Linux Administration: A Beginner's Guide

Cover
Title Page
Copyright Page
Dedication
About the Author
Contents at a Glance
Contents
Acknowledgments
Introduction
Part I Introduction and Installation
	Chapter 1 Introduction to Linux, Distributions, and FOSS
		Linux: The Operating System
		Open Source Software and GNU: Overview
			The GNU Public License
			Upstream and Downstream
		The Advantages of Open Source Software
		Understanding the Differences Between Windows and Linux
			Single Users vs. Multiple Users vs. Network Users
			The Monolithic Kernel and the Micro-Kernel
			Separation of the GUI and the Kernel
			My Network Places
			The Registry vs. Text Files
			Domains and Active Directory
		Summary
	Chapter 2 Installing a Linux Server
		Hardware and Environmental Considerations
		Server Design
			Uptime
		Methods of Installation
		Installing Fedora
			Project Prerequisites
		The Installation
		Installation Summary
			Localization Section
			Software Section
			System Section
			User Settings Section
			The Installation
		Installing Ubuntu Server
			Start the Installation
			Configure the Network
			Configure Proxy
			Configure Ubuntu Archive Mirror
			File System Setup
			Profile Setup
			SSH Setup
			Featured Server Snaps
			Install Complete
		Summary
	Chapter 3 Deploying Linux Servers in the Cloud
		Behind the Cloud
		Obtaining and Spinning Up New Virtual Linux Servers
			Free-to-Run Virtual Linux Servers
			Commercial Cloud Service Providers
		Summary
Part II Single-Host Administration
	Chapter 4 The Command Line
		An Introduction to Bash
			Job Control
			Environment Variables
			Pipes
			Redirection
		Command-Line Shortcuts
			Filename Expansion
			Environment Variables as Parameters
			Multiple Commands
			Backticks
		Documentation Tools
			The man Command
			The texinfo System
		Files (Types, Ownership, and Permissions)
			Normal Files
			Directories
			Hard Links
			Symbolic Links
			Block Devices
			Character Devices
			Listing Files: ls
			Change Ownership: chown
			Change Group: chgrp
			Change Mode: chmod
		File Management and Manipulation
			Copy Files: cp
			Move Files: mv
			Link Files: ln
			Find a File: find
			File Compression: gzip
			File Compression: bzip2
			File Compression: xz
			Create a Directory: mkdir
			Remove Files or Directories: rm
			Show Present Working Directory: pwd
			Tape Archive: tar
			Concatenate Files: cat
			Display a File One Screen at a Time: more or less
			Show the Directory Location of a File: which
			Locate a Command: whereis
		Editors
			vi
			emacs
			pico
			sed
		Miscellaneous Tools
			Disk Utilization: du
			Disk Free: df
			List Processes: ps
			Show an Interactive List of Processes: top
			Send a Signal to a Process: kill
			Show System Information: uname
			Who Is Logged In: who
			A Variation on who: w
			Switch User: su
		Putting It All Together (Moving a User and Its Home Directory)
		Summary
	Chapter 5 Managing Software
		The Red Hat Package Manager
		Managing Software Using RPM
			Querying for Information the RPM Way (Getting to Know One Another)
			Installing Software with RPM (Moving in Together)
			Uninstalling Software with RPM (Ending the Relationship)
			Other Things RPM Can Do
		Yum
		DNF
		GUI RPM Package Managers
			Fedora or Ubuntu
			openSUSE and SLE
		The Debian Package Management System
			APT
		Software Management in Ubuntu
			Querying for Information
			Installing Software in Ubuntu
			Removing Software in Ubuntu
		Compile and Install GNU Software
			Getting and Unpacking the Source Package
			Looking for Documentation
			Configuring the Package
			Compiling the Package
			Installing the Package
			Testing the Software
			Cleanup
		Common Problems when Building from Source Code
			Problems with Libraries
			Missing Configure Script
			Broken Source Code
		Summary
	Chapter 6 Managing Users and Groups
		What Exactly Constitutes a User?
		Where User Information Is Kept
			The /etc/passwd File
			The /etc/shadow File
			The /etc/group File
		User Management Tools
			Command-Line User Management
			GUI User Managers
		Users and Access Permissions
			Understanding SetUID and SetGID Programs
			Sticky Bit
		Pluggable Authentication Modules
			How PAM Works
			PAM’s Files and Their Locations
			Configuring PAM
			A Sample PAM Configuration File
			The “Other” File
			D’oh! I Can’t Log In!
