Fix Broken Sudo After Chown Mistake

Fix Broken Sudo After Chown Mistake | Generated by AI

Home 2026.02

The error you’re seeing:

sudo: /usr/bin/sudo must be owned by uid 0 and have the setuid bit set

happened precisely because you ran something like:

sudo chown -R $USER /usr

(or similar — probably $USER:$USER or $USER alone). This changed ownership of /usr/bin/sudo (and thousands of other critical files) away from root, and removed the special setuid bit that lets sudo run as root even when you execute it as a normal user.

Fixing just sudo is quick and usually works right away. Fixing the rest of /usr (so the system becomes stable again) is much harder — /usr contains libraries, binaries, headers, etc., and many expect to be owned by root:root (or sometimes root:staff, root:other groups). A recursive chown like that breaks a huge number of things.

Step 1: Fix sudo itself (so you can use it again)

You can’t use sudo right now, so get root access without it:

Option A – Recovery mode (easiest on a desktop/laptop)

Reboot the computer.
Hold Shift during boot (or Esc on some machines) until the GRUB menu appears.
Select Advanced options for Ubuntu → choose any line that ends with (recovery mode) → press Enter.
In the recovery menu, select root → Drop to root shell prompt → press Enter.
→ You now have a # prompt (full root access, no password needed here).
Remount the filesystem read-write:
```
mount -o remount,rw /
```
Fix sudo:
```
chown root:root /usr/bin/sudo
chmod 4755 /usr/bin/sudo
```
After this, run:
```
ls -l /usr/bin/sudo
```
→ You should see something like:
```
-rwsr-xr-x 1 root root ... /usr/bin/sudo
```
(the s instead of x in the owner’s execute position = setuid bit is set)
Exit and resume:
```
exit
```
Then select resume → normal boot.
After reboot, test:
```
sudo -k    # clear any old cache
sudo ls
```
It should now ask for your password and work.

Option B – If recovery mode doesn’t appear or you prefer a live USB

Boot from an Ubuntu live USB (same version if possible — 24.04 or whatever you’re on).

Open Terminal → mount your real system (replace /dev/nvme0n1p2 or /dev/sda1 with your actual root partition — use lsblk to find it):

sudo mkdir /mnt/root
sudo mount /dev/nvme0n1p2 /mnt/root           # adjust device name
sudo mount --bind /dev   /mnt/root/dev
sudo mount --bind /proc  /mnt/root/proc
sudo mount --bind /sys   /mnt/root/sys
sudo mount --bind /run   /mnt/root/run
sudo chroot /mnt/root

Now you’re inside your broken system as root → run:

mount -o remount,rw /
chown root:root /usr/bin/sudo
chmod 4755 /usr/bin/sudo
exit

Reboot (remove USB).

Step 2: After sudo works again — assess and repair the rest of /usr

Now that sudo is back, many things might still be broken (e.g. apt, graphical apps, libraries won’t load correctly because wrong owner).

Run these to see obvious damage:

sudo dpkg --configure -a
sudo apt update
sudo apt install --reinstall sudo   # just in case
ls -l /usr/bin/ls /usr/bin/bash /usr/lib/x86_64-linux-gnu/libc.so*   # should be root:root

Common quick fixes for many files:

# Fix common system binaries & libs (takes time, but helps a lot)
sudo chown -R root:root /usr/bin /usr/sbin /usr/lib /usr/share

# Some directories use other groups (safe to run anyway)
sudo chown root:staff   -R /usr/local   # if you use /usr/local a lot

But this won’t fix everything — some packages expect very specific owners/groups/permissions.

Realistic options at this point

Best & fastest long-term fix
→ Reinstall Ubuntu (keep /home if you want).
Boot live USB → “Try Ubuntu” → use the installer → choose “Something else” → reuse your existing / partition but format it (or just overwrite /usr,/etc,/var if you’re advanced).
→ Takes 20–40 minutes and gives you a clean system.

Try to repair in place (advanced, time-consuming, may not fully succeed)

Reinstall core packages:

sudo apt install --reinstall ubuntu-desktop ubuntu-minimal linux-generic
sudo apt install --reinstall $(dpkg -S /usr/bin/* | cut -d: -f1 | sort -u)

But expect many dependency errors — it can snowball.

Backup important data (from live USB if needed) and reinstall.

Doing a recursive chown on /usr almost always ends with reinstall being the sanest path — especially since many setuid/setgid binaries, shared libraries, etc., are now wrong.

If you want to try more targeted fixes first, tell me:

Your Ubuntu version (cat /etc/os-release if you can run it now)
What breaks when you try to use apt or open a GUI app
Whether you have important unsaved data in /home

Good luck — and never run recursive chown/chmod on system directories again! 😅

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