Explore information related to centos
Error – Cannot find a valid baseurl for repo: base - Fix it Now ?
This article covers methods to resolve Error – Cannot find a valid baseurl for repo: base.
To get rid of these error messages and make it possible to update OP5 Monitor you need to change your Centos Base repos in /etc/yum.repos.d/CentOS-Base.repo as follows:
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os&infra=$infra
baseurl=http://vault.centos.org/centos/$releasever/os/$basearch/
Comment out all mirrorlist lines, remove the comment from baseurl and change it to "vault.centos.org".
This way yum will stop complaining and you will be able to use the OP5 repos.
Plesk error "Can't create transaction directory file" – Fix it Now ?
This article covers how to quickly fix Plesk error "Can't create transaction directory file". Basically, this Plesk error happens due to missing or incorrect permission of the /tmp directory.
Upgrade CentOS 7 to CentOS 8 - Step by Step Process ?
This article covers the step by step process to upgrade your CentOS 7 server to CentOS 8.
To Install the EPEL Repository:
# yum install epel-release -y
To Install the New Kernel Core for CentOS 8:
# dnf -y install kernel-core
Modify the Default SSH Port on any Linux Distribution - Step by Step Process ?
This article covers how to change the default SSH port on your Linux machine.
To change the default port the SSHD daemon is listening on.
We can edit the configuration file using a nano editor:
$ sudo nano /etc/ssh/sshd_config
Once you make a change to the SSHD daemon configuration file, you should restart the services to reload the new changes.
$ sudo service sshd restart
Adding Additional Instances To Nagios Log Server Cluster
This article covers method to add instances to Nagios Log Server Cluster. You will need to have an existing Nagios Log Server cluster before following the steps in this guide. An existing cluster is one or more instances of Nagios Log server.
cPanel error networkmanager is installed and running
This article covers how to resolve the error, NetworkManager is installed and running. Basically, this error happens if cPanel does not support NetworkManager-enabled systems.
To fix this error, simply run the commands below and then restart the installation of cPANEL:
$ systemctl stop NetworkManager.service
$ systemctl disable NetworkManager.service
Install Wazuh Server on CentOS 7 - Step by Step Process ?
This article covers the installation procedure of Wazuh Server on CentOS Linux System. Basically, Wazuh is a free, open-source and enterprise-ready security monitoring solution for threat detection, integrity monitoring, incident response and compliance.
You can use Wazuh for the following applications:
- Security analysis
- Log analysis
- Vulnerability detection
- Container security
- Cloud security
To Install Java on CentOS 8.
1. Run the command below to install JDK:
$ sudo dnf install java-11-openjdk-devel
2. Confirm that you have it installed
$ java -version
NRPE Command Plugin Not Defined - How to fix it ?
This article covers methods to resolve 'NRPE Command Plugin Not Defined' for our customers.
This error is very straight forward. Usually this is caused by a mismatch between the command name declared in Nagios XI to be check through NRPE and the actual command name of the command directive in the remote host's nrpe.cfg file.
This problem will occur in versions of check_nrpe before v3.
What is happening here is that the initial -c check_users is being overwritten by the -a -w 5 -c 10, as check_nrpe thinks the -c 10 argument is the command argument, not one of the -a arguments.
Install PHP 8 on CentOS 7 / CentOS 8 - Step by Step Process ?
This article covers how to install PHP 8.0 on CentOS 8/7 and RHEL 8/7.
PHP is the most used scripting language for web development, both websites and web applications.
This guide will show you how to install PHP 8.0 on CentOS 8 | CentOS 7.
Please note the GA release is fit for running in Production if the application already supports it.
To install any additional PHP package use command syntax:
$ sudo yum install php-xxx
To Check PHP version:
$ php --version
Install Docker CE on AlmaLinux 8 - Step by Step Process ?
This article covers step by Step process to install Docker CE on AlmaLinux.
Docker is a tool that is used to run software in a container.
It's a great way for developers and users to worry less about compatibility with an operating system and dependencies because the contained software should run identically on any system.
To Install Docker on AlmaLinux:
1. We can add the Docker repository to our system with the following command.
$ sudo dnf config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo
2. Before we begin installing Docker, we need to remove the podman and buildah packages from our system, as they conflict with Docker and will inhibit it from being installed.
$ sudo dnf remove podman buildah
3. Finally, we can install the three Docker packages we'll need by executing the following command.
$ sudo dnf install docker-ce docker-ce-cli containerd.io
4. Once installation is completed, start the Docker service and, optionally, enable it to run whenever the system is rebooted:
$ sudo systemctl start docker.service
$ sudo systemctl enable docker.service
5. You can verify that Docker is installed and gather some information about the current version by entering this command:
$ sudo docker version
Enable EPEL repository on AlmaLinux 8 - Step by Step Process ?
This article covers how to enable EPEL repository on AlmaLinux 8.
Extra Packages for Enterprise Linux (EPEL) is repository with a high quality set of additional packages for Enterprise Linux operating systems such as Red Hat Enterprise Linux (RHEL), CentOS and Scientific Linux (SL), Oracle Linux (OL), AlmaLinux and any other Linux distribution from the RHEL family.
Run the command below to install EPEL Repository on AlmaLinux OS 8:
# sudo yum install https://dl.fedoraproject.org/pub/epel/epel-release-latest-8.noarch.rpm
Accept installation using the y key.
Install WHM Cpanel on AlmaLinux 8 Server - Step by Step Process ?
This article covers the complete steps to install WHM Cpanel on AlmaLinux 8 Server.
To manage Linux servers for hosting purposes most of the services are using WHM's Cpanel.
Although there are many hosting manager software, because of its easy-to-use interface and features, it is one of the best control panels for Web hosting services.
cPanel, Control Panel, is a control panel developed in 1997 that offers us high-quality web hosting with excellent features that, thanks to WHM (Web Host Manager), can be managed from a graphics console, with everyone doing their job.
Install NDOUtils in CentOS RHEL and fix related error
This article covers how to install NDOUtils in CentOS. NDOUtils is an addon for Nagios Core that allows you to export current and historical data from one or more Nagios Core instances to a MySQL database. NDOUtils is included with Nagios XI. A source in Nagios Network Analyzer is the data collector. Outside of Nagios Network Analyzer a source is the location where data is originating from.
NDOUtils uses the kernel message queue for transferring the data from Nagios to NDOUtils. We are going to increase the default values the Kernel boots with to ensure it operates optimally.
1. Downloading NDOUtils Source
cd /tmp
wget -O ndoutils.tar.gz https://github.com/NagiosEnterprises/ndoutils/releases/download/ndoutils-2.1.3/ndoutils-2.1.3.tar.gz
tar xzf ndoutils.tar.gz
2. Compile NDOUtils
cd /tmp/ndoutils-2.1.3/
./configure
make all
3. Install Binaries
This step installs the binary files.
make install
4. Initialize Database
This prepares the database for NDOUtils.
cd db/
./installdb -u 'ndoutils' -p 'ndoutils_password' -h 'localhost' -d nagios
cd ..
Welcome to Emergency mode in Linux - Fix this boot error now
This article covers how to fix boot error, Welcome to Emergency mode in Linux. This issue happens after an emergency power outage on a server, a system crash, or similar situations.
The Emergency Mode sometime means that your file system may be corrupted.
In such cases, you will be left out with a prompt to go nowhere.
All you have to do is perform a file system check using,
fsck.ext4 /dev/sda3
where sda3 can be your partition and if you are using ext3 file system, change the command as follows:
fsck.ext3 /dev/sda3
About the partition number, Linux shows you the partition before arriving at the prompt.
This should solve the problem.
To fix Emergency Mode On Ubuntu:
1. use Ubuntu Live USB to boot, and open terminal:
$ sudo fsck.ext4 /dev/sda3
2. Adding sudo because it needs root permission.
(Replace ext4 with ext3 if applicable to you)
3. Cycle through the SDAs by changing the last number in the sda to see which file system has problems.
Ex: sda1, sda2, sda3, sda4, and so on
4. As I encountered, the problem might be with the 'home' directory.
5. Once you run the above command, you'll be prompted to fix the issue right inside the terminal itself.
6. Keep hitting y (for yes) until the end of the fix.
(or you can use -fy for automatically response yes to all.)
7. Navigate to the home folder of your sda using your files explorer.
(This will be mounted from the HDD since you are working with a Live USB)
8. Check inside 'home' if you can see all your files. If yes, then you're ready to reboot to your system (remove the Live USB).
Files and Processes in SELinux on CentOS 7 - More information
This article covers Files and Processes in SELinux. Basically, managing file and process context are at the heart of a successful SELinux implementation.
With SELinux, a process or application will have only the rights it needs to function and NOTHING more. The SELinux policy for the application will determine what types of files it needs access to and what processes it can transition to.
SELinux policies are written by app developers and shipped with the Linux distribution that supports it. A policy is basically a set of rules that maps processes and users to their rights.
SELinux enforces something we can term as “context inheritance”. What this means is that unless specified by the policy, processes and files are created with the contexts of their parents.
