30 Things to Do After Minimal RHEL/CentOS 7 Installation

1. Register and Enable Red Hat Subscription
2. Configure Network with Static IP Address
3. Set Hostname of Server
4. Update or Upgrade CentOS Minimal Install
5. Install Command Line Web Browser
6. Install Apache HTTP Server
7. Install PHP
8. Install MariaDB Database
9. Install and Configure SSH Server
10. Install GCC (GNU Compiler Collection)
11. Install Java
12. Install Apache Tomcat
13. Install Nmap to Monitor Open Ports
14. FirewallD Configuration
15. Installing Wget
16. Installing Telnet
17. Installing Webmin
18. Enable Third Party Repositories
19. Install 7-zip Utility
20. Install NTFS-3G Driver
21. Install Vsftpd FTP Server
22. Install and Configure sudo
23. Install and Enable SELinux
24. Install Rootkit Hunter
25. Install Linux Malware Detect (LMD)
26. Server Bandwidth Testing with Speedtest-cli
27. Configure Cron Jobs
28. Install Owncloud
29. Enable Virtualization with Virtualbox
30. Password Protect GRUB

1. Register and Enable Red Hat Subscription

After minimal RHEL 7 installation, it’s time to register and enable your system to Red Hat Subscription repositories and perform a full system update. This is valid only if you have a valid RedHat Subscription. You need to register your in order to enable official RedHat System repositories and update the OS from time-to-time.

We have already covered a detailed instructions on how to register and active RedHat subscription at the below guide.

Note: This step is only for RedHat Enterprise Linux having a valid subscription. If you are running a CentOS server immediately move to further steps.

2. Configure Network with Static IP Address

The first thing you need to do is to configure Static IP address, Route and DNS to your CentOS Server. We will be using ip command the replacement of ifconfig command. However, ifconfig command is still available for most of the Linux distributions and can be installed from default repository.

# yum install net-tools             [Provides ifconfig utility]

But as I said we will be using ip command to configure static IP address. So, make sure you first check the current IP address.

# ip addr show

Now open and edit file /etc/sysconfig/network-scripts/ifcfg-enp0s3 using your choice of editor. Here, I’m using Vi editor and make sure you must be root user to make changes…

# vi /etc/sysconfig/network-scripts/ifcfg-enp0s3

Now we will be editing four fields in the file. Note the below four fields and leave everything else untouched. Also leave double quotes as it is and enter your data in between.

IPADDR = “[Enter your static IP here]” 
GATEWAY = “[Enter your Default Gateway]”
DNS1 = “[Your Domain Name System 1]”
DNS2 = “[Your Domain Name System 2]”

After making the changes ‘ifcfg-enp0s3‘, looks something like the image below. Notice your IP, GATEWAY and DNS will vary, please confirm it with your ISP. Save and Exit.

Network Details

Restart service network and check the IP is correct or not, that was assigned. If everything is ok, Ping to see network status…

# service network restart

Restart Network Service

After restarting network, make sure to check the IP address and network status…

# ip addr show
# ping -c4 google.com

Verify IP Address

Check Network Status

3. Set Hostname of Server

The next thing to do is to change the HOSTNAME of the CentOS sever. Check the currently assignedHOSTNAME.

# echo $HOSTNAME

Check System Hostname

To set new HOSTNAME we need to edit ‘/etc/hostsname‘ and replace old hostname with the desired one.

# vi /etc/hostname

Set System Hostname

After setting hostname, make sure to confirm hostname by logout and login again. After login check new hostname.

$ echo $HOSTNAME

Confirm New Hostname

Alternatively you may use command ‘hostname‘ command to view your current hotsname.

$ hostname

4. Update or Upgrade CentOS Minimal Install

This will not install any new packages other than updating and installing the latest version of installed packages and security updates. Moreover Update and Upgrade are pretty same except the fact that Upgrade = Update + enable obsoletes processing during updates.

# yum update && yum upgrade

Update Minimal CentOS Server

Important: You can also run the below command which will not prompt for the packages update and you do not need to type ‘y‘ for accepting the changes.

However it is always a good idea to review the changes which is going to take place on the sever specially in production. Hence using the below command may automate the update and upgrade for you but it is not recommended.

