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Three tools to help you configure iptables

Post date: May 25, 2005, 14:05 Category: Network Views: 3557 Comments
Tutorial quote: Every user whose client connects to the Internet should configure his firewall immediately after installation. Some Linux distributions include firewall configuration as a part of installation, often offering a set of defaults configurations to choose from. However, to ensure that your machine presents the minimum "attack surface" (a measure of the number of vulnerable ports, user accounts, and sockets exposed to attack) to the predatory inhabitants of the Internet, you may need to do some manual configuration of your firewall. Here are three tools that can help.
The Linux kernel (version 2.4 onwards) contains a framework for packet filtering and firewalling using netfilter and iptables. Netfilter is a set of hooks inside the Linux kernel that allows kernel modules to register callback functions with the network stack. Iptables is a generic table structure for the definition of rulesets. Each rule within an IP table consists of a number of classifiers (iptables matches) and one connected action (iptables target). Iptables has extensive documentation that can be accessed online or by typing man iptables at the command line. Yet despite the depth of the documentation available for iptables, its complexity can be baffling.

Setting up yum on SUSE LINUX 10.0

Post date: October 16, 2005, 16:10 Category: System Views: 6031 Comments
Tutorial quote: Why should I use yum and not yast? Well, yast is nice, but has some disadvantages: It can#t check for gpg keys, you have to trust the mirrors you add. And, speaking about mirrors, yast has no real mirror management for one source. Especially in these times the most and best known SUSE mirrors are very slow or just closed down, so you have to add other sources in yast. But yast needs your clicks when a mirror is not reachable, and if you enter several sources just as mirrors, it checks every single source - that takes quite a long time!
A last reason (which is not important know because SUSE LINUX has a ugly workaround) is that yast is not able to handle packages for different architectures - it can only install packages for one architecture.

Installing Adobe AIR 1.1 For Linux Beta On Ubuntu 8.04

Post date: October 5, 2008, 16:10 Category: Desktop Views: 3369 Comments
Tutorial quote: Adobe AIR is a technology that lets you run Internet applications on the desktop. With AIR you do not need a browser to run such desktop applications. This tutorial explains how you can install Adobe AIR 1.1 for Linux beta on an Ubuntu 8.04 desktop and how you can install AIR applications.

Cleaning up a Debian GNU/Linux system

Post date: November 25, 2006, 08:11 Category: System Views: 3951 Comments
Tutorial quote: You arrive at a Debian GNU/Linux server which has some history of neglection. Let's suppose someone else neglected it but if your new-year resolution is to stop neglecting your beloved server, this applies as well.

One form of neglection is to install, install, install and never un-install any package. The common utility to perform installation and un-installation of packages is apt-get which adds to the problem because it doesn't have automatic removal of non-needed dependences.

That means that when phpMyAdmin was installed it also installed Apache, PHP and ton of other packages. phpMyAdmin was removed when it was no longer needed but Apache, PHP and the ton of packages remain there.

Aptitude to the rescue.

NFS over CIPE-VPN tunnels

Post date: May 23, 2005, 16:05 Category: Network Views: 3368 Comments
Tutorial quote: The Network File System (NFS) is a standard protocol for sharing file services with Linux and Unix computers. It is a distributed file system that enables local access to remote disks and file systems and is based on the client\server architecture. Although easy to configure, it is typically used only to transfer data over an intranet or LAN because of its transparency and security potholes when exposed to the risks of the Internet. However, it still can be employed -- without compromising security -- to share files over the Internet by configuring it to run on a Virtual Private Network (VPN) connection. This article will show you how to set up NFS to run over a CIPE-VPN connection between two Linux systems.

Backing Up and Restoring Using the cpio Command in Linux and Unix

Post date: May 26, 2006, 18:05 Category: System Views: 3263 Comments
Tutorial quote: The cpio command is one of the most commonly used Linux back up tools.

The cpio command has two unusual features

Unlike tar , in which the files to back up are typed in as part of the command, cpio reads the files to work with from the standard input (in other words, the screen).

This feature means that cpio must be used as part of a multiple command or with a redirection pipe. Examples of this usage are shown in the tables below.

cpio must always be used with one of three flags. Flags are options that set the mode in which the command runs. Only one flag can be used at a time, and it must come before any other options. In addition, the choice of flags limits the options that can be used. Each flag also has a gnu option that can used in its place. The gnu option gives a convenient name for each flag: extract, create, and pass- through.

Boot Debian from an external firewire drive on PowerPc Mac

Post date: December 14, 2005, 19:12 Category: Installing Views: 2983 Comments
Tutorial quote: Messing with a boot process is a delicate matter even on a Mac. Note that the Debian installer will fail at some point during the procedure.
I offer no warranty and assume no responsibility for whatever loss or damage might be caused to your hardware, software or data.
There are other ways to boot Linux from an external firewire drive documented elsewhere on the net. See the Resources section.

Adding or removing peripherals like usb keys, digital cameras, other external HDs, cdroms etc, or installing/removing devfs, udev, and similar stuff might alter the way Linux sees the firewire drive, i suggest becoming familiar with supplying boot options to yaboot during the boot process. See Man pages of yaboot and yaboot.conf.

Execute Commands on Multiple Linux or UNIX Servers part II

Post date: December 28, 2005, 10:12 Category: System Views: 3882 Comments
Tutorial quote: I have already covered how to execute commands on multiple Linux or UNIX servers via shell script. The disadvantage of script is commands do not run in parallel on all servers. However, several tools exist to automate this procedure in parallel. With the help of tool called tentakel, you run distributed command execution. It is a program for executing the same command on many hosts in parallel using ssh (it supports other methods too). Main advantage is you can create several sets of servers according requirements. For example webserver group, mail server group, home servers group etc. The command is executed in parallel on all servers in this group (time saving). By default, every result is printed to stdout (screen). The output format can be defined for each group.

Arcane Linux Commands: dc

Post date: September 26, 2007, 09:09 Category: Software Views: 3924 Comments
Tutorial quote: A beginner-friendly guide to dc, the Unix command-line calculator. Answers many questions that the man page doesn't.

Creating DjVu Documents Linux HOWTO

Post date: July 16, 2006, 16:07 Category: Miscellaneous Views: 4443 Comments
Tutorial quote: This document explains some of the uses of djvulibre implementation of DjVu for creating quality DjVu documents in linux. DjVu format features bitmap document compression and hypertext structure. It is used by numerous web sites all around the world for storing and distributing digital documents including scanned documents and high-resolution pictures. One of the advantages of DjVu files is that they are notably small, often smaller than PDF or JPEG files with the same content. This makes DjVu a helpful tool for digitizing books and journals, especially scientific ones.

Below it is considered the case when a DjVu document is created from a number of separate JPEG files each containing a single page. Here JPEG format is not a limitation, and the examples can cover arbitrary image formats. Conversion from PDF to DjVu is also discussed. Usage of scanner software is not explained: refer to the relevant documentation.
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