So if we have a process called “proc_a” spawning another process called “proc_b”, the spawned process will run in the same domain as “proc_a” unless specified otherwise by the SELinux policy.
SELinux in Action: Testing a File Context Error
1. First, let's create a directory named www under the root. We will also create a folder called html under www:
mkdir -p /www/html
2. If we run the ls -Z command, we will see these directories have been created with the default_t context:
ls -Z /www/
drwxr-xr-x. root root unconfined_u:object_r:default_t:s0 html
3. Next we copy the contents of the /var/www/html directory to /www/html:
cp /var/www/html/index.html /www/html/
The copied file will have a context of default_t. That's the context of the parent directory.
We now edit the httpd.conf file to point to this new directory as the web site's root folder.
i. We will also have to relax the access rights for this directory.
vi /etc/httpd/conf/httpd.conf
ii. First we comment out the existing location for document root and add a new DocumentRoot directive to /www/html:
# DocumentRoot "/var/www/html"
DocumentRoot "/www/html"
iii. We also comment out the access rights section for the existing document root and add a new section:
#<Directory "/var/www">
# AllowOverride None
# Allow open access:
# Require all granted
#</Directory>
<Directory "/www">
AllowOverride None
# Allow open access:
Require all granted
</Directory>
We leave the location of the cgi-bin directory as it is. We are not getting into detailed Apache configuration here; we just want our site to work for SELinux purposes.
iv. Finally, restart the httpd daemon:
service httpd restart
Once the server has been restarted, accessing the web page will give us the same “403 Forbidden” error (or default “Testing 123” page) we saw before.
The error is happening because the index.html file's context changed during the copy operation. It needs to be changed back to its original context (httpd_sys_content_t).
restorecond Will not restore a file with more than one hard link - How to resolve this issue
This article covers Tips to fix 'restorecond: Will not restore a file with more than one hard link' error.
To fix this problem type the following commands:
# rm /etc/sysconfig/networking/profiles/default/resolv.conf
# restorecon /etc/resolv.conf
# ln /etc/resolv.conf /etc/sysconfig/networking/profiles/default/resolv.conf
dhclient to persistently look for an IP address lease - Configure it Now
This article covers how to use dhclient command. Basically, Linux dhclient command can provide an IP lease until DHCP Server/Router grants one.
With this guide, you can easily configure Linux dhclient command to continuously requests an IP lease until one is granted by DHCP Server / Router.
Create CentOS Fedora RHEL VM Template on KVM - How to do it
This article covers how to create CentOS/Fedora/RHEL VM Templates on KVM. VM Templates are more useful when deploying high numbers of similar VMs that require consistency across deployments. If something goes wrong in an instance created from the Template, you can clone a fresh VM from the template with minimal effort.
To install KVM in your Linux system:
The KVM service (libvirtd) should be running and enabled to start at boot.
$ sudo systemctl start libvirtd
$ sudo systemctl enable libvirtd
Enable vhost-net kernel module on Ubuntu/Debian.
$ sudo modprobe vhost_net
# echo vhost_net | sudo tee -a /etc/modules
How to Prepare CentOS / Fedora / RHEL VM template ?
1. Update system
After you finish VM installation, login to the instance and update all system packages to the latest versions.
$ sudo yum -y update
2. Install standard basic packages missing:
$ sudo yum install -y epel-release vim bash-completion wget curl telnet net-tools unzip lvm2
3. Install acpid and cloud-init packages.
$ sudo yum -y install acpid cloud-init cloud-utils-growpart
$ sudo sudo systemctl enable --now acpid
4. Disable the zeroconf route
$ echo "NOZEROCONF=yes" | sudo tee -a /etc/sysconfig/network
5. Configure GRUB_CMDLINE_LINUX – For Openstack usage.
If you plan on exporting template to Openstack Glance image service, edit the /etc/default/grub file and configure the GRUB_CMDLINE_LINUX option. Your line should look like below – remove rhgb quiet and add console=tty0 console=ttyS0,115200n8.
GRUB_CMDLINE_LINUX="crashkernel=auto rd.lvm.lv=cl/root rd.lvm.lv=cl/swap console=tty0 console=ttyS0,115200n8"
Generate grub configuration.
$ sudo grub2-mkconfig -o /boot/grub2/grub.cfg
6. Install other packages you need on your baseline template.
7. When done, power off the virtual machine.
How to Clean VM template ?
You need virt-sysprep tool for cleaning the instance.
$ sudo virt-sysprep -d centos7
Add Compute Host to oVirt Virtualization - How to do it
This article covers oVirt Virtualization and how to add Compute Host to oVirt Virtualization. oVirt is a free and open-source distributed virtualization solution that can be used to manage your entire infrastructure.
oVirt allows you to manage virtual machines, compute, storage and networking resources from the web-based interface. It uses KVM hypervisor and built upon several other community projects, including libvirt, Gluster, PatternFly, and Ansible.
To Add Compute Host to oVirt:
1. Validate oVirt Engine installation by logging into the console.
2. Navigate to Compute > Hosts > New and fill all required information.
3. Modify other settings in the left panel as you see fit and click "OK" button to provision the node.
4. The Status should change to Installing and will finish in few minutes.
To Configure Host Networking:
1. If you want to add additional networks – extra bridges with VLANs e.t.c, this can be done once the host is added.
2. First create a Logical Network on Network > New. Give Virtual Network correct details. For VLAN ID check "Enable VLAN tagging".
3. With the Host added and active you can configure its networking under Network Interfaces > Setup Host Networks.
4. Assign the Logical network to an interface.
5. Drag Virtual Network for mapping to host interface.
6. Configure IP addressing if required.
7. Once saved and successful it should turn green.
8. You can then proceed to create virtual machines using oVirt Management interface.
SELinux users on CentOS 7 – Actions and Deciphering error messages
This article covers more information about SELinux users on CentOS 7.
Deciphering SELinux Error Messages
We looked at one SELinux error message. We were then using the grep command to sift through /var/log/messages file. Fortunately SELinux comes with a few tools to make life a bit easier than that. These tools are not installed by default and require installing a few packages, which you should have installed in the first part of this tutorial.
The first command is ausearch. We can make use of this command if the auditd daemon is running. In the following code snippet we are trying to look at all the error messages related to the httpd daemon. Make sure you are in your root account:
ausearch -m avc -c httpdIn our system a number of entries were listed, but we will concentrate on the last one:
----
time->Thu Aug 21 16:42:17 2014
...
type=AVC msg=audit(1408603337.115:914): avc: denied { getattr } for pid=10204 comm="httpd" path="/www/html/index.html" dev="dm-0" ino=8445484 scontext=system_u:system_r:httpd_t:s0 tcontext=unconfined_u:object_r:default_t:s0 tclass=fileEven experienced system administrators can get confused by messages like this unless they know what they are looking for. To understand it, let’s take apart each of the fields:
type=AVC and avc: AVC stands for Access Vector Cache. SELinux caches access control decisions for resource and processes. This cache is known as the Access Vector Cache (AVC). That's why SELinux access denial messages are also known as “AVC denials”. These two fields of information are saying the entry is coming from an AVC log and it’s an AVC event.
denied { getattr }: The permission that was attempted and the result it got. In this case the get attribute operation was denied.
pid=10204. This is the process id of the process that attempted the access.
comm: The process id by itself doesn’t mean much. The comm attribute shows the process command. In this case it’s httpd. Immediately we know the error is coming from the web server.
path: The location of the resource that was accessed. In this case it’s a file under /www/html/index.html.
dev and ino: The device where the target resource resides and its inode address.
scontext: The security context of the process. We can see the source is running under the httpd_t domain.
tcontext: The security context of the target resource. In this case the file type is default_t.
tclass: The class of the target resource. In this case it’s a file.
Install ClickHouse on Ubuntu 20.04 - Step by step process to perform it
This article covers how to install ClickHouse on Ubuntu. Basically, ClickHouse is an open-source analytics database developed for big data use cases.
Install of ClickHouse on Ubuntu involves a series of steps that includes adjusting the configuration file to enable listening over other IP address and remote access.
Column-oriented databases store records in blocks grouped by columns instead of rows.
By not loading data for columns absent in the query, column-oriented databases spend less time reading data while completing queries.
As a result, these databases can compute and return results much faster than traditional row-based systems for certain workloads, such as OLAP.
Online Analytics Processing (OLAP) systems allow for organizing large amounts of data and performing complex queries.
They are capable of managing petabytes of data and returning query results quickly.
In this way, OLAP is useful for work in areas like data science and business analytics.
Aggregation queries are queries that operate on a set of values and return single output values.
In analytics databases, these queries are run frequently and are well optimized by the database.
Some aggregate functions supported by ClickHouse are:
1. count: returns the count of rows matching the conditions specified.
2. sum: returns the sum of selected column values.
3. avg: returns the average of selected column values.
Some ClickHouse-specific aggregate functions include:
1. uniq: returns an approximate number of distinct rows matched.
2. topK: returns an array of the most frequent values of a specific column using an approximation algorithm.
