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Secure your Server with iptables

Post date: April 20, 2005, 11:04 Category: Security Views: 3649 Comments
Tutorial quote: Central to securing a Linux server that's connected to the Internet is having a good firewall and specific policies in place. Numerous options exist for those considering firewalls for Linux, however, a free and included solution is onoffer through Netfilter and iptables.
Linux

Building a Linux Cluster, Part 1

Post date: April 18, 2005, 03:04 Category: Network Views: 2929 Comments
Tutorial quote: Linux clusters have escaped. As the general popularity of the Linux operating system increases, more complex solutions built with it are becoming increasingly common in the "traditional" (more conservative) IT world. Linux computer clusters, whose provenance was originally universities and research institutions such as the U.S. National Laboratories, are showing up in increasing numbers as high-performance computing solutions within such areas as oil and gas exploration, computer-aided engineering, visualization, and software development. Linux clusters providing highly-available web, mail, and other infrastructure services are also increasingly common. If past computing history is any indicator of future trends, widespread use of Linux clusters in the mainstream IT world cannot be far behind.
Linux

Building a Linux Cluster, Part 2

Post date: April 18, 2005, 03:04 Category: Network Views: 3344 Comments
Tutorial quote: In this installment, we consider the what of cluster building: the hardware and software components that make up a Linux cluster, and some ways to think about integrating them into a solution for your environment.
Linux

Traffic shaping and bandwidth management

Post date: April 17, 2005, 10:04 Category: Network Views: 4877 Comments
Tutorial quote: This article is from the perspective of a small network, possibly a couple of people sharing one connection. It will explain traffic shaping and bandwidth management in general and with linx. It (sort of) walks through building a traffic shaping router.
Linux

Automating the Login Script

Post date: April 17, 2005, 10:04 Category: Miscellaneous Views: 3078 Comments
Tutorial quote: In a perfect world, you could spend a few weeks creating a system and the result would be a system that never required manual maintenance or modifications. Whether this ideal will ever be achieved is debatable, but it definitely won't happen in the near future. In the meantime, we still have to do things manually, even if only once in a while. When I must do things manually, I'm not usually happy about it. In fact, it usually means that there has been an emergency, so other people aren't happy about it either. In times like this, it is nice to have a consistent and efficient user interface on every machine. The information and examples presented in this article assume that you are using the bash shell. However, you can modify all of the scripts so that they work in other shells. In some cases, they might even work unmodified (like in the standard Bourne Shell [sh]). Other shells will also work, but they might have different methods for changing the prompt and creating command aliases. The principles in this article should be relatively easy to adapt to the shell of your choice.
Linux

Port Knocking

Post date: April 16, 2005, 10:04 Category: Network Views: 3526 Comments
Tutorial quote: Firewall administrators are challenged to balance flexibility and security when designing a comprehensive rule set. A firewall should provide protection against malfeasants, while allowing trusted users to connect. Unfortunately, it is not always possible to filter out the bad guys, because filtering on the basis of IP addresses and ports does not distinguish connecting users. Bad guys can and do come from trusted IP addresses. Open ports remain a necessary vulnerability: they allow connections to applications but also may turn into open doors for attack. This article presents a new security system, termed port knocking, in which trusted users manipulate firewall rules by transmitting information across closed ports.
Linux

USB Flash Memory HOWTO

Post date: April 16, 2005, 00:04 Category: Hardware Views: 3745 Comments
Tutorial quote: The purpose of this document is to describe procedures for implementing USB flash memory devices (memory sticks) on Linux.
Linux

Monitoring and Managing Linux Software RAID

Post date: April 15, 2005, 23:04 Category: System Views: 3349 Comments
Tutorial quote: Systems administrators managing a data center face numerous challenges to achieve required availability and uptime. Two of the main challenges are shrinking budgets (for hardware, software, and staffing) and short deadlines in which to deliver solutions. The Linux community has developed kernel support for software RAID (Redundant Array of Inexpensive Disks) to help meet those challenges. Software RAID, properly implemented, can eliminate system downtime caused by disk drive errors. The source code to the Linux kernel, the RAID modules, and the raidtools package are available at minimal cost under the GNU Public License. The interface is well documented and comprehensible to a moderately experienced Linux systems administrator.

In this article, I'll provide an overview of the software RAID implementation in the Linux 2.4.X kernel. I will describe the creation and activation of software RAID devices as well as the management of active RAID devices. Finally, I will discuss some procedures for recovering from a failed disk unit.
Linux

Linux 2.6: Compiling and Installing

Post date: April 15, 2005, 22:04 Category: System Views: 3401 Comments
Tutorial quote: We'll look at the process of compiling and installing a new kernel safely, without overwriting the existing kernel.

You can install as many kernels as you like on a Linux system, and select the one you want to run at boot time. This makes it easy to test different kernels, and different kernel configurations, with particular sets of hardware or applications. The wise network admin always tests new kernels before running them on production machines.
Linux

Building an LDAP Server on Linux, Part 2

Post date: April 15, 2005, 17:04 Category: Network Views: 4147 Comments
Tutorial quote: Welcome back! In Part 1 we learned basic concepts of LDAP and the uses for an LDAP server. Today we'll install and configure an OpenLDAP directory.

A quick note before we get started: this is LDAP 101. We are not installing any kind of encryption or strong authentication; we'll get to that in part 3. In my experience, learning LDAP in small chunks works best. (Then again, perhaps I'm just a bit dim.) So sit back, strap in, and keep your fingers away from the training wheels.

"The wise sysadmin will consult the documentation for their distro; it's quite possible that OpenLDAP will be packaged and ready to go in a pleasing manner (or ready to go in an odd manner--you never know). I'm all for easy--if your particular distribution provides an easy way, use it. RPMs can also be obtained from rpmfind.net, which thoughtfully lists all the required additional packages.

"Debian of course goes its own merry way. apt-get does the job just fine; the tricky bit is finding out the package names. Debian users want ldap-utils; slapd, which is OpenLDAP; and libdb4.1, to get the Sleepycat DB. These three components are enough to get you up and running. apt-get will walk you through a minimal configuration and will automatically start up slapd, the LDAP server daemon.
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