Linux - SecurityThis forum is for all security related questions.
Questions, tips, system compromises, firewalls, etc. are all included here.
Welcome to LinuxQuestions.org, a friendly and active Linux Community.
You are currently viewing LQ as a guest. By joining our community you will have the ability to post topics, receive our newsletter, use the advanced search, subscribe to threads and access many other special features. Registration is quick, simple and absolutely free. Join our community today!
Note that registered members see fewer ads, and ContentLink is completely disabled once you log in.
If you have any problems with the registration process or your account login, please contact us. If you need to reset your password, click here.
Having a problem logging in? Please visit this page to clear all LQ-related cookies.
Introduction to Linux - A Hands on Guide
This guide was created as an overview of the Linux Operating System, geared toward new users as an exploration tour and getting started guide, with exercises at the end of each chapter.
For more advanced trainees it can be a desktop reference, and a collection of the base knowledge needed to proceed with system and network administration. This book contains many real life examples derived from the author's experience as a Linux system and network administrator, trainer and consultant. They hope these examples will help you to get a better understanding of the Linux system and that you feel encouraged to try out things on your own.
Click Here to receive this Complete Guide absolutely free.
[ I am assuming the following scenario -- you have ssh access to a box that you admin, and you want to change firewall rules. You don't want to accidentally filter yourself out. Been there. ]
Along the same lines of the previous recommendation on handling this, here are two more:
You can make the very first rule in your INPUT chain to allow access to port 22 from your source IP. That way, even as you append (and possibly break) later rules in the chain, your first rule should still always allow you access.
While making any changes, you can first back up your current firewall script file to iptables-rules.orig. Next make your changes to the iptables-rules script. Then, before running your updated iptables-rules script, submit an at job that will run in 10 minutes. That at job will simply run the iptables-rules.orig script. If you really bork things good, the at job will save you. If your updated rules are ok, then just cancel the at job.
Hope those ideas are helpful. (To give credit, they're not my own ideas; they are both based on firewall management strategies I read in "Mastering FreeBSD and OpenBSD Security", by Yanek Korff, Paco Hope, Bruce Potter. No, I don't work for O'Reilly.)