Configure the Server
I assume you already configured the server using this guide: Nagios 4.4.1 Install from Source on Ubuntu 18.04
Log in to your Nagios server and su into the nagios user. You might have to su from root since that account usually doesn’t have a password.
[root@server]$ su - nagios
Out of curiosity, see if you have a .ssh folder.
[nagios@server]$ ls -alh ~/.ssh ls: cannot access '/home/nagios/.ssh': No such file or directory
More than likely you don’t. So that also means that there is no SSH key pair. Let’s create one.
[nagios@server]$ ssh-keygen
Basically mash the enter key until you see the fingerprint art. We don’t want a passphrase on this key because it will be used by automated scripts.
Now output the public key and save locally for later.
[nagios@server]$ cat .ssh/id_rsa.pub
Configure the Client(s)
Install Option #1 – Install From Source
[root@client]$ useradd -m -s /bin/bash nagios
[root@client]$ cd ~ [root@client]$ wget http://www.nagios-plugins.org/download/nagios-plugins-2.2.1.tar.gz [root@client]$ tar -xzvf nagios-plugins-2.2.1.tar.gz
By the way, this tar command was written without referencing the docs.
Install some required packages.
[root@client]$ apt-get install libgd-dev php build-essential unzip libnet-snmp-perl libperl5.26 libpq5 libsensors4 libsnmp-base libsnmp30 libtalloc2 libtdb1 libwbclient0 samba-common samba-common-bin smbclient snmp whois libmysqlclient-dev libssl-dev
Now install them
[root@client]$ cd ~/nagios-plugins-2.2.1 [root@client]$ ./configure --with-nagios-user=nagios --with-nagios-group=nagios [root@client]$ make [root@client]$ make install
Option #2 – Apt Install
[root@client]$ useradd -m -s /bin/bash nagios
[root@client]$ apt-get install nagios-plugins
I reference all plugin paths from the source install, so create a link if you do the deb package.
[root@client]$ ln -s /usr/lib/nagios/plugins /usr/local/nagios/libexec
Additional Plugin Install
[root@client]$ cd /usr/local/nagios/libexec [root@client]$ wget https://raw.githubusercontent.com/justintime/nagios-plugins/master/check_mem/check_mem.pl [root@client]$ chmod +x check_mem.pl
Authorize Connections
[nagios@client]$ mkdir ~/.ssh [nagios@client]$ vim ~/.ssh/authorized_keys
Paste in the SSH public key created earlier on the server.
Fix some file permissions.
[nagios@client]$ chmod 0600 ~/.ssh/authorized_keys
Test Commands
Run this lengthy command on the server:
[nagios@server]$ /usr/local/nagios/libexec/check_by_ssh -H 10.0.36.7 -C "/usr/local/nagios/libexec/check_load -w 2,1,1 -c 8,4,4" OK - load average: 0.14, 0.10, 0.09|load1=0.140;2.000;8.000;0; load5=0.100;1.000;4.000;0; load15=0.090;1.000;4.000;0;
Note that the load average returned is from the client, not the server.
Example Configuration
Below is an example config to start with. You can have a generic command that will call most any remote command. In the service definition, pass the remote command in the first parameter and the warning/critical thresholds in the following parameters. The fourth parameter, $ARG4$ can be used to pass any additional parameters if needed.
define command {
command_name check_by_ssh
command_line /usr/local/nagios/libexec/check_by_ssh -t 30 -H '$HOSTADDRESS$' -C "/usr/local/nagios/libexec/$ARG1$ -w '$ARG2$' -c '$ARG3$' $ARG4$"
}
define hostgroup {
hostgroup_name hg-linux
alias Linux Servers
}
define service {
use generic-service
hostgroup_name hg-linux
service_description CPU Load
check_command check_by_ssh!check_load!4,2,2!8,4,4
check_interval 1
retry_interval 1
}
define host {
use host-generic
host_name server-01
alias server-01
address 192.168.0.10
hostgroups hg-linux
}