CertiGuide to A+ (A+ 4 Real)  9  Chapter 5: The Linux Operating System       9  The Major Components and Interfaces of Linux and Their Functions            9  /etc

/etc/grub.conf 1 /etc/rc.d Run Level Directories

User account information is stored within this file. This information is stored in fields separated by colons (:). A partial example passwd file is shown:

root:x:0:0:root:/root:/bin/bash

bin:x:1:1:bin:/bin:/sbin/nologin

daemon:x:2:2:daemon:/sbin:/sbin/nologin

adm:x:3:4:adm:/var/adm:/sbin/nologin

tbowe:x:501:502:Travis Bowie:/home/tbowe:/bin/bash

aflores:x:503:504:Avelina Flores:/home/aflores:/bin/bash

slucio:x:504:505:Steve Lucio:/home/slucio:/bin/bash

cmilford:x:505:506:Craig Milford:/home/cmilford:/bin/bash

The various fields in the file can be identified as follows:

• UserID: This is the user’s login ID for the system.
  
  
• Password: If this field is empty the user does not have a password (return key as password is very dangerous), an * will lock the account, and an x means that the hashed password is stored in the file /etc/shadow.
  
  
• User ID Number: A number that uniquely identifies the user.
  
  
• Group ID Number: A number that identifies the default group for the user.
  
  
• Comment Field: Any comment can be placed here; usually it is the user’s full name.
  
  
• Home Directory: The directory given here will be the user’s home directory, the current working directory when the user logs in to the system.
  
  
• Default Shell: The user’s shell that will be started when the user logs in or opens a terminal window.

Modifications to this file can be made using a text editor from the root account, however caution is in order. Incorrect modifications can lock out accounts and if the root account is disabled it can be difficult recovering from such an error. Use the proper commands (useradd, userdel, usermod) to modify this file.

/etc/grub.conf 1 /etc/rc.d Run Level Directories