10 Must-Have Linux Tools

Having the right tools and utilities makes any job easier. Whether it's diagnosing a troublesome system, deploying a new device or managing a complicated environment, what's in a solution provider's Linux toolbox can make the difference for tasks that would otherwise be labor-intensive and mind-numbing.

In this TechBuilder Recipe, the Test Center uncovers 10 tools that every Linux solution provider or administrator should be familiar with. While some of these are readily available for download, many of the command-line utilities generally are bundled with the distribution.

1. -pie hits the spot: Linux administrators can spend the bulk of their time creating and modifying scripts and other files on the system. The scripts can be fairly straightforward with system configurations or complex with database parameters. The most annoying thing about working with these kinds of files is realizing that a particular string of text needs to be replaced with another in a large file. And that the string occurs 1,382 times in the file. Even worse, it appears in 49 different files.

Instead of struggling to edit each file manually, give this command a shot:
perl -p -i -e 's/regexp/REGEXP/g' filename

The command requires PERL to be installed on the system, but most distributions come with it installed by default. And if PERL isn't already installed, installing it is quicker than going through 49 different files. The -pie command is just one of the many examples of PERL's versatility.

The command takes the regexp that's enclosed within quotes to search (s) and replace for all (g) instances in the file. Instead of just one file, the command can take a wildcard such as *.html, or even a list of file names.

2. Wireless, wireless, everywhere: With new wireless networks sprouting up every few days, piggybacking on a network for quick access has never been easier. When solution providers are at a client site troubleshooting a system, finding and accessing an available network can make it easier to diagnose and resolve a job. The software tool of choice for discovering wireless networks is Kismet, available as a .tar.gz file from www.kismetwireless.net. Kismet also has a friendly GUI, Kismet-Qt, which provides all the information needed to sniff and connect to the wireless networks in the immediate vicinity.

Standard named networks, networks with hidden SSIDs and non-beaconing networks are all fair game for Kismet. Kismet locates available wireless networks by passively capturing packet data. This way, it can also discover and report the IP range used for a particular wireless network, identify the network's signal and noise levels and detect network intrusions. It can also capture management data packets for available networks and optimize signal strength for access points.

Kismet is an 802.11 Layer 2 wireless network detector that can sniff 802.11a/b/g traffic. It's important to note, however, that Kismet only works with wireless cards that support raw monitoring mode, such as the ones based on the PRISM 2, 2.5, 3 and GT chipsets. Some of the more popular supported wireless adapters include the ORiNOCO Gold, the original Apple Airport (not Extreme) card, and Intel Centrino.

3. Now where was it again? Perhaps a script is failing during the start up routine. Perhaps the logs are showing some odd sequence of characters. The perl -pie command helps globally search and replace, but what if you just want to find where that particular string is occurring?

The grep command comes to the rescue. It comes with a plethora of flags and options, but the most common usage is: grep string filename. The output would list every line in the file that contains that string. This is particularly handy if the logs indicate a script is referencing a non-existent file or directory. The grep command would show every line where that file or directory is called. The filename argument can also use wildcards or have a list of filenames.

Seeing just a single line can be confusing and uninformative. As such, the command has a context flag, -C, that allows the administrator to see a number of lines before and after the relevant line: grep -C # string filename.

NEXT: Going to the dump