guide to linux installation and administration, 2e1 chapter 8 basic administration tasks
TRANSCRIPT
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Guide to Linux Installation and Administration, 2e 1
Chapter 8
Basic Administration
Tasks
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Guide to Linux Installation and Administration, 2e 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
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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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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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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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Special Users
• Special accounts cannot be used to log in• Special accounts are used by programs running
on Linux
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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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
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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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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