Laravel is a powerful MVC-PHP framework, designed for developers who need a simple and elegant..."yum" to find out path where a package is installed on CentOS/RHEL
yum, command is an interactive, open source, rpm based, the package manager for a CentOS/RHEL and.../etc/rsyslog.conf – Setup a Filter to Discard or Redirect Messages
The post outlines steps to create a Property-Based Filter to Discard( suppress ) a particular...5 Useful Examples of firewall-cmd command
The command-line tool firewall-cmd is part of the firewalld application, which is installed by...6 Useful journalctl Command Examples in CentOS / RHEL 7 (Cheat Sheet)
Use the journalctl command to view the journal logs. By default, the listed entries include a...Apache HTTP server – most commonly used configuration directives
The main configuration file for Apache is /etc/httpd/conf/httpd.conf. Apache runs as installed,...Apache HTTP server – most commonly used containers (special configuration directives)
Apache containers are special configuration directives that group other directives. The...Audit Rule Configuration not Reflected – How to troubleshoot
We have added new audit rules to the configuration file /etc/audit/rules.d/audit.rules as shown...Audit rules to log reboot command executions in CentOS/RHEL
auditd is the userspace component to the Linux Auditing System. It’s responsible for writing...Beginners Guide to Automounting File Systems in CentOS / RHEL
Automounting is an alternative to creating NFS mount entries in /etc/fstab or using the mount...Beginners Guide to DHCP – Install and configure DHCP server and client
Dynamic Host Configuration Protocol (DHCP) allows client machines to automatically obtain network...Beginners Guide to Linux Software Management with RPM
Maintaining Software Using RPM (Red Hat Package Manager) RPM is a powerful software manager...Beginners Guide to NFS in CentOS / RHEL
A Network File system (NFS) allows a server to share directory hierarchies (file systems) with...Beginners Guide to Samba (Installation and Configuration)
Samba is an open-source implementation of the Server Message Block (SMB) protocol. It allows...Beginners Guide to Swap Space Management in Linux
Swap space is used in Linux when there is insufficient physical memory (RAM) on your system to...Beginners guide to Apache HTTP Server – Installation and Configuration
Apache HTTP server The Apache HTTP Server, an open-source web server developed by the Apache...Beginners guide to Kernel Module Configuration in Linux
The Linux kernel is loaded into memory by the boot loader. Kernel modules are dynamically loaded...Beginners guide to vsftpd (installation and configuration) for CentOS / RHEL
File Transfer Protocol (FTP) is a commonly used method of downloading and uploading files between...CentOS / RHEL 6,7 : How to increase system log message verbosity (rsyslogd)
The Linux system log daemon is responsible for logging system messages. Starting RHEL 6, The...CentOS / RHEL 7 : GRUB2 configuration file /boot/grub2/grub.cfg explained
The GRUB2 configuration file /boot/grub2/grub.cfg – Starting RHEL 7 GRUB 2 is the bootloader....CentOS / RHEL 7 : How to configure kdump using GUI
Kdump is the Linux kernel crash dumping mechanism. In the event of a system crash, Kdump provides...CentOS / RHEL 7 : How to install and configure ftp server (vsftpd)
The FTP service/server is provided by the vsftpd daemon. Very Secure FTP Daemon (vsftpd) is the...CentOS / RHEL 7 : How to modify the kernel command line
The post outlines the steps to modify the kernel command line (and, thus, kernel boot parameters)...CentOS / RHEL 7 : Unable To Start The Samba Service
The SMB service is unable to start, SAMBA shares can’t be accessed. Using systemctl fails to...CentOS / RHEL 7 : Understanding Kexec and Kdump
Kdump is the Linux kernel crash dumping mechanism. In the event of a system crash, Kdump provides...CentOS / RHEL 7 : sysctl kernel parameter doesn’t take effect after reboot
sysctl parameter didn’t take effect after a reboot on RHEL 7 server. Parameter...CentOS / RHEL 7 : unable to start vsftpd service
While starting or restarting the vsftpd service you might get below error on an RHEL 7 system. #...CentOS / RHEL : How to add new swap partition
For the purpose of this post, let’s assume that you do not have any swap configured on your...CentOS / RHEL : How to create and host yum repository over httpd
YUM (Yellowdog Updater, Modified) provide more services and functionality than is available with...CentOS / RHEL : How to exclude kernel or other packages from getting updated using YUM Versionlock Plugin
Due to application certification and other restrictions in a production environment, it may be...CentOS / RHEL : How to log all LVM commands
By default, the LVM configuration does not allow you to log the commands that are used in a shell...Centos Error: needs 10MB on the /boot filesystem
When I'm trying to update my centos, it's not a vm, i have this error message: installing...Check and Change current TimeZone in CentOS 6/7
Check Date of your Machine which includes Time. date Check Current TimeZone. date +’%Z %z’...DNS configuration file /etc/named.conf explained
The default configuration of the /etc/named.conf file provides a caching-only nameserver. The...Downloading RPM Packages with dependencies [ yumdownloader Vs yum-downloadonly Vs repoquery]
You may sometime need to download packages without installing them. This could become difficult...Features of the “Btrfs” Filesystem
Btrfs is an open-source, general-purpose file system for Linux. The name derives from the use of...Guide to Open And Close Ports on CentOS 6/7
Requirements Root Access for the server Procedure Open Port in CentOS 6 Log in to...How To Auto Mount a FileSystem Using Systemd?
