Raspberry Pi 3 Specs:

• SoC: Broadcom BCM2837
• CPU: 64-bit 1.2GHz quad-core ARM Cortex-A53 CPU
• GPU: Broadcom VideoCore IV
• RAM: 1GB LPDDR2 (900 MHz)
• Networking: 10/100 Ethernet, 2.4GHz 802.11n wireless
• Bluetooth: Bluetooth 4.1 Classic, Bluetooth Low Energy
• Storage: microSD
• GPIO: 40-pin header, populated
• Video: HDMI – VideoCore IV 3D
• Audio: 3.5mm analogue audio-video jack,
• USB: 4× USB 2.0
• Other Ports: Camera Serial Interface (CSI), Display Serial Interface (DSI)
• Power: 2.5 Amps
• Operating system support – Linux and Unix or Windows 10 IoT

Below I have shared some photos of my Raspberry Pi 3 B that I had planned to possibly install Nagios on to monitor my home network but before I find a main use for it I plan to try a bunch of different tasks with it and experiment a bit.

This guide contains network configuration steps in both GUI and command mode.

Setup Network on Centos 7

At the command prompt type

nmcli d

which will give you a quick identification of Ethernet cards installed on your machine

Here we have 2 interfaces named “enp0s17” and “enp0s18“. It might be different in your case however.

Setup GUI Mode

Recommended for beginners

Step 1

Type in this command

nmtui

to open network manager and press enter after choosing “edit  a connection” (use tab for choosing options)

Step 2

Now you can see all network interfaces, choose one and click “Edit”

DHCP Configuration

Step 3

for dhcp,

1. Choose “Automatic” in IPv4 CONFIGURATION.
2. Choose Automatic connect check box.
3. Press Ok and quit Network manager.

Now restart network services by typing this command

systemctl restart network

Now your server will get an IP from DHCP

Step 4

For manual IP address,
1. Choose “Manual” in IPv4 CONFIGURATION.
2. Add IP Address with Subnet , Gateway and DNS server ( Refer below image ).
3. Choose Automatic Connect check box.
4. Press OK and quit Network manager.

Now restart network services by typing this command

systemctl restart network

Now your server will have a static IP.

Command Mode

Step 1

Network interface config files are located in /etc/sysconfig/network-scripts/ directory. Open ifcfg-enp0s17 file ( For interface enp0s17 ) and you can see the content like below.

[root@krizna ~]# vi /etc/sysconfig/network-scripts/ifcfg-enp0s17
TYPE=Ethernet
BOOTPROTO=none
DEFROUTE=yes
IPV4_FAILURE_FATAL=no
IPV6INIT=yes
IPV6_AUTOCONF=yes
IPV6_DEFROUTE=yes
IPV6_FAILURE_FATAL=no
NAME=enp0s17
UUID=7f1aff2d-b154-4436-9497-e3a4dedddcef
ONBOOT=no
HWADDR=00:0C:29:A1:B5:D6
PEERDNS=yes
PEERROUTES=yes
IPV6_PEERDNS=yes
IPV6_PEERROUTES=yes

DHCP Configuration

Step 2

For DHCP
Find the below lines in config File.

BOOTPROTO=none
ONBOOT=no

and replace with

BOOTPROTO=dhcp
ONBOOT=yes

Now Restart network service by typing below command.

systemctl restart network

Now your server will get IP Address from DHCP

» Static configuration

Step 3 » For Static IP.
Find the below lines in config File.

BOOTPROTO=none
ONBOOT=no

and replace with

BOOTPROTO=static
ONBOOT=yes

And add the below lines at the end of the file.

IPADDR=172.27.0.32
NETMASK=255.255.255.0
GATEWAY=172.27.0.1
DNS1=172.27.0.5

File will look like below after changes.

TYPE=Ethernet
BOOTPROTO=static
DEFROUTE=yes
IPV4_FAILURE_FATAL=no
IPV6INIT=yes
IPV6_AUTOCONF=yes
IPV6_DEFROUTE=yes
IPV6_FAILURE_FATAL=no
NAME=enp0s17
UUID=f0c5b37d-299a-43cb-b74b-618bb252d129
ONBOOT=yes
HWADDR=00:0C:29:A1:B5:CC
IPV6_PEERDNS=yes
IPV6_PEERROUTES=yes
IPADDR=192.168.1.10
NETMASK=255.255.255.0
GATEWAY=192.168.1.1
DNS1=192.168.1.5

Now Restart network service by typing below command.

systemctl restart network

Now Interface will have static IP.
Additionally you can use /etc/sysconfig/network file for hostname and DNS .

HOSTNAME=server.krizna.com
DNS1=192.168.1.5
DNS2=8.8.8.8
SEARCH=krizna.com

I hope this helps anybody reading. Have a great day!

Well I’ve finally have gotten Nagios 4 to work with the help of Nagios Support and these were the steps that I took to complete it.

The Orange text are commands to input into CentOS. I used a minimal install of CentOS.

The first problem I always ran into is that CentOS wasn’t online. I took these steps to resolve it  then I ran the commands below

yum install wget
yum install nano

Net tools isn’t required but I find it useful for troubleshooting network issues so I installed it anyways.

yum install net-tools

If installing on a Raspberry PI , I found I had to install these tools as well.

yum install wzip
yum install make

SELINUX:

setenforce 0
nano /etc/selinux/config

change enforcing -> disabled, save and close.

INSTALL PRE-REQS:

yum install httpd php php-cli gcc glibc glibc-common gd gd-devel net-snmp openssl-devel wget unzip -y

useradd nagios
groupadd nagcmd
usermod -a -G nagcmd nagios
usermod -a -G nagcmd apache

DOWNLOAD & INSTALL NAGIOS:

cd /tmp
wget https://assets.nagios.com/downloads/nagioscore/releases/nagios-4.1.1.tar.gz
wget http://www.nagios-plugins.org/download/nagios-plugins-2.1.1.tar.gz
tar zxf nagios-4.1.1.tar.gz
tar zxf nagios-plugins-2.1.1.tar.gz
cd nagios-4.1.1
./configure --with-command-group=nagcmd
make all
make install
make install-init
make install-config
make install-commandmode
make install-webconf
htpasswd -c /usr/local/nagios/etc/htpasswd.users nagiosadmin
service httpd start
service nagios start

PLUGINS:

cd /tmp/nagios-plugins-2.1.1
./configure --with-nagios-user=nagios --with-nagios-group=nagios --with-openssl
make all
make install
service nagios restart

POSSIBLE ERRORS:
Can’t access web page? Check firewalld and at port 80 through.
firewall-cmd –zone=public –add-port=80/tcp –permanent
firewall-cmd –reload

Still can’t access web page? Check IPV6 listening in the apache configuration.
modify /etc/httpd/conf/httpd.conf
Listen 0.0.0.0:80
service httpd restart