# yum -y update && yum -y upgrade

5. Install Command Line Web Browser

In most cases, specially in production environment, we usually install CentOS as command line with no GUI, in this situation we must have a commandline browsing tool to check websites via terminal. For this, we going to install a most famous tool called ‘links‘.

# yum install links

Links: Commandline Web Browsing

For usage and examples to browse web sites u links tool, read our article Command Line Web Browsing with Links Tool

6. Install Apache HTTP Server

No matter for what purpose you will be using the server, in most of the cases you need a HTTP server to run websites, multimedia, client side script and many other things.

# yum install httpd

Install Apache Server

If you would like to change default port (80) of Apache HTTP Server to any other port. You need to edit the configuration file ‘/etc/httpd/conf/httpd.conf‘ and search for the line that starts typically like:

LISTEN 80

Change port number ‘80‘ to any other port (say 3221), save and exit.

Change Apache Port

Add the port you just opened for Apache through firewall and then reload firewall.

Allow service http through firewall (Permanent).

# firewall-cmd --add-service=http

Allow port 3221 through firewall (Permanent).

# firewall-cmd -permanent -add-port=3221/tcp

Reload firewall.

# firewall-cmd --reload

After making all above things, now it’s time to restart Apache HTTP server, so that the new port number is taken into effect.

# systemctl restart httpd.service

Now add the Apache service to system-wide to start automatically when system boots.

# systemctl start httpd.service
# systemctl enable httpd.service

Now verify the Apache HTTP Server by using links command line tool as shown in the below screen.

# links 127.0.0.1

Verify Apache Status

7. Install PHP

PHP is a server-side scripting language for web based services. It is frequently used as general-purpose programming language as well. Install PHP on CentOS Minimal Server as.

# yum install php

After installing php, make sure to restart Apache service to render PHP in Web Browser.

# systemctl restart httpd.service

Next, verify PHP by creating following php script in the Apache document root directory.

# echo -e "<?php\nphpinfo();\n?>"  > /var/www/html/phpinfo.php

Now view the PHP file, we just created (phpinfo.php) in Linux Command Line as below.

# php /var/www/html/phpinfo.php
OR
# links http://127.0.0.1/phpinfo.php

Verify PHP

8. Install MariaDB Database

MariaDB is a fork of MySQL. RedHat Enterprise Linux and its derivatives have shifted to MariaDB from MySQL. It is the Primary Database management System. It is again one of those tools which is necessary to have and you will need it sooner or later no matter what kind of server you are setting. Install MariaDB on CentOS Minimal Install server as below.

# yum install mariadb-server mariadb

Install MariaDB Database

Start and configure MariaDB to start automatically at boot.

# systemctl start mariadb.service
# systemctl enable mariadb.service

Allow service mysql (mariadb) through firewall.

# firewall-cmd --add-service=mysql

Now it’s time to secure MariaDB server.

# /usr/bin/mysql_secure_installation

Secure MariaDB Database

9. Install and Configure SSH Server

SSH stands for Secure Shell which is the default protocol in Linux for remote management. SSH is one of those essential piece of software which comes default with CentOS Minimal Server.

Check Currently Installed SSH version.

# SSH -V

Check SSH Version

Use Secure Protocol over the default SSH Protocol and change port number also for extra Security. Edit the SSH configuration file ‘/etc/ssh/ssh_config‘.

Uncomment the line below line or delete 1 from the Protocol string, so the line seems like:

# Protocol 2,1 (Original)
Protocol 2 (Now)

This change force SSH to use Protocol 2 which is considered to be more secure than Protocol 1 and also make sure to change the port number 22 to any in the configuration.

Secure SSH Login

Disable SSH ‘root login‘ and allow to connect to root only after login to normal user account for added additional Security. For this, open and edit configuration file ‘/etc/ssh/sshd_config‘ and change PermitRootLogin yes tPermitRootLogin no.

# PermitRootLogin yes (Original) 
PermitRootLogin no (Now)

Disable SSH Root Login

Finally, restart SSH service to reflect new changes..

# systemctl restart sshd.service

10. Install GCC (GNU Compiler Collection)

GCC stands for GNU Compiler Collection is a compiler system developed by GNU Project that support various programming languages. It is not installed by default in CentOS Minimal Install. To install gcc compiler run the below command.

