chown
Change the owner of file/directory.
Syntax
chown {username}[.group-name] {file/directory-name}
Options
-R Recursively change group owner of files/directory
Examples
$chown vivek.users *.jsp
All files ending with .jsp are now owned by user vivek of the group users.
clear
Clear the screen.
Syntax
clear
cp
To Copy files.
Syntax
cp {source} {destination}
Options
-f force the cp to copy files even if file exist (overwrite the files).
-i Ask y/n confirmation before coping each file.
Examples
$ cp -f /mnt/floppy/* /home/vivek
cmp
To use to compare files
Syntax
cmp {file1} {file2}
Examples
$ cmp myfile myfile.old
date*
Change or set current date and time.
Syntax
date [date or time string ]
Examples
$date # will show current date & time
$date --date=“2001-3-15“ # will set date to 2001-Mar-15
$date --date=“2001-3-15 11:59 AM” # date as well as time
df
Display the disk space used file system.
Syntax
df
Options
-m Displays information in MB.
-k Displays information in KB.
-h Displays information in easy-to-understand format.
diff
Display differences (Comparison between two files) in files.
Syntax
diff {file1} {file2}
dmesg
To display kernel log messages. (Which are shown when your system first time boot)
Syntax
dmesg
du
Displays the disk usage according to space used by file/directory.
Syntax
du [directory name]
Options
-a all files
-k Displays information in KB.
-h Displays information in easy-to-understand format.
-s Displays only total not details.
fdisk*
To create/ modify/ delete partition table.
Syntax
fdisk {device -name}
Options
This are command of fdisk, you have to use this command after fdisk program starts.
a Mark bootable partition.
d Delete partition.
m Help
n Create new partition.
p Print partition table on screen.
q Quit without saving changes.
t Changes the partition type ID (type)
w Quit and save changes to disk.
Examples
$fdisk /dev/hda
find
To Search files.
Syntax
find dirname -name files-to-find -print
Examples
$ find / -name *.c -print
finger
Get user information.
Syntax
finger [user-name]
Examples
$finger
$finger vivek
fsck*
To check the file system for errors, and if found repair it.
Syntax
fsck {device name}
Options
-f force to repair.
-y Assume “yes” for all questions.
Caution Do’t run fsck in multiuser mode, first run system in single mode then un mount file system and then
run the fsck.
Examples
$ init 1 # go to single user mode or you can type linux single at
# LILO prompt while booting the system. Note that if your
# LILO is password protected, then you have to supply
# password for it.
$ umount /dev/hdx # replace x with your partition number for e.g
# umount /dev/hda1
$ fsck /dev/hda1
$ reboot
grep
To search text files for particular text.
Syntax
grep “patter-to-search” file-name
Examples
grep “Red Hat” /etc/*
gzip
To compress or decompress file.
Syntax
gzip file-nane
Options
-d decompress
-S suffix
Examples
$ gzip ltips
$ ls
$ gzip -d ltips
init*
Use to switch between different run-levels.
Syntax
init 0123456
Options
0 halt the system
1 Single-user mode
2 Multi-user without NFS
3 Full Multi-user (Default)
4 Unused
5 Start X windows
6 Reboot system
Examples
$ su -l
# init 6 # reboot
# init 1 # single user mode.
logout
To login out
Syntax
logout
last/lastlog*
To Display login, telnet and ftp log of your Linux Server.
less
To display file contains
Syntax
less filename
ln
Create a link.
Syntax
ln -s {file/directory} {file/directory}
Examples
$ln -s p longprogname
$ls -l
locate*
To quickly (securely also) search file.
Syntax
locate {file name}
Options
-R Recursively display the files & directory.
-l Long listing of files & directory.
Note
If you are running locate first time then run following command, which will create database file. (Run as root user)
$ su
password
#/etc/cron.daily/slocate.cron
Examples
$locate -l foo
ls
Shows list of files and dirs
Syntax
ls [file/dir name]
Options
-R Recursively display the files & directory.
-l Long listing of files & directory.
-a Show all files start with . (DOT) # for e.g.: .bash_profile
-N Name wise sorting.
Examples
$ ls
$ ls -lR / > alist &
$ ls –a
mail
Read or send the mail.
Syntax
mail {user-name}
Options
If you are reading mail use following command
d - Delete the mail.
q - Quit the mail program.
s - Save the mail to mailbox.
