thewild@ubuntu:~$ sudo blockdev --setro /dev/sda
thewild@ubuntu:~$ sudo blockdev --getro /dev/sda
1
thewild@ubuntu:~$ echo whatever | sudo tee /dev/sda
whatever
tee: /dev/sda: Operation not permitted
thewild@ubuntu:~$ sudo blockdev --getro /dev/sda
0
thewild@ubuntu:~$