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FreeBSD

Installing FreeBSD on IBM Netvista S40

Post date: May 8, 2005, 21:05 Category: Installing Views: 4441 Comments
Tutorial quote: In this note we shall talk about installing FreeBSD on a very interesting and elegant machine: IBM Netvista S40. In its creator own terminology, it is "legacy-free". The computer has no parallel, serial, AT keyboard, nor PS/2 mouse ports. No floppy controller either. Instead, it has 5 USB ports (2 frontal and 3 rear) connected to a single USB controller. Besides these USB ports, the system only counts with standard video and audio connectors. The video controller is Intel 82810E SVGA and audio chip is Intel ICH 82801AA, both integrated onboard. The CPU is Intel PIII at 866MHz. The machine is further equipped with a fast Intel Pro PCI network adapter containing a PXE/RIPL boot prom. A quiet 20G Quantum Fireball HDD and a Liteon ATAPI CD-ROM, both connected as masters, constitute the storage subsystem. The case is Flex ATX, a small form factor.
Linux

Removing A User

Post date: April 8, 2006, 00:04 Category: System Views: 4935 Comments
Tutorial quote: Employee turnover in most organizations runs high. So unless you run a small shop with a stable user base, you need to learn how to clean up after an employee leaves. Too many so-called system administrators do not understand the stakes involved when they manage users. Disgruntled former employees can often cause significant trouble for a company by gaining access to the network.

To remove a user, you need to learn to manage all of his or her files, mailboxes, mail aliases, print jobs, recurring –(automatic) personal processes such as the backing up of data or remote syncing of directories, and other references to the user. It is a good idea at first to disable the account in /etc/passwd, after which you can search for the user's files and other references. Once all traces of the user have been cleaned up, you can remove the user completely—but if you remove the entry from /etc/passwd while these other references exist, you have a harder time referring to them .

When you remove a user, it's a good idea to follow a pre-determined course of action so you don't forget any important steps; it may even be a good idea to make a checklist so that you have a routine. Following, you will find several items requiring attention.
Unix+clones

Easy Automated Snapshot-Style Backups with Linux and Rsync

Post date: February 1, 2006, 00:02 Category: Software Views: 4085 Comments
Tutorial quote: This document describes a method for generating automatic rotating "snapshot"-style backups on a Unix-based system, with specific examples drawn from the author's GNU/Linux experience. Snapshot backups are a feature of some high-end industrial file servers; they create the illusion of multiple, full backups per day without the space or processing overhead. All of the snapshots are read-only, and are accessible directly by users as special system directories. It is often possible to store several hours, days, and even weeks' worth of snapshots with slightly more than 2x storage. This method, while not as space-efficient as some of the proprietary technologies (which, using special copy-on-write filesystems, can operate on slightly more than 1x storage), makes use of only standard file utilities and the common rsync program, which is installed by default on most Linux distributions. Properly configured, the method can also protect against hard disk failure, root compromises, or even back up a network of heterogeneous desktops automatically.
Linux

Three tools to help you configure iptables

Post date: May 25, 2005, 14:05 Category: Network Views: 3894 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.
Linux

Linux Web Filtering in 7 steps

Post date: April 12, 2005, 18:04 Category: Network Views: 4906 Comments
Tutorial quote: How to install a transparent Squid proxy server with real-time HTTP virus scanning on Mandrake 10.0 using DansGuardian and ClamAV?

People quickly and easily access volumes of research on the Internet and correspond with a mouse click. For more and more companies, content filtering is part of the large battle to combat all kinds of online threats, including hackers, worms and viruses. Linux content filtering allows administrators to configure and manage Internet access across the entire network and to block unwanted Web content like pornography, shopping Web sites, games and gambling.

This guide contains all the necessary information for installing and understanding the architectural layout of the implementation. It was written with the assumption that you understand how to install programs and have a basic understanding of Linux Mandrake. This includes installing Linux Mandrake and RPM packages, editing files, making directories, compiling software and understanding general UNIX commands. This guide doesn’t explain how to use or configure Squid, DansGuardian and ClamAV but information on where to obtain this information can be found in the “Additional information” section.
Gentoo

Tunneling the hard way: using slirp, pppd and socat

Post date: January 29, 2006, 13:01 Category: Network Views: 13386 Comments
Tutorial quote: Every now and then you might come across a "bad" ISP. The one I have at home for example is dropping UDP packets ever so often when I try to play online games -- and it tends to drop random packets while I try to log onto a gameserver too which makes a certain game I like to play crash during the loading phase so it can't recover. I also heard of other ISPs blocking certain ports on external servers -- universities for example seem to like blocking p2p network ports and the school i was attending till last august blocked everything but port 80 for http -- including ftp which made even on-topic "research" a pita at times.
Usually there's three ways of working around this problem if "giving up" is not an option to you: a) change your ISP, b) use ssh to redirect ports, c) connect to an external VPN to route for you. a) can be tricky -- it's impossible if you're sharing the link with your parents and they insist on their email addresses or in the university/workplace/school scenario. b) will only work with single port/host combinations and for c) you will need a full-fledged rootbox idling around on the internet -- which tend to be expensive and "virtual servers" might not work because those often don't include tun/tap devices and/or kernel-level ppp support if you rent them and in case you rented them you probably can't fiddle around with its kernel to enable it (that was my problem at least). If any of this rings a bell to you, read on and discover method d)
FreeBSD

Lightweight Web Serving with thttpd

Post date: December 1, 2005, 00:12 Category: Software Views: 8870 Comments
Tutorial quote: The Apache HTTP Server is the most popular web server due to its functionality, stability, and maturity. However, this does not make it suitable for all uses: slow machines and embedded systems may have serious problems running it because of its size. Here is where lightweight HTTP servers come into play, as their low-memory footprints deliver decent results without having to swap data back to disk.

Similarly, these small HTTP servers are suitable to serve static content efficiently so as to allow Apache, mod_perl, mod_python, or even servlet containers to handle dynamic requests without tying up memory-hungry children to serve small images. In other words, these applications can serve as a complement to your existing full-featured web server, not as a replacement.

One of these servers is thttpd, a simple, small, portable, fast, and secure HTTP server. Among its features are support for the HTTP/1.1 standard, CGIs, virtual hosts, and IPv6. This article shows how to install and configure this software under NetBSD. I chose NetBSD not only because it is my preferred OS, but also because it has the ability to run on the most disparate old hardware, where thttpd shows its strengths. I had a Macintosh Performa 630 (a 68LC040 chip at 33MHz) running NetBSD/mac68k 2.0 with thttpd on top of it, serving pages to my home network nicely.
Web-based applications and online marketing solutions - LumoLink