groupadd
This is the command used to create new group. At OS level group is used to give and take  pivillages.
Syntax : groupadd <group name>
Ex : [root@rac5 ~]# groupadd group1
View : [root@rac5 ~]# cat /etc/group -This command used to view which user belongs to which group.
Output: group1:x:607:
useradd
This is the command used to create a new user in a group.
Syntax : useradd -g <group name> <user name>
Ex : [root@rac5 ~]# useradd -g group1 user1
passwd
This is the command used to give password for create use or to update the password.
Syntax : passwd <user name>
Ex: [root@rac5 ~]# passwd user1
Output :
[root@rac5 ~]# Changing password for user soufir.
New UNIX password:
BAD PASSWORD: it is based on a dictionary word
Retype new UNIX password:
passwd: all authentication tokens updated successfully.
date
a. This is the command used to view the current system date.
Syntax : date
Output : Wed Oct 27 21:55:36 IST 2010
b. In order to update the date we can give :
Syntax : [root@rac5 ~]# date -s “2 OCT 2010 14:00:00″Â Â OR
[root@rac5 ~]# date –set=”27 OCT 2010 21:56:00″
Output : Sat Oct 2 14:00:00 IST 2010
cal
This command shows the calender of current year or any.
Ex : [root@rac5 ~]#Â Cal
Output : [root@rac5 ~]#Â Â Â October 2010
Su Mo Tu We Th Fr Sa
1Â 2
3Â 4Â 5Â 6Â 7Â 8Â 9
10 11 12 13 14 15 16
17 18 19 20 21 22 23
24 25 26 27 28 29 30
31
pwd
This command is to view the present working directory.
Ex : [root@rac5 ~]# pwd
Output : [root@rac5 ~]# /root.
cd
a.This is the command used to change a directory
Ex : [oracle@rac5 ~]$ ls
authorized_keys file  file2 oraInventory stand.ora
authorized-keys file1 file3 soufir
[oracle@rac5 ~]$ cd soufir
[oracle@rac5 soufir]$
b.This is used to go back to parent directory
Ex : cd ..
mkdir
This command is used for make a new directory.
Ex : mkdir dir1
rmdir
This commad is used for remove a directory.
Ex : rmdir dir1
rm -rf
This command is used to forcefully remove a direcory.
Ex : rm -fr dir1
man
This command is used to show the online manual pages of related commands
Ex : man ls
ls
This command is used to list all contents of directories
Ex : ls
ls -lt
This command is used to list lot of information about contents of directories
Ex : ls -lt
The permissions are the first 10 characters of the line (-rwxrwx—) and can be broken down as follows.
|
–
|
rwx
|
r–
|
r–
|
1
|
root
|
root
|
765
|
Apr 23
|
file.txt
|
|
File type
|
Owner
|
Group
|
All
|
Links
|
Owner
|
Group
|
Size
|
Mod date
|
Filename
|
touch
This command is used create an empty file
Ex : touch file1
cat
This command is used to create and view files of directories
Ex : cat file1
cat file1 > newfile  // owerwrite newfile with file1
cat file1 >> newfile // append newfile the contents with file1
cp
This command is used to copy a file from one to another
Ex : cp file1 filenew
mv
This command is used to rename the name of a file to other
Ex : mv file1 filenew
su
This command is used to switch one user to other. it doesnot change the current working directory. so you cant access the /usr/sbin directories.
Ex : su soufir
su –
This command is used to switch one user with changing current working directory.
Ex : su – soufir
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Note : Please not do make backups before using these queries and also confirm them yourself or by aother means as
well.
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