Mount ReadWrite

To have the boot drive automatically mounted as read/write, create a file at the root of the drive named .readwrite; you can create it with this command:

sudo touch /.readwrite

The hidden /etc/rc boot script checks for the existence of the file, and if found, the drive is mounted read/write automatically. To create this file, you need to mount read-write first using one of the one-liners below.

Note that /Users, /etc, /tmp, and /var are mounted on the Scratch volume, which is always writable.

Problem caused by /.readwrite on Apple TV 1.1

Creating the file /.readwrite on Apple TV 1.1, can cause problems when booting the 1.1 OS. When booting, if the system concludes that a disk check is needed, the system will halt if the system volume is mounted read/write - as is the case if the file /.readwrite exists. It is thus recommended that the disk is kept read-only and only mounted for reading and writing temporarily as explained below.

Alternative One Liners

ReadWrite On:

sudo mount -uw /

ReadWrite Off:

sudo mount -ur /

I prefer to leave it mounted read only when I'm not writing