Guide to Linux Installation and Administration, 2e1 Chapter 8 Basic Administration Tasks

Guide to Linux Installation and Administration, 2e 1

Chapter 8

Basic Administration

Tasks


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


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


Types of User Accounts

• Types of user accounts include:– root account

– Regular accounts

– Special accounts


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


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


Special Users

• Special accounts cannot be used to log in• Special accounts are used by programs running

on Linux


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


A User as a Member of Multiple Groups


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


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


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


Configuring Users Graphically in Red Hat Linux 7.3


useradd Command Options


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


Creating New Groups

• To create a new group, use the groupadd command

• To add a new group, include the group name as a parameter


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


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


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


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


Automatically Mounted File Systems


File Systems Mounted in a Linux Directory Structure


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


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


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


fdisk Commands


Sample Output of the p Command in fdisk


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


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


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


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


Option Field Settings for the mount Command


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


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


Simple Task Management

• To control processes running on Linux, you can use the following:– The ps command

– The bg command

– The fg command


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


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 text-based login sessions on the same computer

• The virtual consoles are assigned to the function keys


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


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


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


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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Guide to Linux Installation and Administration, 2e1 Chapter 8 Basic Administration Tasks