Red Hat RHCE troubleshooting Test prediction

As the RedHatEnterpriseLinux System Administrator, you need to know how to correct the configuration files related to the startup process. For this reason, there will be some questions to test your troubleshooting and analysis skills. The following cases and solutions list the problems and solutions you may encounter during the startup process. These are far from enough. These solutions work on my computer and I have already configured them. However, there are many causes. In the RedHat test, this solution may not work. Note

As the Red Hat Enterprise Linux system administrator, you need to know how to correct the configuration files related to the startup process. For this reason, there will be some questions to test your troubleshooting and analysis skills.

The following cases and solutions list the problems and solutions you may encounter during the startup process. These are far from enough. These solutions work on my computer and I have already configured them. However, there are many causes. In the Red Hat exam, this solution may not work. You need to know why. You need to do more experiments.

To gain more experience, you need to try different scenarios (remember: Do not do these things on production computers ). If you are familiar with the linux rescue environment, try other scenarios. I have tested these scenarios in RHEL5, but problems may occur in RHEL3 or RHEL4.

In the first scenario, rename grub. conf, which causes no guidance. Restart your system. Use the linux rescue environment to start RHEL to fix your system.

The second scenario covers MBR. Use the following command under the SATA/SCSI Driver (if your system uses the IDE/PATA driver, use hda to replace sda ):
# Dd if =/dev/zero of =/dev/sda bs = 446 count = 1

In the third scenario, run the/sbin/mount. nfs overwrite/bin/mount command and restart.

The fourth scenario overwrites the/bin/init command.

The fifth scenario is based on the lost/etc/inittab. You may see some major errors (or comment out some key commands ).

In the sixth scenario, the information is displayed. The cause is that I set the running level to 3 and comment out the mingetty command line in the/etc/inittab.
Starting smartd; [OK]
INIT; no more processes left in this runlevel

In the seventh scenario, write the root command in/boot/grub. conf incorrectly, and you will see the following information:
Root (hd1, 0)
Filesystem type unknown, partition type 0xfd
Kernel/vmlinuz-2.6.18-0.1.1.e15 ro root =/dev/VolGroup00/LogVo100 rhgb quit

Error 17: Cannot mount selected partition

Press any key to continue...

Sometimes, problems may occur when you enter the default startup level. Don't worry, there are two ways to start to different levels. You can go to the GRUB configuration menu or start the linux rescue environment.

------------------------------------
Case study <------------------> Solution

1. When it is started, you will see the grub> prompt
You may encounter a problem when the Startup Program reads the Startup File grub. conf. The file is lost or incorrect. In this case, you need to re-create the grub. conf file based on the menu. lst file in the/usr/share/doc/grub-verisonnum directory.

2. When you start the system, such as "Missing operating System" or "Operating system Not Found .".
Your primary boot partition (MBR) may be overwritten. You need to use the grub-install command to re-load GRUB on the MBR. (If it is outside the lab, I believe everything in MBR will be erased .)

3. During the startup process, you will see information about "cocould not start the X server (graphical environment) due to some internal error.
The problem may be that the/tmp or/home partition is full or not mounted. If these directories are not mounted, the mount command may be faulty. Use the mount RPM package to reinstall them.

4. You saw "exec of init (/sbin/init) failed !!! "Error
Your init command may be damaged. Use the SysVinit RPM package to reinstall the agent.

5. You can see the following message: "INIT: No inittab file found"
It is obvious that the/etc/inittab has a problem. If so, RHEL5 will prompt you "Enter runlevel ". If/etc/inittab is lost, the bash prompt is displayed when the key is s.

6. You can see messages similar to the following:
INIT; no more processes left in this runlevel

You may not start any character or graphic interface at the current level; start of the/etc/inittab.

7. You can see the following message: (Note the message mentioned above)
Root (hd1, 0)
Filesystem type unknown, partition type 0xfd
Kernel/vmlinuz-2.6.18-0.1.1.e15 ro root =/dev/VolGroup00/LogVo100 rhgb quit

Error 17: Cannot mount selected partition

Press any key to continue...

RHEL encountered a problem when reading the grub. conf file. Start the linux rescue environment and check the file and the/boot directory.