Building a Wireless Network with Linux
Wireless networking has been around for a while, but until recently, it was out of reach for Linux users with modest means. Fortunately, a number of manufacturers are beginning to see new venues in marketing inexpensive wireless hardware. One manufacturer, Webgear, Inc., recently introduced a Linux-compatible wireless networking kit.
In this article, I will show how to create an inexpensive wireless network and a wireless networking bridge using Webgear's Aviator 2.4 wireless networking kit, IP masquerading, software routing, a surplus laptop and Linux.
Webgear's Aviator 2.4 wireless kit consists of two Type II PCMCIA cards and two ISA PCMCIA card slots. The kit uses 2.4GHz radio technology to offer 2MBps networking using IEEE 802.11 specifications (frequency-hopping, spread-spectrum networking). The cards appear as Ethernet devices, such as eth0 or eth1, when installed and configured. The original intent of the kit is to offer the ability to create a high-speed wireless link between two desktop PCs, two laptops, or a laptop and desktop PC.
Although the kit is advertised as supporting Linux, it comes with software drivers for only Microsoft operating systems. You'll have to download the Linux device driver, a loadable kernel module named ray_cs.o, from the Web. Even though you can get a stable version through Webgear's support link at www.webgear.com/support/software_top.html, the best place to download the latest version is from the author's web site (see Resources).
Thanks to the generosity of the author, Corey Thomas, you can use the Aviator 2.4 (or more expensive Aviator Pro or Raytheon Raylink series) wireless system with Linux. I downloaded the latest driver, ray_cs version 1.68, onto one of my laptops, then followed his directions on building and installing the driver:
cp ray_cs-1.68.tgz /usr/src/linux/pcmcia-cs-3.1.5 tar xvzf ray_cs-1.68.tgz make config make all make install
These steps should then be repeated on another computer. I initially used two laptops to test the connectivity of the cards. This is essential to ensure the cards and software are working correctly. I had great success with a later version of David Hinds' Card Services, pcmcia-cs 3.1.5, along with the next version, pcmcia-cs 3.1.6.
As sold, the kit allows for connection between two wireless points: point A-->point B.
Before enabling the cards, you must first edit /etc/pcmcia/config.opts and insert the line
Upon starting, Card Services will then read in the ray_cs.opts configuration file for the wireless cards (ray_cs.opts is copied into the /etc/pcmcia directory as part of make install). This file contains several important settings, in the form of setup strings, used to configure the Aviator 2.4 card after insertion. The settings line (there are several, as the driver supports at least three different wireless cards) I used was:
module "ray_cs" opts "pc_debug=2 essid=LINUX\ hop_dwell=128 beacon_period=256 translate=1"Make sure to use the same settings for each end of the wireless connection. The pc_debug=2 option is a handy way to get more information from /var/log/messages upon insertion or removal of the card. The essid=LINUX option designates a network name of LINUX for the wireless cards (according to Webgear, 61 cards may be on the same network). After installing and configuring the software, I used Red Hat's netcfg tool to create an eth0 interface on each laptop. You can also create your own by editing the /etc/sysconfig/network-scripts/ifcfg-eth0 file:
DEVICE=eth0 IPADDR=192.168.2.37 NETMASK=255.255.255.0 NETWORK=192.168.2.0 BROADCAST=192.168.2.255 ONBOOT=yes BOOTPROTO=none USERCTL=noThe cards must be started sequentially. I went to the first laptop, ensured Card Services was running (you can do an /etc/rc.d/init.d/pcmcia start), then inserted one of the Aviator cards. Upon hearing two beeps, I looked at the output of /var/log/messages (not all the output is shown here):
$Id: ray_cs.c,v 1.68 1999/11/21 10:43:35 corey Exp $-Corey Thomas firstname.lastname@example.org ray_cs Detected: WebGear PC Card WLAN Adapter Version 4.88 Jan 1999 eth0: RayLink, irq 4, hw_addr 00:00:8F:48:E8:DB ray_cs interrupt network "LINUX" startedThe important thing to look for is the “started” string. I then enabled the interface using netcfg, as according to Thomas, you cannot use the ifconfig command to set the IP address using the ray_cs driver. I then went to the other laptop, inserted the other Aviator card, listened for the two beeps, and looked at /var/log/messages:
$Id: ray_cs.c,v 1.68 1999/11/21 10:43:35 corey Exp $-Corey Thomas email@example.com ray_cs Detected: WebGear PC Card WLAN Adapter Version 4.88 Jan 1999 eth0: RayLink, irq 10, hw_addr 00:00:8F:48:E8:45 ray_cs interrupt network "LINUX" joinedAgain, the important string to look for is “joined”. This means the cards are communicating. I then enabled the eth0 interface, and voil<\#224>--I could use ping, telnet, ftp and talk between the two laptops wirelessly. FTP file transfers were about 180K per second, and that speed is reasonable enough for remote X11 client launching. This shows that Linux can be used to support wireless networking in a variety of situations where cabled installations are impractical or unnecessary.
Practical Task Scheduling Deployment
July 20, 2016 12:00 pm CDT
One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
Cron traditionally has been considered another such a tool for job scheduling, but is it enough? This webinar considers that very question. The first part builds on a previous Geek Guide, Beyond Cron, and briefly describes how to know when it might be time to consider upgrading your job scheduling infrastructure. The second part presents an actual planning and implementation framework.
Join Linux Journal's Mike Diehl and Pat Cameron of Help Systems.
Free to Linux Journal readers.Register Now!
- SUSE LLC's SUSE Manager
- Managing Linux Using Puppet
- Tech Tip: Really Simple HTTP Server with Python
- Returning Values from Bash Functions
- Murat Yener and Onur Dundar's Expert Android Studio (Wrox)
- My +1 Sword of Productivity
- Non-Linux FOSS: Caffeine!
- Rogue Wave Software's Zend Server
- Doing for User Space What We Did for Kernel Space
- Parsing an RSS News Feed with a Bash Script
With all the industry talk about the benefits of Linux on Power and all the performance advantages offered by its open architecture, you may be considering a move in that direction. If you are thinking about analytics, big data and cloud computing, you would be right to evaluate Power. The idea of using commodity x86 hardware and replacing it every three years is an outdated cost model. It doesn’t consider the total cost of ownership, and it doesn’t consider the advantage of real processing power, high-availability and multithreading like a demon.
This ebook takes a look at some of the practical applications of the Linux on Power platform and ways you might bring all the performance power of this open architecture to bear for your organization. There are no smoke and mirrors here—just hard, cold, empirical evidence provided by independent sources. I also consider some innovative ways Linux on Power will be used in the future.Get the Guide