Mounting and unmounting filesystems
The following utilities work with filesystems:
By default, filesystems are mounted as read-write if the physical media permit it. You can use the -r option for mount to mount the filesystem as read-only. The io-blk.so library also supports an ro option for mounting block I/O filesystems as read-only.
You can also use the -u option for the mount utility to temporarily change the way the filesystem is mounted. For example, if a filesystem is usually mounted as read-only, and you need to remount it as read-write, you can update the mounting by specifying -uw. For example:
mount -uw /
To return to read-only mode, use the -ur options:
mount -ur /
You should use umount to unmount a read-write filesystem before removing or ejecting removable media.
See the Utilities Reference for details on usage and syntax.