Sync an accurate time using ntpdate on RHEL7 Linux server

To sync a correct time on your Redhat server with a NTP publicly available time servers first you need to install ntpdate package:

[root@rhel7 ~]# yum install ntpdate

To check your current time use date command:

[root@rhel7 ~]# date
Thu Sep  4 17:20:42 WST 2014

Next, we can use pool.ntp.org timeserver to synchronize our time. This is be done with ntpdate command:

[root@rhel7 ~]# ntpdate pool.ntp.org
11 Dec 06:08:13 ntpdate[2225]: step time server 173.230.144.109 offset 8426822.014383 sec

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Update GRUB2 menu timeout on RHEL 7 Linux

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"

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Persistent/Automatic after reboot kernel module loading on CentOS/Redhat Linux

This config will describe a procedure on how to persistently load kernel modules during a boot time on CentOS or Redhat Linux system. In the below commands will use nf_conntrack_pptp as a sample module. Replace the name of this module with a module name you wish to load.

First, create a script within /etc/sysconfig/modules/ directory with a file extension modules. Where the name of the script can be any name of your choice. In our case the script will be called nf_conntrack_pptp.modules. Enter a following code into your new nf_conntrack_pptp.modules script while replacing the name of the module with the one you wish to load:

#!/bin/sh
exec /sbin/modprobe nf_conntrack_pptp  >/dev/null 2>&1

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How to reset the root password in RHEL7/CentOS7/Scientific Linux 7- based systems

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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VNC connection to RHEL

Configuring VNC Server Access on a Redhat Linux

Most of the time as a Linux system administrator you are managing your servers over the network. It is very rare that you will need to have a physical access to any of your managed servers. In most cases all you need is to SSH remotely to do your administration tasks. In this article we will configure a GUI alternative to a remote access to your RHEL server, which is VNC. VNC allows you to open a remote GUI session to your server and thus providing you with a full graphical interface accessible from any remote location.

In this tutorial you will learn:

  • How to install required VNC packages
  • How to setup and start the VNC server on RHEL
  • How to connect to a graphical session remotely
  • How to run graphical programs in the xterm session

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