Ubuntu 16.04无法启动求助：联想Legion Y520加载BIOS默认值后故障

Hey there, let's work through this boot issue together—your important files are safe as long as we take the right steps, so don't stress too much!

第一步：先排查BIOS设置问题 #

Since you loaded BIOS defaults, some settings that Ubuntu relies on might have been reset. Let's fix those first:

• Reboot your Legion Y520 and press F2 (that's the usual key for Lenovo BIOS) to enter the setup screen.
• Look for Secure Boot—Ubuntu 16.04 often has trouble with this enabled, so switch it to Disabled.
• Check the SATA Mode option: Lenovo laptops often default to RAID, but Ubuntu needs AHCI to recognize the hard drive properly. Switch this to AHCI.
• Double-check the boot order to make sure your main hard drive is listed as the first boot device.

第二步：先备份你的重要文件（Critical Step!） #

Before we try any repairs, let's make sure your files are safe. Here's how:

1. Grab an empty USB drive (at least 4GB) and create an Ubuntu 16.04 Live USB on another computer (using the same Ubuntu version as your installed system works best).
2. Plug the USB into your Legion, reboot, and press F12 to bring up the boot menu. Select the USB drive to boot from.
3. Choose "Try Ubuntu without installing" when prompted—this lets you access your system without making changes to it.
4. Open the file manager, find your installed Ubuntu partition (it'll be labeled as an ext4 filesystem), navigate to /home/[your-username], and copy all your important files to the USB or an external hard drive.

第三步：修复GRUB引导 #

If your files are backed up, let's fix the bootloader:

1. In the Live Ubuntu system, open a terminal (press Ctrl+Alt+T).
2. Identify your Ubuntu partition by running:

   sudo fdisk -l
   

   Look for the entry labeled "Linux filesystem"—it might be something like /dev/sda2.
3. Mount that partition to the Live system:

   sudo mount /dev/sda2 /mnt
   

   (Replace /dev/sda2 with the partition you found.)
4. Bind the necessary system directories to access your installed system:

   sudo mount --bind /dev /mnt/dev
   sudo mount --bind /proc /mnt/proc
   sudo mount --bind /sys /mnt/sys
   

5. Switch to your installed system's environment:

   sudo chroot /mnt
   

6. Update the GRUB configuration:

   sudo update-grub
   

7. Reinstall GRUB to your hard drive's MBR:

   sudo grub-install /dev/sda
   

   (Note: /dev/sda is your entire hard drive, not a partition—don't add a number here.)
8. Exit the chroot environment and reboot:

   exit
   sudo reboot
   

   Remove the USB drive when prompted, and see if Ubuntu boots normally.

第四步：修复文件系统错误 #

If the bootloader fix didn't work, your partition might have filesystem errors from the BIOS change:

1. Back in the Live Ubuntu system, run this command to check and repair your Ubuntu partition:

   sudo fsck /dev/sda2
   

   (Again, replace /dev/sda2 with your actual partition.)
2. When prompted to fix errors, type y and press Enter. Let the process finish, then reboot and test.

If you hit any specific error messages (like being stuck on a black screen, or seeing GRUB errors), let me know the details and we can troubleshoot further!

内容的提问来源于stack exchange，提问作者Nico