Basic Administration

1
Chapter 8

• Basic Administration
• Tasks

2
Objectives

• In this chapter, you will
• Create and manage Linux user accounts
• Install and maintain types of Linux systems
• Manage processes on Linux using basic commands

3
Managing User Accounts
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• To complete any operation in Linux, a person must
  first log in using a valid user account name and
  password
• Setting up and maintaining these user accounts is
  an important part of the work of a system
  administrator

4
Types of User Accounts
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• Types of user accounts include
• root account
• Regular accounts
• Special accounts

5
The root Account
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• The administrative account (the superuser) on a
  Linux system is named root
• The root user can perform any operation on a
  Linux system
• The su utility (for substitute user) temporarily
  changes your access rights to those of another
  user

6
Regular Users
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• Regular user accounts are for users who log in at
  a keyboard and use the Linux system
• Regular user account names typically use a
  combination of first name or initial and last
  name or initial

7
Special Users
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• Special accounts cannot be used to log in
• Special accounts are used by programs running on
  Linux

8
Linux Groups
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• A group is a collection of user accounts that can
  be collectively granted access to files and
  directories
• A user can be a member of multiple groups, but
  can only have one primary group
• A User Private Group system creates a group with
  a single member for each new user account

9
A User as a Member of Multiple Groups
10
User and Group Files
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• User account information is stored in the file
  /etc/passwd
• To edit the /etc/passwd file, use the special
  editing program vipw
• Groups on a Linux system are defined in
  /etc/group
• To edit the /etc/group file, use the command vigr

11
Shadow Passwords
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• Encrypted passwords are stored in /etc/shadow
• Regular users cannot read encrypted passwords
• Shadow Password Suite is a collection of
  password-related programs that have been modified
  to recognize the /etc/shadow file

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Creating New User Accounts
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• New user accounts can be created
• With the useradd command
• With various graphical utilities
• Default settings apply when using the useradd
  command alone
• Default settings can be modified on the command
  line or by editing a configuration file for
  useradd

13
Configuring Users Graphically in Red Hat Linux 7.3
14
useradd Command Options
15
Changing User Passwords
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• A password is not defined by useradd when a new
  user account is created
• The passwd command is used to define or change a
  users password
• You must enter the new password twice

16
Creating New Groups
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• To create a new group, use the groupadd command
• To add a new group, include the group name as a
  parameter

17
Modifying User and Group Accounts
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• The usermod command allows you to modify user
  account parameters stored in /etc/passwd or
  /etc/shadow
• The groupmod command lets you modify membership
  of a group

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Automating Home Directory Creation
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• Files contained in /etc/skel are automatically
  copied into each users home directory at the
  time you create the account
• You should place files in /etc/skel when you
  first install Linux

19
Disabling User Accounts
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• You can temporarily or permanently disable a user
  account
• Accounts can be deleted using the userdel command
• To temporarily disable a users account, change
  the password with the passwd command

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Maintaining File Systems
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• File system refers to an organized set of data
  that can be accessed via the standard Linux
  directory structure
• To access a file system in Linux, it must first
  be mounted into the root directory structure
• A mount point is the path in the directory
  structure where you access the data in a file
  system
• Use the mount command to make a new file system
  accessible via a mount point

21
Automatically Mounted File Systems
22
File Systems Mounted in a Linux Directory
Structure
23
Checking File System Status
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• The df command displays space usage information
  for each file system that is currently mounted
• The du utility lists the size of a directory and
  all its subdirectories
• You can use various graphical tools and system
  administration scripts to check the status of
  file systems

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Creating New File Systems
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• You can install new file systems that are
  permanent or temporary
• File systems can be stored on a device with
  removable media or fixed media
• Once the hard disk or other device is installed,
  you can use the Linux fdisk command to examine
  its partitions, creating new Linux partitions

25
Using the fdisk Utility
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• To manage partitions in Linux after the operating
  system is installed, use the fdisk utility
• The fdisk utility can configure partition data on
  a hard disk
• Your modifications to the partition table are
  only effective when you write the changes to disk
  with the w command to exit fdisk

26
fdisk Commands
27
Sample Output of the p Command in fdisk
28
Formatting File Systems
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• File system journaling is a feature that protects
  against data corruption by tracking each write
  to the hard disk in a special way so that it will
  either be completely finished or left completely
  undone
• New partitions must be formatted using mke2fs or
  mkswap before they can be used

29
Mounting File Systems
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• After you have formatted a file system, you can
  mount it
• To access a file system, you use the mount
  command
• The floppy disk drive and CD-ROM drive are
  mounted to /mnt/floppy and /mnt/cdrom

30
Unmounting File Systems
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• To unmount a file system, use the umount command
  with the device name or mount point
• A file system cannot be in use when you unmount it

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Automating File System Mounting
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• The new file systems that you create from
  additional hard disks or other devices can also
  be automatically mounted at boot time
• The key to automounting file systems is the
  /etc/fstab configuration file which contains one
  line for each file system that you want to have
  automounted when Linux boots

32
Option Field Settings for the mount Command
33
Managing Swap Space
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• The swap space is a special partition type used
  by the Linux kernel for virtual memory
• You can use the mkswap command to format a swap
  partition
• Swap space is activated by the swapon command
  within the system initialization scripts
• The vmstat command displays current status
  details for how virtual memory is being used

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Setting Quotas on Disk Usage
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• Limits on the amount of hard disk space that any
  user or group can use are called disk quotas
• Use the edquota command to establish a quota for
  one or more users or groups
• Activate the quota system using the quotaon
  command

35
Simple Task Management
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• To control processes running on Linux, you can
  use the following
• The ps command
• The bg command
• The fg command

36
Job Control in the Shell
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• When you start a program, that program takes
  control of the command line where you are working
• The jobs command lists all jobs or processes that
  are running from the current shell
• The fg command places processes in the foreground
• The bg command places processes in the background
  command

37
Using Virtual Consoles
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• A virtual console is a separate login screen that
  you access by pressing a combination of keys on
  your keyboard
• A virtual console allows you to start multiple
  text-based login sessions on the same computer
• The virtual consoles are assigned to the function
  keys

38
Learning about Processes
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• A simple ps command shows you only the commands
  that you have started in the current
  command-line environment
• Multiple processes can be started from a single
  shell

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Controlling Processes
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• The kill command is used to kill, or end,
  processes
• Signals are messages that can be sent between
  processes
• The killall command sends a signal to all
  processes started by a given command

40
Summary

• Types of user accounts include root, regular
  accounts, and special accounts
• New user accounts can be created with the useradd
  command or with various graphical utilities
• New groups can be created with the groupadd
  command
• File systems are accessed by using the mount
  command to specify a device and a mount point
• The df and du commands display status and size
  information about file systems

41
Summary

• The fdisk utility can configure partition data on
  a hard disk.
• The vmstat command displays how virtual memory is
  being used
• Within a shell, the jobs command manages these
  processes, placing them in the foreground or
  background
• Virtual consoles let you log in at multiple
  independent text-mode screens
• The kill command sends signals to processes or to
  the Linux kernel when necessary to end a process