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

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

Changing a timezone on Redhat 7 Linux server is a easy task which can be done on a command line with a few commands. First find your timezone using timedatectl command. The following linux command will list all timezones:
[root@rhel7 ~]# timedatectl list-timezones
To narrow down the search you can use grep to search for a specific city. For example:
[root@rhel7 ~]# timedatectl list-timezones | grep -i bratislava
Europe/Bratislava

In order to install of PIP the Python packaging tool on RHEL 7 Linux we first need to install its only pre-requisite and that is setuptools package otherwise we will get a following error message:
Downloading/unpacking pip
  Cannot fetch index base URL https://pypi.python.org/simple/
  Could not find any downloads that satisfy the requirement pip
Cleaning up...
No distributions at all found for pip
Storing debug log for failure in /root/.pip/pip.log
From this reason we first install setuptools:
[root@rhel7 ~]# wget https://pypi.python.org/packages/source/s/setuptools/setuptools-7.0.tar.gz --no-check-certificate
[root@rhel7 ~]# tar xzf setuptools-7.0.tar.gz
[root@rhel7 ~]# cd setuptools-7.0
[root@rhel7 ~]# python setup.py install
...
Installed /usr/lib/python2.7/site-packages/setuptools-7.0-py2.7.egg
Processing dependencies for setuptools==7.0
Finished processing dependencies for setuptools==7.0

The following config will help you to configure a virtual network interface to allow you to have multiple additional network IP address on a single hardware network interface. For example our RHEL server has currently a single hardware network interface called eth0. This interface is used as a master network interface with an IP address of 10.1.1.110. To this network interface we will attach two additional virtual network interfaces eth0:0 - 10.1.1.111 and eth0:1 - 10.1.1.112. Let's get started by showing a current network configuration:
[root@rhel7 ~]# ip addr show
Show network configuration on RHEL7 linux
From the above output we can see that currently we have configured eth0 network interface only. Next, we are going to locate a corresponding network interface configuration file for eth0:
# grep -l DEVICE.*eth0 /etc/sysconfig/network-scripts/*

In this config we are going to configure a network interface to receive an IP configuration settings from DHCP server. First get the name of the network interface you would like to set as DHCP client. To do this you can run command:
# ip addr show
2: enp0s3:  mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 08:00:27:15:38:b7 brd ff:ff:ff:ff:ff:ff
       valid_lft forever preferred_lft forever
    inet6 fe80::a00:27ff:fe15:38b7/64 scope link 
       valid_lft forever preferred_lft forever
Once we have located a name of the network interface in question open a corresponding configuration file. So as an example, for network interface epn0s3 vi will edit a /etc/sysconfig/network-scripts/ifcfg-enp0s3. Open this file and enter the minimum configuration settings in order to make this network interface act as a DHCP client:
DEVICE=enp0s3
BOOTPROTO=dhcp
ONBOOT=yes

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