			Debugging PAM
		A Grand Tour
			Creating Users with useradd
			Creating Groups with groupadd
			Modifying User Attributes with usermod
			Modifying Group Attributes with groupmod
			Deleting Users and Groups with userdel and groupdel
		Summary
	Chapter 7 Booting and Shutting Down
		Boot Loaders
			GRUB Legacy
			GRUB 2
			Bootstrapping
		The init Process
		Systemd Scripts
			Writing Your Own rc Script
		Enabling and Disabling Services
			Enabling a Service
			Disabling a Service
		Odds and Ends of Booting and Shutting Down
			fsck!
			Booting into Single-User (“Recovery”) Mode
		Summary
	Chapter 8 File Systems
		The Makeup of File Systems
			i-Nodes
			Blocks
			Superblocks
			ext4
			Btrfs
			XFS
		Managing File Systems
			Mounting and Unmounting Local Disks
			Using fsck
		Adding a New Disk
			Overview of Partitions
			Traditional Disk and Partition Naming Conventions
		Volume Management
			Creating Partitions and Logical Volumes
		Creating File Systems
		Summary
	Chapter 9 Core System Services
		systemd
			systemd’s Role
			How systemd Works
		xinetd
			The /etc/xinetd.conf File
			Examples: A Simple (echo) Service Entry
		The Logging Daemon
			rsyslogd
			systemd-journald (journald)
		The cron Program
			The crontab File
			Editing the crontab File
		Summary
	Chapter 10 The Linux Kernel
		What Exactly Is a Kernel?
		Finding the Kernel Source Code
			Getting the Correct Kernel Version
			Unpacking the Kernel Source Code
		Building the Kernel
			Preparing to Configure the Kernel
			Kernel Configuration
			Compiling the Kernel
			Installing the Kernel
			Booting the Kernel
			The Author Lied! It Didn’t Work!
		Patching the Kernel
			Downloading and Applying Patches
			If the Patch Worked
			If the Patch Didn’t Work
		Summary
	Chapter 11 Knobs and Dials: API (Virtual) File Systems
		What’s Inside the /proc Directory?
			Tweaking Files Inside of /proc
		Some Useful /proc Entries
			Enumerated /proc Entries
		Common proc Settings and Reports
			SYN Flood Protection
			Issues on High-Volume Servers
		SysFS
		cgroupfs
		tmpfs
			tmpfs Example
		Summary
Part III Networking and Security
	Chapter 12 TCP/IP for System Administrators
		The Layers
			Packets
			TCP/IP Model and the OSI Model
		Headers
			Ethernet
			IP (IPv4)
			TCP
			UDP
		A Complete TCP Connection
			Opening a Connection
			Transferring Data
			Closing the Connection
		How ARP Works
			The ARP Header: ARP Works with Other Protocols, Too!
		Bringing IP Networks Together
			Hosts and Networks
			Subnetting
			Netmasks
			Static Routing
			Dynamic Routing with RIP
		tcpdump Bits and Bobs
			Reading and Writing Dumpfiles
			Capturing More or Less per Packet
			Performance Impact
			Don’t Capture Your Own Network Traffic
			Troubleshooting Slow Name Resolution (DNS) Issues
		IPv6
			IPv6 Address Format
			IPv6 Address Types
			IPv6 Backward Compatibility
		Summary
	Chapter 13 Network Configuration
		Modules and Network Interfaces
			Network Device Configuration Utilities (ip, ifconfig, and nmcli)
			Sample Usage: ifconfig, ip, and nmcli
			Setting Up NICs at Boot Time
		Managing Routes
			Sample Usage: Route Configuration
			Displaying Routes
		A Simple Linux Router
			Routing with Static Routes
		VPCs, Subnets, IPs, and Route Configuration (AWS Cloud Example)
			VPCs and Subnets (AWS)
			Internet Gateways and Routing (AWS)
			Security Groups (AWS)
			Launch a Linux Server in Its Own Subnet (AWS)
		Hostname Configuration
		Summary
	Chapter 14 Linux Firewall (Netfilter)
		How Netfilter Works
			A NAT Primer
			Chains
		Installing Netfilter
			Enabling Netfilter in the Kernel
		Configuring Netfilter
			Saving Your Netfilter Configuration
			The iptables Command
			firewalld
		Cookbook Solutions
			Simple NAT: iptables
			Simple NAT: nftables
			Simple Firewall: iptables
		Summary
	Chapter 15 Local Security
		Common Sources of Risk
			SetUID Programs
			Unnecessary Processes
		Picking the Right Runlevel
		Nonhuman User Accounts
		Limited Resources
		Mitigating Risk
			chroot
			SELinux
			AppArmor
		Monitoring Your System
			Logging
			Using ps and netstat
			Watch That Space (Using df)
			Automated Monitoring
			Staying in the Loop (Mailing Lists)