You can set up a ClickHouse database instance on your server and create a database and table, add data, perform queries, and delete the database.
You can start, stop, and check the ClickHouse service with a few commands.
To start the clickhouse-server, use:
$ sudo systemctl start clickhouse-server
The output does not return a confirmation.
To check the ClickHouse service status, enter:
$ sudo systemctl status clickhouse-server
To stop the ClickHouse server, run this command:
$ sudo systemctl stop clickhouse-server
To enable ClickHouse on boot:
$ sudo systemctl enable clickhouse-server
To start working with ClickHouse databases, launch the ClickHouse client.
When you start a session, the procedure is similar to other SQL management systems.
To start the client, use the command:
$ clickhouse-client
Unable to allow access for disk path in libvirtd - Fix it Now
This article covers tips to fix the error Unable to allow access for disk path in libvirtd. By default, migration only transfers the in-memory state of a running guest (such as memory or CPU state). Although disk images are not transferred during migration, they need to remain accessible at the same path by both hosts.
To fix Unable to allow access for disk path in libvirtd error:
Set up and mount shared storage at the same location on both hosts. The simplest way to do this is to use NFS:
1. Set up an NFS server on a host serving as shared storage. The NFS server can be one of the hosts involved in the migration, as long as all hosts involved are accessing the shared storage through NFS.
# mkdir -p /exports/images
# cat >>/etc/exports <<EOF
/exports/images 192.168.122.0/24(rw,no_root_squash)
EOF2. Mount the exported directory at a common location on all hosts running libvirt. For example, if the IP address of the NFS server is 192.168.122.1, mount the directory with the following commands:
# cat >>/etc/fstab <<EOF
192.168.122.1:/exports/images /var/lib/libvirt/images nfs auto 0 0
EOF
# mount /var/lib/libvirt/images
Install PowerDNS and PowerAdmin on CentOS 7 - How to do it
This article covers the step by step procedure to install PowerDNS on CentOS 7. PowerDNS (pdns) is an open source DNS server written in C++ and released under GPL License. It has become a good alternative for the traditional DNS server Bind, designed with better performance and low memory requirements.
PowerDNS provides two products, the Authoritative server, and the Recursor.
The PowerDNS Authoritative server can be configured through the different backend, including the plain Bind zone files, RDBMS such as MySQL, PostgreSQL, SQLite3 or LDAP.
To Install PowerDNS on CentOS 7:
1. First let's start by ensuring your system is up-to-date:
$ yum clean all
$ yum -y update
2. Install PowerDNS and backend.
First, you need to enable EPEL repository and all required packages on your system:
$ yum install epel-release
$ yum install bind-utils pdns pdns-recursor pdns-backend-mysql mariadb mariadb-server
Enable PowerDNS on boot and start PowerDNS server:
$ systemctl enable mariadb
$ systemctl enable pdns
$ systemctl enable pdns-recursor
3. Configure MariaDB.
By default, MariaDB is not hardened. You can secure MariaDB using the mysql_secure_installation script. you should read and below each steps carefully which will set root password, remove anonymous users, disallow remote root login, and remove the test database and access to secure MariaDB:
mysql_secure_installation
4. Create PowerDNS Database and User in MariaDB.
Login as a MariaDB root and create a new database and tables:
### mysql -uroot -p
5. Configure PowerDNS.
Open the /etc/pdns/pdns.conf file.
Finally, restart the Power DNS service:
$ systemctl restart pdns.service
$systemctl enable pdns.service
6. Configure Recursor.
Open the /etc/pdns-recursor/recursor.conf file.
Add Remote Linux Host to Cacti for Monitoring - Do it now
This article covers how to add a #Linux host to #Cacti.
Basically, Cacti is a network #monitoring device that creates personalized graphs of server efficiency.
SNMP, short for Simple Network Management Protocol is a protocol used for gathering information about devices in a network. Using SNMP, you can poll metrics such as CPU utilization, memory usage, disk utilization, network bandwidth, and so on.
To install snmp agent on Ubuntu, run the command:
$ sudo apt install snmp snmpd -y
To install #snmp agent On CentOS 8, run the command:
$ sudo dnf install net-snmp net-snmp-utils -y
SNMP starts automatically upon installation.
To confirm this, confirm the status by running:
$ sudo systemctl status snmpd
If the service is not running yet, start and enable it on boot as shown:
$ sudo systemctl start snmpd
To Add Remote Linux Host to Cacti for Monitoring:
1. Install SNMP service on Linux hosts. SNMP, short for Simple Network Management Protocol is a protocol used for gathering information about devices in a network.
2. Configuring SNMP service.
3. Configure the firewall rules for snmp.
4. Adding remote Linux host to Cacti.
To Install and Configure Cacti:
1. Cacti require few more dependencies, run the following command to install them:
yum -y install net-snmp rrdtool net-snmp-utils
2. As we have all the dependencies ready, we can now download the install package from Cacti website.
cd /var/www/html
wget http://www.cacti.net/downloads/cacti-1.1.10.tar.gz
3. You can always find the link to the latest version of the application on Cacti download page. Extract the archive using the following command.
tar xzvf cacti*.tar.gz
4. Rename your Cacti folder using:
mv cacti-1*/ cacti/
5. Now import the Cacti database by running the following command.
cd /var/www/html/cacti
mysql cacti_data < cacti.sql -u root -p
6. The above command will import the cacti.sql database into cacti_data using the user root.
It will also ask you the password of root user before importing the database.
7. Now edit Cacti configuration by running the following command.
nano /var/www/html/cacti/include/config.php
8. Now find the following lines and edit them according to your MySQL database credentials.
/* make sure these values reflect your actual database/host/user/password */
$database_type = 'mysql';
$database_default = 'cacti_data';
$database_hostname = 'localhost';
$database_username = 'cacti_user';
$database_password = 'StrongPassword';
$database_port = '3306';
$database_ssl = false;
SELinux on CentOS 7 - Set it up now
This article covers how to set up SELinux on #CentOS 7. #SELinux is a security mechanism built into the Linux kernel. Linux distributions such as CentOS, RHEL, and Fedora are equipped with SELinux by default.
SELinux improves server security by restricting and defining how a server processes requests and users interact with sockets, network ports, and essential directories.
To check SELinux mode:
The easiest way on how to check SELinux ( Security Enhanced Linux ) operation mode is to use getenforce command.
This command without any options or arguments will simply print a current status SELinux operational mode.
Furthermore, the current status of SELinux operational mode can be set permanently or temporarily.
To check whether SELinux is enabled or not:
1. Use the getenforce command. [vagrant@vagrantdev ~]$ getenforce Permissive.
2. Use the sestatus command.
3. Use the SELinux Configuration File i.e. cat /etc/selinux/config to view the status.
To configure SELinux to enforcing mode:
1. Open the /etc/selinux/config file in a text editor of your choice, for example: # vi /etc/selinux/config.
2. Configure the SELINUX=enforcing option: # This file controls the state of SELinux on the system.
3. Save the change, and restart the system: # reboot.
To enable SELinux without rebooting:
1. Changing the SELinux mode at run time. If SELinux is disabled it cannot be enabled without rebooting.
2. To detemine the current Mode of SELinux.
3. Changing the SELinux mode Permanently. In the /boot/grub/grub.conf file add a line: selinux=0.
4. Or in /etc/sysconfig/selinux change.
To permanently change mode to permissive:
1. Edit the /etc/selinux/config file as follows: # This file controls the state of SELinux on the system. # SELINUX= can take one of these three values: # enforcing - SELinux security policy is enforced.
2. Restart the system: $ reboot.
Install Monit monitoring system on CentOS 8 - How to do it
This article covers how to #install Monit on #Centos 8 system. Also, we dealt with how to configure Monit on Centos, adjusting the configuration and setting up alerts to notify the users.
#Monit is a free, open-source process supervision tool for Unix and Linux. With Monit, system status can be viewed directly from the command line, or via the native HTTP(S) web server. Monit is able to do automatic maintenance, repair, and run meaningful causal actions in error situations.
To enable web interface you need to make changes in monit configuration file.
The main configuration file of monit located at /etc/monit. conf under (RedHat/CentOS/Fedora) and /etc/monit/monitrc file for (Ubuntu/Debian/Linux Mint).
Monit is very easy to use nearly out of the box. By default, it is set up to check that services are running every 2 minutes and stores its log file in “/var/log/monit.
To Install Monit to monitor your server running CentOS:
1. Install EPEL repository: yum install epel-release yum update.
2. Install Monit: yum install monit.
3. Activate Monit to start automatically during the system boot and start it: systemctl enable monit systemctl start monit.
To #Install #Monit Package on #Ubuntu:
Run the commands given below;
sudo apt update
sudo apt install monit
After installing Monit, the commands below can be used to stop, start and enable Monit service;
sudo systemctl stop monit.service
sudo systemctl start monit.service
sudo systemctl enable monit.service
Ignore permission denied message from find command in Linux
This article covers how to resolve the error 'ignore permission denied message from find' which occurs while running a 'find' command in Linux.
The find command is used to locate files on a Linux or Unix like operating system.
