Linux Book Center

                 Domain Naming System is a naming convention for computers, which is connected to the internet. Its not possible to remember all the web server IP Address. So, here its comes as a resolution for this. Because, It will translate from the IP Address to Name and Name to IP Address.

We are going to see how to setup DNS in RHEL 7 and Cent OS 7.

Requirement:

Host Name: server.linuxbookcenter.com
IP Address: 192.168.43.226

Packages:
1. bind
2. bind-utils

Installing bind packages:

[root@server]# yum -y install bind*

BIND Configuring:

We are going to configure the “/etc/named.conf” file for BIND configuration.
open the file using vi editor and comment out two lines like shown below. This lines allow your DNS to listen all the IP Address.

Add your network by modifying “allow-query” line in the named.conf file to all the computers to do name transition which connected in this network

#vi /etc/named.conf

[root@server ~]# vi /etc/named.conf 

options {
 #listen-on port 53 { 127.0.0.1; };
 #listen-on-v6 port 53 { ::1; };

 directory "/var/named";
 dump-file "/var/named/data/cache_dump.db";
 statistics-file "/var/named/data/named_stats.txt";
 memstatistics-file "/var/named/data/named_mem_stats.txt";

 allow-query { localhost; 192.168.43.226/24;}; 

And the zone file information will be available in “/etc/named/rfc1912.zones” file by default. Here we should modify the entry based on our requirement.

Note: This entry contains the forward and reverse zone file names.

This file location included in “/etc/named.conf” file. Find the below screenshot.

Now save and exit from the “/etc/named.conf” file.

Provide zone file information entry:

edit the “/etc/named.rfc1912.zones”  file to provide the zone file information entries.

[root@server ~]# vi /etc/named.rfc1912.zones

And make the below entries or modify the existing one based on our requirement.

zone "localhost.localdomain" IN {
 type master;
 file "named.localhost";
 allow-update { none; };
};

zone "lbcdomain.com" IN {
 type master;
 file "fwd.lbcdomain.com.db";
 allow-update { none; };
};

zone "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa" IN {
 type master;
 file "named.loopback";
 allow-update { none; };
};

zone "1.0.0.127.in-addr.arpa" IN {
 type master;
 file "named.loopback";
 allow-update { none; };
};

zone "226.43.168.192.in-addr.arpa" IN {
 type master;
 file "43.168.192.db";
 allow-update { none; };
};

Create and Configure the Zone files:

Default location for the zone file’s :  /var/named

create a forward zone file with “fwd.lbcdomain.com.db”   name.

[root@server named]# vi /var/named/fwd.lbcdomain.com.db

$TTL 86400
@ IN SOA server.lbcdomain.com. root.lbcdomain.com. (
                            20171129 ; serial
                            3600     ; refresh
                            1800 ; retry
                            604800 ; expire
                            86400 ) ; minimum
;Name server info
@ IN NS server.lbcdomain.com.

;Name server Ip info
server IN A 192.168.43.226

;Mail exchanger
lbcdomain.com. IN MX 10 mail.lbcdomain.com.

;A - Record Hostname to IP Address
www IN A 192.168.43.10
mail IN A 192.168.43.15

;CNAME Record
ftp IN CNAME www.lbcdomain.com.

Save and exit from the file and create reverse zone file with the name of “43.168.192.db”

PTR – Pointer

SOA – Start of Authority

[root@server ~]# vi /var/named/43.168.192.db

$TTL 86400
@ IN SOA server.lbcdomain.com. root.lbcdomain.com. (
                        20171129 ; serial
                        3600 ; refresh
                        1800 ; retry
                        604800 ; expire
                        86400 ) ; minimum

;Name server info
@ IN NS server.lbcdomain.com.

;Reverse lookup info
226 IN PTR server.lbcdomain.com.

;PTR Record for IP to Hostname
10 IN PTR www.lbcdomain.com.
15 IN PTR mail.lbcdomain.com.

We completed all the configuration and we should restart the bind service.

[root@server ~]# systemctl restart named

Make it enabled in system startup.

[root@server ~]# systemctl enable named

Output:

Will see how to check and change the hostname in RHEL 7/ Cent OS 7

Using “hostname” command will check the existing hostname.

nmtui:

Will use this Network managet tool to set the hostname and it will edit the “/etc/hostname” in background.

We are going to see Linux kernel update in this post.
Note: Here kernel is already upgraded one. So, we can’t show different here

Using “uname -r” command will check the current kernel version.

[root@localhost ~]# uname -r
3.10.0-514.el7.x86_64


To update the kernel use the below command.

[root@localhost ~]# yum install kernel*



Again use the uname -r command to check whether the kernel has been updated or not.

[root@localhost ~]# uname -r
3.10.0-514.el7.x86_64

Will undo the upgrade or installation using yum. For that have to check the current activity of yum using “yum history list”

We can use the ID to undo the upgrade/ installed packages.

Now am going to use ID 8 do undo the kernel upgrade

#yum history undo 8




Now use the "yum history list" command to check

Again will check whether the kernel upgrade has been removed or not.

Will use same yum option to upgrade/ undo any packages in Linux.

We can see How to do Ubuntu operating system 17.04 installation in this post.
Step 1 : Boot the machine using OS media and click on “Install Ubuntu”.

Step 2:  Now select the language and click on continue to proceed further.

Step 3:  We could see there are two check box which is mentioning here to enable the “Downloading                 updates while installation and Third party software installation” by checking this two box.

Step 4:  Now in next screen will ask for installation type. On this screen select as per your requirement. I’m going to select “Something else” option and click continue.

Step 5: Select the free space and click on “+”

Step 6:  Provide the required information to create root(/) file system and click ok.

Step 7:  Follow above step to create filesystem whatever you want and here i am create one more directory called “swap”  which doesn’t have filesystem type and it is called as virtual memory as well.

Step 8: Now you could see the created filesystem lists like below.

Step 9:  Click on “Install now” to continue with installation and click continue to confirm the changes.

Step 10: Select the time zone from next screen.

Step 11:  Than select Keyboard layout language.

Step 12:  Provide the username details which we need to create new user and which will help us to manage the system(This is not a default administrator – root) and click continue.

Step 13:  Finally files will be copied from the media to our hard disk and will ask for reboot as a final step.

Now the Ubuntu 17.04 has been installed successfully and ready to use.

Thanks for supporting.

Reference: Ubuntu Docs