Below example shows how to create a systemd script to mount a disk under a specific path on...How To Check a Disk for Bad Blocks or Disk Errors on CentOS / RHEL?
Hard disks can fail unexpectedly and it is always best to keep recent backups of all important...How To Configure Django With Apache In CentOS 7?
Django is a Python-based free and open-source web framework that can be used for developing...How To Install Icinga 2 on CentOS 7 / RHEL 7
Icinga 2: It is a free and open source monitoring tool which helps you to monitor network...How To Install Webmin on CentOS 7
Webmin is a web-based interface for system administration for Linux-based servers. Step 1: Login...How To Open A Port In CentOS / RHEL 7?
A TCP/IP network connection may be either blocked, dropped, open, or filtered. These actions are...How systemd-tmpfiles cleans up /tmp/ or /var/tmp (replacement of tmpwatch) in CentOS / RHEL 7?
In CentOS/RHEL 7, tmpfiles cleans up /tmp or /var/tmp by removing unused files. This function was...How to Back Up and Restore XFS File Systems (xfsdump / xfsrestore)?
Use the xfsdump and xfsrestore utilities to back up and restore files in an XFS file system. You...How to Boot into Single User Mode in CentOS/RHEL 7?
First restart your CentOS 7 machine, once boot process starts, wait for the GRUB boot menu to...How to Change Default Permission of /var/log/messages in CentOS/RHEL?
By default, /var/log/messages* are created with read-write permissions for ‘root’ user only....How to Change Time Interval to Fall Back to Secondary DNS Server in CentOS/RHEL?
The parameter timeout:n can be set in the configuration file /etc/resolv.conf to adjust the time...How to Configure ACL(Access Control Lists) in Linux FileSystem?
Traditional Linux access permissions for files and directories consist of setting a combination...How to Configure Device File owner/group with udev rules?
Udev is the mechanism used to create and name /dev device nodes corresponding to the devices that...How to Configure Interface(s) in promiscuous mode on CentOS/RHEL 7 (persistently)?
Promiscuous mode or promisc mode is a feature that makes the ethernet card pass all traffic it...How to Configure Network Teaming in CentOS/RHEL 7?
In earlier versions of RHEL, network bonding was the default method for creating aggregated...How to Configure Static IP Address in CentOS 7 / RHEL 7 / Fedora 27/26?
Setting up the network and bringing servers into the network is the primary administration task...How to Configure UDEV rule to allow read-only permissions on USB devices?
Following steps to configure udev rule which would automatically switch the USB disks to...How to Configure rsyslog to Filter/discard Specific IP Address in CentOS/RHEL 6,7?
Follow below steps to configure rsyslog to filter messages with specific IP address. 1....How to Convert Ext File Systems to Btrfs?
btrfs or Butter FS is a filesystem and has some interesting features: One can have FS...How to Create a New /boot Partition in CentOS / RHEL?
Here is a short howto on creating a new /boot partition in LVM and migrate the existing boot...How to Create and Mount Btrfs Snapshots?
Btrfs is an open-source, general-purpose file system for Linux. The name derives from the use of...How to Disable NUMA in CentOS / RHEL 6,7?
Non-Uniform Memory Access or Non-Uniform Memory Architecture (NUMA) is a physical memory design...How to Disable and Blacklist Linux Kernel Module to prevent it from loading automatically on CentOS / RHEL?
To disallow the loading of malicious or unwanted modules, we can blacklist them. In order to...How to Enable Disk Quotas on an XFS File System?
XFS supports disk quotas by user, by group, and by project. Project disk quotas allow you to...How to Enable SSL For Apache CentOS / RHEL?
Here is a short note on how to configure Apache to use a certificate file for SSL or How to...How to Enable Verbose Logging for VSFTPD?
The main configuration file for VSFTPD is ‘/etc/vsftpd/vsftpd.conf‘. When verbose logging is...How to Enable X11 Forwarding on CentOS/RHEL 5,6,7?
To enable X11 Forwarding on a server client edit the file “/etc/ssh/ssh_config” and on ssh server...How to Enable the Old ethX Style Network Interfaces Names on CentOS / RHEL 7?
At boot time (or whenever a network driver is loaded) interfaces are always assigned ethX style...How to Enable/Disable CPUs (Limiting CPU count) in CentOS / RHEL?
There are three ways to restrict number of CPU’s in CentOS/RHEL. Using maxcpus parameter...How to Extend allowed number of loopback devices?
A loopback device is used to access filesystems that are not associated with a block device (Hard...How to Install Caddy on CentOS 7
Caddy, sometimes clarified as the Caddy web server, is an open source, HTTP/2-enabled web server...How to Install FreeIPA Client on CentOS 7?
FreeIPA is a free and open source Identity, Policy, and Audit (IPA) suite sponsored by RedHat....How to Install GitLab on CentOS 7
GitLab CE (Community Edition) is an open-source application used to host Git repositories with...How to Install Memcached on CentOS?
Memcached is a distributed, high-performance, in-memory caching system. It is often used to...How to Install Node.JS 8 LTS on CentOS 7, Debian 8, and Ubuntu 16?
