Red Hat Certified Engineer Tutorials
Troubleshooting and System Maintenance / Diagnose and Correct Boot Failures
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Subtitles of the Movie (Red Hat Certified Engineer / Troubleshooting and System Maintenance / Diagnose and Correct Boot Failures)
One of the requirements in the RHCE Troubleshooting section as listed in the Exam Prep Guide is to diagnose and correct boot failures arising from bootloader, module, and filesystem errors. Bootloader errors relate to the bootloader, and there is one standard bootloader for Red Hat Enterprise Linux 5, that's GRUB. As described in other videos, errors in the grub dot conf configuration file or even a missing file can cause a boot failure. The best way to learn about what can happen is to introduce your own failures and see what happens. Do this often enough and you'll start recognizing error messages and you'll know the solution. There is an easy way to introduce syntax errors into the GRUB configuration file. When booting, open the GRUB menu. Type e to edit a specific stanza. Pick a command line. Introduce a spelling error, press b to boot. What happens? The advantage of this option is that it doesn't actually edit your GRUB configuration file, so you can edit things again and again and try different sorts of errors. Next, there are module errors. They are actually pretty rare because of the quality of hardware detection. It's now excellent on Linux, however, deliberate errors are certainly possible. For example, on this system, what would happen if the network module, in this case, pcnet32, were no longer loaded? For this purpose I run this modprobe dash r, short for remove, pcnet32 command. That removes the network driver. Could you still access the network? Nope. The network card isn't even up. And if you didn't know that pcnet32 were the driver try the lspci command and look at that. It identifies the Ethernet controller as well as the name of the driver. I could insert it with the insmod command, but that wouldn't necessarily take care of any dependent drivers, so I use the modprobe command, and look at that. The pcnet32 driver is now back in and I've got access to my network, and that's because the network card is back up. Finally, there are possible file system errors. When they exist they're not silent, in fact, your system probably won't boot, at least the configured partition won't be mounted when you boot Linux. The most straightforward way to solve a file system error, say on the first sda partition is with the fsck command. I often use the dash y switch to automatically answer yes to any errors, that's the first sda partition on the first sda drive. Wait a second. I've got to unmount that partition first. And there, I've done it. I've fixed any errors that might exist on that partition and I've remounted that partition. The fsck command may not be the best long-term option, and file system errors may be an early sign of hard disk hardware failure, but fortunately, the RHCE Exam is not a hardware exam, so don't worry about it. Well, those are the basics when looking at bootloader, module, and filesystem errors. You've got to do more to prepare for the exam. Practice creating different errors in the bootloader. When you start recognizing problems associated with certain errors, you're getting closer to being ready for your RHCE Exam.
Tutorial Information
| Course: | Red Hat Certified Engineer |
| Author: | Michael Jang |
| SKU: | 33845 |
| ISBN: | 1-934743-47-X |
| Release Date: | 2008-01-18 |
| Duration: | 6.5 hrs / 94 lessons |
| Captions: | No |
| Compatibility: |
Vista/XP/2000, OS X, Linux QuickTime 7, Flash 8 |
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