Troubleshooting Made Easy In Linux

Expert Reference Series of White Papers
Troubleshooting Made
Easy In Linux
1-800-COURSES www.globalknowledge.comTroubleshooting Made Easy In Linux
David Egan, RHCX
IntroductionPart 1: Troubleshooting OverviewPart 2: Getting Started Part 3: Getting Services Started
Part 1: Troubleshooting OverviewEvery operating system portrays itself as powerful, able to leap tall buildings and applications in single strides, able to weather the storms of prolonged heavy usage, resilient to weathering, and so much more!
One of the necessary evils, albeit less often spoken of, in case we jinx something, is the topic of troubleshooting. What could possibly go wrong? Doesn't everyone believe in fair play, honorable intentions, and being openly honest and straightforward in all things virtual?
Where does one start when the operating system does not start, the application does not load or run correctly, the network hangs or a network service does not listen or perform?
A common practice is to reload the machine, either from the installation media and then patch it, or from some standardized image. Either way, the problem has only been gotten around, not solved.
What if you want to solve the problem itself? What if you need to solve the problem to move ahead?
Linux is noted for being rock solid, stable, and easy to manage but not as user friendly ... 'Where do I click?' is usually not the answer.
There is an ancient, and maybe black, dark, or mysterious 'art' form known as troubleshooting. The idea of troubleshooting problems when they occur, whether with the system bootup or setup, networking or network services, or applications in memory, is a daunting task for anyone. The clues are probably there somewhere, de-pending on experience. Finding the clues and working backwards from them is the intriguing part to the sleuth in anyone interested!
Copyright ©2009 Global Knowledge Training LLC. All rights reserved. 2Starting PointTroubleshooting starts with knowing what is normal for your system. You will just have to get dirty here. Open the hood and see what all the little moving gadgets actually do, how they work together-or not. What makes this baby tick?
Not every system will be identical, but most likely, your servers use one or two common operating systems, Li-nux being one of them. You need to know something, in case there are problems, about the startup, the network software running in memory (or not), the general management services creating logs and other output while keeping the clutter to a minimum, application management and how to 'watch' programs while they are running.
Trend of CompressionThe trend is to do more with less ... run more programs with less equipment. Large box computers dedicated as a server were replaced by 'blade' servers. These blade servers reduced the size of the server box and allowed for more hosts in less space.
Additional applications were added to machines with low usage services. More applications mean more poten-tial issues. Alternatively, many times, due to application collisions, separate servers were created to do just one service.
What if you could run more applications on one more powerful host? What do you do when something goes wrong? You cannot always back out and rebuild or re-image; you have to find the problem and fix it as soon as possible.
RHEL Troubleshooting Options Are VastWhat does Red Hat Enterprise Linux, RHEL, provide for troubleshooting?
There are many ways to troubleshoot in Linux depending on where the problem appears to be coming from: from the bootup to the services, application, and kernel.
This white paper will explore the various options that make Linux a 'fun' place to be when it comes to trouble-shooting. The 'fun' is a relevant term. Having to work over the weekend or die trying is never really fun, but the cool array of tools and options for troubleshooting make it more 'fun' than some of the competition.
Just think, you probably will not have to reboot ... unless it is a bootup problem.
Usually No Reboot NecessaryIn Linux, other than a few kernel issues, you are not forced to reboot to re-initiate. You do not have to reboot to replace old software with new, unless if it is specifically a kernel. You can access the source code if necessary. You can use a debugger or system tracing utility. You can dump memory in the... [download for more]