While using vi as superuser.

The wq! command is used to save a file and quit the vi editor, even if the file is read-only. The w command means write, the q command means quit, and the ! command means force. By combining these commands, the vi editor will override the file permissions and save the changes to the file, then exit the editor. The other options are either invalid syntax or do not force the write operation. For example, wq will save and quit only if the file is writable, ql will quit without saving, and fw! will force write but not quit. References:

[vi] - FreeBSD vi(1) Manual Page

[wq!] - How to save a file in vi / vim editor in Linux / Unix