The find command will search directory to match the supplied search criteria.
You can search for files by type, name, owner, group, date, permissions and more. By default the find will search all subdirectories for you.
Linux divides the file permissions into read, write and execute denoted by r,w, and x.
The permissions on a file can be changed by 'chmod' command which can be further divided into Absolute and Symbolic mode.
The 'chown' command can change the ownership of a file/directory.
If you prefer using the command line, you can easily find a file's permission settings with the ls command, used to list information about files/directories.
You can also add the –l option to the command to see the information in the long list format.
To change directory permissions in Linux, use the following:
1. chmod +rwx filename to add permissions.
2. chmod -rwx directoryname to remove permissions.
3. chmod +x filename to allow executable permissions.
4. chmod -wx filename to take out write and executable permissions.
dbus launch terminated abnormally
This article covers tips to resolve this #dbus #error message, dbus-launch terminated abnormally. You need to install D-Bus. It is nothing but a message bus system, a simple way for applications to talk to one another.
In addition to interprocess communication, D-Bus helps coordinate process lifecycle; it makes it simple and reliable to code a "single instance" application or daemon, and to launch applications and daemons on demand when their services are needed.
The dbus-launch command is used to start a session bus instance of dbus-daemon from a shell script.
It would normally be called from a user's login scripts.
With no arguments, dbus-launch will launch a session bus instance and print the address and PID of that instance to standard output.
To fix /bin/dbus-launch terminated abnormally without any error message on a CentOS/RHEL:
Type the following yum command to install D-Bus and Fonts:
$ sudo yum install dbus-x11
To install Fonts, type:
$ sudo yum groupinstall 'Fonts'
Now, you can run and tunnel X over ssh:
$ ssh -X user@server1.ibmimedia.com
$ xeyes
$ firefox
DirectAdmin error is not a valid username
This article covers tips to resolve DirectAdmin error: is not a valid username which happens if the username length of the account is larger than the value set in the DirectAdmin configuration file.
To fix DirectAdmin Admin Backup/Transfer restore error with no details, try to restore to a number than 10 characters.
You have to edit directadmin configuration and set this variable.
[root@mx ~]# vi /usr/local/directadmin/conf/directadmin.conf
then edit max_username_length to larger value. I my example 20.
max_username_length=20
Ansible error Shared connection to server closed
This article covers the Shared connection to server closed error which occur when we run an Ansible command to execute commands on two newly deployed CentOS 8 servers.
Ansible is an open-source automation tool, or platform, used for IT tasks such as configuration management, application deployment, intraservice orchestration, and provisioning.
While you can write Ansible modules in any language, most Ansible modules are written in Python, including the ones central to letting Ansible work. By default, Ansible assumes it can find a /usr/bin/python on your remote system that is either Python2, version 2.6 or higher or Python3, 3.5 or higher.
A quick fix to Ansible error Shared connection to server closed is to just add the path to python 3 in your inventory file.
It would look something like this:
ip_address ansible_python_interpreter=/usr/bin/python3
Then you could test if it works with the ping module:
ansible -m ping all
From the error details, the connection failed because the shell(s) in the remote system couldn't find the Python interpreter (/usr/bin/python) as indicated by the line: "module_stdout": "/bin/sh: /usr/bin/python: No such file or directory\r\n".
After checking the remote hosts, we discovered that the systems don't have Python 2 installed.
Check Python Binary
They have Python 3 installed by default and its binary is /usr/bin/python3.
According to the Ansible documentation, Ansible (2.5 and above) works with Python version 3 and above only.
Also, Ansible is supposed to automatically detect and use Python 3 on many platforms that ship with it.
However, if it fails to, then you can explicitly configure a Python 3 interpreter by setting the ansible_python_interpreter inventory variable at a group or host level to the location of a Python 3 interpreter.
Manage Networking with NetworkManager in RHEL CentOS 8
This article covers NetworkManager daemon for managing the networking service to dynamically configure and control network devices and keep connections up and active when they are available.
Netstat is a command line utility that can be used to list out all the network (socket) connections on a system.
It lists out all the tcp, udp socket connections and the unix socket connections.
To reboot Linux using the command line: To reboot the Linux system from a terminal session, sign in or “su”/”sudo” to the “root” account.
Then type “ sudo reboot ” to reboot the box. Wait for some time and the Linux server will reboot itself.
To troubleshoot network connectivity with Linux server:
i. Check your network configuration.
ii. Check the network configuration file.
iii. Check the servers DNS records.
iv. Test the connection both ways.
v. Find out where the connection fails.
vi. Firewall settings.
vii. Check Host status information.
To change the hostname in Linux Ubuntu:
i. Type the following command to edit /etc/hostname using nano or vi text editor: sudo nano /etc/hostname. Delete the old name and setup new name.
ii. Next Edit the /etc/hosts file: sudo nano /etc/hosts.
iii. Reboot the system to changes take effect: sudo reboot.
To reinstall #network service in #Linux (#Ubuntu / #Debian):
i. Use the following command to restart the server networking service. # sudo /etc/init.d/networking restart or
# sudo /etc/init.d/networking stop # sudo /etc/init.d/networking start else # sudo systemctl restart networking.
ii. Once this done, use the following command to check the server network status.
KVM live migration to resolve performance issues
This article covers how to use KVM live migration to achieve load balancing which is important in a server virtualization system to maintain server performance.
Migration enables an administrator to move a virtual machine instance from one compute host to another. A typical scenario is planned maintenance on the source host, but migration can also be useful to redistribute the load when many VM instances are running on a specific physical machine.
Kernel-based Virtual Machine (KVM) is an open source virtualization technology built into Linux.
Specifically, KVM lets you turn #Linux into a #hypervisor that allows a host machine to run multiple, isolated virtual environments called guests or virtual machines (VMs).
Live migration of virtual machines is necessary when you need to achieve high-availability setups and load distribution.
The #KVM hypervisor has been a powerful alternative to Xen and VMware in the Linux world for several years.
To make the virtualization solution suitable for enterprise use, the developers are continually integrating new and useful features.
An example of this is live migration of virtual machines (VMs).
Live #migration involves:
The instance keeps running throughout the migration.
This is useful when it is not possible or desirable to stop the application running on the instance.
Live migrations can be classified further by the way they treat instance storage:
1. Shared storage-based live migration. The instance has ephemeral disks that are located on storage shared between the source and destination hosts.
2. Block live migration, or simply block migration. The instance has ephemeral disks that are not shared between the source and destination hosts. Block migration is incompatible with read-only devices such as CD-ROMs and Configuration Drive (config_drive).
3. Volume-backed live migration. Instances use volumes rather than ephemeral disks.
Block live migration requires copying disks from the source to the destination host.
It takes more time and puts more load on the network. Shared-storage and volume-backed live migration does not copy disks.
Ispconfig vs vestacp
This article will guide you on how to choose the best control panel for customers. Basically, many factors depends to choose the right panel like Ispconfig and Vestacp.
Vesta control panel (#VestaCP) is an open source hosting control panel, which can be used to manage multiple websites, create and manage email accounts, FTP accounts, and #MySQL databases, manage DNS records and more.
To Install And Use Vesta Control Panel:
1. Install SSH Client.
2. Choose The Configuration Panel.
3. Login to Putty and VestaCP Installation.
4. Create a new user.
5. Add a new domain and database.
6. Add Cloudflare nameservers.
7. Add files to your domain via FTP.
8. Repeat the process for all your websites.
ISPConfig is a free open-source control panel application that allows website owners to easily administer their sites, similar to cPanel and Plesk.
It also allows resellers to manage multiple accounts on multiple physical or virtual servers.
ISPConfig only runs on #Linux servers.
To log into ISPConfig:
Navigate to the URL of your ISPConfig system (e.g. https://www.domain.tld:81 or http://www.domain.tld:81; replace "www. domain. tld" appropriately) with your Browser and enter your user name and your password into the form "Login". Confirm by clicking on "Login".
Roundcube empty startup greeting
This article will guide you on methods to resolve #Roundcube empty startup greeting error which occurs due to many reasons which include improper configuration of SSL, network #problem, firewall #error and so on.
Roundcube is a webmail client with strong security features and extensive customization options from its plugin repository.
It is important to set Roundcube config file as follows:
$config['default_host'] = 'imaps://domain.tld';
// TCP port used for IMAP connections
$config['default_port'] = 993;
To fix cPanel Roundcube Webmail "An error occurred":
This error indicates a potentially corrupt index file.
1. establish an SSH session with the server and navigate to:
/home/<username>/mail/<domain name>/<email account name>/
2. Find dovecot.index and rename it to dovecot.index.bak.
OpenLDAP and phpLDAPadmin on Linux
This article will guide you on how to install #OpenLDAP and phpLDAPadmin on #Ubuntu. Also, we covered the prospective error affacting OpenLDAP and phpLDAPadmin and its solution as well.
#LDAP (Lightweight Directory Access Protocol) is an open and cross platform protocol used for directory services authentication. LDAP provides the communication language that applications use to communicate with other directory services servers.
