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)

The sshd_config file

We will have a look at the directives that can be the most useful for our everyday service usage, but if we need to know all the details about all the configuration options, we can just invoke man:

man sshd_config

The main SSH daemon configuration file is located at the /etc/ssh/sshd_config event, though we can specify any file at the daemon startup using the -f option on the command line. That said, let's go through and have a look at the most interesting configuration bits:

  • AcceptEnv: This allows the client to copy the environment variable into the session environment sent by the client. It can be useful, but it can also be dangerous, and the default is not to accept any client environment variable.
  • AllowGroups: By default, the log in is only allowed for members from all groups available on the system, but with this directive, you can restrict it to...