Introduction

Unbound is a validating, recursive, and caching DNS server. Having said that, Unbound DNS server cannot be used as an authoritative DNS server, which means it cannot be used to host custom domain name records. As a result, if your goal is to build a cache-only or forwarding DNS server, Unbound may be your preferred choice, as it does just that and it does it well.

Objective

The objective is to provide quick and easy to follow installation and configuration guide for the Unbound cache-only DNS server on Redhat 7 Linux. At the end of this guide you will be able to use Unbound DNS server from all clients on your local area network.

Requirements

Privileged access to your Redhat 7 Linux server with configured standard RedHat repositories.

Difficulty

MEDIUM

Conventions

  • # - requires given linux commands to be executed with root privileges either directly as a root user or by use of sudo command
  • $ - requires given linux commands to be executed as a regular non-privileged user

Instructions

Unbound and DNS tools installation

In the first step we are going to install the actual Unbound DNS server as well as DNS tools which will be eventually used to test your DNS cache-only server configuration. Given that you have your Redhat repository configured correctly you can install both by executing the following linux command:
# yum install unbound bind-utils

Objective

The objective is to permanently disable a last login message after user terminal or ssh login on Redhat Linux. Example:
$ ssh This email address is being protected from spambots. You need JavaScript enabled to view it.
	
This email address is being protected from spambots. You need JavaScript enabled to view it.'s password: 
Last login: Tue Dec  6 11:23:11 2016 from 10.1.1.3
rhel linux last login message disable or clear

Requirements

Privileged access to your Redhat Linux server.

Difficulty

EASY

Conventions

  • # - requires given linux commands to be executed with root privileges either directly as a root user or by use of sudo command
  • $ - requires given linux commands to be executed as a regular non-privileged user

Instructions

Single user

To permanently suppress a Last Login message as per on user basis, create a hidden .hushlogin file inside a user's home directory. For example to suppress a Last Login message for a linuxconfig user run:
# touch /home/linuxconfig/.hushlogin

Objective

By default the regular user does not have an ability to execute commands with root privileges. As a result the following message will appear:
$ sudo -i
[sudo] password for linuxconfig: 
linuxconfig is not in the sudoers file.  This incident will be reported.
redhat 7 user not in sudoers file
The objective is to gain a superuser ( root ) access on Redhat 7 Linux server using sudo command.

Requirements

Privileged root access to your Redhat 7 Linux server installation.

Difficulty

EASY

Conventions

  • # - requires given linux commands to be executed with root privileges either directly as a root user or by use of sudo command
  • $ - requires given linux commands to be executed as a regular non-privileged user


Instructions

Add user to WHEEL group

Using your current shell or log in as a root user execute the following linux command to add any user you wish to grant a sudo access. The example below will give a sudo access to linuxconfig user:
# usermod -G wheel linuxconfig

Objective

The objective is to mount a CD/DVD block device with ISO 9660 disk image/media.

Requirements

Privileged access to your Redhat 7 system.

Difficulty

EASY

Conventions

  • # - requires given linux commands to be executed with root privileges either directly as a root user or by use of sudo command
  • $ - requires given linux commands to be executed as a regular non-privileged user

Instructions

Locate Block device

First we need to find a correct CD/DVD block device. To do this execute a command blkid:
# blkid
/dev/xvda1: UUID="b4f59ae4-f5c8-49c2-94cf-103e10eef407" TYPE="xfs" 
/dev/xvda2: UUID="zcwKzx-w2EM-NH4E-wQW3-7QTu-62JZ-s6Ok0j" TYPE="LVM2_member" 
/dev/sr0: UUID="2016-10-19-18-32-06-00" LABEL="RHEL-7.3 Server.x86_64" TYPE="iso9660" PTTYPE="dos" 
/dev/mapper/rhel-root: UUID="ea637699-1d70-49ef-9a0a-54bc87d1e571" TYPE="xfs" 
/dev/mapper/rhel-swap: UUID="617ccf82-602c-472d-bff6-484d95530293" TYPE="swap" 

Objective

Resetting the root password in RHEL7/CentOS7/Scientific Linux 7

Requirements

RHEL7 / CentOS7 / Scientific Linux 7

Difficulty

MODERATE

Instructions

Things have changed in the RHEL7 world and so has the preferred way of resetting the root password. Although the old way of interrupting the boot process (init=/bin/bash) still works, it is no longer bulletproof and recommended. 'Systemd' uses 'rd.break' to interrupt the boot. Let's have a quick walk through the whole procedure.

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