#Kerberos is used to manage credentials securely (authentication) while LDAP is used for holding authoritative information about the accounts, such as what they're allowed to access (authorization), the user's full name and uid.
To access #phpLDAPadmin:
Point your browser to http://IP_OF_SERVER/phpldapadmin (IP_OF_SERVER is the actual IP address of your LDAP server).
From the main window, click the login button in the left pane.
When prompted, you will log into your DN and enter the password for the admin user created during the slapd reconfiguration.
FFmpeg on CentOS
This article will guide you on how to install FFMPEG on #CentOS and fix its related #errors. FFmpeg is a powerful tool that can do almost anything with #multimedia files.
FFmpeg is a standard package on many #linux systems.
You can check if it is installed with a #command like dpkg -s ffmpeg .
If it is not installed, you should be able to install with your system's package manager. i.e. sudo apt-get install ffmpeg or search 'ffmpeg' in the Software Center on Ubuntu.
To run #FFmpeg in #Linux:
1. Start by updating the packages list: sudo apt update.
2. Next, install FFmpeg by typing the following command: sudo apt install ffmpeg.
3. To validate that the package is installed properly use the ffmpeg -version command which prints the FFmpeg version: ffmpeg -version.
Install SQL Server 2019 on Linux
This article will guide you the process to install #MSSQL Server 2019 on #CentOS 7 and Ubuntu 16.04.
SQL Server 2019 #Developer is a full-featured free edition, licensed for use as a development and test database in a non-production environment.
SQL Server 2019 allows us to integrate data from structured and unstructured data sources.
We can now process diverse big data and relational data sources using Transact-SQL from SQL Server using PolyBase.
We can see below PolyBase support external databases.
SQL Server Express can be used in production (beware of the limitations, like the 10GB cap), but according to this link Express is available for Linux. SQL Server Express is available to use in Production.
Starting with SQL Server 2017, SQL Server runs on Linux. It's the same SQL Server database engine, with many similar features and services regardless of your operating system. It's the same SQL Server database engine, with many similar features and services regardless of your operating system.
To run a SQL script in #Linux terminal:
1. Open Terminal and type mysql -u to Open the MySQL command line.
2. Type the path of your #mysql bin directory and press Enter.
3. Paste your #SQL file inside the bin folder of mysql server.
4. Create a #database in MySQL.
5. Use that particular database where you want to import the SQL file.
Install WireShark CentOS
This article will guide you on how to install WireShark on #CentOS. WireShark is one of the leading #network analyzing tools. It helps in troubleshooting the traffic problems of a server and malicious activity.
Wireshark is an open-source, free network packet analyzer, used to capture and analyze network traffic in real-time.
Basically, with Wireshark you can capture and view data traveling through your network.
You can install WireShark with yum install wireshark-gnome .
After you install it, the Wireshark application will be at /usr/sbin/wireshark .
To install #wireshark on RHEL 8 / CentOS 8 Linux step by step instructions:
1. Install package called Whireshark using the dnf command. For a GUI Wireshark application execute: # dnf install wireshark To install Wireshark command line tool only execute: # dnf install wireshark-cli.
2. Launch Wireshark.
To install Wireshark from #terminal:
Open terminal and type the #commands:
i. sudo apt-get install wireshark.
ii. sudo dpkg-reconfigure wireshark-common.
iii. sudo adduser $USER wireshark.
iv. wireshark.
Monitor System Metrics with the TICK Stack on CentOS 7
This article will guide you on how the TICK stack can be a powerful tool for storing, analyzing, and visualizing time series data. To monitor InfluxDB _internal metrics in a production #cluster, use Telegraf and the influxdb input plugin to capture these metrics from the InfluxDB /debug/vars endpoint and store them in an external InfluxDB monitoring instance.
More about Kapacitor:
#Kapacitor is a native data processing engine for #InfluxDB 1. x and is an integrated component in the InfluxDB 2.0 platform.
Kapacitor can process both stream and batch data from InfluxDB, acting on this data in real-time via its programming language TICKscript.
A retention policy (RP) is the part of InfluxDB data structure that describes for how long InfluxDB keeps data.
InfluxDB compares your local server's timestamp to the timestamps on your data and deletes data that are older than the RP's DURATION .
A single database can have several RPs and RPs are unique per database.
OpenVPN on Linux
This article will guide you on steps to set up OpenVPN on Linux.
OpenVPN config files (. ovpn) offer an easy way to configure #OpenVPN on your computer to work with our servers. These files contain the correct cipher types, #Certificate Authority, Certificate, and Private Keys. You can use these files on Mac, Linux, #Windows, Android, and iOS.
By default the OpenVPN Access Server comes configured with OpenVPN daemons that listen on port 1194 UDP, and OpenVPN daemons that listen on port 443 TCP. While the best connection for an OpenVPN #tunnel is via the #UDP port, we implement TCP 443 as a fallback method.
To Set up OpenVPN Server on Ubuntu #Linux:
1. Find and note down your public IP address.
2. Download openvpn-install.sh script.
3. Run openvpn-install.sh to install OpenVPN server.
4. Connect an OpenVPN server using iOS/Android/Linux/Windows client.
5. Verify your connectivity.
Install XRDP Server
This article will guide you on steps to install XRDP #Server on #Ubuntu. To provide remote access via RDP, a Windows native protocol, XRDP behind the scenes uses #VNC, a remote access protocol more common in Linux.
After #xrdp is installed you can start the server with the following command:
Service xrdp start.
Service xrdp-sesman start (Thanks to Greg for pointing that out) — UPDATE!!
If want it to auto start after reboot you need to run this command also: update-rc.d xrdp enable (It will not start xrdp-sesman automatic).
To use XRDP Linux:
1. With #Ubuntu 18.04 first install xrdp: sudo apt-get -y install xrdp.
2. Next, one may adjust the configuration file: sudo nano /etc/xrdp/xrdp.ini.
3. Set encryption level to high: encrypt_level=high.
4. Next, allow just RDP through the local firewall: sudo ufw allow 3389/tcp.
Using CSF firewall to block countries
This article will guide you on how to block/allow countries in the CSF #firewall. CSF is used to restrict or allow countrywide IP ranges in the server using the country codes. For every country you want to deny, you just enter those letters in the field (separated by a comma). Once you're done, scroll to the bottom of the page and click CHANGE. This will restart the firewall, and you're now all set to go.
ConfigServe Firewall (#CSF) is a firewall configuration script created to provide better security for your server while giving you an easy to use and advanced interface for managing your #firewall settings in cPanel servers.
To limit the ability to connect on a specific port or ports to visitors with IP addresses originating in a specific country or countries, you must:
1. close the ports in the firewall.
2. define the country code allowed to connect on those blocked ports.
3. specify the blocked #ports to be opened for the specified country.
Install Vesta control panel in Ubuntu
This article will guide you on easy steps to install Vesta control panel in #Ubuntu. VestaCP is a control panel for Linux with many features that facilitate the administration of a #server.
Vesta Development team provides an installer script that automates setting up of Vesta hosting control panel on Ubuntu / Debian and RHEL based Linux distributions. Login to your Ubuntu / #Debian system and ensure the system is updated. Download #Vesta installer. Run install with sudo if you're logged in as standard user.
To install vestaCP on Ubuntu:
1. # Connect to your server as root via #SSH
ssh root@your.server
2. # Download installation script
curl -O http://vestacp.com/pub/vst-install.sh
3. # Run it
bash vst-install.sh
To change my VestaCP port:
i. conf file and change the port that NGINX listens on from 8083 to 2083 (or the port you chose to use). listen 2083;
ii. Once the port has been changed, press CTRL+X , followed by y , and then hit enter to save your changes.
iii. The final step is removing the firewall entry for the previous port we were using.
GlusterFS install CentOS 7
This article will guide you on the steps to install and setup #GlusterFS.
GlusterFS is a scalable #network filesystem suitable for data-intensive tasks such as cloud storage and media streaming.
GlusterFS has a client and #server component. Servers are typically deployed as storage bricks, with each server running a glusterfsd daemon to export a local file system as a #volume.
To install GlusterFS:
1. Have at least two nodes. CentOS 7 on two servers named "server1" and "server2".
2. Format and mount the bricks.
3. Installing GlusterFS.
4. #Iptables configuration.
5. Configure the trusted pool.
6. Set up a GlusterFS volume.
7. Testing the GlusterFS volume.
Configure and host an application in Apache web server on Ubuntu
This article will guide you on how to configure #Apache on #Linux. This includes #firewall configuration, managing Apache services, setting up virtual hosts, changing default listening ports, and allowing/denying specific IPs from accessing the #sites.
Apache #HTTP Server is a free and open-source web server that delivers web content through the internet. It is commonly referred to as Apache and after development, it quickly became the most popular HTTP client on the web.
The httpd. conf file is the main configuration file for the Apache web server. It's highly recommended to run Apache in standalone type for better performance and speed. ServerRoot "/etc/httpd" The option ServerRoot specifies the directory in which the configuration files of the Apache server lives.