		Summary
	Chapter 16 Network Security
		TCP/IP and Network Security
			The Importance of Port Numbers
		Tracking Services
			Using the netstat Command
			Security Implications of netstat’s Output
		Binding to an Interface
		Shutting Down Services
			Shutting Down xinetd and inetd Services
			Shutting Down Non-xinetd Services
		Monitoring Your System
			Making the Best Use of syslog
			Monitoring Bandwidth with MRTG
		Handling Attacks
			Trust Nothing (and No One)
			Change Your Passwords
			Pull the Plug
		Network Security Tools
			nmap
			Snort
			Nessus and OpenVAS
			Wireshark/tcpdump
		Summary
Part IV Internet Services
	Chapter 17 Domain Name System (DNS)
		The Hosts File
		How DNS Works
			Domain and Host Naming Conventions
			The Root Domain
			Subdomain
			The in-addr.arpa Domain
			Types of Servers
		Installing a DNS Server
			Understanding the BIND Configuration File
			The Specifics
		Configuring a DNS Server
			Defining a Primary Zone in the named.conf File
			Defining a Secondary Zone in the named.conf File
			Defining a Caching Zone in the named.conf File
		DNS Records Types
			SOA: Start of Authority
			NS: Name Server
			A and AAAA: Address Records
			PTR: Pointer Record
			MX: Mail Exchanger
			CNAME: Canonical Name
			RP and TXT: The Documentation Entries
		Setting Up BIND Database Files
			DNS Server Setup Walkthrough
		The DNS Toolbox
			host
			dig
			resolvectl
			nslookup
			whois
			nsupdate
			The rndc Tool
		Configuring DNS Clients
			The Resolver
			Configuring the Client (Traditional)
		Summary
	Chapter 18 File Transfer Protocol (FTP)
		The Mechanics of FTP
			Client/Server Interactions
		Obtaining and Installing vsftpd
			Configuring vsftpd
			Starting and Testing the FTP Server
		Customizing the FTP Server
			Setting Up an Anonymous-Only FTP Server
			Setting Up an FTP Server with Virtual Users
		Summary
	Chapter 19 Apache Web Server
		Understanding HTTP
			Headers
			Ports
			Process Ownership and Security
		Installing the Apache HTTP Server
			Apache Modules
		Starting Up and Shutting Down Apache
			Starting Apache at Boot Time
		Testing Your Installation
		Configuring Apache
			Creating a Simple Root-Level Page
			Apache Configuration Files
			Common Configuration Options
		Troubleshooting Apache
		Summary
	Chapter 20 Simple Mail Transfer Protocol (SMTP)
		Understanding SMTP
			Rudimentary SMTP Details
			Security Implications
			E-mail Components
		Installing the Postfix Server
			Installing Postfix via DNF in Fedora, CentOS, or RHEL
			Installing Postfix via APT in Ubuntu
		Configuring the Postfix Server
			The main.cf File
			Checking Your Configuration
		Running the Server
			Checking the Mail Queue
			Flushing the Mail Queue
			The newaliases Command
			Making Sure Everything Works
		Summary
	Chapter 21 Post Office Protocol and Internet Mail Access Protocol (POP and IMAP)
		POP3 and IMAP Protocol Basics
		Dovecot (IMAP and POP3 Server)
		Installing Dovecot
			Dovecot Configuration Files and Options
			Configuring Dovecot
			Running Dovecot
			Checking Basic POP3 Functionality
			Checking Basic IMAP Functionality
		Other Issues with Mail Services
			SSL/TLS Security
			Availability
			Log Files
		Summary
	Chapter 22 Voice over Internet Protocol (VoIP)
		VoIP Overview
			VoIP Server
			Analog Telephone Adapter (ATA)
			IP Phones
			VoIP Protocols
		VoIP Implementations
		Asterisk
			How Asterisk Works
		Asterisk Installation
			Starting and Stopping Asterisk
		Understanding Asterisk Configuration Files and Structure
			The Dialplan: extensions.conf
			Modules: modules.conf
		Asterisk Network, Port, and Firewall Requirements
			Configuring the Local Firewall for Asterisk
		Configuring the PBX
			Local Extensions
			Outside Connection (VoIP Trunking)
			Trunking Using Twilio Elastic SIP Trunks
		Asterisk Maintenance and Troubleshooting
			Asterisk CLI Commands
			Helpful CLI Commands
			Common Issues with VoIP
		Summary
	Chapter 23 Secure Shell (SSH)
		Understanding Public Key Cryptography
			Key Characteristics
		SSH Backstory (Versions)
			OpenSSH and OpenBSD
			Alternative Vendors for SSH Clients
			Installing OpenSSH on RPM-Based Systems
