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Red Hat Certified Engineer Tutorials
Troubleshooting and System Maintenance / Use the Rescue Environment
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Subtitles of the Movie (Red Hat Certified Engineer / Troubleshooting and System Maintenance / Use the Rescue Environment)
There are times when you might have some difficulty booting into Red Hat Enterprise Linux 5, including during the RHCE Exam. For that reason, and to help you install Red Hat Enterprise Linux 5, you do get access to the first Red Hat Enterprise Linux 5 installation CD during the exam. So, what could go wrong that requires the rescue environment? Well, among the variety of possible errors are typos in the GRUB configuration file, or that file might even be missing. There might be a problem with the etc slash inittab file. There could be other problems with boot script files such as etc slash rc dot sysinit. There might even be a problem mounting a key partition, such as that associated with the boot directory. In any of these cases, the rescue environment can help. Starting the rescue environment is fairly easy. Just boot from that first installation CD and when you get to the boot prompt, type linux rescue, and press enter to start that process. If it detects your system it may mount your standard directories in mnt slash sysimage subdirectories in read-write, or in read-only mode. If, for some reason, your file systems are not mountable, you also get an option to skip the mounting and open a command prompt, so you can continue with your troubleshooting. There are a couple of steps required in the rescue environment. You have to select a language and a keyboard. You should also set up networking, especially if packages you might need to install during rescue mode are available only on a remote system, and when you do, make sure to follow any instructions given by your proctor during your exam. I've arbitrarily set up a static IPv4 address, and that's on my own personal network. The network you configure during your exam will probably be different. You get three choices when you complete configuring the rescue environment. Continue, read-only, and skip. Generally, you should try continue first. If the rescue mode finds undamaged partitions, it'll mount them automatically in read-write mode as mnt slash sysimage subdirectories. If that doesn't work, you can try rescue mode again, and when you return to this screen, try read-only mode. That mounts those directories in read-only mode, again, on mnt slash sysimage subdirectories. If that doesn't work, go back into rescue mode and select the skip option when you see this line. That doesn't mount any directories and gets you directly to a command line where you can start analyzing your system. Let's try read-only mode. Like the continue option, it searches the local hard drives for an available Red Hat Enterprise Linux 5 installation, and it's found one, so I get this OK, and note how it has mounted a logical volume and subdirectories on various partitions. Then I can get to work. For example, I can run the fsck command to fix a damaged partition. Say my dev slash sda1 is damaged. But wait a second. I shouldn't run that yet. Since it's already mounted on the mnt slash sysimage slash boot directory. I need to unmount that first. Now we can run the fsck command on that partition, and then let's remount that partition on the mnt slash sysimage boot directory. You might notice that it's now mounted in read-write mode. If you have a read-only partition that you're ready to remount in read-write mode you can use a command like this. Note how mnt sysimage, that's your top level root directory for the regular Red Hat Enterprise Linux 5 installation, is mounted in read-only mode. That's the ro. We remount it in read-write mode, that's the rw, and now that change is reflected in the output to the mount command. Once partitions are mounted in the way you want, you can set mnt slash sysimage as the new top level directory. Just run the chroot command on that directory, and there. There are the directories available as subdirectories of your top level root directory.
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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