Vanilla is free, open source discussion forum written in PHP. Vanilla Forum software is...How to Log all Bash History Commands to syslog (/var/log/messages) in CentOS/RHEL?
The user wants to see the list of commands used in the syslog messages. This way the user can...How to Manually Modify the GRUB parameters in CentOS/RHEL 7 before Booting?
An incorrect configuration in /etc/grub2.conf or /boot/grub2/grub.cfg can cause CentOS/RHEL 7 to...How to Modify GRUB2 Arguments with grubby CentOS / RHEL 7?
Starting RHEL 7, GRUB2 is the default boot loader. The configurations and settings of GRUB2 are...How to Prevent Users from Using the Last 10 Passwords CentOS / RHEL7?
The requirement here is that the user should not use the last 10 used passwords again when...How to Recover Missing GRUB2 Files from /boot?
The GRUB2 files went missing under the /boot directory. Missing ‘/boot’, /boot/grub2 folder and...How to Remove virbr0 and lxcbr0 Interfaces on CentOS/RHEL 6,7?
There is only one Network card on machine but ifconfig shows 2 interface by name virbr0 and...How to Resize / Expand a Btrfs Volume / Filesystem?
It is a common task to resize/expand btrfs file system since btrfs is widely used in CentOS/RHEL...How to Run a Script When USB Devices Is Attached or Removed Using UDEV?
The post outlines steps to create UDEV rules that run a specific script when a USB device is...How to Secure Kibana using Nginx as a reverse proxy on CentOS 7
Kibana is an open source data visualization plugin for Elasticsearch. It provides visualization...How to Set Up a Firewall with FirewallD on CentOS 7?
FirewallD is a complete firewall solution that manages the system’s iptables rules and provides a...How to Start/Stop and Enable/Disable process accounting (psacct)?
The psacct service is responsible for starting and stopping process accounting at system boot...How to Stop SSH Session From Getting Timed Out?
The Linux ssh server never disconnects ssh session from server side by default, check...How to Throttle Bandwidth while applying yum package updates?
It is possible to limit bandwidth used by yum while downloading package updates using throttle...How to Tune Btrfs Filesystem for Better Performance?
Btrfs is a filesystem which is very new and is still under development and benchmarking phase. As...How to Use Iperf to Test Network Performance in Linux?
The iperf is a tool used for testing the network performance between two systems. The iperf...How to Use “repoquery” Command to List Package Dependencies?
“repoquery” is a program for querying information from YUM repositories similarly to rpm queries....How to Verify if ALUA Mode is Enabled on a LUN in CentOS/RHEL
ALUA stands for Asymmetrical Logical Unit Access. Midrange arrays usually have an internal...How to add a custom script to the systemd in CentOS/RHEL 7?
The systemd facility replaces the older System-V initialization scripts from earlier releases....How to add or delete a samba user under Linux?
To add a new user to access a samba share you need to first create a server user account using...How to allow or deny Users to login to VSFTP Server on CentOS / RHEL?
After installation and start of the VSFTPD service, two files are created in the /etc/vsftpd/...How to allow or deny telnet login to specific users only in CentOS/RHEL?
The login to specific users can be allowed or denied using the file /etc/pam.d/remote. Other...How to avoid the “promiscuous mode” messages being logged repeatedly in /var/log/messages?
The Soluition – During normal operation, a network interface filters out received unicast...How to backup Linux OS using “dd” Command?
“dd” command can be really handy when it comes to taking an Operating System backup to clone the...How to boot into rescue mode from installation DVD/ISO CentOS / RHEL 7 ?
When there is an issue with booting up RHEL / CentOS 7 system you can boot it into rescue mode...How to calculate the size of hugepage used by a specific process/application on RHEL/CentOS 6,7?
You have a system configured with hugepages and you want to find per-process hugepages...How to change the Default Log Directory(/var/log) in Rsyslog for CentOS/RHEL 6,7?
The default location of /var/log/messages file can be changed to any location of your choice....How to change the default permissions of log files created by rsyslog?
The user wants to change the default permissions of the log file /var/log/messages to make it...How to change the number of commands stored in Bash History?
The 2 environment variables which majorly affects the Bash History setting of saving the last run...How to change the path of the auditd log file /var/log/audit/audit.log?
An important task related to troubleshooting can arise from an understanding of activities...How to change the verbosity of debug logs during booting CentOS / RHEL 7?
Removing the rhgb and the quiet kernel command-line parameters, either by editing the...How to check Linux for Spectre and Meltdown vulnerability?
Installation The script must be run as root user. You can view the source code here. Use the...How to check the status of a service using systemd on CentOS / RHEL 7 ?
Previous versions of CentOS/RedHat Linux use init scripts located in the /etc/rc.d/init directory...How to clean YUM cache in CentOS / RHEL?
For some operations (for example, a yum install operation), Yum downloads the packages to install...How to clear the buffer/pagecache (disk cache) under Linux
Are you facing a performance issue and you suspect it might be related to cache usage? High cache...How to configure DM-Multipath from an iSCSI initiator to an iSCSI target in CentOS / RHEL?
The procedure to configure DM-Multipath from an iSCSI initiator to an iSCSI target is presented,...How to configure NTP server and client in CentOS / RHEL 7?
The example discussed below is for a basic NTP server and client. NTP stands for Network...How to configure Nginx with Let’s Encrypt on CentOS 7?