On most systems if you installed Apache with a package manager, or it came preinstalled, the Apache configuration file is located in one of these locations:
1. /etc/apache2/httpd. conf.
2. /etc/apache2/apache2. conf.
3. /etc/httpd/httpd. conf.
4. /etc/httpd/conf/httpd. conf.
Enable firewalld in Centos 7 How to do it
This article will guide you on steps to enable firewalld on #centos 7 servers for our customers. The firewall is one of the most important features of webservers. The #firewalld supports both IPv4 and IPv6 #firewall #settings.
Never run the iptables service and FirewallD service at the same time! The #iptables service is now provided by a separate package called iptables-services: Stop and disable the firewalld service first. # systemctl stop firewalld.
The firewalld daemon manages groups of #rules using entities called "zones". Zones are basically sets of rules dictating what traffic should be allowed depending on the level of trust you have in the networks your #computer is connected to.
To use FirewallD:
1. Installing and Managing FirewallD.
2. To start the service and enable FirewallD on boot: sudo systemctl start firewalld sudo systemctl enable firewalld.
3. Check the firewall status.
4. To view the status of the FirewallD daemon: sudo systemctl status firewalld.
5. To reload a FirewallD configuration: sudo firewall-cmd --reload.
Imagick php install
This article will guide you on how to install #Imagick #PHP #extension. Imagick is the most popular PHP extension which helps to create edit convert, and/or manipulates images. ImageMagick is a free and open source, feature-rich, text-based and cross-platform image manipulation tool used to create, edit, compose, or convert bitmap images. It runs on #Linux, #Windows, #Mac Os X, iOS, Android OS, and many other operating systems.
To use Imagick with PHP in your server, you can easily achieve it with the following #command:
sudo apt-get install php-imagick.
php -m | grep imagick.
sudo service apache2 restart.
How Chmod 777 works
This article will guide you on how to give #Chmod 777 to folders and files in #Linux. We also discussed the risks and more information about file permissions.
If you are managing a Linux system, it is crucial to know how the Linux #permissions work.
You should never set 777 (rwxrwxrwx) permissions #files and #directories permissions. 777 means that anyone can do anything with those files.
To Give Root Privileges to a User in Linux:
1. Adding to Root Group using usermod. Let see how we can grant normal user root access by adding to root group.
2. Adding to #Root Group using Useradd Command.
3. Editing /etc/passwd file.
4. Setting as Sudo User.
Add User To Group in Linux
This article will guide you on how to add a #user to a #group in #Linux. The group permissions apply only to the group that has been assigned to the file or directory, they will not effect the actions of other users. The others permissions apply to all other users on the system, this is the permission group that you want to watch the most.
Groups can be thought of as levels of #privilege. A person who is part of a group can view or modify files belonging to that group, depending on the permissions of that file. User belonging to a group has privileges of that group, for example - sudo groups lets you run software as super user.
To view all groups present on the system simply open the /etc/group file. Each line in this file represents information for one group. Another option is to use the getent command which displays entries from #databases configured in /etc/nsswitch.
To Create a New Sudo User:
1. Log in to your server as the root user. #ssh root@server_ip_address.
2. Use the adduser command to add a new user to your system. Be sure to replace username with the user that you want to create.
3. Use the usermod command to add the user to the wheel group.
4. Test sudo access on new user account.
To List Users in Linux:
i. Get a List of All Users using the /etc/passwd File.
ii. Get a List of all Users using the getent Command.
iii. Check whether a user exists in the Linux system.
iv. System and Normal Users.
Ansible Playbook to Install WordPress with LAMP
This article will guide you on the step to follow to use #Ansible Playbook to install #WordPress with #LAMP on #Ubuntu 18.04.
In Ansible, the role is the primary mechanism for breaking a #playbook into multiple files. This simplifies writing complex #playbooks, and it makes them easier to reuse. The breaking of playbook allows you to logically break the playbook into reusable components.
To start using Ansible:
1. Prerequisites.
2. Install Ansible.
3. Establish a manual connection to a managed node.
4. Run your first network Ansible command.
5. Create and run your first network Ansible Playbook.
6. Gathering facts from network devices.
Install imagemagick on CentOS
This article will guide you on steps to #install #ImageMagick and fix its errors. Basically, ImageMagick is used to manipulate the digital images.
ImageMagick helps to create, edit, compose, or convert #bitmap images. It can read and write images in a variety of formats (over 200) including #PNG, JPEG, GIF, HEIC, TIFF, DPX, EXR, WebP, Postscript, PDF, and #SVG.
To install ImageMagick from the source:
1. First #download the latest version of the program sources - ImageMagick.
2. Unzip the package to a folder of choice.
3. In the folder where you have unzipped ImageMagick run the configuration script.
4. If no errors were found, you can start the install process.
Install Froxlor on CentOS 7
This article will guide you on steps to #install Froxlor on #CentOS 7 and also resolve common Froxlor #errors.
#Froxlor is a simple but powerful server administration #software for managing #domains, emails and files.
To install Froxlor web hosting control panel:
1. Ensure that your webserver serves /var/www.
2. Extract froxlor into /var/www.
3. Point your browser to http://[ip-of-webserver]/froxlor.
4. Follow the #installer.
5. Login as #administrator.
6. Adjust "System > Settings" according to your needs.
7. Choose your distribution under "System > Configuration".
8. Follow the steps for your services.
Yum http error 416 How to fix it
This article will guide you on steps to fix #yum #HTTP #error 416 which occurs while updating, installing, upgrading packages. This is rectified easily via disabling the delta #rpm problem, reinstalling a #package, clear #caching and so on.
To fix this error:
1. yum clean all
2. yum upgrade --exclude=polkit*
3. reboot
4. yum clean all
5. yum upgrade
List installed software Linux
This article will guide you on different methods to #list all #software, the number of #packages available on the server along with the method to copy them and use them when we reinstall our operating system(#OS).
Yum automatically refreshes the list of packages, whilst with apt-get you must execute a command 'apt-get update' to get the fresh packages.
To list of installed programs in #Linux:
1. Aptitude-based distributions (#Ubuntu, #Debian, etc): dpkg -l.
2. RPM-based distributions (#Fedora, #RHEL, etc): rpm -qa.
3. pkg*-based distributions (#OpenBSD, #FreeBSD, etc): pkg_info.
4. Portage-based distributions (#Gentoo, etc): equery list or eix -I.
5. pacman-based distributions (Arch Linux, etc): pacman -Q.
Add Glance Cloud images to OpenStack
This article will guide you on steps to add #Glance #Cloud images to #OpenStack with different #Linux distributions which enables users to discover, register, and retrieve virtual machine images.
After images are created they should be registered in Openstack Glance - #image operation service.
Upload Image Into Glance:
1. Replace <NAME> with the name that users will refer to the disk image by.
2. Replace <IMAGE_FILE> with the local path to the image file to upload.
Directadmin Unable to write users httpd conf configuration
This article will guide you on how to fix the #error, Unable to write user's httpd.conf in Directadmin which occurs when we try to add a #domain in #DirectAdmin.
The httpd. conf file is the main configuration file for the Apache web server. It's highly recommended to run Apache in standalone type for better performance and speed. ServerRoot "/etc/httpd" The option ServerRoot specifies the directory in which the configuration files of the Apache server lives.
Before you edit httpd.conf, you should first copy the original file to something like httpd.conf-old, for example.
By creating a #backup, you can recover potential mistakes made while editing the new configuration file.
Cant locate LWP UserAgent pm in @INC
This article will guide you on how to get rid of error "Can't locate LWP/UserAgent.pm in @INC" which occurs in the process of installing #applications like CSF in the DirectAdmin server or any other #Linux #distros.
libwww-perl (also known as LWP) is a collection of #Perl #modules that provide a simple and consistent programming interface (API) to the World-Wide Web.
In order to install and use this #package you will need Perl version
5.8.1 or better:
Some modules within this package depend on other packages that are distributed separately from Perl. We recommend that you have the following #packages installed before you install
libwww-perl:
i. Digest-MD5
ii. Encode-Locale
iii. HTML-Form
iv. HTML-Parser
v. HTML-Tagset
vi. HTTP-Cookies
vii. HTTP-Date
viii. HTTP-Message
ix. HTTP-Negotiate
x. libnet
xi. LWP-MediaTypes
xii. MIME-Base64
xiii. Net-HTTP
xiv. URI
xv. WWW-RobotRules
If you want to access sites using the https protocol, then you need to
install the LWP::Protocol::https module from CPAN.
Install Graylog on CentOS 7 How to do it
This article will guide you on steps to #Graylog on #CentOS 7 and an effective method to make the logs more structured and searchable.
Graylog is a leading centralized log management solution built to open standards for capturing, storing, and enabling real-time analysis of terabytes of #machine data.
Graylog is an open source log management platform which enables you to aggregate up to terabytes of log data, from multiple log sources, DCs, and geographies with the capability to scale horizontally in your data center, #cloud, or both.
