The python version 3 is not available from CentOS 7 repositories. The following config will show you how to compile and install Python version 3 from source on CentOS 7 Linux. Let's start by installation of some required tools which you will need for this tutorial.
# yum install yum-utils make wget
Next, we will install all python build prerequisites to meet all compilation requirements:
# yum-builddep python

In order to install VirtualBox virtualization software on CentOS Linux first install prerequisites:
yum install kernel-devel gcc
Next, download relevant RPM package to your CentOS version from https://www.virtualbox.org/wiki/Linux_Downloads.

Once downloaded, navigate to directory where you have downloaded the VirtualBox RPM and execute check its signature eg.:
# rpm --import https://www.virtualbox.org/download/oracle_vbox.asc
# rpm --checksig VirtualBox-5.0-5.0.0_101573_el7-1.x86_64.rpm
If signature match use below command to install VirtualBox package while replacing package version number with the one you have downloaded previously:
yum localinstall VirtualBox-5.0-5.0.0_101573_el7-1.x86_64.rpm

The default installation of CentOS Linux 7 does not come with installation of adobe flash player for Firefox web browser and thus must be installed separately. To begin flash player installation first we need to include Adobe's repository. This can be achieved by the following linux command:
# yum -y install http://linuxdownload.adobe.com/linux/x86_64/adobe-release-x86_64-1.0-1.noarch.rpm
Confirm that Adobe repository has been included:
# yum repolist | grep -i adobe
adobe-linux-x86_64      Adobe Systems Incorporated                            2
At this stage we are ready to install adobe flash player using yum command:
# yum install flash-plugin

This article will describe a way on how to change/set a primary display on CentOS/RHEL 7 with dual monitors and GNOME. The easiest and perhaps recommended way is to use GUI and navigate to Applications->System Tools->Settings->Displays.
show current primary display redhat/centos

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The current primary screen is highlighted by a black top bar. To change you primary display simply drag-n-drop the black top bar from one screen to another:
change primary display redhat/centos
. Another alternative is to you command line tool xrandr. First get all your connected screens:
$ xrandr | grep -w connected
DVI-D-1 connected 1680x1050+0+0 (normal left inverted right x axis y axis) 474mm x 296mm
HDMI-1 connected primary 1920x1080+1680+0 (normal left inverted right x axis y axis) 598mm x 336mm

If you currently do not hold a Red Hat Subscription and yet you need to enable EPEL ( Extra Packages for Enterprise Linux ) repository on your RHEL 7 Linux you need to download and install following file directly from Fedora project:
epel-release-7-5.noarch.rpm

Once you configure NTPD service on your RHEL7 linux you will need to allow traffic through the firewall on port 123. Te following linux command will enable all public traffic on UDP port 123:
# firewall-cmd --zone=public --add-port=123/udp --permanent
success

Below you can find a list of most frequently used commands in association with systemd targets:
List current active default target
# systemctl get-default
List all active systemd targets:
# systemctl list-units --type target

When not using NTP you may need to set your system time manually. You have two options to set time and date on your RHEL7 linux. First option is to use date command to do this job or engage dedicated systemd timedatectl command. By default and without any arguments timedatectl will display a current time, local, universal and RTC times:
[root@rhel7 ~]# localectl
   System Locale: LANG=en_AU.iso88591
       VC Keymap: us
      X11 Layout: us
[root@rhel7 ~]# timedatectl
      Local time: Thu 2014-09-04 18:30:11 WST
  Universal time: Thu 2014-09-04 10:30:11 UTC
        RTC time: Thu 2014-09-04 10:30:10
        Timezone: Australia/Perth (WST, +0800)
     NTP enabled: n/a
NTP synchronized: no
 RTC in local TZ: no
      DST active: n/a

Use localectl to see your currently active locale on Redhat 7 Linux. For example:
[root@rhel7 ~]# localectl
   System Locale: LANG=en_AU.UTF-8
       VC Keymap: us
      X11 Layout: us

