NEMS – Nagios Enterprise Monitoring Server for Raspberry Pi 3

NEMS – Nagios Enterprise Monitoring Server for Raspberry Pi

NEMS is a modern pre-configured, customized and ready-to-deploy Nagios Core image designed to run on the Raspberry Pi 3 micro computer. At its core it is a lightweight Debian Stretch deployment optimized for performance, reliability and ease of use.

NEMS is free to download, deploy, and use. Its development however is supported by its community of users. Please consider contributing if you can.

Please Note: NEMS 1.2.x is my most ambitious NEMS release yet. Please consider throwing a little gift in my Tip Jar if you find NEMS saves you time or money. Thanks!

[NEMS Documentation]
[NEMS Community Forum]
[NEMS User Comments]


NEMS 1.1 Featured on Category5 Technology TV

What Is Nagios Core?

Nagios® Core™ is an Open Source system and network monitoring application. It watches hosts and services that you specify, alerting you when things go bad and when they get better.

Some of the many features of Nagios Core include:

  • Monitoring of network services (SMTP, POP3, HTTP, NNTP, PING, etc.)
  • Monitoring of host resources (processor load, disk usage, etc.)
  • Simple plugin design that allows users to easily develop their own service checks
  • Parallelized service checks
  • Ability to define network host hierarchy using “parent” hosts, allowing detection of and distinction between hosts that are down and those that are unreachable
  • Contact notifications when service or host problems occur and get resolved (via email, pager, or user-defined method)
  • Ability to define event handlers to be run during service or host events for proactive problem resolution
  • Automatic log file rotation
  • Support for implementing redundant monitoring hosts
  • Optional web interface for viewing current network status, notification and problem history, log file, etc.


Nagios doesn’t need a big fancy supercomputer to offer exceptional enterprise monitoring of network assets and resources, so our temptation is to re-purpose older servers to perform this reasonably lightweight task.

If you ask me, that’s not only overkill, but the attempt to save money by reusing older hardware will actually cost more due to higher electricity usage vs. a tiny Raspberry Pi 3 Microcomputer… which ironically may in fact have more modern system specifications than that old beast of a server you’ve been using.

It can be a wee bit daunting to setup a Raspberry Pi Nagios server from scratch, and there were no projects I found which were actively maintained at a level adequate for professional use. So I decided to start a new project–called NEMS: Nagios Enterprise Monitoring Server (for Raspberry Pi).

This project uses freely available applications such as Debian Linux, Nagios Core and a variety of other goodies, and I too release a fully ready-to-use image for you to use within yours or your customer’s network environments.

About NEMS

The goal with NEMS is to provide a free, full-featured, up to date drop in Nagios Enterprise Monitoring Server for Raspberry Pi 3. It has all the bells and whistles while being optimized for solid stability and fast performance.

The original NEMS release was based (with big thanks to Ryan Siegel) on NagiosPi, with many of the settings reflective of the NagiosPi Wheezy distro (which is now obsolete).

Here is what Ryan Siegel (the creator of NagiosPi) has to say about NEMS: “I’d love to upgrade NagiosPi, but i don’t have ability to make a GUI that can beat that of NEMS. I strongly feel that it has always been a necessary addition to NagiosPi and NEMS was able to deliver what is essentially an updated and improved version of NagiosPi. No reason not to start using NEMS for the time being. Nice work Robbie!” [source]

NEMS has since become a popular drop-in Nagios distro for Raspberry Pi, with a major release twice per year.

If you like NEMS, please donate:

The Out-Of-The-Box NEMS Experience:

System Requirements

  • Raspberry Pi 3 Micro Computer
  • 8GB+ Micro SD Card (Recommend 16GB+)
  • Network Connection (will obtain IP address via DHCP: create your reservation in the DHCP server for ease of access)
  • Internet Connection


  • Purchase and assemble your Raspberry Pi 3.
  • Download the most current version of NEMS below.
  • Unzip and “Burn” the image to your Micro SD card.
  • Boot your NEMS server.
  • Login to NEMS console by either connecting a monitor and keyboard, or using ssh (Username: pi / Password: raspberry)
  • Type: sudo nems-init
  • After rebooting, reconnect and restore your backup.nems NEMS-Migrator file if you have one.
  • Edit /etc/nagios3/resource.cfg and add your SMTP information.
  • Login to NagVis and change the password (default is: admin/admin)
  • Reboot your Pi and enjoy NEMS when it comes online (see below for further details).

