Category Archives: Musings

Just the musings of technical minds.

Monitoring & Graphing Eldewrito Server Statistics In LibreNMS

LibreNMS is a fantastic open source NMS which I have been using for some time to monitor statistics on my network devices and servers.  The SNMP-based monitoring it offers is very simple to set up and provides fantastic insights into a variety of devices.

I recently spun up some Halo Online \ Eldewrito servers and wanted to keep track of the performance of the servers, so I could know the capacity of my VM hypervisor which I dedicated to the project.  My first step was configuring LibreNMS and monitoring the basic server statistics, but I really wanted to take this a step further, and correlate that data to the player count on the server.  Since Eldewrito is a community based game, a lot of tools are very limited, so tools such as GameTracker aren’t supportive of the game.

Fortunately, Eldewrito has a very simple query port usage and returns simple JSON data, so I was off to figuring out how to get this done.

The Approach
After consulting with some LibreNMS community members on their Discord, it was pointed out to me that LibreNMS supports Nagios plugins, so I got to work writing my own.

My Nagios Plugin
I have published the code for my Nagios plugin on Github.  The repository can be found here, and a direct link to the plugin file here.

If you are setting this up, download the plugin file, and proceed with this article.

LibreNMS Nagios Plugin Setup
LibreNMS provides excellent documentation on how to set up Nagios plugin support, you can find it here.  I am not going to cover this entire setup here, only the parts necessary to get this plugin working.  If you aren’t going to use other Nagios plugins, you don’t need to follow the rest of their guide’s steps either, but it’s there for your reference if the configuration steps change down the road.

The only steps which were required for the setup I wanted were:

  • Update the LibreNMS config.php, add the following lines:

  • Create the Nagios plugins directory:

  • Place my plugin file (found in the above section) in this directory.
  • Make the plugin file executable:

  • Your LibreNMS cron in /etc/cron.d/librenms needs a line which is checking the services.  Mine had this line already, so I didn’t need to change anything.  If yours doesn’t, you could try adding mine or consult the LibreNMS documentation above.

Set Up Your Monitor!
Now that you’ve done the above, LibreNMS should display a Services tab at the top.  Navigate there to add a new service monitor.

On this tab, your next step is filling in the details for the plugin to work.

You will need to know the IP address of your Eldewrito server, as well as the query port.  The default query port is 11775.

Enter the following options:

  • Device – Choose the server which you are hosting the Eldewrito server on.
  • Type  – Select check_eldewrito to use our script.  This should be the filename of the file you put in your plugins folder, if you changed it.
  • Description – Enter whatever you please here, I don’t care. 🙂
  • IP Address – Can be left blank and LibreNMS will autofill the device’s IP, or you can type the device’s IP if you enjoy verbosity like I do.
  • Parameters – Just enter the query port of the Eldewrito server here, default is 11775.

Locating The Graph & Data
Once you’ve set up your first service monitor, go grab a cup of coffee or some dinner.  Allow at least 5-10 minutes for the graphing to start.

The graph is located under the Services tab, you can either click on the device and go to its services tab, or you can go to the services tab on the top and click “All Services”.  You’ll need to toggle the tab from Basic to Detailed as well to see the graph.

Unfortunately on my version of LibreNMS there are some styling issues, the last check time overlaps the plugin check name a bit.  Maybe they will correct this in a future update, it is mostly a cosmetic issue anyway.

There you have it!  You can add this plugin on multiple server devices in LibreNMS, or use it on the same server several times across multiple ports.  The possibilities are quite endless!  It’s possible to extend the plugin to gather other statistics from the server as well, but for the moment, player count was of the most interest to me.

Please feel free to leave a comment here or open an issue on the Github if you run into any questions or problems with the plugin, and I’ll be happy to take a look.

Reinstall GRUB When Your System Isn’t Bootable

From time to time, I have encountered a system where due to some conditions the GRUB installation has become corrupted.  It is a fairly simple matter to reinstall GRUB, and sometimes this can quickly salvage a broken installation.

This is not meant to be a comprehensive guide, but is a compilation of information I found online ([1], [2]) that was useful to me in repairing a few problematic GRUB loaders.  Please feel free to contribute in the comments section if you have something to add.