The following linux command will list all available locales currently available on the Redhat 7 system:
[root@rhel7 ~]# localectl list-locales
The list of all available locales on your system my be quite long so use grep command to narrow down your search. Bellow command will display for example all German available locales:
[root@rhel7 ~]# localectl list-locales | grep ^de
de_AT
de_AT.iso88591
de_AT.iso885915@euro
de_AT.utf8
de_AT@euro
de_BE
de_BE.iso88591
de_BE.iso885915@euro
de_BE.utf8
de_BE@euro
de_CH
de_CH.iso88591
de_CH.utf8
de_DE
de_DE.iso88591
de_DE.iso885915@euro
de_DE.utf8
de_DE@euro
de_LU
de_LU.iso88591
de_LU.iso885915@euro
de_LU.utf8
de_LU@euro
deutsch

Instead of changing a hostname on your Redhat 7 server manually by editing /etc/hostname you may preferably use a dedicated command hostnamectl to do this job. By default when no other options are supplied the hostnamectl command will display basic information including static hostname:
[root@rhel7 ~]# hostnamectl 
   Static hostname: rhel7
         Icon name: computer
           Chassis: n/a
        Machine ID: 75387b56d72b44b380810499805ec28a
           Boot ID: 6ad251d0e12a10e3af1894eae5fe5cb6
    Virtualization: oracle
  Operating System: Red Hat Enterprise Linux Server 7.0 (Maipo)
       CPE OS Name: cpe:/o:redhat:enterprise_linux:7.0:GA:server
            Kernel: Linux 3.10.0-123.el7.x86_64
      Architecture: x86_64

The easiest way to create a Cisco VPN client connection on Redhat 7 Linux is to use vpnc client which is an opensource alternative to Cisco VPN client. Let's start by VPNC installation on RHEL7. The VPNC package is located within EPEL ( Extra Packages for Enterprise Linux 7 ) repository thus first enable EPEL repository:
# subscription-manager repos --enable=rhel-7-server-optional-rpms

Previously we have talked about how to configure a default gateway on RHEL7 Linux. This time we will talk about how to add a static route on RHEL7 Linux.

Any network we are trying to reach is accessed via default gateway only if it is not implicitly overwritten by another static route definition. Let's have a look at a current routing table on our Redhat 7 Linux box:
root@rhel7 ~]# ip route show
default via 10.1.1.1 dev enp0s3  proto static  metric 1024 
10.0.0.0/8 dev enp0s3  proto kernel  scope link  src 10.1.1.110

The way on how you can reset a forgotten root password on a Linux system have not changed for many years. Resetting a root password on RHEL7 Linux system have not change much except that now we deal with SElinux and the system is now using systemd instead of init. Nevertheless, those who have already did reset root password on the Linux system will be with the following steps familiar. Here is the procedure of what needs to be done in order to recover a forgotten root password on Redhat 7 Linux:
  1. We need to edit GRUB2 boot menu and enter user single mode
  2. Next, we need to remount / partition to allow read and write
  3. Reset the actual root password
  4. Set entire system for SElinux relabeling after first reboot
  5. Reboot the system from a single mode
Now that we understand the procedure we can proceed with Redhat 7 password recovery.

The firewall on Redhat 7 Linux system is enabled by default. Normally there should not be a need to disable firewall but it may be quite handy for testing purposes etc. On Redhat 7 Linux system the firewall run as firewalld daemon. Bellow command can be used to check the firewall status:
[root@rhel7 ~]# systemctl status firewalld
firewalld.service - firewalld - dynamic firewall daemon
   Loaded: loaded (/usr/lib/systemd/system/firewalld.service; enabled)
   Active: active (running) since Thu 2014-09-04 19:18:47 EST; 3 months 28 days ago
 Main PID: 539 (firewalld)
   CGroup: /system.slice/firewalld.service
           └─539 /usr/bin/python -Es /usr/sbin/firewalld --nofork --nopid

Sep 04 19:18:45 rhel7 systemd[1]: Starting firewalld - dynamic firewall daemon...
Sep 04 19:18:47 rhel7 systemd[1]: Started firewalld - dynamic firewall daemon.

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