Shut Down Computers on the Network⚓︎

With the Freetz packages wol and callmonitor, it is easy to start a
computer on the network by mobile phone or through the Freetz web
interface. Shutting down a computer behind a FRITZ!Box can be just as
simple. The configuration is not difficult and works for both Linux and
Windows computers.

Requirements⚓︎

FRITZ!Box with the packages dropbear, including the SSH client, and
callmonitor

Configure the FRITZ!Box⚓︎

Generate Keys⚓︎

Log in to the FRITZ!Box, create a directory, and generate keys:

    mkdir /var/tmp/flash/ssh
    cd /var/tmp/flash/ssh
    dropbearkey -t rsa -f rsakey_box

Extract the public key:

    dropbearkey -y -f rsakey_box | grep ssh > rsakey_box.pub

Configure the FRITZ!Box for a Linux Computer to Shut Down⚓︎

On the FRITZ!Box, create a file such as
/var/tmp/flash/ssh/shutdown_linux_computer.sh with the following
content. Some distributions prevent user root from logging in by
default. Change that setting, or preferably replace root with a user
that, for security reasons, only has permission to shut down the
computer.

    ssh -i /var/tmp/flash/ssh/rsakey_box root@<computer_ip> "shutdown -h now"

As the final configuration step on the FRITZ!Box, add this line to the
Callmonitor listeners:

    in:request ^<outgoing_number> ^<incoming_number> HOME=/mod/root && /var/tmp/flash/ssh/shutdown_linux_computer.sh

Configure the FRITZ!Box for a Windows Computer to Shut Down⚓︎

On the FRITZ!Box, create a file such as
/var/tmp/flash/ssh/shutdown_windows_computer.sh with the following
content. Replace <username> with the Windows user name:
```
ssh -i /var/tmp/flash/ssh/rsakey_box <username>@<computer_ip> "shutdown -s"
```

Add this line to the Callmonitor listeners:

in:request ^<outgoing_number> ^<incoming_number> HOME=/mod/root && /var/tmp/flash/ssh/shutdown_windows_computer.sh

Configure the Linux Computer to Shut Down⚓︎

Copy the public key, the one extracted earlier, from the FRITZ!Box to
the target computer and authorize it. Replace root with
/home/<username> if necessary, and make sure that this user is
allowed to shut down the computer:
```
    cat rsakey_box.pub >> /root/.ssh/authorized_keys
```
Install and start the OpenSSH server.

Configure the Windows Computer to Shut Down (Tested on Windows XP)⚓︎

Copy the public key from the FRITZ!Box to the target computer, rename
it to authorized_keys, and place it in
c:\\Documents and Settings\\username\\.ssh\\. On the
author's computer, the folder had to be created in the terminal with
mkdir .ssh because of the leading dot.
Install OpenSSH.

Adjust the configuration file c:\\Program Files\\OpenSSH\\etc\\sshd_config.
Correct these values:

    StrictModes no
    RSAAuthentication yes
    PubkeyAuthentication yes
    AuthorizedKeysFile  .ssh/authorized_keys

The computer can now be shut down by calling the phone number configured
in the Callmonitor listener. It also works through the Freetz web
interface under Extras, Test call.

Notes⚓︎

The computer to be shut down must be listed in
/mod/root/.ssh/known_hosts. The easiest way to achieve that is to
connect once from the FRITZ!Box to the computer through SSH.
To make sure the created files are not lost after a FRITZ!Box reboot,
run modsave flash.