How to make a file readonly in linux

- How to make a file read only in linux
- How to make a file not read only in linux
- How to make a read only file editable in linux
- How to make a read only file writable in linux
- How to make read only file system writable in linux
- How to make a read only file system read write in linux
- File is read only in intellij
- Read elf file