Setting Up The Environment
The first thing you will want to do is locate a live CD as close to the version of Linux you have installed as possible.  Boot into the Live CD.

You need to set up a functional chroot.  For the purposes of this guide, I will assume /dev/sda1 is your partition on your installation.  We will make a chroot in /mnt/chroot/.

Next, you need to bind the directories that GRUB needs to access.

Finally, chroot to your environment.

Reinstalling GRUB Automatically
You can try a simple reinstall of GRUB automatically first, see if any insightful errors are produced.

Failing that, try the following which will rescan the BIOS drives and update information in the GRUB configuration.

Reinstalling GRUB Manually
If the automatic reinstall does not work for you, try reinstalling via the GRUB shell.

Comcast’s Awesomely Accurate Progress Bar

One of my favorite parts of being a Comcast customer is getting to login to my client portal and see my data usage.  (Of course I will enjoy this much less if they eventually decide to enforce their 250GB cap in my area, that will require me to find another ISP or pay their unlimited usage charge or a business class tier).

What I do get a good laugh out of is their ridiculously arbitrary progress bar.

Here is my data usage for January 2016:

As you can see, I used 560GB of data… which although their (non-enforced) cap is 250GB, this appears to be roughly 60% of some arbitrary maximum?


I was quite surprised to login today on February 2nd and see this fantastic usage meter appear:

It would seem that 4GB is almost as much usage as 560GB, who’d have thought?!

I checked on the other page as well and found the same ridiculousness:

I would love to know what’s going on in Comcast’s heads sometimes!

Configuration of OVH IP Failover on VMs

I have had a server with OVH for the past several years, and one of the things that took me many months of research, as well as trial and error, to get right was my IP address configuration for virtual machines.  The documentation available from OVH has been consistently lacking these past few years on how to properly configure it.

Debian \ Ubuntu systems will add to the complications, because they do not agree with the necessary configuration.  If you try to add it traditionally, just by editing /etc/network/interfaces, you will most likely end up with no default gateway when you’re all said and done, and your connection still won’t work.

For the first few months I was with OVH, I was launching my networking through a shell script in a cron job, because configuring it with /etc/network/interfaces just didn’t seem possible.


What You Need For This Guide \ Assumptions About Your Setup
1. A dedicated server on the OVH network.  This guide has been tested in the Roubaix datacenter, Gravelines datacenter, and the BHS datacenter.
2. A virtualization platform installed, and a virtual switch bridged with your network interface.  I have been using VMWare, and a vSwitch bridged with my eth0 interface.  This guide should be applicable to any virtualization suite (Xen, OpenVZ, etc) as long as your networking is bridged.
3. A Debian \ Ubuntu VM.  You can apply the knowledge gained from this guide to other operating systems (eg. CentOS) but the configuration will be different as the files are located in different places and are parsed differently.
4. A purchased IP range.  You can purchase IP addresses from OVH in your Manager Panel.


Gather Your Information \ Initial Setup On OVH Side
1. Your dedicated server’s Main IP will be needed for this guide.   Say, for example, your main IP is
2. Your dedicated server’s Gateway IP will be needed for this guide.  On the OVH network, this is the first three octets of your main IP, ending in 254.  For, the gateway is
3. A Fail Over IP Range registered with OVH.  You can register any size IP block, and you can pick any IP from the block.  Say for example, you bought  All of the Fail Over IPs are usable at OVH, so you have available all 8 IPs from to for use for your VMs.  You can purchase an IP block from your Manager Panel.
4. A Registered VM MAC Address associated on OVH’s routers.  Without this step, your connection will not work.  You can register VM MACs in your Manager Panel.


How To Register A VM MAC Address
In the new OVH Manager panel, you can register a VM MAC address by going to the “Manage IPs” page, clicking the gear icon next to the IP(s) you want to assign to the VM, and clicking “Add A Virtual MAC”.  You can choose an existing MAC address if you are assigning more than 1 IP, otherwise OVH will assign a new MAC address to you, and you will edit your VM preferences so your network interface has this MAC address.  Make sure you select the MAC address type “VMWare” if you are using a VMWare server, as this will generate MAC addresses which VMWare will accept.  You can use type “OVH” for any other virtualization platform.  The “name of virtual machine” field is just for your notes, and can be anything.


