Man pages are written by sys-admin and developers for IT techs, and are intended more as a reference than as a how to. Man pages are very useful for people who are already familiar with Linux, Unix, and BSD operating systems. Use man pages when you just need to know the syntax for particular commands or configuration file, but they are not helpful for new Linux users. Man pages are not good for learning something new for the first time. Here are thirty best documentation sites on the web for learning Linux and Unix like operating systems.
OpenBSD has a reputation for high security and difficult operating systems for new user. But, some orginsations are using OpenBSD for everything including firewall, servers and desktop computers. This is quite impressive, from the article:
So our paid job is hacking on and deploying, maintaining, supporting… OpenBSD installations. We are also required to hack on things that can be merged back into OpenBSD itself and when it’s not possible, then we change what we did so that it can be. Of course some developments are very specific to what we do and have no place in the project’s CVS tree.
So, amongst other services, we set up and maintain several 100% OpenBSD-based infrastructures (going from the entry site firewall to the secretary’s workstation) and this is what I’m going to talk about here.
As a side note, it is important to know that we are working exclusively for Fortune 500 companies (each operating in totally different and unrelated sectors).
Read more: A Puffy in the corporate aquarium.
OpenBSD 4.6 has been released and available for download from the official website. OpenBSD is well known for record of more than ten years with only two remote holes in the default install. The OpenBSD is widely known for the quality open source code and documentation, uncompromising position on software licensing, and focus on security and code correctness.
This article continues mini-series started with the post Introduction to Firewall Builder 4.0. This article is also available as a section in the “Firewall Builder Cookbook” chapter of Firewall Builder Users Guide 4.0.
Firewall Builder 4.0 is currently in beta testing phase. If you find it interesting after reading this post, please download and try it out. Source code archives, binary deb and rpm packages for popular Linux distributions and commercially distributed Windows and Mac OS X packages are available for download here.
In this post I demonstrate how Firewall Builder can be used to generate firewall configuration for a clustered web server with multiple virtual IP addresses. The firewall is running on each web server in the cluster. This example assumes the cluster is built with heartbeat using “old” style configuration files, but which high availability software is used to build the cluster is not really essential. I start with the setup that consists of two identical servers running Linux but in the end of the article I am going to demonstrate how this configuration can be converted to OpenBSD with CARP.
This entry is part 1 of 4 in the series Linux Firewall Cluster Configuration with Firewall Builder v4.:
- Firewall Builder: Generate The Web Server Firewall Cluster Running Linux or OpenBSD
- HowTo: Creating Firewall and Cluster Objects In Firewall Builder
- Linux Building Rules For The Cluster With Firewall Builder
- Firewall Builder: Convert Linux Iptables Configuration to OpenBSD and PF
Lets see how much effort it is going to take to convert this configuration to entirely different firewall platform – PF on OpenBSD. There are different ways to do this. I could make a copy of each member firewall (linux-test-1 and linux-test-2), set platform and host OS in the copy to PF and OpenBSD and then create new cluster object. This would be a sensible way because it preserves old objects which helps to roll back in case something does not work out. However, to make the explanation shorter, I am going to make the changes in place by modifying existing objects.
Now that all objects are ready and heartbeat is configured on the machines, we can move on and build some firewall rules. Since this is a cluster configuration, all rules go into the rule set objects that belong to the cluster rather than its member firewalls.
Linux and other Unix-like operating systems use the term “swap” to describe both the act of moving memory pages between RAM and disk, and the region of a disk the pages are stored on. It is common to use a whole partition of a hard disk for swapping. However, with the 2.6 Linux kernel, swap files are just as fast as swap partitions. Now, many admins (both Windows and Linux/UNIX) follow an old rule of thumb that your swap partition should be twice the size of your main system RAM. Let us say I’ve 32GB RAM, should I set swap space to 64 GB? Is 64 GB of swap space really required? How big should your Linux / UNIX swap space be?
I’ve already written about tentakel tool and shell script hack to run a single command on multiple Linux / UNIX / BSD server. This is useful to save time and run UNIX commands on multiple machines. Linux.com has published an article about a new tool called pssh:
If you want to increase your productivity with SSH, you can try a tool that lets you run commands on more than one remote machine at the same time. Parallel ssh, Cluster SSH, and ClusterIt let you specify commands in a single terminal window and send them to a collection of remote machines where they can be executed.
OpenBSD 4.4 has been released and available for download (jump to download link ) from official project website. OpenBSD is often the first to add new security tools to make it harder to break, developers have also carefully read through the programming code to check for mistakes more than once.