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.

Here is a short config to show you how to display and monitor CPU temperature on a Linux system running Redhat 7 Linux. First we need to install lm_sensors:
# yum install lm_sensors
Next, use sensors command to display CPU temperature:
$ sensors | grep Core
Core 0:         +43.0°C  (high = +86.0°C, crit = +100.0°C)
Core 1:         +43.0°C  (high = +86.0°C, crit = +100.0°C)

Installation of Memtest+ RAM memory test tool on Redhat 7 Linux Memtest is a quite handy tool when troubleshooting hardware problem and specifically problems related to Random Access Memory (RAM). After installation the memtest+ tool will become available among other boot options. To install memtest+ on RHEL 7 Linux server execute the following linux command:
# yum install memtest86+
...
Running transaction
  Installing : memtest86+-4.20-12.el7.x86_64      1/1 
  Verifying  : memtest86+-4.20-12.el7.x86_64      1/1 

Installed:
  memtest86+.x86_64 0:4.20-12.el7

There are two handy tools to help you provide an additional information about system packages. The first tool is the package manager yum and the second is yumdb. Both tools display a different type of information. The other difference is that yumdb command can be only used on packages currently installed on the system.

Symptom

When trying to start a service with service or systemctl commands on the Redhat 7 Linux system the following error message can appear on the screen:
Failed to issue method call: Unit service_name.service failed to load: No such file or directory.

Basic NFS Configuration

In this config will guide you trough a quick and basic configuration of NFS server on RHEL7 Linux system. We do not take any security concerns into the consideration, nor we will be concerned with fine tuning and access control. In our scenario we define two hosts:
  • NFS Server, IP 10.1.1.100
  • NFS Client, IP 10.1.1.18
Assuming your already have a running Redhat 7 Linux system in order to setup NFS server you will need to install few additional packages:

NFS Server configuration

Run the below commands to begin the NFS Server installation:
[nfs-server ]# yum install nfs-utils rpcbind

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