# yum install gcc

Install GCC GNU Compiler

Check the version of installed gcc.

# gcc --version

Check GCC Version

11. Install Java

Java is a general purpose class based, object-oriented Programming language. It is not installed by default in CentOS Minimal Server. Install Java from repository as below.

# yum install java

Install Java

Check version of Java Installed.

# java -version

Check Java Version

12. Install Apache Tomcat

Tomcat is a servlet container designed by Apache to run Java HTTP web server. Install tomcat as below but it is necessary to point out that you must have installed Java prior of installing tomcat.

# yum install tomcat

Install Apache Tomcat

After tomcat has been installed, star the tomcat service.

# systemctl start tomcat

Check Version of tomcat.

# /usr/sbin/tomcat version

Check Tomcat Version

Add service tomcat and default port (8080) through firewall and reload settings.

# firewall-cmd --zone=public --add-port=8080/tcp --permanent
# firewall-cmd --reload

Now it’s time to secure tomcat server, create a user and a password to access and manage. We need to edit file ‘/etc/tomcat/tomcat-users.xml‘. See the section which looks like:

<tomcat-users>
....
</tomcat-users>
<role rolename="manager-gui"/>
<role rolename="manager-script"/>
<role rolename="manager-jmx"/>
<role rolename="manager-status"/>
<role rolename="admin-gui"/>
<role rolename="admin-script"/>
<user username="tecmint" password="tecmint" roles="manager-gui,manager-script,manager-jmx,manager-status,admin-gui,admin-script"/>
</tomcat-users>

Secure Tomcat

Here we added user “tecmint” to administer/manage tomcat using password “tecmint”. Stop and start the service tomcat so that the changes are taken into effect and enable tomcat service to start at system boot.

# systemctl stop tomcat
# systemctl start tomcat
# systemctl enable tomcat.service

13. Install Nmap to Monitor Open Ports

Nmap for Network Mapper creates a map of the network by discovering host on which it is running as well as by analyzing network. nmap is not included in the default installation and you have to install it from repository.

# yum install nmap

Install Nmap Monitoring Tool

List all open ports and corresponding services using them on host.

# nmap 127.0.01

Monitor Open Ports

You may also use firewall-cmd to list all the ports, however I find nmap more useful.

# firewall-cmd --list-ports

Check Open Ports in Firewall

14. FirewallD Configuration

firewalld is a firewall service which manages the server dynamically. Firewalld removed iptables in CentOS 7. Firewalld is installed by default on RedHat Enterprise Linux and its derivatives by default. With iptables every change in order to be taken into effect needs to flush all the old rules and create new rules.

However with firewalld, no flushing and recreating of new rules required and only changes are applied on the fly.

Check if Firewalld is running or not.

# systemctl status firewalld
OR
# firewall-cmd --state

Check Firewalld Status

Get a list of all the zones.

# firewall-cmd --get-zones

Check Firewalld Zones

To get details on a zone before switching.

# firewall-cmd --zone=work --list-all

Check Zone Details

To get default zone.

# firewall-cmd --get-default-zone

Firewalld Default Zone

To switch to a different zone say ‘work‘.

# firewall-cmd --set-default-zone=work

Swich Firewalld Zones

To list all the services in the zone.

# firewall-cmd --list-services

List Firewalld Zone Services

To add a service say http, temporarily and reload firewalld.

# firewall-cmd  --add-service=http
# firewall-cmd –reload

Add http Service Temporarily

To add a service say http, permanently and reload firewalld.

# firewall-cmd --add-service=http --permanent
# firewall-cmd --reload

Add http Service Permanent

To remove a service say http, temporarily.

# firewall-cmd  --remove-service=http
# firewall-cmd --reload

Remove Firewalld Service Temporarily

To remove a service say http, permanently.

# firewall-cmd --zone=work --remove-service=http --permanent
# firewall-cmd --reload

Remove Service Permanently

To allow a port (say 331), temporarily.

# firewall-cmd --add-port=331/tcp
# firewall-cmd --reload

Open Port Temporarily

To allow a port (say 331), permanently.

