Three simple antidotes to sys admin headaches

Penguin Computing's Phil Pokorny pops kernel panic, introduces getent, and gives the infinite command.

If you make your breakfast while your login is taking place, go blank during a kernel panic or repeat the same

command ad infinitum, you need to add these three helpers to your IT toolbox.

We gleaned these three IT tips from an interview with Phil Pokorny, Penguin Computing's director of engineering. You'll find more of Pokorny's tips, culled from his years of experience as a systems administrator, in Five easy ways to stop IT administration and deployment hassles and Linux migration tips for Windows admins.

Tip # 1: Pick up your camera when there's a kernel panic.

A kernel panic, the Linux equivalent of a Windows "blue screen of death," is a hair-raising event for any IT administrator. Sure, they are a relatively rare occurrence with Linux but they do happen.

Rather than try to write down what's happening on the screen, Pokorny advises IT managers to take a digital picture of the screen. Even better, use a camera phone and then send the photo to your tech support organization, he says. With that photo they can see exactly what was on the screen thus eliminating any confusion.

Tip #2: Get to know and use getent, a program that gathers entries from a targeted database using specific search keys.

A common data center problem is initial logins that take a long time, even though the system works and performs normally once the initial login is completed. This is almost always a DNS name resolution problem, where the reverse name look ups weren't working correctly or the DNS servers weren't configured correctly, according to Pokorny.

"Getent is a nifty command that is not widely known," says Pokorny. On Linux, getent allows one to make particular name resolution calls to probe the name resolution system to see what IP addresses work and don't work. This can give a sys admin a better feel for what part of DNS might be broken.

Tip # 3: Use the watch command on the Linux command line to repeatedly run a command.

"What is cool about watch is that you can give it a command, and it runs that command as often as you wish, showing you the output so you can watch it change," says Pokorny.

So, if you're waiting to see if a job is completed, you can use watch to get real-time updates. You don't have to type the command over and over again to see the information you need.

"You can turn a command that basically runs once and gives you some numbers into dynamic update program just by prefixing the command with the word, watch," says Pokorny. "That comes in handy in Linux for watching software configurations, network statistics or traffic.

This was first published in October 2005

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