In an earlier post, I asked for your interest in a how-to on graphing several network statistics using MRTG, an open-source application that generates graphs using data pulled from SNMP. I used an Airport Extreme (802.11n, gigabit) for this, but it should work with Snow / Graphite Airport base stations and up (Express and Extreme). For other routers, your mileage may vary, and it may even not be possible, so I decided not to make a guide for anything else than Apple’s routers. If you want to have graphs in your desktop, updated in real time, as seen here, read on!
For this how-to, you need;
- an Apple Airport wireless base station.
- Airport Utility
- OS X 10.4 or higher (yes, Leopard is fine)
- your Mac’s installation discs if you don’t have the Developer tools installed yet.
Ready? Let’s go!
Step One: First of all, authenticate with your wireless network and open your Airport Utility. You should see something like this;
Note the name of the base station here; we will need it later. As you can see in the source list on the left, mine’s “Prokyon”. Click “Manual Setup”, and once the settings have been loaded, select “Advanced” from the toolbar.
This is the selection of tabs you will find under “Advanced”. The first tab, “Logging & SNMP”, is the tab we need. Check ‘allow SNMP’ (it doesn’t have to be over WAN, as this will allow you to monitor statistics over the internet, exposing a possible security hole). That’s it for Airport Utility for now. Save the settings and quit the utility.
Step Two: Now we’re going to set up MRTG. You can get an easy-to-use binary from here; follow the basic instructions, namely;
Open a terminal,
cd (directory containing )mrtg-2.9.4-mosx.tgz
enter your root password
tar xzf mrtg-2.9.4-mosx.tgz
If all goes well, you now have ‘mrtg’ installed. Test it by typing ‘mr’ at the command line followed by pressing the ‘tab’ key. It should, given you don’t have other utilities installed beginning with ‘mr’, autocomplete to ‘mrtg’.
Step Three: Now, before we start setting up MRTG to use the SNMP services of your router, let’s test if it actually works. Open a terminal, and enter;
snmpwalk -v 2c -c public -M /usr/share/snmp/mibs:$HOME/share/mibs -m+AIRPORT-BASESTATION-3-MIB (Base station name).local 22.214.171.124.126.96.36.1991
All on one line. In this case, replace ‘-c public’ with either the community string you set in the Airport Utility (‘-c thestringyouentered’) – if you left this blank in the Airport Utility, it either defaults to ‘public’ or your base station password. Try both; it will either time out or spit out a huge amount of information. Also replace ‘Base station name’ with your base station name, as I told you to note in the first step. Mine would be ‘Prokyon.local’. Done filling the blanks? Press enter, and let it roll.
If it times out, check if SNMP is enabled or restart your Airport (also remember to check if the community string you set with the -c flag is either ‘public’ or your password). If it gives an error about missing something, download the Airport MIB from Apple and copy it to “/usr/share/snmp/mibs” (you can ‘Go to folder’ with CMD+Shift+G in Finder to reach this directory), then try again.
You should get a whole lot of output in your terminal. Working? Great, let’s go to the next step.
Step Four: Along with MRTG, we installed a utility called ‘cfgmaker’, that will generate MRTG configuration files for us. In the terminal, we will have to generate such a configuration. Don’t sweat, it’s very painless.
cfgmaker firstname.lastname@example.org > ~/mrtg.cfg
Ensure that ‘public’ is your community string. As described in the last step, this is most likely either your base station password (-not- the network password) or just ‘public’. 192.168.2.5 is my router’s IP address in this case; you should check what yours is, either by doing a ‘port scan’ with the Network Utility on your Mac, or by checking with your network preferences in System Preferences. It’s possibly also listed in the trusty Airport Utility. Fill in your IP address (ensure the community string and the IP address are separated by just a ‘@’) and let it do its job. The file ‘mrtg.cfg’ has been generated in your home directory.
Step Five: Now we can let MRTG do it’s first run. For sharing on the local network, I placed my MRTG web-pages and graphs in “~/Sites/MRTG/” – note that ‘~’ stands for /Users/myname/ here – as it is also very convenient. If you want to go on the safe side and do the same thing, make the directory in advance; MRTG -will not- do this for you.
