Fix and update grub2 system boot

Fix and update grub2 system boot 1. if the system is reinstalled or the boot system crashes, the system boot guide item cannot be entered, so that the system cannot be installed. take UbuntuGrub2 as an example to describe how to fix the previous system boot. (The following describes the Ubuntu system as an example... fix and update grub2 system boot 1. fix the problem that if the system is reinstalled or the boot system crashes, it cannot enter the boot guide and thus cannot enter the installation system. take the Ubuntu Grub2 boot as an example to describe how to fix the previous system boot. (The following describes how to install a USB flash drive in Ubuntu as an example. The following describes how to install a USB flash drive in other systems! 2. after selecting the applicable option, go to the Ubuntu graphic interface and open the terminal. 3. select Ubuntu to install the disk. if you are not sure which disk the disk is located, run the [plain] sudo fdisk-l 4 command. mount the Ubuntu system to install the disk (my disk is 8th, so it is sda8) [plain] sudo mount/dev/sda8/mnt 5. start to recover grub2 system boot [plain] sudo grub-install -- root-directory =/mnt/dev/sda 6. after the command is executed, if no error is reported, it is restored successfully and restarted. 2. after the update is restored, it is the previous system boot interface. if the newly installed system is not displayed on the page, you can go to the Ubuntu system and perform grub2 updates. Open the terminal and enter the [plain] sudo update-grub2 successfully, there will be a record of all system boot found on the disk after the update. (Take my own example) [plain] hugo @ hugo-HP :~ $ Sudo update-grub2 [sudo] password for hugo: Generating grub. cfg... found linux image:/boot/vmlinuz-3.5.0-26-generic Found initrd image:/boot/initrd. img-3.5.0-26-generic Found linux image:/boot/vmlinuz-3.5.0-25-generic Found initrd image:/boot/initrd. img-3.5.0-25-generic Found linux image:/boot/vmlinuz-3.5.0-17-generic Found initrd image:/boot/initrd. img-3.5.0-17-generic Found memtest86 + im Age:/boot/memtest86 +. bin Found Windows 8 (loader) on/dev/sda1 Found CentOS release 6.4 (Final) on/dev/sda3 Found Mac OS X on/dev/sda9 done and then restart.