Book Image

Mastering Bash

By : Giorgio Zarrelli
Book Image

Mastering Bash

By: Giorgio Zarrelli

Overview of this book

System administration is an everyday effort that involves a lot of tedious tasks, and devious pits. Knowing your environment is the key to unleashing the most powerful solution that will make your life easy as an administrator, and show you the path to new heights. Bash is your Swiss army knife to set up your working or home environment as you want, when you want. This book will enable you to customize your system step by step, making your own real, virtual, home out of it. The journey will take you swiftly through the basis of the shell programming in Bash to more interesting and challenging tasks. You will be introduced to one of the most famous open source monitoring systems—Nagios, and write complex programs with it in any languages. You’ll see how to perform checks on your sites and applications. Moving on, you’ll discover how to write your own daemons so you can create your services and take advantage of inter-process communication to let your scripts talk to each other. So, despite these being everyday tasks, you’ll have a lot of fun on the way. By the end of the book, you will have gained advanced knowledge of Bash that will help you automate routine tasks and manage your systems.
Table of Contents (15 chapters)

Configuration files

Before playing with ssh and having a look at what it can do for us, let's take some time to see what are the most relevant files that are used to manage the ssh service and client. The configuration files for the SSHD daemon are usually stored in /etc/ssh where we can find some interesting files:

  • moduli: This file contains the prime numbers and generators used by sshd in the Diffie-Hellman group exchange key exchange method, which is needed to create the shared session master encryption key.
  • sshd_config: This is the configuration file for the ssh daemon. We will have a closer look at it later to see some interesting and useful directives, which alter the way we connect to a remote server.
  • ssh_config: This is the system-wide SSH client configuration file that is used when no user-specific configuration file is found in the user home directory ~/.ssh/config...