Edit the newly generated mrtg.cfg with an editor like TextMate or nano (in the terminal). For the least hassle, I will describe using nano in your terminal to add the final changes to let MRTG know where to put its files.
Is what you need to type into your terminal. You’ll see something a bit like this;
Move your cursor to the line “# FOR UNIX” and delete the single leading hash mark (#) in the line beneath it. Enter the path of where you want to store the files here, as you can see, I chose /Users/superuser/Sites/mrtg/, as my account’s short name is ‘superuser’. To save the changes, press CTRL+X, and “Y”.
Step Six: Now we will run the MRTG application. Since on Leopard, MRTG complained that I used a Unicode environment, I set the shell’s environment variable ‘LANG’ to ‘C’ before using it. The whole command to run MRTG then looks like this;
env LANG=C mrtg ~/mrtg.cfg
This is provided you followed my instructions and your .cfg file is located in ~/ (your user directory). If all goes well, MRTG should just do its thing and return your control over the prompt after a second or a few. If it outputs errors, check the steps to see if you didn’t do something a bit different. You can now check your directory (~/Sites/mrtg/ for me) to see your first graphs.
This is my MRTG output directory, and as you can see, it generated files with (your router IP address).html as a name, with a number appended to indicate the interface. Several interfaces exist on the Airport Extreme; the most interesting ones are the WAN and ATH0 interfaces, respectively your internet connection port and the wireless interface. The graphs for these, provided you run MRTG periodically, show the data throughput graphed over time. Now, since it is a bit tiresome to run MRTG all day in your terminal, we need something to do that -for- us.
Step Seven: Fortunately, there’s an excellent tool for adding such a ‘daemon’ function to our system. Running Leopard, mind that there is an extra step here, which I will let Tiger users do as well for certainty. Download ‘Lingon’, Peter Borg’s excellent GUI for launchd, OS X’s initialisation system and more. Once the download has completed, run it, and open a terminal.
In the terminal, we’re going to make a shell script with the single line of instructions that loads up MRTG. Let’s use nano for convenience again, so enter;
and enter the command you used to run MRTG (
env LANG=C mrtg ~/mrtg.cfg in my case), but add the complete paths this time. My command would look like this;
env LANG=C /opt/local/bin/mrtg Users/superuser/mrtg.cfg
Exit and save again with Ctrl + X. Remember to make sure the paths are accurate and the command works (test run it in your terminal to see if you get any errors). Place the shell-script somewhere out of your user directory, like /Users/Shared/, and switch to Lingon.
In Lingon, press ‘New’ and make an appropriate choice; you can use these settings as an example;
At the bottom, you can see I let it run every three minutes. You can make it run as often as you want. Save settings, and depending on your choice of Agent, reboot or log out to make the changes happen.
Congratulations! If all went well, you should have an auto-updating set of graphs now. You can choose to do two things now; check these graphs occasionally, or present them on your desktop using GeekTool like I did. Geektool’s website is down right now, so download it from last post and install it to your System Preferences by double-clicking the preference pane in the disk image.
Last Step: Once it’s installed, System Preferences opens and shows you the preference pane. Make sure you have just System Preferences shown so you can see your entire desktop (most importantly, the top left). Add an item to the left list; and set something like this;
The blue rectangle is the active overlay that will contain the image you choose. You can set a refresh interval (I use 10 seconds because it’s the default), resize the image, and place it wherever you like. Although GeekTool is old (well, it hasn’t seen a lot of updates), it’s well coded in that it won’t vanish when you use Exposé or even Spaces.
My result can be seen here; if there’s demand for it, I will upload the PSD of my little ‘comm station’ overlay so you can use it with whatever wallpaper you desire. Perhaps I will write a second part with how to put this into a widget form, and tracking the amount of users on your wireless network and graphing other miscellaneous statistics. Enjoyed this how-to? Comments / blog reactions / email is welcome!