Install acme.sh client and use it on a CentOS/RHEL 7 to get an SSL certificate from Let’s...How to configure VLAN Tagging using nmcli on CentOS / RHEL 7?
A VLAN is a type of local area network that does not have its own dedicated physical...How to configure cache-only nameserver on CentOS / RHEL 7?
Caching-only nameservers, or recursive nameservers, offer resolution services but they are not...How to configure chrony statistics in CentOS / RHEL 7?
The chronyd service uses the /etc/chrony.conf configuration file to set synchronization...How to configure encrypted swap using LUKS in CentOS/RHEL?
In environments such as government companies, users may want to secure their data which can...How to configure hugepages CentOS / RHEL 6,7?
HugePages is a feature integrated into the Linux kernel with release 2.6. This feature basically...How to configure iSCSI Initiator (client) in CentOS / RHEL 7?
Internet Small Computer System Interface (iSCSI) is an IP-based standard for connecting storage...How to configure iSCSI target using targetcli in CentOS / RHEL 7?
Internet Small Computer System Interface (iSCSI) is an IP-based standard for connecting storage...How to configure interface in “Promiscuous Mode” in CentOS/RHEL?
Promiscuous mode or promisc mode is a feature that makes the ethernet card pass all traffic it...How to configure multicast on an IP address (interface)?
Multicast can be used to send IP packets to a group of interested receivers. Compared with...How to configure rsysnc in daemon mode (allow rsync and disable SSH login) in CentOS/RHEL?
To allow rsync and disable ssh by configuring rsync in daemon mode. In order to achieve this...How to connect to an Active Directory Domain using Realmd (Configure CentOS/RHEL 7 as active directory client)?
Realmd provides a simple way to discover and join identity domains. It configures Linux system...How to create an XFS Filesystem?
The XFS filesystem is a high performance journalling filesystem. XFS is the default file system...How to create custom script to run automatically during boot CentOS / RHEL 7?
In RHEL 5 and 6, we were using automatic startup feature of RHEL through /etc/rc.d/init.d to run...How to create partitions and file systems on DM-Multipath devices?
Device-Mapper Multipath (DM-Multipath) is a Linux native multipath tool, which allows you to...How to create partitions inside loopback device?
In most of the situations you would simply create a loopback device using “losetup” and mount it...How to create virtual block device (loop device/filesystem) in Linux?
Linux supports a special block device called the loop device, which maps a normal file onto a...How to delete a partition using fdisk?
The post list out the steps to delete a disk partition using fdisk command. Please note the...How to delete an iSCSI Target on the initiator (iSCSI client)?
Internet Small Computer System Interface (iSCSI) is an IP-based standard for connecting storage...How to disable IPv6 on a specific interface only CentOS / RHEL 7?
We have already seen how to disable ipv6 globally on CentOS / RHEL 7. There could be an ask to...How to disable PREAUTH permanently in CentOS/RHEL 7
1. Login to the server as root. 2. Take backup of the file /lib/systemd/system/sssd.service....How to disable Transparent Huge pages (THP) on CentOS / RHEL 7?
Explicit Huge Pages V/s Transparent Huge Pages There can be two types of HugePages in the...How to disable all tty consoles and enable only 1 on CentOS / RHEL 7?
Upon system bootup there should be a single tty console running Xorg on it. New tty consoles are...How to disable avahi-daemon service in CentOS/RHEL?
The avahi-daemon Linux service runs on client machines to perform network-based Zeroconf service...How to disable firewalld and and switch to iptables in CentOS / RHEL 7?
By default, RHEL 7 uses the FirewallD service to provide network security. Firewalld may not be...How to disable lvmetad in CentOS/RHEL?
LVM can optionally use a central metadata cache, implemented through a daemon (lvmetad) and a...How to disable or delete virbr0 interface CentOS / RHEL 6,7 ?
If you check the ‘ifconfig -a’ after a fresh install of RHEL/CentOS 6,7 system, you would find...How to disable ping responses from CentOS/RHEL system?
To disable ping or ICMP responses from a CentOS/RHEL system, we can use kernel parameter...How to disable rtkit-daemon in CentOS/RHEL?
As per package description, RealtimeKit is a D-Bus system service that changes the scheduling...How to disable the default apache “Welcome Page” in CentOS/RHEL 7
Disabling Apache Welcome Page Method 1: removing/renaming Welcome Page 1. In order to...How to disable “Alt+Ctrl+Del” causing system reboot in CentOS/RHEL 7?
In CentOS/RHEL 7, /etc/init/control-alt-delete.override no more works to override the key...How to enable IPv6 on CentOS / RHEL 7?
IPv6 is enabled by default on RHEL / CenOS 7 systems. So, if IPv6 was disabled on the system...How to enable SFTP Logging without chroot in CentOS/RHEL?
Secure File Transfer Protocol (SFTP) is a great tool for performing secure file transfers. This...How to enable bind query logging to find out Who’s Querying a Name Server?
Bind query logging can be very handy if you are troubleshooting a problem. However, it generates...How to enable or disable XDMCP service (GDM) on CentOS / RHEL 6,7?
GDM can be configured to allow remote access via XDMCP (X Display Manager Control Protocol). We...How to enable or disable automatic updates (via packagekit) in CentOS / RHEL 7?
