當Linux系統(tǒng)無法啟動時，使用Live USB是解決問題并恢復文件的有效方法。首先準備一個包含Ubuntu或Fedora等Linux發(fā)行版的Live USB，并通過重啟電腦、進入啟動菜單（通常按F12、Esc等鍵）選擇USB為啟動設備，從而進入Live環(huán)境。接著，在Live環(huán)境中打開終端，運行“sudo fdisk -l”識別根分區(qū)（如/dev/sda1），并使用“sudo mount /dev/sda1 /mnt”掛載該分區(qū)；若存在單獨的/boot、/home或/efi分區(qū)，也需分別掛載。隨后，可瀏覽/mnt目錄下的文件以進行修復或復制重要數(shù)據(jù)。若需修復GRUB引導程序，可在綁定/dev、/dev/pts、/proc、/sys和/run目錄后，使用“sudo chroot /mnt”進入系統(tǒng)環(huán)境，執(zhí)行“grub-install /dev/sda”和“update-grub”，再退出chroot并卸載所有掛載點。最后，取出USB重啟即可。若僅需恢復數(shù)據(jù)，直接訪問/mnt/home/用戶名目錄，通過文件管理器或終端命令（如“cp -r”）將文件復制到外部存儲設備即可完成操作。

When your Linux system won’t boot, it can be frustrating — especially if you need to recover files or fix the issue without reinstalling everything. Fortunately, using a Live USB is one of the most effective ways to access and repair your system. Here’s how to do it effectively.

Prepare Your Live USB and Boot Into It

Before anything else, make sure you have a working Live USB with a Linux distribution like Ubuntu or Fedora. If you don’t already have one, create it using tools like Rufus (on Windows) or dd (on Linux/macOS).

Once ready:

• Plug in the Live USB.
• Restart your machine.
• Enter the boot menu (usually by pressing F12, Esc, or another function key during startup).
• Select the USB drive as the boot device.

You should now boot into the Live environment. Choose "Try Ubuntu" or equivalent (not install), which will give you full access to your system's files and tools needed for recovery.

Access Your Installed System’s Files

Once in the Live environment, you’ll want to mount your installed system’s partitions so you can access them.

First, open a terminal and run:

sudo fdisk -l

This will show you the list of drives and partitions. Identify your root partition (typically something like /dev/sda1).

Then mount it:

sudo mount /dev/sda1 /mnt

If you have a separate /boot, /home, or /efi partition, mount those too:

sudo mount /dev/sda2 /mnt/boot
sudo mount /dev/sda3 /mnt/home
sudo mount /dev/sda4 /mnt/boot/efi

Replace /dev/sdaX with the actual identifiers from your system.

Now you can browse files under /mnt and perform repairs or copy out important data.

Repair GRUB (Bootloader)

A common reason Linux won’t boot is because the bootloader (GRUB) is broken. You can fix this from the Live USB by chrooting into your system.

After mounting your partitions as above, bind some special directories:

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

Then chroot into your system:

sudo chroot /mnt

Inside the chrooted environment, reinstall GRUB:

grub-install /dev/sda
update-grub

Exit the chroot and unmount everything:

exit
sudo umount /mnt/dev/pts /mnt/dev /mnt/proc /mnt/sys /mnt/run
sudo umount /mnt/boot/efi /mnt/boot /mnt/home /mnt

Reboot your system without the USB, and it should now start normally.

Recover Important Data

If your main goal is just to get files off the system, things are much simpler.

Mount your root partition as shown earlier, then navigate to /mnt/home/yourusername to find user files. From there:

• Use the file manager to drag and drop files onto an external drive.
• Or use the terminal:

  cp -r /mnt/home/yourusername/Documents /media/ubuntu/USB_DRIVE/

  Make sure to replace yourusername and USB_DRIVE with the correct names.

  Also check other partitions if you had separate drives for media or backups.

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  That’s basically all you need to know. Whether you're fixing the boot process or grabbing important documents, a Live USB gives you full control. Just take care not to write changes accidentally to the wrong drive — especially when copying files or running commands in the terminal.

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