Chapter 8
Basic Administration
Tasks
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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
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Valued Gateway
Client:
Managing User Accounts
• 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
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Client:
Types of User Accounts
• Types of user accounts include:
– root account
– Regular accounts
– Special accounts
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The root Account
• 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
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Client:
Regular Users
• 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
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Client:
Special Users
• Special accounts cannot be used to log in
• Special accounts are used by programs running
on Linux
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Client:
Linux Groups
• 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
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A User as a Member of Multiple Groups
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User and Group Files
• 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
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Client:
Shadow Passwords
• 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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Valued Gateway
Client:
Creating New User Accounts
• 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
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Configuring Users Graphically in Red
Hat Linux 7.3
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useradd Command Options
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Client:
Changing User Passwords
• A password is not defined by useradd when a
new user account is created
• The passwd command is used to define or
change a user’s password
• You must enter the new password twice
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Client:
Creating New Groups
• To create a new group, use the groupadd
command
• To add a new group, include the group name as a
parameter
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Client:
Modifying User and Group Accounts
• 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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Client:
Automating Home Directory Creation
• Files contained in /etc/skel are automatically
copied into each user’s home directory at the
time you create the account
• You should place files in /etc/skel when you first
install Linux
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Client:
Disabling User Accounts
• You can temporarily or permanently disable a
user account
• Accounts can be deleted using the userdel
command
• To temporarily disable a user’s account, change
the password with the passwd command
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Valued Gateway
Client:
Maintaining File Systems
• 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
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Automatically Mounted File Systems
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File Systems Mounted in a Linux
Directory Structure
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Client:
Checking File System Status
• 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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Valued Gateway
Client:
Creating New File Systems
• 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
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Valued Gateway
Client:
Using the fdisk Utility
• 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
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fdisk Commands
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Sample Output of the p Command in
fdisk
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Client:
Formatting File Systems
• 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
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Client:
Mounting File Systems
• 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
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Valued Gateway
Client:
Unmounting File Systems
• 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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Valued Gateway
Client:
Automating File System Mounting
• 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
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Option Field Settings for the mount
Command
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Client:
Managing Swap Space
• 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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Client:
Setting Quotas on Disk Usage
• 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
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Simple Task Management
• To control processes running on Linux, you can
use the following:
– The ps command
– The bg command
– The fg command
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Client:
Job Control in the Shell
• 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
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Valued Gateway
Client:
Using Virtual Consoles
• 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 textbased login sessions on the same computer
• The virtual consoles are assigned to the function
keys
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Valued Gateway
Client:
Learning about Processes
• 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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Client:
Controlling Processes
• 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
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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
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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
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