How to install Nmon for Monitor Linux Performance in CentOS 7

Nmon is a resource monitoring tools designed for use on Linux which can monitor CPU, Memory, Disks, Network and File systems. You can easily monitor your system's CPU usage, memory, network, disks, file systems, NFS, top processes, resources and power micro-partition information using nmon.

How to configure HAProxy to redirect multiple domains

Follow the below steps to configure HAproxy to redirect multiple domains.

How to disable Server Signature using .htaccess

In the default configuration of Apache, it shows sensitive server information like Apache version, Operation System version etc. Attackers can use sensitive server information to their advantage when performing an attack. You can Disable Server Signature by editing .htaccess file to hide such sensitive information.

Apache SSL Certificate expiry monitoring With Nagios

Nagios plugin “check_http” provides SSL Certificate monitoring to check certificates expiration dates and Nagios generate alerts when SSL certificates near their expiration date. So the same can renew their certificates before problems occur.

How to Push an Existing Project to Git Server

Step 1: Initialize Git in the project folder

How to change password for a MySQL user

Follow the below MySQL commands to reset the password for a MySQL user. You can change the password for any other users as well with the below commands.

How to configure apache mod_status module in CentOS 7

Apache module mod_status is an open source module that allow to monitoring web server load, statistics, current state including worker processes and active connections.

How to Block a specific IP Address using Routing Table in CentOS 7

The Linux routing table can block the incoming connection to prevent the Denial of Service (DoS) and save resource utilization. The Linux routing tables can used to block such IP addresses or whole subnet with reject route and null route.

How to Zip and unZip Files to a specific directory in CentOS 7

Zip is a simple and commonly used utility for compression and decompression folders that can compress from level 1 to 9.

How to create Database Dump with routine, triggers and procedures using MySQLDump

Mostly, MySQLDump is used for taking backup of MySQL data backups. MySQL provide a mysqldump scripts with the multiple options to take dump of MySQL Databases. MySQLDump will take backup by default of all the triggers but not the stored procedures and functions.

How to create Database Dump using MySQLDump

Mostly, MySQLDump is used for taking backup of MySQL data backups. MySQL provide a mysqldump scripts with the multiple options to take dump of MySQL Databases.

How to copy data from AWS instance using Rsync in Centos 7

Rsync is open source software that used to synchronize files/folders from local to local computers and remote computers as well over SSH with compression and encrypted files.

How to enable SCL Repository in Cent OS 7

The Software Collections (SCL) repository is created to provide safely installation on Cent OS and RHEL and also provide installation of multiple software versions on the same machine. The SCL is available yum default repository on Cent OS 6.5 and later.

How to Change Default MTA in CentOS 7

If there is two or more programs (sendmail, postfix, SSMTP and exim etc) are installed for MTA and required to change default MTA. CentOS 7 provide alternatives command to select a default MTA.

Change Default MTA: Run the below command and follow instructions to change default MTA:

[root@linuxcnf ~]# alternatives --config mta There is 1 program that provides 'mta'.   Selection    Command ----------------------------------------------- *+ 1           /usr/sbin/sendmail.postfix    2           /usr/sbin/sendmail.ssmtp Enter to keep the current selection[+], or type selection number: 2 [root@linuxcnf ~]#

There are 2 programs which provide 'MTA'. Enter number 2 and press enter for ssmtp selection as a default MTA. Also stop the postfix service and disable to start on boot up.

How to Install and Configure SSMTP in CentOS 7

SSMTP is a very simple and useful alternative of send mail and postfix. It provides the functionality to send mails via the standard user/agents and authentication with valid mail account to send mails. It is used to send mails on local and external domains.

SSMTP is available in EPEL repository (Extra Packages for Enterprise Linux) for CentOS 7.

How to Encrypt/Decrypt Files in CentOS7/RHEL7 using Ccrypt

Ccrypt is a command line utility for encryption and decryption of files and streams in Linux [CentOS 7]. It is a light weighted tool and available in EPEL repository (Extra Packages for Enterprise Linux) for Cent OS 7 and RHEL.