PackageKit is the graphical software updater in RedHat based linux distributions. The posts...How to enable telnet for a group of users CentOS / RHEL 7?
In CentOS/RHEL 7, the /etc/pam.conf is depreciated and /etc/pam.d/remote will be used for...How to exclude a file/directory from auditd rules?
In order to allow users to see what is going on, auditd can record all the audit-related events...How to find if NUMA configuration is enabled or disabled?
Non-Uniform Memory Access or Non-Uniform Memory Architecture (NUMA) is a physical memory design...How to find the commands run by user before reboot in CentOS/RHEL?
Installing psacct (process accounting) The psacct service is responsible for starting and...How to find which specific ethernet device corresponds to a specific port on a multi-interface network card in CentOS/RHEL?
Method 1: If you only have remote access to the server If the server’s management module (such...How to follow the mount order in /etc/fstab CentOS / RHEL 7 ?
With the introduction of systemd in RHEL 7 the boot process has become a lot faster because many...How to grow/extend XFS filesytem in CentOS / RHEL using “xfs_growfs” command?
Use the xfs_growfs command to increase the size of an XFS file system. The XFS file system must...How to install Apache CouchDB on CentOS 7?
Apache CouchDB is open source database software that focuses on ease of use and having a scalable...How to install CentOS Web Panel?
Here, we will show you how to install a CentOS Web Panel. To complete this, you might need a VPS...How to install Drupal with PHP 7 on CentOS 7?
Drupal is a free and open source content management framework written in PHP and distributed...How to install GoAccess on CentOS 7
Install EPEL repository Although we are going to install GoAccess from source, we need some...How to install Jenkins on CentOS 7
Jenkins is an open source automation server written in Java. Jenkins helps to automate the...How to install LAMP (Apache, MySQL, PHP) stack on CentOS 7
assuming that you have root permission, otherwise, you may start commands with “sudo”. Install...How to install Laravel 5.5 + PHP 7.1 with Apache on CentOS 7
Laravel is a powerful MVC-PHP framework, designed for developers who need a simple and elegant...How to install MEAN Stack (MongoDB, Express.JS, Angular.JS, Node.JS) on CentOS 7
Mod_evasive is a module for Apache that provides evasive action in the event of an HTTP...How to install Moodle on CentOS 7?
Moodle is a free and open-source learning management system written in PHP. Moodle is used for...How to install Nginx 1.12 with PageSpeed module on CentOS 7?
PageSpeed is one of the Nginx’s modules developed by Google to speed up the web site or web...How to install NodeBB with Redis Database on CentOS 7?
NodeBB Forum Software is powered by Node.js and built on either a Redis or MongoDB database. It...How to install Open Virtual Machine Tools for Virtual machines Hosted on VMWare in CentOS / RHEL?
Open VM Tools (OVT) consists of a suite of virtualization utilities that improves the...How to install PHP 7.2 on CentOS 7/RHEL 7?
Install PHP 7.2 on CentOS 7 Turn on EPEL repo on a CentOS and RHEL 7.x sever by typing the...How to install Redis 4 on Centos 6 / 7, Ubuntu 16 and Debian 8 (Updated)?
Note: Redis 4 is not stable yet so if you know what are you doing put your gloves on....How to install Redis with auto restart on CentOS 6 & 7?
Requirements- Linux Machine with CentOS 6/7 with Root Permissions Internet Connection...How to install Ruby on Rails on CentOS?
Ruby on Rails, or Rails, is a server-side web application framework written in Ruby. It provides...How to install Vue.JS for Development on CentOS 7?
Caddy, sometimes clarified as the Caddy web server, is an open source, HTTP/2-enabled web server...How to install and Configure VNC (TigerVNC) server in CentOS / RHEL 7
Virtual Network Computing (VNC) works by capturing the display’s frame buffer and making it...How to install and Secure Elasticsearch and Kibana on CentOS 7?
Elasticsearch is a search engine based on Lucene. It provides a distributed, multitenant-capable...How to install and configure ABRT (Automatic Bug Reporting Tool) in CentOS/RHEL?
ABRT (Automatic Bug Reporting Tool), is a set of tools that help users detect and analyze...How to install and configure MariaDB in CentOS / RHEL 7?
MariaDB is the default implementation of MySQL in Red Hat Enterprise Linux 7. MariaDB is a...How to install and configure Samba in CentOS / RHEL?
To provide printer and file sharing, Microsoft Windows uses a facility known as SMB (Server...How to install and configure sosreport under CentOS / RHEL?
The sosreport tool collects information about a system, such as hardware configuration, installed...How to install and configure telnet CentOS / RHEL 7?
It’s not recommended to use telnet as it is not secure. The passwords are transferred using a...How to install and configure “setroubleshootd” on CentOS/RHEL?
SELinux (Security Enhanced Linux) provides mandatory access control to the Linux operating...How to install and secure phpMyAdmin on Centos 7
phpMyAdmin is a free and open source administration tool for MySQL and MariaDB. As a portable web...How to install and setup Docker on RHEL 7/CentOS 7?
Docker is free and open-source software. It automates the deployment of any application as a...How to install and start a project with Django framework on CentOS 7?
Django is a free and open-source web framework, written in Python. It's primary goal is to ease...How to install kernel from rescue mode CentOS / RHEL 7?
