Basic UNIX Knowledge for a DBA - I

What is UNIX?

         Is a computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs including Ken Thompson, Dennis Ritchie and Douglas McIlroy.

What is SHELL?

            ·         An interface between the Linux system and the user

·         Used to call commands and programs

·         An interpreter

·         Powerful programming language

·         Many available (bsh; ksh; csh; bash; tcsh). Mostly used shell is bash shell.

Basic Commands in UNIX:

Creating a User : useradd username      -----> Press ENTER
Once the user is created, we should set the password for this user. 

To set the password for a user : Passwd username    -----> Press ENTER
It will ask the user to enter the password for the given username. 
Note: For confirmation, it will ask the user to retype the same password. So, we need to provide the same password to set properly.

Creating a Group : groupadd group_name    -----> Press ENTER

HELP in UNIX : In Unix, there are lot of commands to know the usage of each Unix command. Here are some of the useful commands which we will be using regularly.

(i) MAN : #] man command_name

Example : #] man ls

(ii)INFO : #] info command_name

Example : #] info grep

PS : PS is a command to view the processes running on the server (By default it only shows a small subset, but there are options to select larger sets of processes to display).

Example: #] ps                 -----> Press ENTER

                      #] ps aux           -----> Press ENTER  -- List all the processes on the system
Find : Searches a given file hierarchy specified by path, finding files that match the criteria  given by expression.

     Example: #] find -name "*.c"   -----> Press ENTER  
                        -- It will display all the files which are having the extension as  ".c"