Troubleshooting Ubuntu Server

Skanda Bhargav

• Publisher: Packt Publishing
• Year: 2015
• ISBN:
  9781785284144
• Edition: 1
• Topic: Informatique
• Subtopic: Cloud Computing

Make life at the office easier for server administrators by helping them build resilient Ubuntu server systems

About This Book

• Tackle the issues you come across in keeping your Ubuntu server up and running
• Build server machines and troubleshoot cloud computing related issues using Open Stack
• Discover tips and best practices to be followed for minimum maintenance of Ubuntu Server 3

Who This Book Is For

This book is for a vast audience of Linux system administrators who primarily work on Debian-based systems and spend long hours trying fix issues with the enterprise server. Ubuntu is already one of the most popular OSes and this book targets the most common issues that most administrators have to deal with. With the right tools and definite solutions, you will be able to keep your Ubuntu servers in the pink of health.

What You Will Learn

• Deploy packages and their dependencies with repositories
• Set up your own DNS and network for Ubuntu Server
• Authenticate and validate users and their access to various systems and services
• Maintain, monitor, and optimize your server resources and avoid tremendous load
• Get to know about processes, assigning and changing priorities, and running processes in background
• Optimize your shell with tools and provide users with an improved shell experience
• Set up separate environments for various services and run them safely in isolation
• Understand, build, and deploy OpenStack on your Ubuntu Server

In Detail

Ubuntu is becoming one of the favorite Linux flavors for many enterprises and is being adopted to a large extent. It supports a wide variety of common network systems and the use of standard Internet services including file serving, e-mail, Web, DNS, and database management. A large scale use and implementation of Ubuntu on servers has given rise to a vast army of Linux administrators who battle it out day in and day out to make sure the systems are in the right frame of operation and pre-empt any untoward incidents that may result in catastrophes for the businesses using it. Despite all these efforts, glitches and bugs occur that affect Ubuntu server's network, memory, application, and hardware and also generate cloud computing related issues using OpenStack.

This book will help you end to end. Right from setting up your new Ubuntu Server to learning the best practices to host OpenStack without any hassles. You will be able to control the priority of jobs, restrict or allow access users to certain services, deploy packages, tackle issues related to server effectively, and reduce downtime.

Also, you will learn to set up OpenStack, and manage and monitor its services while tuning the machine with best practices. You will also get to know about Virtualization to make services serve users better. Chapter by chapter, you will learn to add new features and functionalities and make your Ubuntu server a full-fledged, production-ready system.

Style and approach

This book contains topic-by-topic discussion in an easy-to-understand language with loads of examples to help you take care of Ubuntu Server. Plenty of screenshots will guide you through a step-by-step approach.

Troubleshooting Ubuntu Server

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Table of Contents

Troubleshooting Ubuntu Server

Credits

About the Author

About the Reviewer

www.PacktPub.com

Support files, eBooks, discount offers, and more

Why subscribe?

Free access for Packt account holders

Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Reader feedback

Customer support

Errata

Piracy

Questions

1. Package Management

Getting started with packages

Package

Repository

The .deb packages

Dependency

Open source

Using dpkg for package management

Understanding the apt-get package management tool

Updating the repository list with the apt-get update command

Installing a package with the apt-get install command

Upgrading a package with the apt-get upgrade command

Cleaning with the apt-get clean command

Purging a package with the apt-get purge command

Fixing unsuccessful installations with the apt-get –f command

Checking for broken dependencies with the apt-get check command

The apt-cache tool

Searching for a package with the apt-cache search command

Package management with aptitude

Configuration and extra repositories

Resolving the "failed to get" error

Downloading software from an outside repository

Automatic updates

Security updates

Kernel updates

Application updates

The unattended-upgrades package

Creating a repository mirror

Setting up a mirror machine

Configuring the /etc/apt/mirror.list file

Using the local mirror

Summary

2. Networking and DNS

Networking concepts

IP addressing

DHCP client for dynamic addresses

Assigning a static IP address

DHCP

Installation

Configuration

Network sniffing with tcpdump

Capturing packets from eth0

Saving the tcpdump results in a file

Reading packets saved in a file by tcpdump

Readable timestamps in packets

Reading packets of a specific protocol

Reading packets on a specific port

Reading TCP packets between two hosts

Binding and bonding

Binding

Bonding

DNS

Setting up DNS

Setting up primary and secondary DNS servers

The hints file – zone "."

The local host file – zone "0.0.127.in-addr.arpa"

The reverse zone file – zone "24.126.10.in-addr.arpa"

The primary zone file – zone "ubuntuserver.org"

The primary zone file

The reverse zone file

PTR records

Summary

3. Network Authentication

OpenLDAP

Installation

Populating the database

Logging

Access control

Kerberos

Installation

Database setup

Setting up the Kerberos client

Kerberos SSH and logon

Integrating LDAP with Kerberos

Installation

Database setup

OpenSSH, public, and private keys – passwordless SSH

The SSH client and the server

Setting up passwordless SSH

Disabling password authentication

Allowing or denying users to SSH

Greeting users with a banner

Summary

4. Monitoring and Optimization

Nagios

The Nagios setup

Adding another host in Nagios

Nagios templates

Nagios hostgroups and services

Nagios setup alerts

Writing a Nagios plugin

The NRPE plugin

Enabling external commands

Puppet

Installing Puppet

Setting up the client

Setting up the manifest

ClusterSSH

Summary

5. Process Management

The basics of process management

$$ and $PPID

pidof

Parent and child

fork() and exec()

exec

ps

pstree

ps fx

ps -C and pgrep

top

Signaling processes

kill

Listing all signals

kill -1 or SIGHUP

kill -15 or SIGTERM

kill -9 or SIGKILL

SIGSTOP and SIGCONT

pkill

killall

Process priorities

renice

nice

Background processes

jobs

& (ampersand)

jobs -p

Suspended state with Ctrl + Z

bg

fg

Summary

6. Shell Management, Tools, and User Management

The Secure Shell server

Installing the SSH server

Configuration

Default settings for the SSH server

The SSH configuration file

Using passphrases

Scheduling jobs with cron

Scheduling user cron jobs

Configuring jobs using at

Job schedule security

Optimizing the shell

Bash profiles

The /etc/bash.bashrc file

The /etc/profile file

Variables in bash

User management and file permissions

User management in Ubuntu

Adding and removing users

Managing file permissions

Understanding file permissions

Changing permissions with chmod

Modifying ownership using chown and chgrp

Setting default permissions with umask

Speci...