CentOS Basic Configuration

The CentOS Project is a community-driven free software effort focused on delivering a robust open source ecosystem. For users, CentOS offers a consistent manageable platform that suits a wide variety of deployments. For open source communities, CentOS offers a solid, predictable base to build upon, along with extensive resources to build, test, release, and maintain their code.

1. Find Out Installed Package

[john@linux1 /]$ rpm -qa |less plymouth-0.8.9-0.24.20140113.el7.centos.x86_64 libsoup-2.48.1-3.el7.x86_64 libaio-0.3.109-13.el7.x86_64 dmidecode-2.12-9.el7.x86_64 passwd-0.79-4.el7.x86_64 bind-libs-lite-9.9.4-29.el7_2.2.x86_64 sed-4.2.2-5.el7.x86_64 grub2-2.02-0.34.el7.centos.x86_64 libcom_err-1.42.9-7.el7.x86_64 rsyslog-7.4.7-12.el7.x86_64 biosdevname-0.6.2-1.el7.x86_64 dracut-config-rescue-033-360.el7_2.x86_64 libacl-2.2.51-12.el7.x86_64 openssh-clients-6.6.1p1-23.el7_2.x86_64 xe-guest-utilities-6.5.0-1432.x86_64 libgcrypt-1.5.3-12.el7_1.1.x86_64 libpcap-1.5.3-8.el7.x86_64 cronie-1.4.11-14.el7.x86_64 iwl6050-firmware-41.28.5.1-43.el7.noarch iwl4965-firmware-228.61.2.24-43.el7.noarch iwl3160-firmware-22.0.7.0-43.el7.noarch libunistring-0.9.3-9.el7.x86_64 iwl100-firmware-39.31.5.1-43.el7.noarch perl-parent-0.225-244.el7.noarch newt-0.52.15-4.el7.x86_64 perl-Pod-Escapes-1.04-286.el7.noarch gdbm-1.10-8.el7.x86_64 perl-libs-5.16.3-286.el7.x86_64 ....... [john@linux1 /]$ rpm -qa |grep syslog rsyslog-7.4.7-12.el7.x86_64

2. Network Interface Configuration

DHCP or Static:
Step 1 » Check the network interface name by typing below command

[root@linux1 ~]# ip a 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN      link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00     inet 127.0.0.1/8 scope host lo        valid_lft forever preferred_lft forever     inet6 ::1/128 scope host         valid_lft forever preferred_lft forever 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000     link/ether 9a:4a:27:66:a4:4c brd ff:ff:ff:ff:ff:ff     inet 10.9.1.26/24 brd 10.91.128.255 scope global eth0        valid_lft forever preferred_lft forever     inet6 fe80::984a:27ff:fe66:a44c/64 scope link         valid_lft forever preferred_lft forever

Here “lo” is the loopback interface and “eth0” is the network interface that you need to configure .

Step 2 » you can see the file named ifcfg-eth0 ( Interface name ) in the location “/etc/sysconfig/network-scripts/” , open the file and you can see the lines as below, which is static ip 10.9.1.26 assigned to interface eth0

1 2 3 4

[root@linux network-scripts]$ cat ifcfg-eth0TYPE=Ethernet BOOTPROTO=static NAME=eth0 ONBOOT=yes IPADDR=10.9.1.26 NETMASK=255.255.255.0 DEVICE=eth0

Just modify the lines like this

DEVICE="eth0" HWADDR="00:22:19:09:4D:3C" NM_CONTROLLED="yes" ONBOOT="yes"    # Interface enabled BOOTPROTO="dhcp"  #Assigning IP from DHCP

Step 3 » Start the network service and you can see the status as below .

[root@linux1~]# service network start
Bringing up loopback interface:                [  OK  ]
Bringing up interface p4p1:
Determining IP information for p4p1... done.   [  OK  ]

3. Disable IPv6

There are three different ways to do it. 

3.1 Edit Sysctl.conf file

vi /etc/sysctl.conf

Add following two lines:

net.ipv6.conf.all.disable_ipv6 =1
net.ipv6.conf.default.disable_ipv6 =1

if only want to disable IPv6 for specific network card, such as  enp0s3, add following line instead:

net.ipv6.conf.enp0s3.disable_ipv6 =1

Save and exit VI. 

Run following command to make the change effect:

sysctl -p

3.2 

echo 1>/proc/sys/net/ipv6/conf/all/disable_ipv6echo 1>/proc/sys/net/ipv6/conf/default/disable_ipv6

3.3 

sysctl -w net.ipv6.conf.all.disable_ipv6=1sysctl -w net.ipv6.conf.default.disable_ipv6=1

Note: Some caveats to be aware from How to disable IPv6 on Linux.

4. Install IPTABLES 

For Iptables lovers , here are some commands to install it to replace default firewall :

yum install policycoreutils iptables-services -y
systemctl stop firewalld.service
systemctl disable firewalld.service
service iptables restart

5. TBC

Reference:

• http://www.krizna.com/
• Basic Linux Commands (Tips and Tricks)