A Python script simulating munin-node, which can be called through SSH directly using the below instructions.
It is targeted towards TrueNAS Core / FreeNAS, but may be used on other system that don't allow installation of munin-node (like ESXi). The goal is to be persistent over reboots.
Requirements are SSH and Python.
In the TrueNAS Core (FreeNAS) GUI, perform following steps:
- Storage -> Pools -> add new dataset called "munin-data"
- Services -> SSH -> enable and start automatically
- Accounts -> Users -> Add
- Username: munin
- Password: 1neDifficultToGuessPasswordIsProvidedHere22
- Home Directory: /mnt/mypool/munin-data
- Note that this needs to be part of /mnt per the GUI - e.g. using /home/munin/ will not work.
- Also, note that this needs to be set through the GUI. A "pw user mod -n munin -d /mnt/mypool/munin-data" will not persist reboots.
On the server running Munin Master, generate a new SSH key pair:
root@MonServ:~# su - munin --shell=/bin/bash
munin@MonServ:~$ ssh-keygen
Generating public/private rsa key pair.
Enter file in which to save the key (/var/lib/munin/.ssh/id_rsa):
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /var/lib/munin/.ssh/id_rsa.
Your public key has been saved in /var/lib/munin/.ssh/id_rsa.pub.
The key fingerprint is:
(...)
Copy over the public id to the Munin Node (this will automatically create an .ssh/ directory with a file 'authorized_keys' containing the public SSH key of the Munin Master):
munin@MonServ:~$ ssh-copy-id [email protected]
The authenticity of host '10.0.0.2 (10.0.0.2)' can't be established.
ECDSA key fingerprint is 7d:39:e9:5f:25:71:cf:15:04:18:a8:8a:42:90:73:35.
Are you sure you want to continue connecting (yes/no)? yes
/usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
/usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys
[email protected]'s password:
Number of key(s) added: 1
Now try logging into the machine, with: "ssh '[email protected]'"
and check to make sure that only the key(s) you wanted were added.
munin@MonServ:~$
As per the suggestion, login onto TrueNAS without a password (as a test) and insert a 'command' section to .ssh/authorized_keys, dictating which script should be started upon login and securing the login a bit more:
command="./munin-node-sim.py",no-port-forwarding,no-x11-forwarding,no-agent-forwarding ssh-rsa AAAAB3NzaC1yc2EAAAA<snip> munin@MonServ
On the server running the Munin Node (TrueNAS in this case), place the munin-node-sim.py file in the /home/munin/ folder and ensure a plugins/ directory exists with some plugins.
Now test:
munin@MonServ:~$ ssh [email protected]
# munin node at servername
fetch load
load.value 0.14
.
config load
graph_title Load average
graph_vlabel load
load.label load
graph_args --base 1000 -l 0
graph_scale no
graph_category system
load.warning 10
load.critical 120
graph_info The load average of the machine describes how many processes are in the runqueue (scheduled to run "immediately").
load.info Average load for the five minutes.
.
list
ip_forwarding ip_host df ip_drops load
Proceed to the actual Munin configuration on the Munin Master. Add following section in /etc/munin/munin.conf:
[TrueNAS-v1.mydomain.com]
address ssh://[email protected]
use_node_name no
Now try to execute the Munin plugin manually as a test:
root@MonServ:~# su - munin --shell=/bin/bash
munin@MonServ:~$ /usr/share/munin/munin-update --debug --nofork --host TrueNAS-v1.mydomain.com
→ should work and yield output as “FETCH from <service>”
Some example plugins are included for use on TrueNAS (feel free to add more).
df: Python script plugin that shows disk usage in % of the disk poolsload: Shell script plugin that shows the 5 minute average
It should be possible to use any TrueNAS compatible plugin. Feel free to update the below list with supported ones or add them to the plugins/ directory in this repo.
- Generic FreeBSD Munin plugins from https://github.com/munin-monitoring/munin/tree/master/plugins/node.d.freebsd
- ZFS related plugins from https://github.com/freebsd/freebsd-ports/tree/main/sysutils/munin-node/plugins
- NUT plugin from https://github.com/munin-monitoring/contrib/blob/master/plugins/power/nut (plugin filename: nut_ups_AT_localhost)
- Add battery.runtime if required
- ip_host, ip_drops, ip_forwarding from https://github.com/farrokhi/freebsd-munin-plugins
MIT