To #Install Graylog 3 with Elasticsearch on CentOS 7:
1. Configure #SELinux.
2. Add required #repositories
3. Install #Java, #Elasticsearch, and #MongoDB.
4. Configure Elasticsearch for Graylog.
5. Install Graylog 3 on CentOS 7.
6. Start Graylog service on CentOS 7.
Backup and Restore Nagios Log Server
This article will guide you on the steps to perform #backup and #restore a #Nagios #Log #Server cluster. Taking Backup and Restore of Nagios Log Server helps not to lose any data as it is held in other instances.
Backup and recovery describes the process of creating and storing copies of #data that can be used to protect organizations against data loss. #Recovery from a backup typically involves restoring the data to the original location, or to an alternate location where it can be used in place of the lost or damaged data.
To do a backup and system restore:
1. Click Start.
2. Go to Control Panel.
3. Go to System and Security.
4. Click Backup and Restore.
5. At the Back up or restore your files screen, click Restore my files.
6. Browse to locate the backup file.
Install InfluxDB on CentOS 7
This article will guide you on steps to Install #InfluxDB on #CentOS 7. You can Turn any InfluxData #instance into a production-ready cluster that can run anywhere. Easily create and share a comprehensive monitoring solution.
InfluxDB is similar to a #SQL #database, but different in many ways. Relational databases can handle time series data, but are not optimized for common time series workloads. InfluxDB is designed to #store large volumes of time series data and quickly perform real-time analysis on that data.
The local InfluxDB configuration file is located here: Linux: /etc/influxdb/influxdb. conf. macOS: /usr/local/etc/influxdb.
To Install InfluxDB:
Option 1 : Download the InfluxDB archive via the browser.
Option 2 : Adding the #repositories to your package manager.
i – Start your InfluxDB service.
ii – Configure your InfluxDB instance.
iii – Test your InfluxDB instance.
iv – #Download InfluxDB 2.0 archive from the website.
OpenLDAP on Ubuntu Steps to install it
This article will guide you on the steps to #install and configure #OpenLDAP on #Ubuntu.
OpenLDAP is a open source implementation of #LDAP in Linux.
If it's your #server, you will know just by looking at the running services. When you are there, run #netstat and probably you will see LDAP listening only on localhost . Remotely, if the server is listening on #localhost , you cannot know just by running nmap , the port will not answer for the public #interface.
To Install and Configure OpenLDAP on #CentOS / #RHEL #Linux:
1. Install OpenLDAP Packages. On CentOS and RedHat, use yum install as shown below, to install the openldap related packages.
2. LDAP #Config Files. config.
3. Create olcRootDN Account as Admin.
4. Create olcRootPW Root Password.
5. Create olcSuffix #Domain Name.
6. Verify The #Configuration Files.
7. Start the LDAP Server.
8. Verify the LDAP Search.
Apache Performance Tuning via MPM Directives
This guide will help you to configure #MPM directives in the #Apache server. You can simply configure MPM #directives by logging into the server and create an optimization file and add the necessary directive change.
Starting with Apache 2.0, Apache extended its features with a selection of Multi-Processing Modules (#MPMs), which are responsible for binding to #network ports on the machine, accepting and handling the requests. These modules determine the basis of how Apache addresses multi-processing.
To know which MPM Apache is using:
1. Enable Apache mod_info.
2. Query the mod_info url, typically curl localhost/server-info.
3. The "Server Settings" section will show "MPM Name: #Worker"
4. Run httpd -V again. It will still show prefork, not worker.
How to Install OpenNMS on CentOS 8
This article will guide via a step-by-step procedure to #install OpenNMS in #CentOS.
OpenNMS is a free, Open Source network monitoring system that can be used to #monitor tens of thousands of unlimited devices with a single #instance.
It will discover and monitor the services or nodes automatically in your #network, or you can assign a particular service to monitor by OpenNMS.
To configure #OpenNMS:
1. Install OpenNMS Horizon. Add yum repository and import GPG key.
2. Initialize and set up #PostgreSQL. Initialization of the PostgreSQL database will start.
3. Initialize and start OpenNMS Horizon.
4. First Login and change default password.
How To Install MariaDB on Ubuntu Focal Fossa
This article will guide you on steps to install #MariaDB from the #Ubuntu #repositories and from the official MariaDB repositories. You can install MariaDB in two different ways.
To install MariaDB on Ubuntu, follow these steps:
1. Update #packages index. sudo apt update.
2. Once the packages list is updated, install MariaDB by issuing the following command: sudo apt install mariadb-server.
3. The MariaDB service will start automatically.
The default data directory for the MariaDB database server is /var/lib/mysql. The configuration file of MariaDB database server is /etc/mysql/mariadb. conf. d/50-server.
SQL Server and create a database on Ubuntu How to install
This article will guide you on how to #install MS SQL on #Ubuntu Server 18.04.
To Install #Microsoft SQL Server 2017:
1. Visit Microsoft's official SQL Server 2017 download page.
2. Select the edition you want to #download.
3. Click Download now below your selected edition.
4. The wizard will prompt you to select an installation type.
5. On the next page, select a directory for the installation folder.
To connect to the SQL Server using #SSMS:
i. From the Connect menu under the Object Explorer, choose the #Database Engine.
ii. Then, enter the information for the Server name (localhost), Authentication (SQL Server Authentication), and password for the sa user.
iii. Click the Connect button to connect to the SQL Server.
oVirt Guest Agent on CentOS 8 and RHEL 8 Steps to install
This article will guide you on how to install oVirt Guest Agent on CentOS and RHEL. oVirt / #RedHat V#irtualization guest agent provides information, notifications, and actions between the #oVirt web interface and the guest.
To install oVirt guest agent:
1. Log in to the Red Hat Enterprise Linux virtual machine.
2. Enable the Red Hat Virtualization Agent #repository.
3. Install the guest #agent and #dependencies: # yum install ovirt-guest-agent-common.
4. Start and enable the ovirt-guest-agent service.
5. Start and enable the qemu-guest-agent service.
NFS Server on RHEL CentOS 8 Steps to install and configure
This article will guide you on the steps to Install and Configure #NFS Server on #RHEL or #CentOS.
The terms client and server are used to describe the roles that a computer plays when sharing file systems. The NFS service enables any given computer to access any other computer's file systems and, at the same time, to provide access to its own file systems.
To install NFS server:
1. Install NFS #Kernel Server.
2. Create the #Export #Directory.
3. Assign server access to client(s) through NFS export file.
4. Export the shared directory.
5. Open #firewall for the client (s).
VirtualHost cannot occur within virtualhost section in WAMP
This article will guide on steps to fix #VirtualHost cannot occur within virtualhost section in #WAMP which occurs while we try to add VirtualHost #directive and reconfigure #vhost.
Directory directive works only for filesystem objects (e.g. /var/www/mypage, C:\www\mypage), while Location directive works only for URLs (the part after your site #domain name, e.g. www.mypage.com/mylocation).
To Configure name-based virtual #hosts:
1. Install Apache webserver. Make sure you have installed #Apache webserver.
2. Create web directory for each host.
3. Create demo web pages for each host.
4. Create configuration file for each host.
5. Enable virtual host configuration files.
6. Test Virtual hosts.
Manage a Linux Server with systemd
Like the init #daemon, #systemd is a daemon that manages other daemons, which, including systemd itself, are background #processes. systemd is the first daemon to start during booting and the last daemon to terminate during shutdown.
This article will guide you on how to manage #Linux server using systemd. Additionally, we saw the different commands used to Manage Linux serves with systemd. While systemd is compatible with SysV and Linux Standard Base (LSB) init scripts, systemd is meant to be a drop-in replacement for these older ways of getting a Linux system running.
To start (activate) a service , you will run the command 'systemctl start my_service. service', this will start the service immediately in the current session.
To enable a service at boot , you will run 'systemctl enable my_service. service'.
Using Cron to Automate Tasks on CentOS 8
This article will guide you on the steps to set up #Cron job on #CentOS 8 to help automate #tasks. Cron is a #clock daemon, whose name originates from #Chronos, the Greek word for time. It enables users to automate the execution of #commands, scripts (a group of commands) or programs at specified time intervals.
The simplest way to validate that cron tried to run the #job is to simply check the appropriate log file; the log files however can be different from system to system. In order to determine which log file contains the cron #logs we can simply check the occurrence of the word cron in the log files within /var/log .
Deploy Laravel using Nginx on Ubuntu
This guide will help to set up Laravel with #Nginx on #Ubuntu 16.04. Laravel is the most popular, free, and open-source #PHP #framework in the world, known for its expressive and elegant syntax.
To move laravel project from localhost to production server, do:
1. Zip your #laravel app files.
2. Export your app's #database then set it up on your server.
3. After you have uploaded your laravel app files, open the . env file found on the root.
4. That's it!, now check your live #site.
How to install Metricbeat on CentOS 7 to Gather Infrastructure Metrics
This article will guide you on the steps to install #Metricbeat and configure the Elastic Stack to collect and analyze system metrics. Metricbeat is configured using a #YAML configuration file. On Linux, this file is located at: /etc/metricbeat/metricbeat. yml. On #Docker, you will find it at: /usr/share/metricbeat/metricbeat.
