Linux System Recovery: A Complete Step-by-Step Guide

Introduction / Why This Is Needed

Linux system recovery is the process of returning an operating system to a working state after a crash, file corruption, or bootloader errors. This guide is useful if your system won't boot, you've forgotten your password, or lost data. After completing it, you will be able to:

• Restore the system from a backup.
• Fix the GRUB bootloader.
• Regain access to files via a LiveCD.
• Reset the root password.

The instructions are suitable for Ubuntu, Debian, Fedora, CentOS, and other systemd-based distributions.

Requirements / Preparation

Before starting, ensure you have:

1. A bootable medium (Live USB/DVD) with any Linux distribution (Ubuntu 22.04 or similar is recommended). If the system won't boot, create it on another computer.
2. Terminal access — basic knowledge of Linux commands.
3. A system backup (recommended) — created via tar, timeshift, or other tools. If no backup exists, file recovery will be limited.
4. Administrator privileges (sudo) in the Live session.
5. A list of partitions (if you remember the disk structure) — this will simplify the process.

💡 Tip: If the system partially boots, create a backup of important data before recovery to avoid information loss.

Step-by-Step Instructions

Step 1: Prepare the Bootable Medium

If the system won't boot, use another computer to create a Live USB.

1. Download a Linux image (e.g., Ubuntu 22.04 LTS).
2. Write the image to a USB drive (minimum 4 GB). On Linux/macOS:

   sudo dd if=ubuntu-22.04.iso of=/dev/sdX bs=4M status=progress && sync
   

   Replace sdX with your USB device (e.g., sdb). On Windows, use Rufus.
3. Eject the medium and proceed to the next step.

Step 2: Boot from LiveCD and Identify Partitions

1. Insert the USB into the affected computer, boot from it (boot key: F12, ESC, Del — depends on manufacturer). Select "Try Ubuntu" (or a similar option).
2. Open the terminal (Ctrl+Alt+T).
3. Identify disk partitions:

   sudo lsblk -f
   

   Example output:

   NAME   FSTYPE  LABEL   UUID                                 MOUNTPOINT
   sda
   ├─sda1 ext4    root    1234abcd-5678-ef90-1234-567890abcdef
   ├─sda2 swap    swap    abcd1234-5678-ef90-1234-567890abcdef [SWAP]
   └─sda3 vfat    boot    ABCD-1234                            /boot/efi
   

   Find the root partition (usually ext4, mountpoint not listed) and, if present, the /boot partition (type vfat or ext2). Note the names (e.g., sda1, sda3).

Step 3: Mount Partitions

1. Create a mount point:

   sudo mkdir -p /mnt/root
   

2. Mount the root partition (replace sda1 with yours):

   sudo mount /dev/sda1 /mnt/root
   

3. If there is a separate /boot, mount it:

   sudo mount /dev/sda3 /mnt/root/boot
   

4. For partitions requiring filesystems (e.g., /var, /home), mount them similarly under /mnt/root/var, etc.
5. Verify mounts:

   mount | grep /mnt/root
   

   
   Mounted partitions should be displayed.

Step 4: Restore Files from Backup

If you have a backup, restore your data:

• tar backup (e.g., backup.tar.gz on an external drive):

  sudo tar -xzf /path/to/backup.tar.gz -C /mnt/root
  

• timeshift backup (if saved in /timeshift):

  sudo timeshift --restore --snapshot-days 1 --target /mnt/root
  

  Or manually copy from the /timeshift folder to /mnt/root.
• Manual copy: if the backup is on another partition, mount it and copy files.

⚠️ Important: Ensure the backup matches your system's architecture and version. Restoring a backup from a different version may cause errors.

Step 5: Reinstall the GRUB Bootloader

If the system fails to boot due to a corrupted GRUB:

1. Prepare the chroot environment:

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

2. Enter chroot:

   sudo chroot /mnt/root
   

3. Reinstall GRUB (replace /dev/sda with your disk, not a partition):

   grub-install /dev/sda
   update-grub
   

   For UEFI systems, also ensure the grub-efi package is installed.
4. Exit chroot:

   exit
   

Step 6: Final Check and Reboot

1. Unmount all partitions:

   sudo umount -R /mnt/root
   

2. Remove the USB drive.
3. Reboot:

   sudo reboot
   

4. After booting, check:
   • If services are running: systemctl status.
   • If your files are accessible.
   • If the system boots without errors (review dmesg or logs in /var/log).

Verify the Result

• Successful boot: the login screen appears.
• File check: ensure home directories and system files are intact.
• GRUB: the GRUB menu with a list of kernels appears during boot.
• Network settings: if a backup was used, check ip a and /etc/resolv.conf.

If the system boots but has errors (e.g., network not working), check configuration in /etc/network/interfaces or netplan.

Possible Issues

If the issue persists, consult specific guides on FixPedia (e.g., for recovering a particular distribution or tool).