# firewall-cmd --add-port=331/tcp --permanent
# firewall-cmd --reload

Open Port Permanently

To block/remove a port (say 331), temporarily.

# firewall-cmd --remove-port=331/tcp
# firewall-cmd --reload

Remove Port Temporarily

To block/remove a port (say 331), permanently.

# firewall-cmd --remove-port=331/tcp --permanent
# firewall-cmd --reload

Remove Port Permanently

To disable firewalld.

# systemctl stop firewalld
# systemctl disable firewalld
# firewall-cmd --state

Disable Firewalld Service

To enable firewalld.

# systemctl enable firewalld
# systemctl start firewalld
# firewall-cmd --state

Enable Firewalld

15. Installing Wget

wget is a Linux command line based utility that retrieves (downloads) content from web servers. It is an important tool you must have to retrieve web contents or download any files using wget command.

# yum install wget

Install Wget Tool

For more usage and practical examples on how to use wget command to download files on the terminal, read 10 Wget Command Examples.

16. Installing Telnet

Telnet is a network protocol that enables a user to login into another computer on the same network over TCP/IP. Once connection etablished to the remote computer it becomes a virtual terminal and allow you to communicate with the remote host within your computer as per whatever privileges provided to you.

Telnet also very useful for checking listening ports on remote computer or host.

# yum install telnet
# telnet google.com 80

Telnet Port Checking

17. Installing Webmin

Webmin is a Web based configuration tool for Linux. It acts as a central system to configure various system configuration like users, disk quota, services and configurations of HTTP server, Apache, MySQL, etc.

# wget http://prdownloads.sourceforge.net/webadmin/webmin-1.740-1.noarch.rpm
# rpm -ivh webmin-*.rpm

Install Webmin

After webmin installation, you will get a message on terminal to login to your host (http://ip-address:10000) using your root password on port number 10000. If running a headless server you can forward the port and access it on a machine/server that is headed.

18. Enable Third Party Repositories

It is not a good idea to add untrusted repositories specially in production and it may be fatal. However just for example here we will be adding a few community approved trusted repositories to install third party tools and packages.

Add Extra Package for Enterprise Linux (EPEL) Repository.

# yum install epel-release

Add Community Enterprise Linux Repository.

# rpm -Uvh http://www.elrepo.org/elrepo-release-7.0-2.el7.elrepo.noarch.rpm

Install Epel Repo

Attention! Extra care is needs to be taken while adding Third Party Repository.

19. Install 7-zip Utility

In the CentOS Minimal Install you don’t get utility like unzip or unrar. We have the option to install each utility as required or an utility that servers for all. 7-zip is such an utility which compress and extract files of all known types.

# yum install p7zip

Install 7zip Tool

Notice: The package is downloaded and installed from Fedora EPEL 7 Repository.

20. Install NTFS-3G Driver

A small yet very useful NTFS driver called NTFS-3G is available for most of the UNIX-like distribution. It is useful to mount and access Windows NTFS file system. Though other alternatives like Tuxera NTFS is available, NTFS-3G is most widely used.

# yum install ntfs-3g

Install NTFS-3G to Mount Windows Partition

After installing ntfs-3g has been installed, you can mount Windows NTFS partitions (where /dev/sda5 is my windows drive) using following command.

# mount -ro ntfs-3g /dev/sda5 /mnt
# cd /mnt
# ls -l

21. Install Vsftpd FTP Server

VSFTPD which stands for Very Secure File Transfer Protocol Daemon is a FTP server for UNIX-like System. It is one of the most efficient and secure FTP Server available today.

# yum install vsftpd

Install Vsftpd FTP

Edit the configuration file located at ‘/etc/vsftpd/vsftpd.conf‘ to secure vsftpd.

# vi /etc/vsftpd/vsftpd.conf

Edit a few fields and leave other as it is, unless you know what you are doing.

anonymous_enable=NO
local_enable=YES
write_enable=YES
chroot_local_user=YES

You may also change the port number and open vsftpd port through the firewall.

# firewall-cmd --add-port=21/tcp
# firewall-cmd --reload

Next restart vsftpd and enable to start at boot time.