Both #Filebeat and #Logstash can be used to send #logs from a file-based data source to a supported output destination.
Steps To Harden OpenSSH Client on Ubuntu 18 04
This article will guide you on how to harden #OpenSSH Client by following some quick and easy steps.
#Hardening of the #OS is the act of configuring an OS securely, updating it, creating #rules and #policies to help govern the system in a secure manner, and removing unnecessary applications and services. This is done to minimize a computer OS's exposure to threats and to mitigate possible #risk.
Steps to Edit Sudoers File in Linux Process to get it done
This article will guide you on how to edit #Sudoers File in Linux which involves #root privileges, with a special focus on editing the /etc/sudoers file. You can configure who can use #sudo #commands by editing the /etc/sudoers file, or by adding configuration to the /etc/sudoers. To edit the sudoers file, we should always use the #visudo command. This uses your default editor to edit the sudoers configuration.
HAProxy Logging with Rsyslog on CentOS 8
This article will guide you on how to set up #HAProxy Logging #Rsyslog with some quick and easy steps. HAProxy is installed with RightScale load #balancer ServerTemplates. Load-balancer servers are also known as front-end servers. Generally, their purpose is to direct users to available #application servers. HAProxy can be installed in front of them to provide load balancing and high availability.
Using Bpytop to monitor Linux and FreeBSD Resources
This article will guide you on how to use Bpytop Monitoring for Linux & FreeBSD Resources.
#Bpytop is a great utility which is useful on your #Linux, #macOS, and #FreeBSD as a #resource #monitor. It is much faster than bashtop and works pretty well as Python 3 is standard on many Unix boxes.
Steps to create a Self-Signed SSL Certificate for Apache in CentOS 8
This article will guide you on how to configure #Apache to serve encrypted requests using a self-signed SSL certificate and to redirect unencrypted HTTP requests to #HTTPS. Self-signed #certificates or certificates issued by a private CAs are not appropriate for use with the general public. It can only properly verify the identity of the server when it is signed by a trusted third party because any attacker can create a self-signed certificate and launch a man-in-the-middle attack.
Send NXLogs with SSL TLS to Nagios Log Server
This guide will guide you on how to send NXLogs with SSL/TLS to #Nagios #Log #Server. Encryption ensures that the traffic between the #Windows machine and Nagios Log Server is not sent in plain text.
Install and configure Grafana on CentOS 7
This article will guide you on the steps to #install #Grafana on #CentOS 7 which is a #visualization and #analytics #monitoring software. Grafana is Free and Open Source which Runs on all major #OS operating systems.
Step by step process to Secure Apache with Lets Encrypt on CentOS 8
This article will guide you on the process to secure #Apache with Let’s Encrypt by installing Let's Encrypt #Certbot client, downloading #SSL #certificates for the #domain, and setting up automatic certificate renewal.
The objective of Let's Encrypt and the #ACME protocol is to make it possible to set up an #HTTPS server and have it automatically obtain a browser-trusted certificate, without any human intervention.
YUM History command Ways to use it
This article will guide you on #YUM history #command in #Linux which provides a detailed history of YUM #transactions in order to find out information about installed packages and those that where removed/erased from a #system.
The yum history command allows users to review information about a timeline of Yum transactions, the dates and times they occurred, the number of packages affected, whether transactions succeeded or were aborted, and if the RPM #database was changed between transactions.
How To Troubleshoot Common HAProxy Errors
This article will guide you on the different methods to #troubleshooting and fix common #HAProxy errors which can range from diagnosing #errors with the service itself to locating misconfigured options for modules.
ifconfig centos 7
This article will guide you on the steps to #install #ifconfig in #CentOS using the yum #package #manager.
The ifconfig command can tell you a lot about your Unix server's connection to your #network and the role it's playing in both generating and receiving network traffic.
Install and Configure ModSecurity on Ubuntu
This article will guide you on the steps to perform #ModSecurity installation on #Ubuntu which involves enabling Core Rule Set to handle malicious activities.
NFS server not responding timed out error How to fix
This article will guide you on how to fix #NFS server not responding timed out #error which occurs when there is a heavy #server or #network load.
Why NFS is not working?
i. Check the file /proc/fs/nfs/exports and make sure the volume and client are listed correctly.
ii. Finally, try to ping the client from the server, and try to ping the server from the client.
iii. If this doesn't work, or if there is packet loss, you may have lower-level network problems.
Install Prometheus Network Monitoring Server on CentOS 7
#Prometheus collects metrics from targets by scraping 3metrics #HTTP endpoints. Since Prometheus exposes #data in the same manner about itself, it can also scrape and monitor its own health.
This article will guide you on the steps to perform #installation of Prometheus on #CentOS 7 along with the method used for the #setup.
Resizing the Nagios VM disk size for CentOS 7
This article will guide you on the process to resize the #Nagios #VM #disk size.
Sync Two CentOS 8 Servers Using File Replication
The #sync command forces an immediate write of all cached data to disk. Run sync if you anticipate the system to be unstable, or the storage device to become suddenly unavailable, and you want to ensure all data is written to disk. Individual files may be synced, or the entire filesystem containing the specified files.
This article will guide you on the right steps to sync two #CentOS 8 #servers using file replication.
Backup, Restore and Migrate a MongoDB database on CentOS 8
MongoDB is highly scalable, using shards. Horizontal scalability is a big plus in most #NoSQL databases. MongoDB is no exception. It is also highly reliable due to its replica sets, and the data is replicated in more nodes asynchronously.
This article will guide you on the steps to perform #backup, #restore and #migrate a #MongoDB #database on #CentOS 8.
Steps to Install Pure-FTPD on Ubuntu 18.04 LTS Server
#Pure-FTPd is a fast, production-quality, standard-conformant #FTP (SSL/TLS) server, based upon Troll-FTPd.
This article will guide you through the processes to install Pure-FTPd on your #Ubuntu server.
Zimbra Multi-Server Installation on CentOS 7
This article will help you to go about Installing a single server in Zimbra by following some steps.
Different methods to List Users in CentOS 7
This article will guide you on the different methods to list users in CentOS 7.
Virtualmin common installation errors
This article will guide you on the different common errors in Virtualmin / Webmin and their fixes.
Install Squid Proxy on CentOS 7
This guide will show you the steps to install squid on Centos 7 as well as configure the port and adjusting the access control list.
Install DHCP Server Client on Centos
This article will guide you on the steps to install and configure a DHCP server on CentOS 8.
Major effects of shifting focus to CentOS Stream
This article is about the major effects of shifting focus to the CentOS Stream which is a sudden move by Red Hat.
Install Kamailio SIP proxy server on CentOS 7 in a few steps
This article will guide you on the steps to install and configure Kamailio sip proxy on CentOS.
RM cannot remove read-only file system tips to fix
This article will guide you on how to fix 'rm cannot remove the read-only file system' error by simply removing files from the read-only file system.
Install Nagios XI in an offline environment
This article will guide you on how to install Nagios XI in an offline environment using powershell.
TigerVNC Server installation and configuration
This article will guide you on how to install TigerVNC server CentOS 7.
Steps to Install Terraform On Ubuntu
This guide will show you how to install terraform on CentOS 7/Ubuntu 18.04.
Puppet installation on CentOS 7
This article will guide you through the steps you need to follow to get Puppet installed and configured on CentOS 7 Machine.
Htop installation on Linux
This article will show you how to install Htop across different Linux Distributions and Operating System.
Odoo installation on Centos
This article will guide you on how to install Odoo software on CentOS 7. Odoo is a very popular business software for managing business application.
Enable Epel repository on Linux
This article will show you how to enable EPEL repository on different Linux distribution. EPEL repo can be installed with the yum utility on CentOS and RHEL.
VirtualBox installation on CentOS 7
This article will help you to install VirtualBox on Centos. VirtualBox Software helps to create and run virtual machines on a single hardware machine.
How to Fix Boot Hole vulnerability CVE-2020-1073
Just recently, on the 29th, July 2020, Popular Linux Distribution RedHat announced that there was a great security concern in the grub2 (CVE-2020-1073) version.
Method to upgrade MySQL in VestaCP
It is very important to upgrade your OS MySQL database to the latest version so as to keep the system more secured and to enjoy the latest features.
Setup openvas on linux Debian and Ubuntu
OpenVAS software framework is a great security tool checking if the system is vulnerable by means of scanning and Management. It helps to safeguard the server from unauthorized access.
To Install OpenVAS on Ubuntu:
By default, the OpenVAS package is not available in the Ubuntu 16.04 repository, so you will need to add OpenVAS PPA to your system's repository list.
1. Add the OpenVAS PPA.
$ sudo add-apt-repository ppa:mrazavi/openvas
2. Update the repository.
$ sudo apt-get update
3. Finally, install OpenVAS.
$ sudo apt-get install openvas
4. Once OpenVAS has finished installing, start the OpenVAS service with the following commands:
$ sudo systemctl start openvas-scanner
$ sudo systemctl start openvas-manager
$ sudo systemctl start openvas-gsa
