Do
How to Change a File's Owner on Linux
With chown, including the recursive option for entire folders.
sudo chown newuser file.txt
Also changing the group
sudo chown newuser:newgroup file.txt
Applying it to an entire folder (with its contents)
sudo chown -R user:group /path/to/folder
-R (recursive) applies the change to the folder AND
everything it contains inside, not just the folder itself.
Tip: the most common case where you need this is after copying files from another user account or from an external drive — they often keep the original owner, not yours, until you change it explicitly.
Frequently asked questions
Why do files copied from an external drive have a different owner?
They keep the original owner and permissions from where they came from — it's common to need to change them manually with chown after copying them, so they're fully yours on the new system.
What does the -R option do in chown?
It applies the owner change recursively — to the specified folder and to all its internal contents, not just the folder itself.