For many years, a small, fanless industrial PC with two Gigabit Ethernet interfaces has served as a firewall in my home storeroom. The hardware is not very powerful, but it is just about sufficient for forwarding network packets and a few iptables rules.

I seem to recall that this device has 2GB RAM – but whether in the form of a 2GB module or as two 1GB modules, I really don't know. How many RAM slots are there anyway, and what is the maximum amount of RAM I could use if I decided to upgrade? I would like to find that out without taking the firewall off the Internet and removing its case, because that always provokes disrespectful comments from my kids: "What kind of availability is that, Dad?"

Hardware Lister, lshw, [1] is a reliable tool for answering questions about hardware. It elicits extensive information from the system about every installed hardware component – usually more than I ever wanted to know.

In daily practice, I usually misuse lshw to find out whether I'm on a physical server or a virtual machine (VM). As always, many roads lead to Rome, but it's hard to get there faster than with lshw:

$ lshw -c system | grep -i product
product: VMware Virtual Platform
[...]

Ah, a VM. Sometimes you see KVM or VirtualBox, and so on, depending on the virtualization platform.

But back to my small firewall and the actual purpose of lshw. For example, typing

lshw -C cpu

gives you all the information that lshw finds about the installed CPU. In this case, it is an Intel Atom with a 32-bit core and two logical CPUs. My question about the RAM is also answered by lshw. The command

lshw -short -C memory

shows that there are four DIMM banks, of which only one is occupied by a 2GB module (Figure 1).

Figure 1: lshw's diagnosis is that there are four DIMM banks in Charly's firewall containing just one lonely 2GB module.

Despite the wealth of information, there is one little thing that lshw can't help me with: It doesn't tell me the maximum amount of RAM I can use. For this, I have to dig a little deeper into the toolbox and pull out dmidecode. The following command gives me the desired results:

$ dmidecode -t memory | grep size -i

With this, I discovered that the maximum expansion capacity is four DIMMs of 4GB each (Figure 2). Now, let me just check what I have available in spare RAM.

Figure 2: Potential to expand: Charly's firewall computer can take up to 16GB RAM.