# systemctl restart vsftpd
# systemctl enable vsftpd

22. Install and Configure sudo

sudo which is commonly called as super do as well as suitable user do is a program for UNIX-like operating system to execute a program with the security privileged of another user. Let’s see how to configure sudo…

# visudo

It will open the file /etc/sudoers for editing..

sudoers File

Give all the permission (equal to root) to a user (say tecmint), that has already been created.

tecmint   ALL=(ALL)    ALL

Give all the permission (equal to root) to a user (say tecmint), except the permission to reboot and shutdown the server.

Again open the same file and edit it with the below contents.

cmnd_Alias nopermit = /sbin/shutdown, /sbin/reboot

Then add alias with Logical (!) operator.

tecmint   ALL=(ALL)    ALL,!nopermit

Give permission to a group (say debian) to run a few root privilege command say (add user and delete user) .

cmnd_Alias permit = /usr/sbin/useradd, /usr/sbin/userdel

And then add the permission to group debian.

debian ALL=(ALL) permit

23. Install and Enable SELinux

SELinux which stands for Security-Enhanced Linux is a security module at kernel level.

# yum install selinux-policy

Install SElinux Policy

Check SELinux Mode.

# getenforce

Check SELinux Mode

The output is enforcing mode which means SELinux policy is in effect.

For debugging, set selinux mode to permissive temporarily. No need to reboot.

# setenforce 0

After debugging set selinux to enforcing again without rebooting.

# setenforce 1

24. Install Rootkit Hunter

Rootkit Hunter abbreviated as Rkhunter is an application that scan rootkits and other potentially harmful exploits in Linux systems.

# yum install rkhunter

Install Rootkit Hunter

Run rkhunter as a scheduled job, from a script file or manually to scan harmful exploits in Linux.

# rkhunter --check

Scan for rootkits

RootKit Scan Results

25. Install Linux Malware Detect (LMD)

Linux Malware Detect (LMD) is a open source Linux malware scanner released under the GNU GPLv2 license, that is
specially designed for threats faced in hosting environments. For complete installation, configuration and usage of LMD can be found at:

Install and Use (LMD) with ClamAV as Antivirus Engine

26. Server Bandwidth Testing with Speedtest-cli

speedtest-cli is a tool written in python to test internet bandwidth including download and upload speed. For complete installation and usage of speedtest-cli tool, read our article at Check Linux Server Bandwidth Speed from Command Line

27. Configure Cron Jobs

This is one of the most widely used software utility. It function as job scheduler i.e., schedule a job now that will execute in future itself. It is useful in logging and maintaining records unattained as well as several other routine work like regular backup. All the schedule is written in /etc/crontab file.

The crontab file contains 6 fields as follows:

Minutes	         Hour		Day of Month		Month of Year		Week Day		Command
(0-59)           (0-23)		  (1-31)                (1/jan-12/dec)       (0-6/sun-sat)          Command/script

Crontab Fields

To run a cron job (say run /home/$USER/script.sh) everyday at 04:30 am.

Minutes 	  Hour   	Day of Month        month of year 	Week Day         command
30                4  		      *		         *		   *            speedtest-cli

Add the following entry to the crontab file ‘/etc/crontab/‘.

30  4  *  *  *  /home/$user/script.sh

After adding the above line to crontab, it will run automatically at 04:30 am everyday and the output depends upon what is there in script file. Moreover script can be replaced by commands. For more examples of cron jobs, read 11 Cron Jobs Examples in Linux

28. Install Owncloud

Owncloud is a HTTP based data synchronization, file sharing and remote file storage application. For more detail on installing own cloud, you may like to see this article : Create Personal/Private Cloud Storage in Linux

29. Enable Virtualization with Virtualbox

Virtualization is a process of creating virtual OS, Hardware and Network, is one of the most sought technology of these days. We will be discussing on how to install and configure virtualization in detail.

Our CentOS Minimal server is a headless server. Lets prepare it to host virtual machines that is accessible over HTTP by installing following packages.

# yum groupinstall 'Development Tools' SDL kernel-devel kernel-headers dkms

Install Development Tools

Change working directory to ‘/etc/yum.repos.d/‘ and download Virtualbox repository.