How to install Ccrypt in CentOS 7 / RHEL 7

Ccrypt is a command line utility for encryption and decryption of files and streams in Linux [CentOS 7].

How to add Linux Host to Nagios Monitoring Server in CentOS 7

Nagios plugins and NRPE are available for Cent OS 7 and RHEL in EPEL repository (Extra Packages for Enterprise Linux).

How to create separate system user account in AWS EC2 instance

Login to the instance and switch to the root user:

How to Generate SSH Keys pairs using command line in Centos 7

Ssh-keygen is command line tool for creating authentication key pairs for SSH Key based authentication. Private Key is used for client and the public key need to upload on server.

How to Use Screen command in Centos/RHEL

Screen utility allows running multi-tasking environment and keeping processes running in the background. By default, package is not available in CentOS distribution. Follow the below article to installed.

How to enable/disable services on boot up in Centos7/RHEL7

In Centos 7 and RHEL 7, the systemctl command added to manage all services.

How to install lsyncd on CentOS 7 / RHEL 7

lsyncd is an rsync-based tool that is used to sync or replicate files & directories locally and remotely.  It is sync changes or modification in a file and directory to the remote or local destination in a specific time interval.

How to install rsync utility in Centos 7

Rsync is open source software that used to synchronize files/folders from local to local computers and remote computers as well over SSH with compression and encrypted files.

How to use rsync utility in Centos 7

Rsync is open source software that used to synchronize files/folders from local to local computers and remote computers as well over SSH with compression and encrypted files.

How to analyze memory usage using SAR command

Sar command with option “-r” to generate memory usage report. %kbmemfree, %kbbuffers and %kbcached are the overall memory used including RAM & Swap. Its shows values at every interval or required time interval.

How to change default Kernel in CentOS 7

In Centos and RHEL 7 systems, the GRUB2 is the most common and default boot loader and grub2-mkconfig utility can use to make any changes in grub configuration.

How to configure proxy settings with user authentication in CentOS 7

Set the following proxy environment variables in CentOS server to use a proxy on the Linux command-line if the internet connection is behind a proxy:

How to configure proxy settings in CentOS 7

Set the following proxy environment variables in CentOS server to use a proxy on the Linux command-line if the internet connection is behind a proxy:

How to fix Authentication refused: bad ownership or modes for directory

This is common issue faced while configuring public-key authentication for other users. Incorrect permission on $HOME/.ssh/ directory and $HOME/.ssh/authorized_keys is root which cause permission denied.

How to install Screen utility in CentOS 7

Screen utility allows running multi-tasking environment and keeping processes running in the background. By default, package is not available in Centos distribution. Follow the below article to installed.

How to enable timestamp in command history CentOS 7

By default, time stamp information is not associated with executed history commands. To enable the time stamp on every bash command follow the below steps:

How to enable and disable GitLab services during start up in CentOS 7

Run the following command to disable GitLab services on startup.

How to enable Multiple PHP versions for websites in CentOS 7

Follow below steps to enable PHP 7.2 for a particular website:

How to Install MySQL Server 5.7 on CentOS 6

MySQL Community Server is an open source free database management system. It uses a relational database and SQL (Structured Query Language) to manage its data.

How to Start/Stop MySQL Server in CentOS 6

The service and chkconfig script are used to verify all the services whether it is running or stopped and enable or disabled at startup.

How to resolve “Too many connections” Error MySQL

The “too many connections” error occur when maximum number of clients may be connected to the server has been reached maximum number of connections that are allowed in MySQL configuration. The default value is 151 for the variable max_connections in MySQL.

How to Change Password for a User in MySQL 5.6

MySQL provides UPDATE and other statements which can use to change the password of a MySQL user. This tutorial will describe how to change password of a MySQL user using UPDATE statement.

How to create database user account in MySQL

MySQL provides the CREATE USER statement that allows creating a new user account.

How to Grant Privileges to a User in MySQL

To grant privileges to a database user account, the GRANT statement can use to provide requires access grants to the user.

