title: read-only files on Ubuntu
body: <p>when trying to delete file, I got the rm command on ubuntu page at <a href="https://help.ubuntu.com/community/DeletingFiles" rel="nofollow">https://help.ubuntu.com/community/DeletingFiles</a>. And on, this page I got the term <strong>read-only</strong> files. I have tried to google <strong>read-only file linux</strong>, but cannot find any definition about this. Could you tell me what read-only mean? Does it mean all owner, group and other have only read permission? Thank you!</p>