			Installing OpenSSH via APT in Ubuntu
		Server Startup and Shutdown
		SSHD Configuration File
		Using OpenSSH
			Secure Shell (ssh) Client Program
			Secure Copy (scp) Program
			Secure FTP (sftp) Program
		Files Used by the OpenSSH Client
		Summary
Part V Intranet Services
	Chapter 24 Network File System (NFS)
		The Mechanics of NFS
			Versions of NFS
			Security Considerations for NFS
			Mount and Access a Partition
		Enabling NFS in Fedora, RHEL, and CentOS
		Enabling NFS in Ubuntu and Debian
		The Components of NFS
			Kernel Support for NFS
		Configuring an NFS Server
			The /etc/exports Configuration File
		Configuring NFS Clients
			The mount Command
			Soft vs. Hard Mounts
			Cross-Mounting Disks
			The Importance of the intr Option
			Performance Tuning
		Troubleshooting Client-Side NFS Issues
			Stale File Handles
			Permission Denied
		Sample NFS Client and NFS Server Configuration
		Common Uses for NFS
		Summary
	Chapter 25 Samba
		The Mechanics of SMB
			Usernames and Passwords
			Encrypted Passwords
			Samba Daemons
			Installing Samba via RPM
			Installing Samba via APT
		Samba Administration
			Starting and Stopping Samba
		Creating a Share
			Using smbclient
		Mounting Remote Samba Shares
		Samba Users
			Creating Samba Users
			Allowing Null Passwords
			Changing Passwords with smbpasswd
		Using Samba to Authenticate Against a Windows Server
			winbindd Daemon
		Troubleshooting Samba
		Summary
	Chapter 26 Distributed File Systems (DFS)
		DFS Overview
		DFS Implementations
			GlusterFS
		Summary
	Chapter 27 Lightweight Directory Access Protocol (LDAP)
		LDAP Basics
			LDAP Directory
			Client/Server Model
			Uses of LDAP
			LDAP Terminology
		OpenLDAP
			Server-Side Daemons
			OpenLDAP Utilities
			Installing OpenLDAP
			Configuring OpenLDAP
			Configuring slapd
			Starting and Stopping slapd
		Configuring OpenLDAP Clients
			Creating Directory Entries
		Searching, Querying, and Modifying the Directory
		Using OpenLDAP for User Authentication
			Configuring the Server
			Configuring the Client
		Summary
	Chapter 28 Printing
		Printing Terminologies
		The CUPS System
			Running CUPS
			Installing CUPS
			Configuring CUPS
		Adding Printers
			Local Printers and Remote Printers
			Using the Web Interface to Add a Printer
			Using Command-Line Tools to Add a Printer
		Routine CUPS Administration
			Setting the Default Printer
			Enabling, Disabling, and Deleting Printers
			Accepting and Rejecting Print Jobs
			Managing Printing Privileges
			Managing Printers via the Web Interface
		Using Client-Side Printing Tools
			lpr
			lpq
			lprm
		Summary
	Chapter 29 Dynamic Host Configuration Protocol (DHCP)
		The Mechanics of DHCP
		The DHCP Server
			Installing DHCP Software via RPM
			Installing DHCP Software via APT in Ubuntu
			Configuring the DHCP Server
			A Sample dhcpd.conf File
		The DHCP Client Daemon
		Summary
	Chapter 30 Virtualization
		Why Virtualize?
			Virtualization Concepts
		Virtualization Implementations
			Hyper-V
			Kernel-Based Virtual Machine (KVM)
			QEMU
			VirtualBox
			VMware
			Xen
		KVM
			KVM Example
			Managing KVM Virtual Machines
		Setting Up KVM in Ubuntu/Debian
		Containers
			Containers vs. Virtual Machines
			Docker
		Summary
	Chapter 31 Backups
		Evaluating Your Backup Needs
			Amount of Data
			Backup Hardware and Backup Medium
			Network Throughput
			Speed and Ease of Data Recovery
			Data Deduplication
			Tape Management
		Command-Line Backup Tools
			dump and restore
			tar
			rsync
		Miscellaneous Backup Solutions
		Summary
Part VI Appendixes
	A Creating a Linux Installer on Flash/USB Devices
		Overview
			Native Solutions
			Distro-Specific Solutions
			Universal Solutions
	B Demo Virtual Machine and Container
		Basic Host System Requirements
		Installing the Virtualization Applications and Utilities
		Download and Prep the Demo VM Image File
		Import the Demo VM Image and Create a New VM Instance
			Managing the Demo Virtual Machine
		Connecting to the Demo VM
			Virtual Network Computing (VNC)
			Virtual Serial TTY Console
			Connecting via SSH
			Cockpit Application
			Just Use It!
		Demo Containers (Docker, podman, buildah, and kubectl)
		Feedback
Index