Buy The Needed Hardware

Raspberry Pi 3 Nagios ServerRaspberry Pi 3 are very affordable, and using our Micro SD image, you simply buy the device, “burn” the image to the Micro SD card, and boot it up.

Here’s our link to buy the device you’ll need, complete with the Micro SD card, a power adapter, a good solid case, and more:

Please buy it through that link, or let me know if you need a customized link to a different model. We get a small percentage of the sale, and it helps to make it possible to offer this as a free download.

Download NEMS 1.2.1

NEMS 1.2.1 Raspberry Pi Image

NEMS 1.2.1 Image File – 1.27 GB ZIP File (4.68 GB Uncompressed)

Released May 22, 2017. Fixes the problems with NEMS 1.2 release.

Unzip and “burn” to 8 GB+ Raspberry Pi 3 Micro SD Card (I recommend you use at least a 16 GB card so there’s plenty of room for logs, configs, data and so-on).

BitTorrent seed coming soon.

Upgrade to NEMS 1.2.1

  • Upgrade from NEMS 1.1+
    1. Connect to your existing NEMS dashboard from your computer and press Migrator->Backup. That will give you your backup.nems file.
    2. Deploy NEMS 1.2 on a new card (please use a new card so you can always revert back to your existing NEMS 1.1 if you have a problem).
    3. Boot your Pi into NEMS 1.2 and initialize it as normal (instructions are provided via your web browser when you connect)
    4. Once you get to the dashboard simply click Migrator->Restore to open the documentation which walks you through restoring your settings from your backup.nems file.
  • Upgrade from NEMS 1.0 or nagiospi
    See legacy upgrade documentation here:

Upgrade to NEMS 1.2.2
NEMS 1.2.2 is the first ever rolling upgrade of NEMS. This means you do not need to reinstall NEMS to get the latest features. You must have NEMS 1.2.1 already installed to upgrade to NEMS 1.2.2.

  • Upgrade from NEMS 1.2.1
    1. Type: sudo nems-upgrade
    2. Reboot.

NEMS 1.2.1 Changelog
NEMS 1.2 was released May 6, 2017. NEMS 1.2.1 was released May 22, 2017 to fix bugs with the migrator and improve the overall release following significant user feedback.

Here is a list of the changes I recorded during development.
– NEMS now requires you to run nems-init when you first deploy. This tool takes care of some of those “first boot” prerequisites like setting passwords and expanding your filesystem.
– Underlying OS upgraded to Raspbian Stretch.
– Kernel upgraded to 4.9.28.
– PHP upgraded to 7.0.19.
Reworking of nConf to make compatible with modern software (ie. PHP7.0, mySQLi).
– Maintenance and info scripts moved to /home/pi/nems-scripts.
– NEMS MOTD upon login now shows local IP address. Also improved how it determines some of the info (see in nems-scripts) and fixes a few bugs. Also set it up to rollover to wlan0 if no response on eth0, in case the user is on wifi.
– Temporary files and Monitorix image cache moved to RAM.
– Added RPi-Monitor as per Hesh’s comment. Reworked the Memory and CPU Frequency modules to correct the accuracy.
– Added nagios-api (JSON on Port 8090) as per Timothy Seibert’s request. [License]
– Added Webmin as per Hesh’s comment. Login as pi user with the password you created when initializing NEMS with the nems-init program.
– Added support for agentless Windows checks using WMI (big thanks to Ryan Siegel).
– Changed Apache log rotation to weekly (was previously daily).
– Upgraded nagvis to 1.9b16.
– Fixed sendemail paths in nConf to ease out-of-the-box email notifications (as they should just work now). Thanks so much to Jim for pointing this typo out!
– Enabled CPU governing (package cpufrequtils). On NEMS 1.0-1.1, NEMS was locked to 600MHz, but now it will automatically go up to 1200 MHz as needed.
– force resolver to generate new DNS resolv.conf at first boot (to ensure the detected DNS servers will be used rather than our development DNS servers which may not work for you).
– NEMS Migrator upgraded to allow direct migration from nagiospi to NEMS.
– Added Monitorix 3.9.0.
– Removed MySQL, replaced with MariaDB 10.1.22.
– Improve quality of Monitorix graphs used on NEMS Dashboard slideshow.
– Minor improvements to Monitorix page based on priority of service and image quality.
– Removed some old (obsolete) kernel modules, InnoDB logs and other bloat to reduce size of stock image.
– Added /var/www/nconf/temp to tmpfs. This way if someone breaks their nCONF (eg., pressing “Back” while generating config) they can just reboot to fix it 😀
nems-init and nems-migrator restore significantly reworked to correct initialization bugs from NEMS 1.2. Now, both initialization of a new NEMS deployment and an import from an old one should work without a hitch.
– nConf and NEMS-Migrator backups now require your password (as set with nems-init).
– NEMS-Migrator no longer replaces the MySQL database with backup. Instead, it now clears the database completely, reconciles your backup with the current set of available commands and services and then imports everything together into the fresh database and activates the hosts. This way, if you restore your NEMS 1.1 settings to NEMS 1.2.1, you don’t miss out on all the WMIC features (which your 1.1 backup would overwrite), for example.
– Documentation updated to reflect changes in commands and versioning.
– I built a quick but lovely interface for Monitorix to make it mobile responsive and a little more dynamic in its functionality.
– Distribution now available via BitTorrent (thanks to our partnership with The Category5 TV Network

