Linux Administration Bootcamp Go from Beginner to Advanced

Linux Administration Bootcamp Go from Beginner to Advanced (LINUX)










How to Change CentOs 6.3 keyboard ( from "qwerty" ) to "azerty" permanently :
   1.edit the file /etc/sysconfig/keyboard .
   2.Configure the KEYTABLE et LAYOUT to "fr"  , then Crtl+S  ( to save ) and exit .


Account: (all the account info is stored in the /etc/passwd )

  • Username (login ID ) 
  • UID ( User ID) this is a unique number
  • Default Group 
  • Comments 
  • Home directory location 
  • Shell ( execute when user logs in ) 

the format of the "/etc/passwd" :
userName : password : UID : GID : comments : home_directory : shell
( example :   joe:x:1000:1000:Joe Henderson:/home/joe:/bin/bash )

in this example of the root account :   root:x:0:0:root:/root:/bin/bash     
( x : encrypted password stored in the "/etc/shadow" file )

Custom for usenames < 8 characters : 
(linux supports usernames up to 32 char length ; if username is longer than 8 char => UID is displayed in place of the username )
                                                                                                        
|       usernames:
|    - less than 8 char by convention
|    - case-sensitive
|    - in lowerCase letters ( convention )
|    - Numbers are allowed
|    - Not use special characters




Passwords are stored in  /etc/shadow : 

passwords used to be stored in /etc/passwd    →→ readabe by everyone.
Now encrypted passwords are stored in   /etc/shadow  →→ readable by root.

UIDs (are unique numbers) :

- Root account is always UID 0 .
- System account have UIDs < 1000 →→ this is configured in /etc/login.defs

GIDs :
- GID listed in the  /etc/passwd in the account's default group 






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