Fixing Corrupted Ubuntu with Chroot

November 16, 2025 · 7 min read

Software Engineer & Tech Enthusiast

Fixed a friend's Ubuntu laptop where networking and touchpad stopped working — settings UI completely vanished. No backup meant reinstalling wasn't an option.

Here's the chroot repair method that saved the system while preserving all user data.

Prerequisites

USB drive (8GB+ for modern Ubuntu ISOs)
Ubuntu live ISO (same or newer version as installed system)
Another computer to create the bootable USB
Ethernet cable (if WiFi drivers are broken)

warning

This method preserves data, but always back up critical files first if possible. In this case, no backup was available.

TL;DR — Quick Repair

Copy-paste script. Replace sdXY, sdXZ, sdX1 with your actual devices (check with lsblk -f). NVMe disks use names like /dev/nvme0n1p2.

# Identify partitions
lsblk -f

# Mount root
sudo mount /dev/sdXY /mnt

# Mount separate /boot and EFI if they exist
sudo mount /dev/sdXZ /mnt/boot
sudo mount /dev/sdX1 /mnt/boot/efi

# Bind essential filesystems
for i in /dev /dev/pts /proc /sys /run; do sudo mount --bind $i /mnt$i; done

# Copy DNS config (not the symlink)
sudo cp --dereference /etc/resolv.conf /mnt/etc/resolv.conf

# Enter chroot
sudo chroot /mnt

# Reinstall desktop environment (or ubuntu-server for servers)
apt update
apt install --reinstall ubuntu-desktop

# Rebuild initramfs and GRUB
update-initramfs -u
update-grub

# Quick health check (optional)
ping -c1 1.1.1.1 && ping -c1 archive.ubuntu.com || echo "Network/DNS not OK"

# Exit and unmount
exit
for i in /run /sys /proc /dev/pts /dev; do sudo umount /mnt$i; done
sudo umount /mnt

What Went Wrong

Networking and touchpad completely broken
Relevant settings missing from the UI
Core packages/drivers corrupted
Critical constraint: no backup, all personal files at risk

The Fix: Live USB + Chroot Repair

The approach: boot from a live USB, mount the broken installation, then use chroot to "enter" the system and repair it from inside.

Step 1: Boot from Live USB

Use a live Ubuntu ISO (same or newer version). Choose "Try Ubuntu" and open a terminal.

Step 2: Mount Your Installed System

Find your root partition:

lsblk -f

Mount it:

sudo mount /dev/sdXY /mnt

Replace sdXY with your root partition (e.g., /dev/sda2 or /dev/nvme0n1p2 for NVMe).

tip

For encrypted partitions (LUKS), decrypt first:

sudo cryptsetup luksOpen /dev/sdXY decrypted_root
sudo mount /dev/mapper/decrypted_root /mnt

Mount separate boot/EFI/home partitions if present:

sudo mount /dev/sdXZ /mnt/boot
sudo mount /dev/sdX1 /mnt/boot/efi
sudo mount /dev/sdXA /mnt/home

Bind essential system directories:

for i in /dev /dev/pts /proc /sys /run; do sudo mount --bind $i /mnt$i; done

Why these mounts matter

/dev — Device files (hardware access)
/dev/pts — Pseudo-terminals (for terminal operations)
/proc — Process/kernel interface
/sys — System/hardware information
/run — Runtime data (package management)

Copy DNS config (use --dereference to copy the real file, not the symlink):

sudo cp --dereference /etc/resolv.conf /mnt/etc/resolv.conf

Important

Skipping bind mounts causes errors. Ensure all five directories are mounted.

Step 3: Enter the Chroot Environment

Enter your installed system:

sudo chroot /mnt

You're now "inside" your broken installation, using the live system's working kernel and hardware access.

Step 4: Reinstall Core Packages

Reinstall the base system:

apt update
apt install --reinstall ubuntu-desktop

For server editions:

apt install --reinstall ubuntu-server

To reinstall all packages (slower but more thorough):

caution

This reinstalls every package. Very time-consuming (can take 1-2 hours). Use only as a last resort.

apt reinstall $(dpkg -l | awk '/^ii/{print $2}')

Preserves config files while reinstalling binaries.

Step 5: Fix Bootloader (if needed)

Detect firmware mode:

if [ -d /sys/firmware/efi ]; then echo "UEFI detected"; else echo "Legacy BIOS detected"; fi

UEFI systems (ensure /boot/efi is mounted):

grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=ubuntu
update-grub

Legacy BIOS systems:

grub-install /dev/sdX   # replace sdX with your disk, not a partition
update-grub

Step 6: Verify and Reboot

Verify critical services:

# Check network manager
dpkg -l | grep network-manager

# Check recent error logs
journalctl -p err -b -1 | tail -20

Exit the chroot and unmount everything:

exit
for i in /run /sys /proc /dev/pts /dev; do sudo umount /mnt$i; done
sudo umount /mnt
sudo reboot

System should boot normally with all data preserved.

What Actually Worked

After following these steps, the laptop came back to life:

✅ Network (WiFi + LAN) fully functional
✅ Touchpad responding
✅ All user files and settings intact

Zero data loss. The chroot method proved its worth.

Common Issues (and Fixes)

During the repair, these problems might come up:

Issue 1: "Failed to Fetch" During apt update

Chroot can't reach package mirrors (DNS or network issue).