# wget -q http://download.virtualbox.org/virtualbox/debian/oracle_vbox.asc

Install the key just downloaded.

# rpm --import oracle_vbox.asc

Update and Install Virtualbox.

# yum update && yum install virtualbox-4.3

Next, download and install Virtualbox extension pack.

# wget http://download.virtualbox.org/virtualbox/4.3.12/Oracle_VM_VirtualBox_Extension_Pack-4.3.12-93733.vbox-extpack
# VBoxManage extpack install Oracle_VM_VirtualBox_Extension_Pack-4.3.12-93733.vbox-extpack

Install Virtualbox Extension Pack

Installing Virtualbox Extension Pack

Create a user ‘vbox‘ to manage virtualbox and add it to group vboxusers.

# adduser vbox
# passwd vobx
# usermod -G vboxusers vbox

Install HTTPD server.

# yum install httpd

Install PHP (with soap extension).

# yum install php php-devel php-common php-soap php-gd

Download PHP virtualBox.

# wget http://sourceforge.net/projects/phpvirtualbox/files/phpvirtualbox-4.3-1.zip

Extract the zip and copy the extracted folder to HTTP working directory.

# unzip phpvirtualbox-4.*.zip
# cp phpvirtualbox-4.3-1 -R /var/www/html

Next, rename file /var/www/html/phpvirtualbox/config.php-example tovar/www/html/phpvirtualbox/config.php.

# mv config.php.example config.php

Open the configuration file to edit and add ‘username‘ and ‘password‘ we just created in the above step.

# vi config.php

Finally, restart VirtualBox and HTTP server.

# service vbox-service restart
# service httpd restart

Now forward the port and access it on a headed server.

http://192.168.0.15/phpvirtualbox-4.3-1/

PHP Virtualbox Login

PHP Virtualbox Dashboard

30. Password Protect GRUB

Password protect your boot loader so that you get an additional level of security right at the booting time. Also you get a protection layer of protection at physical level. Protect your Server by locking GRUB at boot to avoid any unauthorized access.

First make backup of two files, so that if anything goes bad, you have the option to revert back. Create a backup of ‘/etc/grub2/grub.cfg‘ as ‘/etc/grub2/grub.cfg.old‘.

# cp /boot/grub2/grub.cfg /boot/grub2/grub.cfg.old

Also, Create a backup of ‘/etc/grub.d/10_linux‘ as ‘/etc/grub.d/10_linux.old‘.

# cp /etc/grub.d/10_linux /etc/grub.d/10_linux.old

Now open ‘/etc/grub.d/10_linux‘ and add the below line at the end of the file.

cat <<EOF
set superusers=”tecmint”
Password tecmint avi@123
EOF

Password Protect Grub

Notice in the above file, replace “tecmint” as username and “avi@123” as password with your username and password.

Now generate the new grub.cfg file by issuing following command.

# grub2-mkconfig --output=/boot/grub2/grub.cfg

Generate Grub File

After creating new grub.cfg file, reboot the machine and press ‘e‘ to edit. You will find that it requires you to enter ‘valid credentials‘ in order to edit boot menu.

Password Protected Boot Menu

After entering login credentials, you will able to edit grub boot menu.

Grub Menu File

Also you can generate encrypted password in place of plain password as shown in the above step. First generate an encrypted password as suggested below.

# grub2-mkpasswd-pbkdf2
[Enter Normal password twice]

Generate Encrypted Grub Password

Now open ‘/etc/grub.d/10_linux‘ file and add the below line at the end of the file.

cat <<EOF
set superusers=”tecmint”
Password_pbkdf2 tecmint
grub.pbkdf2.sha512**************************************************
EOF

Encrypted Grub Password

Replace the password with the one generated on your system. Don’t forget to cross check the password.

Also note you need to generate grub.cfg in this case as well, as described above. Reboot and next time you press ‘e‘ to edit, you will be prompted for username and password.

We’ve tried to cover most of the necessary post-installation points of industry standard distributions RHEL 7 andCentOS 7. If you find that we’ve missed certain points or you need to extend this post with a new post-install things, you may share with us, we will include your point in this article by extending it.

posted on 2016-07-17 10:59 三叁阅读(454) 评论(0) 编辑收藏举报

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