Static ip and DNS

Configuration

Edit file /etc/sysconfig/network-scripts/ifcfg-ens33:

DEVICE=ens33
BOOTPROTO=none
BROADCAST=192.168.0.255
HWADDR=00:0A:BC:DE:FF:1E
IPADDR=192.168.0.16
NETMASK=255.255.255.0
ONBOOT=yes
GATEWAY=192.168.0.1
TYPE=Ethernet
IPV6INIT=no
DNS1=192.168.0.2
DNS2=192.168.0.3
DOMAIN=my-domain.local

In the file /etc/resolv.conf you will see these lines:

search my-domain.local
nameserver 192.168.0.2
nameserver 192.168.0.3

Troubleshooting

My network interface ens33 is not in the list of the ifconfig command

#!/bin/bash
 
# get current device (i.e. ens33)
currentDevice=`nmcli d | grep connected | awk '{split($1,a,"\t"); print a[1]}'`
 
echo "start manually device $currentDevice"
ifup $currentDevice
 
echo "edit /etc/sysconfig/network-scripts/ifcfg-$currentDevice and set ONBOOT=yes"
sed -i "s/^\(ONBOOT=\).*$/\1yes/g" /etc/sysconfig/network-scripts/ifcfg-$currentDevice
 

“Device ens33 does not seem to be present” (after cloning the server)

Edit /etc/udev/rules.d/70-persistent-net.rules
And update the MAC adress:

# PCI device 0x8086:0x100f (e1000)
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="00:0A:BC:DE:FF:1E", ATTR{type}=="1", KERNEL=="eth*", NAME="ens33"

show gateway IP address

ip route show

Use external repositories

#!/bin/bash
 
echo "get release rpm from fedora"
yum -y install epel-release
 
#echo "enable Red Hat Software Collections (SCL) repository"
#yum -y install centos-release-scl
 
echo "clean all and update"
yum clean all
yum -y install deltarpm
yum -y update
 

Firewall

#!/bin/bash
 
echo "install firewalld"
yum -y install firewalld
 
echo "activate firewalld at startup"
systemctl enable firewalld.service
 
echo "start service"
systemctl start firewalld.service
 

NTP server (date & time)

#!/bin/bash
 
echo "install ntp"
yum -y install ntp
 
echo "activate ntp on boot"
systemctl enable ntpd.service
 
echo "start ntp service"
systemctl start ntpd.service
 

SELinux

Edit the file : /etc/selinux/config and set SELINUX to disabled like this:

#!/bin/bash
 
sed -i "s/SELINUX=enforcing/SELINUX=disabled/g" /etc/selinux/config
 
echo "disable selinux temporary (without reboot)"
setenforce 0

Note: changes will take effect after reboot.

Usefull commands

#!/bin/bash
 
echo "install ifconfig"
yum -y install net-tools
 
echo "install locate"
yum -y install mlocate
updatedb
 
echo "install wget"
yum -y install wget
 
echo "install dos2unix"
yum -y install dos2unix
 
echo "install telnet client"
yum -y install telnet
 
echo "install zip tools"
yum -y install zip unzip
 

Autoupdate

#!/bin/bash
 
## Package Manager
echo "install yum-cron"
yum -y install yum-cron
 
echo "activate yum-cron at startup"
systemctl enable yum-cron.service
 
echo "start service"
systemctl start yum-cron.service
 

Change hostname

• Edit /etc/sysconfig/network
• Change hostname value
• Reboot

Activate nrpe (for nagios)

#!/bin/bash
 
echo "install nrpe"
yum -y install nrpe nagios-plugins-all
 
echo "start nrpe on boot"
systemctl enable nrpe.service
 
echo "add service nrpe (port 5666) to firewall"
firewall-cmd --permanent --zone=public --add-port=5666/tcp
 
echo "sudoers configuration (deal with issue 'NRPE: Unable to read output')"
chmod 755 /etc/sudoers
sed -i "s/^\(Defaults\s*requiretty\)/#\1/" /etc/sudoers
chmod 0440 /etc/sudoers
 
echo "allow every one to connect to nrpe"
sed -i "s/^\(allowed_hosts\)/#\1/" /etc/nagios/nrpe.cfg
 
echo "start nrpe"
systemctl start nrpe.service