A situation where the system has no kernel to boot from maybe because all the kernel are removed...How to join Centos 7/ Rhel 7 servers to Active Directory Domain?
We will need the following packages installed on the CentOS / RHEL server: realmd: This...How to make ethtool settings persistent across reboots in CentOS / RHEL 6,7?
Any change made with the ethtool program does not persist across reboots or network module...How to map /dev/sdX and /dev/mapper/mpathY device from the /dev/dm-Z device?
Sometimes, to troubleshoot some multipath related issues, you would require to map the...How to modify the UUID of a Volume Group (VG) or Physical Volume (PV) in CentOS/RHEL?
The device node name of a disk (/dev/sda, /dev/hda, /dev/vda, etc.) may change in some...How to modify the iSCSI initiator ID in Linux?
In our environment, we have duplicate initiator id in /etc/iscsi/initiatorname.iscsi due to...How to monitor /etc/shadow and /etc/passwd file for changes with Auditd?
System auditing is a very important task that should be a part of every server. It allows us to...How to monitor the Mounting/Umounting of Mount Points Using Auditd on CentOS/RHEL 6,7?
One of the best things about auditd is that it is tightly integrated with the kernel, so it gives...How to monitor time changes using auditd in CentOS/RHEL?
Auditing can provide accountability by tracing the actions of a user or process. It can state...How to patch Meltdown CPU Vulnerability CVE-2017-5754 on Linux?
Please note that fix currently available for the following distros for sure (kernel version that...How to patch Spectre Vulnerability CVE-2017-5753/CVE-2017-5715 on Linux?
Fix the Spectre on a CentOS/RHEL/Fedora/Oracle/Scientific Linux Type the following yum command:...How to query and modify kernel parameters using sysctl (Immediately and persistently) in CentOS / RHEL?
The purpose of this post is to explain how to configure kernel parameters on Red Hat...How to recover an interrupted yum package installation CentOS / RHEL 6,7?
For any reason, if the yum transaction was interrupted before it could complete, you would get an...How to recover from a corrupt RPM database (rebuilding an RPM database)?
Why rpm database gets corrupted There can be multiple reasons which can lead to rpm database...How to recover from deleted root entry in /etc/shadow and/or /etc/passwd files on CentOS / RHEL 7?
The ‘root’ entry was removed from /etc/shadow and /etc/passwd. How to recover the deleted root...How to reinstall GRUB2 from rescue mode CentOS / RHEL 7?
CentOS / RHEL 7 now includes GRUB2 which uses a new way of installing to the MBR of your boot...How to remove rescue image using grubby CentOS / RHEL 7?
The ask is to remove the default rescue image that gets installed when you install a CentOS/RHEL...How to restore/recover a deleted volume group in LVM CentOS / RHEL?
LVM takes a backup of the on-disk metadata before and after running any LVM operation on a...How to run MariaDB as a custom user and group other than mysql on CentOS / RHEL 7?
So the requirement here is, we do not want to run MariaDB as the mysql user and group which is...How to scan newly Assigned LUNs in Multipathd under CentOS / RHEL?
After you have assigned a new disk/LUN from storage to the designated server, you have to follow...How to send Audit Logs to Remote Rsyslog Server in CentOS/RHEL 6,7?
The following are the steps for direct audit logs of a remote rsyslog server on a CentOS/RHEL...How to set custom device names using udev in CentOS/RHEL 7?
There could be a requirement from client to have custom device names such as /dev/asmdisk01 for...How to set date, time / NTP and timezone using timedatectl CentOS / RHEL 7?
RHEL 7 offers another utility to configure and display date and time information, timedatectl....How to set nproc (Hard and Soft) Values in CentOS / RHEL 5,6,7?
This post outlines how a Linux System administrator can limit the allowed number of processes for...How to set udev rules for ASM on multipath disks for CentOS / RHEL 7?
Udev is the mechanism used to create and name /dev device nodes corresponding to the devices that...How to set/disable banner message (MOTD) for a specific user in CentOS/RHEL?
To disable the MOTD or the banner message, only for a specific user in CentOS/RHEL 7. Solution:...How to specify command-line arguments and options when the dhcpd service is started CentOS / RHEL 7?
Dynamic Host Configuration Protocol (DHCP) allows client machines to automatically obtain network...How to test port connectivity using nc utility in CentOS/RHEL?
The nc utility, which is also called netcat, comes in very handy when you want to test TCP/IP...How to troubleshoot NFS transfer latency issues using “nfsiostat” in CentOS / RHEL?
The nfsiostat command works like the iostat command except only for the NFS mount points. The...How to troubleshoot iSCSI issues in CentOS / RHEL 6,7?
Internet Small Computer System Interface (iSCSI) is an IP-based standard for connecting storage...How to use Magic SysRq tool in CentOS / RHEL?
SysRq utility In case your kernel freezes or/and hangs, you can use ‘magic’ SysRq tool. The...How to use auditd to monitor a file deletion in Linux?
cThe auditd service can be a perfect tool to investigate such file deletion issues. The post...How to use auditd to monitor a specific SYSCALL?
A SYSCALL happens whenever a user executes a command that requests that the Linux kernel provide...How to use qperf to measure network bandwidth and latency performance in Linux?
“qperf“, is one of the many tools used to measure bandwidth and latency between two nodes. qperf...How to use rndc command (command-line administration tool for named)?