Bug fixes:
– number of online users count on MOTD fixed.
– undefined constant in apache error log every 5 minutes leading to a bloated error log.
– added missing icons in check_mk.
– NEMS Migrator mail settings fixed when importing backup.nems from NEMS 1.0/nagiospi.
– Fixed MySQL Initialization Bug – was causing NEMS to lose configuration and no longer work.
– Wifi (wlan0) restored after it broken in 1.2 (due to Debian Stretch upgrade and incompatible firmwares for the Pi).
– Fixed nems-init user creation. In NEMS 1.2 it was not adding the new user to the “admin” group correctly in NEMS nCONF, so upon config generation, user would lose access to Nagios Core and other features requiring admin user.
– many miscellaneous bug fixes.

Rolling Updates:
– May 25, 2017 – Monitorix cronjob now detects which network connection is being used (ie., eth0/wlan0) and begins monitoring the correct one if it changes. Requires NEMS 1.2.1 or higher.
– May 26, 2017 – NEMS Migrator updated to fix bug in host presets. Was causing these two errors: “[ERROR] Failed to get host-alive check for host ‘NEMS’. Make sure the host is linked with a host-preset. Aborting.” and “Error: Cannot open main configuration file ‘/var/www/html/nconf/temp/test/Default_collector.cfg’ for reading!” – Thanks to Rick for giving me access to his affected system so I could fix this. Requires NEMS 1.2.1 or higher.
– May 27, 2017 – NEMS web interface has been updated to git repository so I can fix issues with it on the fly without forcing users to reinstall. Requires NEMS 1.2.2 or higher.
– May 30, 2017 – Monitorix graphs clear when rebooting the Pi. This is by design. However, they were meant to regenerate upon boot. Hesh found a bug that was causing the graphs not to generate since the service was not yet loaded. I rewrote the back-end to wait for a network connection, and for the service to respond, before moving on. Requires NEMS 1.2.1 or higher.
– June 1, 2017 – MOTD was displaying the disk usage as what was being used in the home folder. I realized this was absolutely pointless information, so rewrote this section to instead tell you the current % usage of your entire SD card (/dev/root). Requires NEMS 1.2.2 or higher.
– June 6, 2017 – NEMS-Init bug fixed: new user is not authorized_for_system_information, authorized_for_all_hosts, authorized_for_configuration_information, authorized_for_system_commands … and so-on. Wrote this into nems-init. Had caused users to not have access to all screens in Nagios Core. Also added the config to the NEMS Migrator backup. I also added the patch to so users don’t have to re-initialize to get the fix. It will retroactively fix the file, automatically. Requires NEMS 1.2.1 or higher.
– June 7, 2017 – Check_MK Multisite reports “user not found” on some screens. Similar issue to what was happening with Nagios Core: nems-init user was not being migrated correctly to Check_MK as pointed out by Rick. This has been fixed and a retroactive patch added to correct existing deployments. Requires NEMS 1.2.1 or higher.
– June 8, 2017 – Updated nems-migrator to support NEMS 1.2.2. Built nems-upgrade, which will roll NEMS 1.2.1 up to NEMS 1.2.2 without needing to reinstall. You can do this (backup first please) by typing: sudo nems-upgrade
– June 9, 2017 – Email notification service changed to automatically detect TLS. Changes will take effect immediately for new deployments, but if yours is already deployed (before June 9, 2017) please add the following to your service definitions in NEMS-nConf for notify-host-by-email and notify-service-by-email: -o tls=auto – add it immediately after /usr/bin/sendemail so it looks like this: /usr/bin/sendemail -o tls=auto -s $USER7$ ….
– June 21, 2017 – Created nems-benchmark and nems-mailtest.
– June 23, 2017 – Disabled swapfile.

