Install memcached

Install memcached on all your engine hosts.

On Debian-based Linux machines, you can do this by logging in as root and entering the following command:
```
# apt-get install memcached
```
Open /etc/memcached.conf for editing. Find the following line:
```
-l 127.0.0.1
```
and comment it out:
```
# -l 127.0.0.1
```
This allows memcached to listen on all interfaces.
memcached is installed as a daemon and will be started automatically on system reboot. However, to start it now without rebooting, enter:
```
# /etc/init.d/memcached start
```