Examples
$ mail # read your mail
$ mail vivek
mount/umount*
Mount/unmount the file system. Useful to work with floppy,cdrom, other (DOS/Windows) partition etc.
Syntax
mount -t {file system type} { device name } {mount point}
Options
-t can be msdos or vfat
Examples
# must be root user
#To mount your Cd-Rom
# mount /dev/cdrom
# mount –t msdos /dev/fd0 /mnt/floppy
# cd /mnt/floppy
# ls
# mount # to see all mounted device
more
To view text file
Syntax
more {file name}
mv
To move the file(s)/directory.
Syntax
mv {source} {destination}
pr
To print file.
Syntax
pr {file-name}
Examples
$pr myfile
passwd
To change the password.
Syntax
passwd {username}
Options
-d Delete the password. (Use with very carefully)
Examples
$ passwd
ping
Network related command, to verify that network is connected and working properly.
Syntax
ping {host-name | IP Number}
Examples
$ping www.yahoo.com # if connectd to Internet
$ping 192.168.1.78
pwd
Print working directory.
Syntax
$ pwd
rpm*
Red Hat Linux Package Management program. Use this to install/ uninstall/ upgrade software under Linux (Red Hat Linux
Ver. 6.x Only)
Syntax
rpm {option} {.rpm file}
Options
-i Install .rpm software.
-U Upgrade the software.
-e Delete the software.
-l List all files in .rpm software package
Examples
$ rpm -i demo.rpm
rm
Remove the files.
Syntax
rm {filename}
Options
-rf Remove all files/directory with subdirectories. (DOS’s – deltree)
Examples
$ rm foo
$ rm -rf /home/vivek/oldfiles
sort
To sort files.
Syntax
sort {file-name}
Options
-r Reverse normal order
-n Sort in numeric order
-nr Sort in reverse numeric order
Examples
$sort myfile
startx
Start X windows system.
Syntax
startx
Options
Press ctrl + alt + backspace to kill x windows.
shutdown*
Shutdown linux.
Syntax
shutdown
Options
-r Reboot Linux.
-h Halt or Shutdown
Example
$shutdown –h now
smbpasswd*
Samba password change.
Syntax
smbpasswd {username}
Examples
$smbpasswd rani
su*
Become super user if user name is not given, or change the user ID.
Syntax
su [username]
tar
Linux archive program.
Syntax
tar options {tar-file-name} {dir-name-to-archive}
Options
-c Create the file.
-f {filename} Name of archive file
-z Compress the file.
-x Extract the files from archive
Examples
# To create archive file of /home/vivek directory
$ tar -czf mybackup.tar.gz /hove/vivek
#If you want to extract file from above
$ tar -xf mybackup.tar.gz
testparm/testprns*
Test the /etc/smb.conf file for errors.
testparm – To test share setting.
testprns – To test printer setting.
Above will also display setting and error if any.
Syntax
testparm
testprns
top
To see process information in neat format.
Syntax
top
Options
? Get more information about top command.
touch
Create empty file or change/update time stamp of file.
Syntax
touch {filename}
Examples
$ touch /etc/dhcpd.leases #create file for dhcpd demon
$ touch /etc/modules # update time stamp of file
umask
Specify the permission for files when files are created for owner(u),group(g), and others(o).
Syntax
umask –S {u=xx,g=xx,o=xx}
Where xx can be (r)ead,(w)rite.
Or you can use 022 for read only file permission for others and 077 for read and write permission.
Examples
$umask -S u=rw,g=,o=
$umask 022
useradd/userdel*
Add/delete new user to your system
Syntax
useradd -g {group-name} {user-name-to-add}
userdel {user-name-to-delete}
Examples
#add rani user to system (must be root)
#adduser -g oracle rani
#passwd rani
#Delete the user kaju
#userdel kaju
w
Shows who logged on and what they are doing
Syntax
w
who am i
About your self.
Syntax
who am i
which
Show the location of file from which it is executed when you type the name.
Syntax
which {file name}
Examples
$ which gaim
/usr/bin/gaim
$ ls –l `which cc`
whatis
This command gives the brief summary of the command used.
eg
$ whatis gaim
Gaim (3pm) - Perl extension the Gaim instant messenger
gaim (rpm) - A Gtk+ based multiprotocol instant messaging client
xinit
Initializes X window without loading any windows manager.
Syntax
xinit
Examples
$ xinit
$ kde
* For this command you must be root or root equivalent user.
penguin.jpg
 Tux , the Linux penguin
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~`
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