Solution:

# Copy DNS config if you forgot
sudo cp --dereference /etc/resolv.conf /mnt/etc/resolv.conf

If mirrors are broken, fix /etc/apt/sources.list inside chroot:

nano /etc/apt/sources.list

Use working mirrors:

deb http://archive.ubuntu.com/ubuntu/ noble main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu/ noble-updates main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu/ noble-security main restricted universe multiverse

Replace noble with your release (jammy, focal, etc.). Auto-detect codename:

source /etc/os-release
CODENAME=${UBUNTU_CODENAME}
sudo tee /etc/apt/sources.list >/dev/null <<EOF
deb http://archive.ubuntu.com/ubuntu/ ${CODENAME} main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu/ ${CODENAME}-updates main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu/ ${CODENAME}-security main restricted universe multiverse
EOF

Remove stale CD-ROM entries:

sudo sed -i '/^deb cdrom:/d' /etc/apt/sources.list

Then:

apt clean
apt update

Issue 2: "unable to allocate pty: No such device"

Happens when /dev/pts or /proc weren't bind mounted properly.

Solution:

Exit chroot and unmount:

exit
sudo umount -lf /mnt/dev/pts 2>/dev/null
sudo umount -lf /mnt/dev 2>/dev/null
sudo umount -lf /mnt/proc 2>/dev/null
sudo umount -lf /mnt/sys 2>/dev/null
sudo umount -lf /mnt/run 2>/dev/null

Redo Step 2 with proper bind mounts:

for i in /dev /dev/pts /proc /sys /run; do sudo mount --bind $i /mnt$i; done
sudo cp --dereference /etc/resolv.conf /mnt/etc/resolv.conf
sudo chroot /mnt

Issue 3: NVIDIA Driver Errors

NVIDIA drivers like nvidia-driver-535 can fail due to kernel module issues.

Solution:

# Remove all NVIDIA packages
sudo apt purge 'nvidia-*'
sudo apt autoremove --purge

# Clean and fix package database
sudo apt clean
sudo apt update --fix-missing
sudo apt -f install

# Let Ubuntu auto-detect correct driver
sudo ubuntu-drivers devices
sudo ubuntu-drivers autoinstall

# Rebuild modules
sudo update-initramfs -u
sudo update-grub

Secure Boot and NVIDIA

If Secure Boot is enabled, kernel modules are blocked. Either disable Secure Boot in firmware, or enroll a Machine Owner Key (MOK) when prompted. Reboot and complete MOK enrollment to allow module loading.

Updating All Drivers

Refresh all hardware drivers:

# Full system upgrade
apt full-upgrade

# Intel/AMD GPU drivers and firmware
apt install --reinstall xserver-xorg-video-intel xserver-xorg-video-amdgpu linux-firmware

# NVIDIA (if applicable)
apt purge 'nvidia-*'
ubuntu-drivers autoinstall

# Network and other firmware
apt install --reinstall linux-firmware

# Rebuild all kernel modules
dkms autoinstall
update-initramfs -u
update-grub

When This Method Works (and When It Doesn't)

This approach works great for:

Corrupted system libraries/drivers
Broken login/display managers
Need to preserve /home and user data

Don't use this for:

Simple app misconfigurations → just edit the config file
Failing hard drives → focus on data recovery (ddrescue)
Forgotten passwords → use recovery mode

The goal: reinstall Ubuntu's core system while keeping all your personal files untouched.

Key Takeaways

From this repair experience:

Keep a live USB ready — You never know when you'll need it
Order matters — Mount bind points in sequence; use --dereference when copying DNS config
Secure Boot gotcha — Blocks NVIDIA modules; either disable it or enroll a MOK key

This repair took about an hour and saved all the user's data. Sometimes the old-school methods are still the best.

This works for Ubuntu-based systems (Kubuntu, Xubuntu, etc.) — replace ubuntu-desktop with kubuntu-desktop or xubuntu-desktop as needed.

Prerequisites​

TL;DR — Quick Repair​

What Went Wrong​

The Fix: Live USB + Chroot Repair​

Step 1: Boot from Live USB​

Step 2: Mount Your Installed System​

Step 3: Enter the Chroot Environment​

Step 4: Reinstall Core Packages​

Step 5: Fix Bootloader (if needed)​

Step 6: Verify and Reboot​

What Actually Worked​

Common Issues (and Fixes)​

Issue 1: "Failed to Fetch" During apt update​

Issue 2: "unable to allocate pty: No such device"​

Issue 3: NVIDIA Driver Errors​

Updating All Drivers​

When This Method Works (and When It Doesn't)​

Key Takeaways​

Prerequisites

TL;DR — Quick Repair

What Went Wrong

The Fix: Live USB + Chroot Repair

Step 1: Boot from Live USB

Step 2: Mount Your Installed System

Step 3: Enter the Chroot Environment

Step 4: Reinstall Core Packages

Step 5: Fix Bootloader (if needed)

Step 6: Verify and Reboot

What Actually Worked

Common Issues (and Fixes)

Issue 1: "Failed to Fetch" During apt update

Issue 2: "unable to allocate pty: No such device"

Issue 3: NVIDIA Driver Errors

Updating All Drivers

When This Method Works (and When It Doesn't)

Key Takeaways