Simulating Linux boot failures and solutions

Linux startup flowchart

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(i)
simulation of the first phase failure and repair
we use a command to simulate the first 446 bytes of the MBR by overriding the method .
DD If=/dev/zero OF=/DEV/SDA bs=446 count=1
then we restart the Linux system, this time only this interface, and can't get into the system

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Next we will find a way to get the system back to normal, first we have to add the CD-ROM drive, and then reboot, to boot on the CD. At this point the interface will appear:650) this.width=650; "src=" http://s10.sinaimg.cn/mw690/00688Tvygy6ZKIT2vUdf9&690 "width=" 555 " height= "407" name= "image_operate_75141456750273647" alt= "simulate Linux boot failure and solution" title= "simulate Linux boot failure and solution" style= "margin : 0px;padding:0px;border:0px;list-style:none; "/>

Then , we need to enter rescue mode to repair the system. In the boot: Enter a command to enter the rescue mode:
Linux Rescue will enter the interface
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Then we have to go into rescue mode to repair the system. Enter the rescue mode by entering a command at the back of the boot:
Linux Rescue will enter the interface, press ENTER to appear screen select No;

The following screen appears

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at this point, we want to read the information, from which we learned that the file system has been mounted to the/mnt/sysimage directory, then we want to switch to this directory, using chroot/mnt/sysimage this command. Then we can execute the order.
because this is the first stage of the problem, so we have to install the first phase of the required files,
using the command: GRUB-INSTALL/DEV/SDA
At this point the installation is ready, we will restart the system at this time, but this is entered two times exit to reboot, we can see this interface650) this.width=650; "src=" http://s15.sinaimg.cn/mw690/00688Tvygy6ZKITTqKWfe&690 "width=" 555 "height=" name= "image_operate_49351456750502892" alt= "Analog Linux power-on Failure and solution" title= "simulate Linux boot failure and solution" style= "margin:0px;padding:0px; border:0px;list-style:none;line-height:1.5; "/>:

Description, we have solved this error.

(b)
and then we simulate What to do when the second stage goes wrong. When we switch to the/boot/grub directory, we will see an important configuration file grub.conf. At this point we can delete the file or move it to simulate another error, here we delete the file. Then we reboot the system will see the interface 650) this.width=650; "src=" http://s3.sinaimg.cn/mw690/00688Tvygy6ZKITQ4n0f2&690 "width=" 556 "height=" "Name=" image_operate_2601456750561196 "alt=" Simulate Linux boot Fault and solution "title=" simulate Linux boot failure and solution "style=" margin:0px;padding:0px;border:0px;list-style:none;line-height:1.5; "/>

At this point, the system has not come up, and then we solve the problem
At this point we will enter four instructions:

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Next
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such a Error message, at which time we restart the system, the interface;
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Next we still enter four instructions to restart the system
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After the reboot we can normally log in the system, but our problem has not been resolved, because we have deleted the grub.conf file, so we have to manually edit this file.
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Timeout after the parameters can be defined according to their own preferences, it refers to when the system is started, if we do not do anything, the system will wait 3 seconds after entering the system, after the title can also be free to write their own preferences. Then save the above file, restart the system, to this, we also solved the problem.

III)
What happens if we delete the Grub directory from the boot directory?
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At this point we press F2 to enter the BIOS, set to CD-ROM boot
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After you save the restart, the

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At this point we can do it the first time.
The command to enter when we enter rescue mode:

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At this point we look at the boot directory to see the grub directory, but when we look at the contents of the Grub directory, there is no grub.conf file

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Use the second method: Judge Root (hd0,0) after the number can try, to the second line when the input k and then the TAB key to complete, if you can complete the right, and finally go in, reconfigure the grub.conf and restart the good.

Simulating Linux boot failures and solutions