Book Image

Linux Administration Cookbook

By : Adam K. Dean
Book Image

Linux Administration Cookbook

By: Adam K. Dean

Overview of this book

Linux is one of the most widely used operating systems among system administrators,and even modern application and server development is heavily reliant on the Linux platform. The Linux Administration Cookbook is your go-to guide to get started on your Linux journey. It will help you understand what that strange little server is doing in the corner of your office, what the mysterious virtual machine languishing in Azure is crunching through, what that circuit-board-like thing is doing under your office TV, and why the LEDs on it are blinking rapidly. This book will get you started with administering Linux, giving you the knowledge and tools you need to troubleshoot day-to-day problems, ranging from a Raspberry Pi to a server in Azure, while giving you a good understanding of the fundamentals of how GNU/Linux works. Through the course of the book, you’ll install and configure a system, while the author regales you with errors and anecdotes from his vast experience as a data center hardware engineer, systems administrator, and DevOps consultant. By the end of the book, you will have gained practical knowledge of Linux, which will serve as a bedrock for learning Linux administration and aid you in your Linux journey.

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Table of Contents (15 chapters)
Preface
Preface
Who this book is for
What this book covers
To get the most out of this book
Sections
Get in touch
Free Chapter
1
Introduction and Environment Setup
Introduction and Environment Setup
Introduction
Understanding and choosing a distribution
Installing VirtualBox
Installing our chosen distribution manually
Accessing and updating our VM
Understanding how VMs differ
Quick sudo explanation
Using Vagrant to automatically provision VMs
Anecdote - try, try, and try again
2
Remote Administration with SSH
Remote Administration with SSH
Introduction
Technical requirements
Generating and using key pairs with ssh-keygen
SSH client arguments and options
Using a client-side SSH configuration file
Modifying the server-side SSH configuration file
Rotating host keys and updating known_hosts
Technical requirements
Using local forwarding
Using remote forwarding
ProxyJump and bastion hosts
Using SSH to create a SOCKS Proxy
Understanding and using SSH agents
Running multiple SSH servers on one box
Summary
3
Networking and Firewalls
Networking and Firewalls
Introduction
Technical requirements
Determining our network configuration
More examples of using the ip suite
Adding and configuring network interfaces
Modern domain name resolution on Linux
Configuring NTP and the problems we face
Listing firewall rules on the command line
Adding and removing firewall rules on the command line
Determining the running services and ports in use
Debugging with iftop
Summary
4
Services and Daemons
Services and Daemons
Introduction
Technical requirements
Determining running services
Listing installed services
Starting and stopping services
Changing which services start and stop at boot
Common services you might expect to see
Understanding service unit files
Customizing systemd unit files
Testing running services
Writing a basic unit file
Working with systemd timers (and cron)
Other init systems
Round-up - services and daemons
5
Hardware and Disks
Hardware and Disks
Introduction
Technical requirements
Determining hardware
Testing hardware
The role of the kernel
Disk configuration on Linux
The filesystem hierarchy
Configuring a blank disk and mounting it
Re-configuring a disk using LVM
Using systemd-mount and fstab
Disk encryption and working with encryption at rest
Current filesystem formats
Upcoming filesystem formats
Round-up - hardware and disks
6
Security, Updating, and Package Management
Security, Updating, and Package Management
Introduction
Technical requirements
Checking package versions
Checking the OS version
Checking for updates
Automating updates
Checking mailing lists and errata pages
Using snaps
Using Flatpak
Using Pip, RubyGems, and other package managers
Dependency hell (a quick word)
Compiling from source
Technical requirements
Adding additional repositories
Roundup - security, updating, and package management
7
Monitoring and Logging
Monitoring and Logging
Introduction
Technical requirements
Reading local logs
Using journalctl on systemd systems
Centralizing logging
Local resource measuring tools
Local monitoring tools
Remote monitoring tools
Centralizing logging with the Elastic Stack
Roundup - Monitoring and Logging
8
Permissions, SELinux, and AppArmor
Permissions, SELinux, and AppArmor
Introduction
Technical requirements
Linux file permissions
Modifying file permissions
Technical requirements
Users and groups
AppArmor and modification
SELinux and modification
Checking SELinux is running, and the importance of keeping it running
Resetting SELinux permissions
Roundup - permissions, SELinux, and AppArmor
9
Containers and Virtualization
Containers and Virtualization
Introduction
Technical requirements
What is a container?
Installing Docker
Running your first Docker container
Debugging a container
Searching for containers (and security)
What is virtualization?
Starting a QEMU machine with our VM
Using virsh and virt-install
Comparing the benefits of local installs, containers, and VMs
Brief comparison of virtualization options (VMware, proxmox, and more)
Roundup - containers and virtualization
10
Git, Configuration Management, and Infrastructure as Code
Git, Configuration Management, and Infrastructure as Code
Introduction
Technical requirements
What is Git?
Setting up a Git server
Committing to our Git repository
Branching our Git repository and committing changes
Installing Ansible
Using Ansible to install Java from a role
Storing our Ansible configuration in Git
Exploring options for IaC
Roundup - Git, Configuration Management, and Infrastructure as Code
11
Web Servers, Databases, and Mail Servers
Web Servers, Databases, and Mail Servers
Introduction
Technical requirements
Installing and understanding a web server
Basic Apache configuration
Basic Nginx configuration
SSL, TLS, and LetsEncrypt
Basic MySQL or MariaDB Installation
Basic PostgreSQL installation
Local MTA usage and configuration (Postfix)
Local MTA usage and configuration (Exim)
NoSQL documents (MongoDB example)
NoSQL KV (Redis example)
Messaging brokers and queues (RabbitMQ example)
Roundup - web servers, databases, and mail servers
12
Troubleshooting and Workplace Diplomacy
Troubleshooting and Workplace Diplomacy
Introduction
Technical requirements
What is troubleshooting?
Isolating the real issue
Giving estimates and deciding on next steps
Using ss, iftop, tcpdump, and others for network issues
Using cURL, wget, and OpenSSL for remote web issues
Using iotop, top, and vmstat for local resource issues
Using ps, lsof, Strace, and /proc for service issues
Making a copy of problems for later debugging
Temporary solutions and when to invoke them
Handling irate developers
Handling irate managers
Handling irate business owners
Roundup - Troubleshooting and workplace diplomacy
13
BSDs, Solaris, Windows, IaaS and PaaS, and DevOps
BSDs, Solaris, Windows, IaaS and PaaS, and DevOps
Introduction
Determining the type of system you're on
Understanding how the BSDs differ
Understanding how Solaris and illumos differ
Understanding how Windows differs
IaaS (Infrastructure as a Service)
PaaS (Platform as a Service)
The Ops versus DevOps Wars
Roundup - BSDs, Solaris, Windows, IaaS and PaaS, DevOps
14
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Linux file permissions

To begin, we're going to go right back to basics by taking a look at the default Linux file permissions.

In this section, we're going to use a file and a directory on our CentOS box, to highlight some important and basic knowledge that we can use going forward.

File permissions on Unix and Unix-like systems are different from those found on Windows and other OS installations. If you connect a hard drive formatted with a Unix file-system (such as XFS) to a Windows box, it is unlikely it will be able to read the permissions on the files accurately (unless you've got software to do it for you). These lines have been blurred a bit in recent years, thanks to things like the Windows Subsystem for Linux included in Windows 10, but the principle is basically true.
...
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