Revoking Privileges from Users Using MySQL REVOKE

To revoke privileges from a user account, the MySQL REVOKE statement will use to revoke the access/grants one or more privileges or all privileges from a user.

How to delete a Samba user in Centos 7

Use the following commands to delete the samba user. Also need to delete to OS user from the server:

How to add a samba user in Centos 7

To allow access in samba share directory, first need to create a local/OS user account (If already not exist) and then create a samba password for the same account for samba user.

How to disable the Apache default welcome Page in CentOS 7

Post apache (httpd) installation, a default Welcome Page created inside apache document root directory or /etc/httpd/conf.d/ directory.

How to Redirect HTTP to HTTPS on Apache

Before setting up an Apache HTTP to HTTPS redirect for a site, make sure a SSL vhost already created and mod_rewrite module is loaded in Apache.

How to add SSH public key to the Server in Centos 7

In key-based authentication, we need to generate SSH key pairs and the pair use for authentication. The private key is used for client machine and public key uploaded to the remote machine.

How to enable SSL Certificate for Apache CentOS 7/ RHEL 7

SSL (Secure Sockets Layer) is a cryptographic protocol that is used to send secure and encrypted traffic between server and client.

How to install Apache web Server on CentOS 7/RHEL 7

The Apache web Server is an open source web server to serve the hosted web pages and contents. It runs on Unix-like operating systems including Linux and Windows OS.  It is available on CentOS 7/ RHEL 7 default repositories.

How to Set Password Never Expire in CentOS 7

By default, user accounts take aging details mentioned in /etc/login.def configuration file if the password policy are already applied then we need to set user account and password never expire using chage command.

How to upgrade Clam AV with latest version clamav-0.100.1 on Linux

Clam AV is an open source antivirus engine for detecting Trojans, viruses, malware & other malicious threats. It provides a number of utilities including a multi-threaded scanner

How to Check Linux System Reboot Date and Time

There is another command “who” to check last reboot date and time on Linux Systems. The “who” command is by default installed on most of the Linux distributions. Use the ‘who -b’

How to add rules in Firewall Exception in CentOS7

Firewalld is a firewall management tool available by default on CentOS 7 servers. It provides command line and graphical interfaces and is available in the repositories of most Linux

Alfresco: Reset the administrator password

Reset the admin password: In the default alfresco installation, the authentication mechanism users and passwords are stored locally in the Alfresco PostgreSQL database.

How to install XRDP on Centos 7 / RHEL 7

XRDP is an Open Source Remote desktop Protocol server, which is allowing users to take remote of Linux Operating System from RDP clients. XRDP uses RSA Public Key and Private Key encryption to transfer data over the network.

How to compile and install the latest Clam AV antivirus on Linux

Clam AV is an open source antivirus engine for detecting Trojans, viruses, malware & other malicious threats. It provides a number of utilities including a multi-threaded scanner daemon,

How to find out OS version of Oracle Linux

How to get the version/distribution/ release information of Linux that is running Oracle Linux via command line?

How to install perl-Switch package in RHEL7

perl-Switch package is not available in RHEL7 default repository  “rhel-7-server-rpms/7Server/x86_64”. Install the perl-Switch package by enabling RHEL Optional repository

How to Install Clam AV on RHEL 7/CentOS 7

Clam AV is an open source antivirus tool for Linux. Clam AV is used widely for detecting Viruses, Trojans, malware and other malicious threats on Linux.

How to fix df –h command hangs on RHEL7/Centos7

The most common cause of df -h command hanging while reading related files to return output and fails without output.

How to Install Ansible on CentOS 7

Ansible is a free and open source Configuration and automation tool. We can manage a large number of client machines from a central machine. It communicates over SSH and it doesn’t

How to find out top 10 CPU and Memory Consuming Process in Linux

In this article, we will show how to find out the resource consumption in a Linux box to figure out the exact issue? “ps” command is a most powerful and popular to achieve our requirements.

How to resolve wget: command not found

wget command: It is a command-line utility and used to downloads files over a network. wget is a free utility to download files and available most of the Linux distributions.