The rndc utility is a command-line tool to administer the named service, both locally and from a...How to use “btrfs device” comamnd to add/delete device to/from btrfs filesystem?
Btrfs is an open-source, general-purpose file system for Linux. The name derives from the use of...How to use “btrfs scrub” command to manage scrubbing on Btrfs file systems?
You can initiate a check of the entire file system by triggering a file system scrub job. The...How to use “xfs_admin” command to change parameters of an XFS filesystem?
Use the xfs_admin command to change the parameters of an XFS file system. You can also use the...How to work with multiple java versions under Linux?
When i installed a new version of the Java Runtime Environment but the “java -version” command...Input/Output Errors During XFS Filesystem Access In CentOS/RHEL 7
The Problem While accessing a directory mounted on XFS filesystem, it is throwing Input/Output...Installing Security Vulnerabilities with yum on CentOS/RHEL 5,6,7 (Cheat Sheet)
Here is a short note on List of Commands to Install Security Vulnerabilities with yum. To get...Linux OS Service ‘vncserver’
Linux OS Service ‘vncserver’ executes a VNC server daemon, which is used to start a VNC desktop...List of SELinux Utilities
This post lists some of the more commonly used command-line utilities for managing and operating...Maintaining Linux filesystems using “fsck” and “tune2fs”
The best tool for maintaining file systems is fsck, which checks and repairs Linux file systems....Make MySQL Faster by Killing Sleep Connections Automatically
Here’s a Bash script to kill sleeping MySQL connections automatically and almost immediately to...Migrate from single-partition boot device to LVM in CentOS7
Introduction There are times when you have a system that has a single boot partition that...MySQL Fails to Start Using systemctl On systemd Linux Distributions
When trying to start MySQL using systemctl fails to start, for example: # systemctl status...OpenLDAP Server and Client Utilities list
Lightweight Directory Access Protocol (LDAP) is used to access centrally stored information over...Rsyslog : How to Send log files to remote server in CentOS/RHEL 6,7?
Need of a Centralized Rsyslog Server Every *NIX system has some sort of logging facility that...Running repairs on XFS Filesystems
The XFS File system is a high-performance journaling file system. XFS supports a maximum file...SSSD Service Failing with “SSSD is already running” in CentOS/RHEL 7
1. Remove the /var/run/sssd/sssd.pid file if exists else remove /var/run/sssd.pid file. # rm...Sample /etc/multipath.conf file
Below is a sample /etc/multipath.conf file taken from CentOS 7.4, from the directory...Slow SSH login due to unreachable rsyslog server
SSH login to a linux server may get delayed or slow if you have a wrong rsyslog server entry or...Swapon Fails To Mount Swap – Gives Invalid Argument Error
Symptoms will include (but are not limited to): After turning off swap or after a reboot, one...TCP Wrapper (hosts.allow & hosts.deny) Command Options in Linux
Internet Small Computer System Interface (iSCSI) is an IP-based standard for connecting storage...TCP Wrapper (hosts.allow & hosts.deny) Command Options in Linux
TCP wrappers are capable of more than allowing and denying access to services. With the optional...Troubleshooting “connection refused” From Remote Servers in CentOS/RHEL 7 (Either Firewalld or iptables service issue)
This may be a case of Firewall on the local server dropping inbound connection attempts from...Turn off color in Linux terminal/bash session
You can disable all color in your shell. By default, colors are turned on by many commands. The...Unable To Extend LVM File System with Associated Snapshot in CentOS/RHEL
User is unable to Extend the LVM file system which has a snapshot, Error "Snapshot origin volumes...Understanding /etc/security/limits.conf file
UNIX/Linux operating systems have the ability to limit the number of various system resources...Understanding /etc/xinetd.conf file in Linux
The xinetd daemon is a TCP wrapped super service which controls access to a subset of popular...Understanding /etc/xinetd.d directory under Linux
xinetd daemon The xinetd daemon is a TCP wrapped super service which controls access to a subset...Understanding Automatic NUMA balancing
NUMA is a technology that allows the system memory to be divided into zones, also named nodes....Understanding DM-multipath deamon (multipathd)
The multipathd daemon checks for failed paths and reconfigures the multipath map. The daemon runs...Understanding DNS zone files
Information about domains in the DNS database is stored in zone files. A zone file consists of...Understanding Linux SCSI Reservation
SCSI Reservation is a mechanism which allows SCSI initiators to reserve a LUN for exclusive...Understanding RPM Versions and Naming Schemes
RPM is a powerful software manager which can be used to build, install, query, verify, update,...Understanding SELinux Booleans
A given SELinux policy can be customized by enabling or disabling a set of policy Booleans....Understanding SELinux File Labelling and SELinux Context
SELinux File Labeling All files, directories, devices, and processes have a security context (or...Understanding SELinux Policies in Linux
The SELinux policy describes the access permissions for all users, programs, processes, files,...Understanding Samba utilities – nmblookup, smbstatus, smbtar, testparm, wbinfo, smbget
The following list summarizes the command-line utilities included with the Samba packages. Use...Understanding TCP Wrappers (/etc/hosts.allow & /etc/hosts.deny) in Linux
TCP wrappers provide basic traffic filtering of incoming network traffic. Access to “wrapped”...Understanding The /proc File System