Configuring Your NEMS Server:
Browse to: http://NEMS.local/nconf (or http://IPADDRESS/nconf)
Make changes to the config as needed for your environment (eg., add a host, service, edit a setting)
I’ve added a few sample configurations in there (v1.1+) to help you get started.
Click: “Generate Nagios Config”
If there are no errors, you will have the option to Deploy the new Nagios Config.

Using Your NEMS Server:
Browse to: http://NEMS.local  (or http://IPADDRESS)
The navigation should be fairly straightforward. To add hosts or configure your environment, use the built in nConf feature. To access reports, choose one of the reporting options under Reporting. To access info specific to your Pi (eg., memory usage) you’ll find those under System.

When you initialize NEMS, you will provide a password for the NEMS web interfaces. This username/password will be what you use to access most NEMS features (eg., nCONF, Nagios Core, Check_MK) however, Nagvis still uses admin:admin. Please be sure to change that when you first login to Nagvis. To login to Webmin, use the username pi and the password you entered for the pi user during nems-init.

Known Issues:

  • Nagios Core help “?” links give 404 according to – resolve and roll out a fix in NEMS 1.2.3.
  • Webmin administration of Network settings don’t stick, as per kevinds.
  • PNP4Nagios is installed, but not configured. You may encounter errors, which will be addressed in a future release.
  • If you encounter an issue, please report it in the comments below so I can work on a fix (or please post your fix to help others and possibly to have it integrated into the next build).

This list details features which are planned for future releases of NEMS. NEMS is released on a 6 month schedule, with a major release every May and November. Thanks to the NEMS Migrator, upgrading is a cinch.
– Further improve the mobile responsive layout for tablets and smartphones (It’s really rudimentary at the moment due to the nature of Nagios’ interface… frames? C’mon now.)
– Upgrade Nagios to Nagios Core 4. (?) – Unlikely since most of the cool things about NEMS rely on Nagios Core 3.5.1 … at least for now.
– Further streamline the implementation of Check_MK. Deploy check-mk-server.
– Expand the documentation to include setting up SMTP and mail alerts, including a new video demonstration on Category5 Technology TV.
– Create an OVA of NEMS for deployment on existing virtual infrastructures (just for the challenge/fun of it).
– Build a graphical interface for nems-init.
– Build a graphical interface for NEMS-Migrator’s “Restore” feature.
– Make it so nems-benchmark runs a nightly test and saves to a log file. Include this backup in backup.nems for support purposes.
– Create symlinks to nems-benchmark and nems-mailtest.
– I’m open to suggestions! Please post your comments at

Things I Will Not Do:
This is a list of features I will not implement.
– Raspberry Pi Zero, 1 & 2 support. Buy a Raspberry Pi 3. The higher performance of a Pi 3 is a major asset for a project like NEMS, so I will not be focusing any of my efforts on supporting legacy hardware.
– GUI/Desktop. NEMS is a Linux server. If you require a GUI/Desktop Environment, you’re doing it wrong. I have built a very nice, easy to use web interface, and have worked hard to provide good documentation to ease the complication of configuration for novice users. NEMS itself should not even have a screen connected to it. Just power and Ethernet. Everything happens either through your browser, or for advanced users, an SSH connection.

