How to solve the problem of failure to start Ubuntu and grub information loss caused by Windows reinstallation

After windows was reinstalled, I did not care about my ubuntu. As a result, Windows overwrites the startup information and does not want to reinstall ubuntu. According to the experiment on the Internet,

The steps are as follows:

 

1. Create liveusb

Although livecd is written in many places, it is obvious that the USB flash disk is more convenient. Therefore, liveusb is recommended. Of course, the effect of livecd is the same. Liveusb requires at least MB of data to be saved. Of course, the current USB flash drives are very large and the capacity is not a problem. Liveusb mainly uses the "USB Startup Disk creator" function provided by ubuntu. Therefore, you can create an Ubuntu Virtual Machine on Windows and create it on the virtual machine, you can also create an Ubuntu host from another user, which is very convenient.

 

A. After the USB flash drive is inserted, start "system/Administration/USB Startup Disk creator" in the toolbar"

B. Click the other button and select the Ubuntu ISO image file. Your USB flash drive is correctly displayed in "disk to use.

Select the default "stored in reserved extra space" and drag the storage space below. The minimum size is 128 MB, and the maximum size is the size of the USB flash disk minus the ISO size.

Click format to format the USB flash drive.

Click "make Startup Disk" to start production. After the installation is complete, liveusb is ready.

 

2. liveusb boot System

A. Use liveusb to restart the computer and select the language menu (of course, we usually select "simplified Chinese ").

B. Select "Try Ubuntu without changing anything on the computer" in the menu that appears ".

C. Open a terminal after the system is started

 

3. Fixed grub Information

A. run $ sudo fdisk-L to find the root directory partition number of your installed Ubuntu system from the list.

B. Mount your root directory to the current system. For example, the partition of your root directory is/dev/sda2:

Mkdir/mnt/root

Mount-T ext3/dev/sda3/mnt/root

C. Fix windows-covered grub startup information by re-installing:

Grub-install -- root-directory =/mnt/root/dev/SDA

D. restart the system to view the menu selected for Ubuntu and Windows startup.