The proc file system contains a hierarchy of special files that represent the current state of...Understanding The sysfs File System (/sys) in Linux
In addition to /proc, the kernel also exports information to another virtual file system called...Understanding chroot Jail
As the name implies, a chroot operation changes the apparent root directory for a running process...Understanding dm-Multipath Identifiers in Linux
By default, multipath devices are identified by a World Wide Identifier (WWID), which is globally...Understanding iscsiadm Utility in CentOS / RHEL
Internet Small Computer System Interface (iSCSI) is an IP-based standard for connecting storage...Understanding kdump Configuration file /etc/kdump.conf
The configuration file for Kdump is /etc/kdump.conf. The default target location for the vmcore...Understanding mpathconf Utility to configure DM-Multipath
Use the mpathconf utility to configure DM-Multipath. The mpathconf utility creates or modifies...Understanding multipath Utility to Configure DM-Multipath
The multipath utility is the device mapper target auto-configurator, which is used to detect and...Understanding shell profiles in CentOS/RHEL
If you are a Linux system admin you must have dealt with at least one of the shell profile files...Understanding the dm-multipath Configuration file /etc/multipath.conf
The main configuration file for DM-Multipath is /etc/multipath.conf. This file is not created by...Understanding the nfsiostat command output (Examples Included)
The nfsiostat command works as iostat command for the NFS mount points on the server. It uses the...Understanding “yum history” command output
“yum history” is an often overlooked but really useful feature provided in the CentOS/RHEL/Fedora...Upgrade from CentOS 6 to CentOS 7
Installing Redhat upgrade tool: redhat-upgrade-tool is not available on standard...What are SELinux Modes and how to set them?
SELinux Modes SELinux runs in one of three modes (or states). Enforcing This is the default...What are SELinux Users and how to Map Linux Users to SELinux Users?
There are SELinux users in addition to the regular Linux users. SELinux users are part of an...What are different Samba Server Types?
Samba Server type is configured in the [global] section of the /etc/samba/smb.conf file. Below...What are the Network Bonding Modes In CentOS / RHEL?
Network interface bonding is called by many names: Port Trunking, Channel Bonding, Link...What is HBA Queue Depth and How to check the Current Queue Depth Value and how to Change it?
The queue depth indicates the number of I/O requests that are “in flight”, that have been...Where to find ASMLib / oracleasm RPMs for CentOS/RHEL, SUSE, OEL?
Here is a short note, if you are looking for packages (RPM) for Oracle ASMLib (oracleasm) for...Why Does “/var/log/messages” Report Martian Packets?
A Martian packet as one which arrives on an interface where the interface does not use that...Why Does “netstat” Output Show Many Connections in CLOSE_WAIT Status?
Applications that handle a huge number of TCP connections, either as a server or as a client,...Why the files in /tmp directory gets deleted periodically on CentOS / RHEL 6,7?
In CentOS/RHEL 7, tmpfiles.d cleans up /tmp or /var/tmp by removing unused files. This function...Yum Command Fails with “Another app is currently holding the yum lock” in CentOS/ RHEL 7
While issuing any yum command, you would get an error shown below: # yum list Loaded plugins:...fdisk: Unable to write /dev/sdg: Bad file descriptor – error while formatting USB disk
While formatting a USB disk which was mounted in write-protected mode we are getting the below...ifconfig command not found on CentOS 7 Minimal installation
ifconfig command to configure network interfaces, enable or disable the interface, display IP...pvcreate Fails With Error: “Device /dev/mapper/mpatha Not Found (or Ignored By Filtering).”
pvcreate command fails while using multipath device with below error even when the device is...pvcreate error : Can’t open /dev/sdx exclusively. Mounted filesystem?
So, here is the situation – pvcreate and vgcreate command throws errors shown below. # pvcreate...semanage command not found in CentOS 7 / 6 & RHEL 7 / 6 – Quick Fix
Run semanage command to make a change in SELinux policy to allow us access to MongoDB on port...systemd alternatives to ‘service’ ‘chkconfig’ and ‘init ‘ commands in CentOS/RHEL 7
The systemctl command is used to interact with systemd and can be used to list systemd unit...‘ip’ Command cheat sheet (Command Line Reference)
ip command provided by the iproute package is used to adjust addresses, link state, routing...“Bad id for repo: My Repo, byte = 2” yum update error
Error While executing yum commands user is getting below error: # yum update Bad id for repo:...“btrfs” command examples to Create and Manage Btrfs File System
Btrfs is an open-source, general-purpose file system for Linux. The name derives from the use of...“iscsiadm” Discovery TimeOut With Two Or More Network Interfaces in CentOS/RHEL
This issue could occur when two or more Ethernet interfaces are connected to the same subnet or...“mlock failed: Cannot allocate memory” lvcreate command error in CentOS/RHEL 7
The issue is caused by the use_mlockall parameter in the LVM configuration file...“mount.nfs: access denied by server while mounting” – how to resolve
Mounting the nfs share from CentOS/RHEL NFS server on a NFS client gives error as shown below: #...“resize2fs: Permission denied to resize filesystem” error while online resize of a filesystem
On CentOS/RHEL system, an LVM volume group size has been extended and an attempt to do online...Install the Sentora Web Hosting Control Panel on Centos/Ubuntu
IMPORTANT You MUST have setup DNS for the sub-domain that will be assigned to Sentora panel...