Who Creates NEMS:
Robbie Ferguson is the host of Category5 Technology TV. He’s the kind of guy who when he figures stuff out, he likes to share it with others. That’s part of what makes his show so popular, but also what makes NEMS possible.

Support What We Do:
This project is a part of something much bigger than itself, and we’re all volunteers. Please see our Patreon page for information about our network.
– Please support us by simply purchasing your Raspberry Pi at
– We have some support links on the NEMS menu, such as buying from Amazon using our partner link. Please use these every time you use those stores. A small percentage of your purchase will go toward our projects.
– Your donations are VERY MUCH appreciated – – Please consider how many hours (and hours) of work this project has saved you, and how much you’ll save on hardware and even electrical costs as you consider contributing
– Our network also has a Patreon page – Please consider becoming a patron –

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411 Comments on "NEMS – Nagios Enterprise Monitoring Server for Raspberry Pi 3"

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Really think we need a forum and/or wiki…

Anyways, I used Webmin to set static IPs, IPv4 and IPv6 addresses.. They don’t take…

Mind you I had this same issue on Raspbian, I was hoping I didn’t with NEMS.. What am I missing?


How can I check a non standard port using check_http?


I was wondering how to remove a service from a host when it inherits from its hostgroup?


hi everyone i installed Nems on RPI3 and i want to create wifi access point by using hostapd and dnsmasq but it doesn’t work.
any idea plz ?


I’ve overcome 4 dead or limped up sd cards and am fully upgraded to 1.2.2
All modules functional
I had an error when initially using Check_MK. There is a pending user change that needs to be activated. When i try, i get errno 2 and the change continues to pend. By manually starting mkeventd | service mkeventd start | changes are processed and all is good, but it has to be manually started after every reboot
How do I get mkeventd to automatically start at boot?


is it possible to set up a Read Only User?
I want to look at the events on the tablet, but I will not use the root user for it.

Thank you Marek


Why after some updates are downloaded (nem-scripts/ I can’t login again to nagios, like something is changing the password. How do I set a working password again without starting over?

Asha Saha

I forgot the password. How do I change it?


I’m a newbie trying to deploy nems 1.2.1 and 1.2.2 nems-upgrade
Getting dependency problems on mariadb server
“dependency problems prevent configuration of mariadb server, package”
dpkg: dependency problems prevent configuration of mariadb-server:
mariadb-server depends on mariadb-server-10.1 (>= 10.1.23-9+deb9u1); however:
Package mariadb-server-10.1 is not configured yet.

dpkg: error processing package mariadb-server (–configure):
dependency problems – leaving unconfigured
i followed your procedure to the letter, this was the result. I updated and upgraded but the error persists.
I just don’t know what to do next.


After discovering a bad PI, I’ve replaced and started over. Burned a fresh image, loaded and sudo nems-init. During that, I got:

What username would you like to use when
logging in to the NEMS web interfaces? reach
Password (again):
Adding password for user reach
Initializing new Nagios user
Job for mariadb.service failed because a timeout was exceeded.
See “systemctl status mariadb.service” and “journalctl -xe” for details.
ERROR 2002 (HY000): Can’t connect to local MySQL server through socket ‘/var/run/mysqld/mysqld.sock’ (2 “No such file or directory”)

You can SSH to it with the same info as before.

Graham Fletcher

Swap file 100% for last 2 days?
Hey gang – noticed that my swap file (100MB) on my NEMS has been at 100% for the last 2 days – any ideas?
Can I make it bigger?


Afternoon Chaps.

Anyone ran into this problem?
source_file FAILED
Source file does not exist (/tmp/Default_collector/)

Graham Fletcher

Found the place to put the “To:” address – under “Contacts” – per previous comment

Graham Fletcher

Must be missing something – can’t find where to configure the “To:” address for the alerts…



Quicker way to create services? I’ve got a couple of 24-port managed switches and through NConf have to keep cloning all the services – is there a quicker way? Through MYSQL or something?


Where do you find out how to configure email alerts?