Operating System Installation
Install Debian \ Ubuntu to the VM, from a full install media.  Do not plan on doing a network install, as this guide does not cover how to make the OVH networking functional during installation; only after installation.  Skip the step for setting up networking during the installer, leave it unconfigured.


Setting Up /etc/network/interfaces
Now that you have your operating system installed, you are ready to configure your /etc/network/interfaces file.  This guide assumes that eth0 is your Internet interface. I will use IP addresses from the example above under “Gather Your Information”.  Do not use these addresses, substitute your own IP addresses.

A few things to note, for anyone asking any technical questions about what I just did above:

  • You should choose 1 IP address from your IP block.  If you want to add more, see the further instructions below.  This IP is the Main IP of your VM.
  • Regardless of the size of your block, you will treat the IP address as a /32 with a netmask
  • Because you are using a /32, the network\broadcast IP is your IP.
  • Your default gateway should be the same as your dedicated server’s default gateway.  DO NOT try to use what should logically be the gateway IP for your IP block, and DO NOT try to set your dedicated server itself as the gateway.  The IP block is irrelevant, the gateway is always the dedicated server’s gateway IP.
  • The routes have to be added this way, because the configuration is not valid.  The gateway should not be reachable from this network range, because it’s a /32.  However, the gateway will be reachable anyway, and adding the routes this way should work.


DNS Resolution
You will also need to edit your /etc/resolv.conf to put a DNS name server in there, otherwise your server will be able to ping other IPs, but it will not be able to resolve DNS.  You can just put a line in there, like this line which uses the public OpenDNS resolver:


Want To Add More IPs?
Sometimes it is desirable to have more than one IP address on your server.  You can easily add additional IPs from any IP block as an alias IP.  You don’t need to configure any additional gateways, because the gateway is always your dedicated server gateway.  You can purchase as many IP blocks as you want, and assign them all this way, it doesn’t matter if they are totally different IP ranges.  In the example below, I will add 2 additional IPs from the IP range I used as an example,


Having Problems?
If you are having any problems, please review these items:

  • First, reboot the VM to ensure that all of the networking changes you made are fully applied.
  • Can you ping your default gateway?  If not, did your route persist?  Run “route -n” and see if the route is there.  If it isn’t there, try adding it manually by running the commands in the post-up in /etc/network/interfaces.  See if you get any errors.
  • Did you configure DNS?  Try pinging just an IP address, (eg. ping and see if you get any response.
  • Did you remember to register a MAC address, and did you change the MAC address for the VM?  Run “ifconfig eth0” and make sure the MAC address shown matches what’s registered in your OVH Manager Panel.


Need Further Assistance?
As always, feel free to leave a comment below if you need any assistance.  I will be happy to help!

Lenovo ThinkPad W520 – Workaround For Linux Freezing Issue At Boot

I have been a proud Lenovo ThinkPad W520 owner for the past several years, but there has been a persistent issue I have experienced, as I have gone the route of dual booting Windows and Linux on my laptop.

Through the years, I have run Ubuntu 10.04, Xubuntu 12.04, Linux Mint 13, Linux Mint 14, and Linux Mint Debian Edition on this laptop.  Of these distributions, Ubuntu 10.04 is the only one I haven’t had an issue with.

The issue I have experienced is that after a fresh install of Linux, the laptop will freeze every other boot.  Sometimes, it freezes before reaching the login screen, sometimes before even reaching the boot splash screen, and sometimes just moments after logging in.  Other times, it would boot and function normally for hours.  It has been a very flaky issue.

In 2012, I posted a thread on the Ubuntu Forums on how I fixed the issue for 12.04.  I have applied this fix, necessarily, on Linux Mint several times since then as I have done new installs.  I wanted to create this post so others can find this information, and understand that it may apply to other future distributions down the line until this issue gets fixed upstream.


The Workaround
I have consistently resolved this issue by adding a boot flag to GRUB.

Edit /etc/default/grub, and add “nox2apic” to your boot parameters, like so:

After making this change, run update-grub and reboot the computer.

This has saved me so much frustration over the years, I hope it helps you as well!  If you run into a similar issue on another ThinkPad model, please let me know in the comments if this fix worked for you!