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

There are number of ways how to find you what Redhat Linux version is my server running on. First check /etc/os-release file:
# cat /etc/os-release 
NAME="Red Hat Enterprise Linux Server"
VERSION="7.0 (Maipo)"
ID="rhel"
ID_LIKE="fedora"
VERSION_ID="7.0"
PRETTY_NAME="Red Hat Enterprise Linux Server 7.0 (Maipo)"

In this short config we will install FTP file Server on RHEL7 Linux using vsftpd. We will stick to the default vsftpd configuration which enables user accounts on our existing RHEL7 Linux system to login via FTP from a remote location, list and transfer files. Let's begin by the installation:

To install FTP server on Redhat 7 Linux we can use either tftp-server or vsftpd daemon. In this guide we use vsftpd:
[root@rhel7 ~]# yum install vsftpd
Next, we can start the vsftpd service by using a service command:
[root@rhel7 ~]# service vsftpd start
Redirecting to /bin/systemctl start  vsftpd.service
To make the FTP service startup persistent after system reboot use:
[root@rhel7 ~]# systemctl enable vsftpd
ln -s '/usr/lib/systemd/system/vsftpd.service' '/etc/systemd/system/multi-user.target.wants/vsftpd.service'

When setting up FTP server on Redhat 7 Linux box the following error message ftp: connect: No route to host may pop-up during FTP client session:
ftp server error client rhel7 ftp: connect: No route to host


In this quick config we will setup the Berkeley Internet Name Domain (DNS) service named. First, let's briefly describe our environment and proposed scenario. We will be setting up a DNS server to host a single zone file for domain linuxconfig.org. Our DNS server will act as a master authority for this domain and will resolve fully qualified domain (FQDN) linuxconfig.org and www.linuxconfig.org to an IP address 1.1.1.1.

Furthermore, our named daemon will be listening on a two local IP addresses, the loopback IP address 127.0.0.1 and local network interface 10.1.1.100. Lastly, the DNS server will allow queries from any external IP address.

DNS server Installation

Now that we have described our basic scenario let's begin with an DNS server installation. To install DNS server on RHEL7 use yum command below:
# yum install bind
...
RHEL_7_Disc/productid                         | 1.6 kB     00:00     
  Verifying  : 32:bind-9.9.4-14.el7.x86_64                       1/2 
  Verifying  : 32:bind-libs-9.9.4-14.el7.x86_64                  2/2 

Installed:
  bind.x86_64 32:9.9.4-14.el7                                        

Dependency Installed:
  bind-libs.x86_64 32:9.9.4-14.el7                                   

Complete!
Once the DNS installation is finished we will now make a quick configuration to make named daemon listen on our loopback and local network interface address:
[root@rhel7 ~] # ip addr show | grep inet
    inet 127.0.0.1/8 scope host lo
    inet6 ::1/128 scope host 
    inet 10.1.1.110/8 brd 10.255.255.255 scope global enp0s3
    inet6 fe80::a00:27ff:fe15:38b7/64 scope link

The php-mbstring is part of Redhat's server optional packages. If you have a current subscirption all you need to do is to enable this repository using:
[root@rhel7 ~]# subscription-manager repos --enable=rhel-7-server-optional-rpms
and use yum to install php-mbstring. In case that you do not have a current Redhat subscription you can install php-mbstring directly from IUS project repository:
[root@rhel7 ~]# wget http://dl.iuscommunity.org/pub/ius/stable/Redhat/7/x86_64/ius-release-1.0-13.ius.el7.noarch.rpm
[root@rhel7 ~]# wget http://dl.fedoraproject.org/pub/epel/7/x86_64/e/epel-release-7-2.noarch.rpm
[root@rhel7 ~]# rpm -Uvh *release*.rpm

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