How to rebuild corrupt RPMDB in Centos 6

While, working with rpm or yum package management tools in Centos 6 and getting rpmdb database is corrupted. Follow the below steps to resolve the database issue.

How to change database directory in MySQL server

Sometime, we need to change MySQL data directory due to low space on the file system, save the actual data on any dedicated partition or any network drives and enhance MySQL database performance etc. Mostly in Linux based servers, MySQL uses /var/lib/mysql directory as default data directory. Before do anything, take a cold backup or use MySQL dump to take backup for databases. To change database location please follow these steps:

How to zip and compress a directory/file in Centos7

In this article, we are using tar utility for zipping directory or files. This utility is installed by default on most of Linux distributions. The tar utility is capable to create zip file and compress the same as well.

How to check PHP version in Centos 7

To verify the installation and version of installed PHP by checking the version of PHP using command or inbuilt phpinfo() function in php.

How to zip/unzip the directory in Linux with command line

This article will describe, how to zip and unzip a directory and directory in Linux using command line. Zip is a compression and file packaging utility which is available for Linux, UNIX, Windows and various Operating systems.

How to install zip/unzip package in Linux Centos 7

Zip is a compression and file packaging utility which is available for Linux, UNIX, Windows and various Operating systems. This article will describe, how to install zip/unzip packages in Linux Centos 7.

How to install Nginx web server in Centos 7

Nginx is a free and open source high-performance web server and also it is use for reverse proxy. This article will describe installation of Nginx server on a CentOS 7 using EPEL repository.

How to enable IP masquerading/forwarding on CentOS 7

By default, the IP masquerading/Forwarding is disabled most of the Linux distributions. The IP forwarding is required for LVS router to forward network packets properly to the real servers and it should be enabled on each LVS router node on in the kernel level.

How to resolve Clam AV Error while updating virus database

Clam AV fails to start after update to v0.99.4. After the update and getting the below error:

How to fix - ‘Ifconfig’ Command Not Found on CentOS 6.x

The network command line tool ifconfig is not installed by default on CentOS 6 Linux minimal installation. ifconfig command is available for most of the Linux distributions and can be installed from default repository. Follow the below steps to get installed the ifconfig command in centos 6.x.

How to disable remote SSH login for the root user

By default the root access is enabled for outside world. For security reason it’s not a good idea because any cracker can attempt to brute force your root password and potentially get access to your system if they can figure out your password.

It’s much better to disabling the root user and allowing another regular user with root user’s permissions.

How to add user with sudo privileges in Linux

Add a user with administrative privileges that can ssh into the server and switch to on root user using sudo.

How to Set the Time zone in Centos 7/ RHEL 7

By default, In the Centos 7 the time zone will be set to UTC time, so need to change to the time zone according to our setup / site NTP server.

How to configure the Static IP Address on Centos7/RHEL7 Server

To configure the static IP address, Route and DNS to the Linux box Centos 7, edit the interface configuration file under /etc/sysconfig/network-scripts/ directory and append the below line in the end the file:

How to rename a network interface on Centos/RHEL 7

In Centos / RHEL 7, a new NIC naming scheme is the predictable naming rule is adopted by default like ens192, enp3s0 and eth0 so on. To disable the predictable naming rule we can pass "net.ifnames=0" kernel parameter during boot.

How to restore Database Backup in MySQL

If we have a saved MySQL database taken using mysqldump script, use the following command to restore the backup in MySQL database.

How to install Gnome GUI on CentOS 7/RHEL 7

By default, CentOS 7/ RHEL 7 installed as the minimal and also system administrators like to work in a terminal. However if we have installed CentOS7/RHEL7 without the GUI we can always install on the minimal server installation.

How to Take Backup of a specific Table in MySQL

Sometimes, there is a requirement to make a backup of a specific table in MySQL. The complete database backup could take more time to complete. Instead of backing up the entire database, we can make the backup of a single table using mysqldump.

