BSD Hacks

Chapter 5. Networking Hacks

Introduction

You probably spend most of your time accessing servers on the Internet or on your own network. In fact, networking has become so prevalent, it’s becoming increasingly difficult to tolerate even short periods of network outages.

This chapter contains many ideas for accessing networking services when the conventional avenues seem to be unavailable. Have you ever wanted to train your system to notify you of its new network configuration when its primary link becomes unavailable? Would you like to check your email from a system that doesn’t contain a preconfigured email client? How can you maintain network connectivity when your ISP’s DHCP server no longer recognizes your DHCP client?

You’ll also gain insight into how some of the networking services and tools we often take for granted work. Become a tcpdump guru—or at least lose the intimidation factor. Understand your DNS messages and how to troubleshoot your DNS servers. Tame your sendmail daemon.

Finally, meet two excellent open source utilities that allow you to perform routine tasks simultaneously on all of your servers.

See Console Messages Over a Remote Login

View a server’s console messages remotely

As a Unix system administrator, you can do 99% of your work remotely. In fact, it is very rare indeed that you’ll need to sit down in front of a server (assuming the server even has an attached keyboard! [Hack #26] ).

However, one of the key functionalities you lose in remote administration ...