GRUB and Linux system repair (version 2)

GRUB and Linux system repair (version 2)

GRUB configuration Parsing
The configuration file is saved in/boot/grub. conf [/boot partition should be separated]

The soft link is saved in/etc/grub. conf.

1. grub. conf file Analysis

Default # Start the system by default

Timeout # default wait time, in seconds

Splashimage # defines the GRUB startup background image

# (Hd0, 0) # specify the partition where/boot is located-> the first hard disk, the first partition

Hiddenmenu # Hide a menu

Title CentOS (2.6.32-358. el6.i686) # Name of the menu item, whose content can be modified

Root (hd0, 0) # defines the root device of GRUB, that is, the partition where the kernel is located, that is, the/boot Directory, which represents the partition where all startup devices are located.

Kernel/vmlinuz-2.6.32-358.el6.i686 ro root = UU... # define the location of the kernel, note: Here/does not represent the root partition, but indicates the/boot directory

Initrd/initramfs-2.6.32-358.el6.i686.img # load the image file. For more information, see <CentOS 6. X Startup Process> This blog

Single-user mode Application
Case: the root password is missing, and the system suffers an abnormal power failure.

1. When the system starts, Press Esc to enter the GRUB menu

GRUB function key:

E: edit the current menu item // edit

C: Enter the command line mode of GRUB // command

B: Start the current menu item // boot

D: delete the current row // delete

Esc: Return to the GRUB Startup menu interface to cancel any modifications made to the current item.

2. Click a line in the kernel, press e to edit the startup level, and add the corresponding startup and running level at the end of the line, for example, 1 or s. Press enter and press B to enter the single-user mode.

Passwd root # change the root password

# Other settings can be made, such as file system repair after power failure.

Set GRUB Password
Step 1: Set and copy the ciphertext

Method 1. Use the grub-md5-crypt command that comes with GRUB

Method 2. Use the md5crypt command on the GRUB interactive command line interface

Step 2: modify the configuration file/boot/grub. conf

Add: password -- md5 $1 $ EszU60 $ Mc2BwxeWUH/8q3iqbRknz0 # -- md5 indicates that it is encrypted with md5. [It is best to write the password in global mode, for example]

After restart

OK, all done!

GRUB repair
Case: After the instance is started, go to the grub interface, but there is no menu. There is only one grub> prompt left.

Solution:

Grub> cat/grub. conf # An error is found.

Manual guide to Linux:

Grub> root (hd0, 0)

Grub> kernel/vmlinuz-2.6.18-14 ro root = LABEL =/3 # if an error occurs at this time, pay attention to the prompt

Grub> initrd/initrd-2.6.18-14.img

Grub> boot # Use the Tab command to complete

For more details, please continue to read the highlights on the next page:

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