How to disable Network Manager on Centos7/RHEL7

The Network Manager Service is enabled by default on Centos7/RHEL7 installations. Network Manager is not suitable for advanced networking setup, such as configuring network bridge, aliases, Open Stack networking, forwarding network traffic, etc.

How to Setup Network Bridge with NIC bonding in RHEL7/Centos7

Network Bridge: A software bridge can be used within a Linux host in order to emulate a hardware bridge. This network bridge allows virtual machines to have access to the external network and vice-versa and allow communicating between different Network VLANs [Trunk VLANs].

How to reset MySQL root password in Linux

If you encounter problems when you try to connect to the MySQL server and you don’t have root password to login in MySQL.

How to configure SFTP Server on Centos7/RHEL7 - One user

SSH File Transfer Protocol (SFTP) is application protocol designed to allow easily transfer files between computers. Many users prefer to use SFTP. SFTP provides file access, transfer, and management tools that resemble FTP through a secure SSH connection. However, SFTP is not merely FTP over SSH. Instead, it is an entirely separate protocol. 

How to find out version of Amazon Linux AMI

How to get the version/distribution/ release information of Linux that is running on the EC2 instance running Linux via command line?

How to find out OS version in Centos7/RHEL7

How to get the version/distribution/ release information of Linux that is running Centos7/RHEL7 via command line?

How to fix SSH vulnerabilities: HMAC algorithms and CBC Ciphers in CentOS 7

SSH Protocol: Enable protocol version 2: Uncomment Protocol 2 in /etc/ssh/sshd_config as below:

How to fix SSH vulnerabilities: HMAC algorithms and CBC Ciphers in CentOS 6

SSH Protocol: Enable protocol version 2

How to install EPEL repository on Centos7

The EPEL repository is an additional package repository that provides useful software packages that are not included in the official Centos or Red Hat repositories and easy access to install packages for commonly used software.

How to Set Password Policy on CentOS7/RHEL7

Password Policy for user accounts is one of the most important parts in Server Administration. The maximum number of days allowed, minimum number of days allowed, and number of warning days before the password expires refers to password aging, same as the number of characters needed to have for the password to be allowed refers to password length. Centos 7, Red Hat 7 and most of Linux distribution is the ability to manage and implement the password policies. 

How to configure Rsyslog - Client configuration

Install rsyslog package using below command, if not available on the client:

How to Disabling all SSL/TLS Protocols except TLSv1.2 in CentOS7/RHEL7

Secure Socket Layer (SSL) and Transport Layer Security (TLS) are both cryptographic protocols providing encrypted and secure communication between servers, clients, machines and applications operating over a network.

How to join CentOS7/RHEL7 to Active Directory using Winbind

We can integrate a Linux host with Windows Active Directory domain controller for authentication purpose. To complete the scenario, we have Centos / RHEL 7 servers and existing Active Directory domain controller. Also required AD administrator account or user has sufficient rights to join AD.

How to configure NTP Client in Centos7/RHEL7

First, install ntp package on client machine:

How to fix CIFS Error Mount: wrong fs type, bad option, bad superblock while mounting windows share Drive

Not able to mount CIFS share on client getting error "mount: wrong fs type, bad option, bad superblock"

The client must use SMB client signing for connecting to samba servers using smbclient

Packet signing can prevent man-in-the-middle attacks which modify SMB packets in transit. SMB Signing is a feature through which communications using SMB can be digitally signed at the packet level. Digitally signing the packets enables the recipient of the packets to confirm their point of origination and their authenticity.

How to print Number of Processing Units - nproc

The nproc command just prints out the number of processing units available. Note that the number of processing units might not always be the same as number of cores.

How to change the SSH Port in Linux distribution

We can change the default SSH port in Linux distribution as an added security concerns.

How to install and use tcpdump command on Centos7/RHEL7

TCPDump is a command line packet sniffer/ packet analyzer tool which used to capture or filter TCP/IP packets that received or transferred over a network on a specific interface.

Nagios Plugins: Can’t locate utils.pm in @INC

In nagios plugins written in perl, you got the following error while trying to use a nagios.

Error: Table is marked as crashed and should be repaired

If you are getting the following error message: