The default settings for the GRUB2 timeout menu selection during the system boot is 5 seconds. To change this value open /etc/default/grub grub default config file. The content of the file looks similar the the one shown below:
GRUB_TIMEOUT=5
GRUB_DISTRIBUTOR="$(sed 's, release .*$,,g' /etc/system-release)"
GRUB_DEFAULT=saved
GRUB_DISABLE_SUBMENU=true
GRUB_TERMINAL_OUTPUT="console"
GRUB_CMDLINE_LINUX="rd.lvm.lv=rhel/root crashkernel=auto  \ 
rd.lvm.lv=rhel/swap vconsole.font=latarcyrheb-sun16 vconsole.keymap=us rhgb quiet"
GRUB_DISABLE_RECOVERY="true"

In this showr totorial we will show you how to install VirtualBox Guest Additions on RHEL 7 gnome desktop. To start simply boot to virtual RHEL 7 system. First we will install all prerequisites. To do that open terminal and enter following linux commands:
[root@rhel7 ~]# yum groupinstall 'Development Tools'
as well as we will need kernel development package:
[root@rhel7 ~]# yum install kernel-devel

The default Graphical User Interface for Redhat Enterprise Linux 7 server is Gnome. If from some reason you have decided to install KDE Desktop or to switch from a RHEL7's default GUI gnome to KDE this short tutorial will provide you with easy to follow steps.

Installation of KDE desktop manager on RHEL 7

Here we assume that you currently do not have any desktop manager installed on your system. To install KDE desktop manager on RHEL 7 execute below command:
[root@rhel7 ~]# yum groupinstall 'X Window System' 'KDE'

In order to login to RHEL7 Linux server we first need to exchange public keys between server and client machine. To do that we can use ssh-copy-id command.
$ ssh-copy-id user@rhel-server
The authenticity of host 'rhel-server (rhel-server)' can't be established.
ECDSA key fingerprint is 21:4d:71:f6:ef:1f:c1:f7:a9:d9:81:4d:9d:34:4d:a9.
Are you sure you want to continue connecting (yes/no)? yes
/usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
/usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys
user@rhel-server's password: 

Number of key(s) added: 1

Now try logging into the machine, with:   "ssh 'user@rhel-server'"
and check to make sure that only the key(s) you wanted were added.
The above command will propt you for a password based upon which your access to the remote server will be authenticated and password exchanged. If you get an error message saying:
/usr/bin/ssh-copy-id: ERROR: No identities found

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