Most Linux shells, 11 bytes

# echo o>*ger

you have to be in the /proc directory.

This is very straightforward and rather brutal.

Most Linux shells, 15 bytes

# echo o>/p*/*ger

It could be made to be 11 bytes long, if you happen to be in the /proc directory:

# echo o>*ger

This is very straightforward (has no side effects, like unmounting filesystems or killing processes) and rather brutal.