Using screen command to share session on Linux system

Lets take a look at how to share existing ssh session using command called screen. It is very useful in case where you have to show your users something remotely. First install screen program – We assume CentOS7 yum install screen System1 You can create multiple screen sessions or share existing on Create multiple screen…

Change email address from which Nagios sends messages

In some cases you want to change default email address of anonymous@hostname from which Nagios sends notifications. This can easily be done by changing following directives in Nagios configuration files. 1. Open the main Nagios configuration file nagios.cfg and edit the line containing admin_email vim nagios.cfg admin_email=nagios@localhost # change to your desired smtp address 2….

Changing name of salt minion CentsOS 7

We run into situation when we needed to change name of already added salt minion. Here is few simple steps that will get this done. On Salt minion Stop the Salt-Minion Service systemctl stop salt-minion Delete the current keys cd /etc/salt/pki/minion/ rm -rf minion.pub minion.pem Change the minions id in /etc/salt/minion_id vim /etc/salt/minion_id myminion.prolinuxhub.com On…

Building MariaDB Master Salve replication cluster CentOS 7

Assumptions: We have 2 Linux VMs with 5.5.56-MariaDB. IP address 192.168.0.222(cluster1.local) and 192.168.0.223(cluster2.local) We have 3 existing databases on cluster1.local – mydb1, mydb2, mydb3 Setup Master (cluster1.local) Edit my.cnf file vi /etc/my.cnf bind-address = 0.0.0.0 server_id=1 log-basename=master1 log-bin replicate-do-db = mydb1 replicate-do-db = mydb2 Restart MariaDB systemctl restart mariadb Inside MariaDB prompt GRANT REPLICATION SLAVE…

Basic salt on CentOS7 both server and client

Very quick look at how to install and use Saltstack on one vm both server and minion. Also we loot at some basic commands that are needed to manage salt deployment Installing salt Salt server can be installed in many ways Option 1 (saltstack repo) yum install https://repo.saltstack.com/yum/redhat/salt-repo-latest-2.el7.noarch.rpm yum clean expire-cache yum install salt-master yum…

Using Vagrant, VirtualBox and Ansible with CentOS 7

This would be the case when you need to test playbooks locally before using Ansible to deploy them. We assume you already have installed Vagrant, Ansible and VirtualBox. Ansible is one of many provisioners integrated with Vagrant. Lets see how it works Create Vagrant box with CentOS 7 mkdir centtest cd centtest sudo vagrant init…

Installing and using docker CentOS7

We will not cover what docker does and how it works. We assume you already familiar with basic concepts. We will look into basics of installing and operating docker on CentOS 7. We will be looking into CE )(Community Edition) Installation We will go over install using repositories yum install -y yum-utils device-mapper-persistent-data lvm2 yum-config-manager…

Installing and using LXC Containers on CentOS 7

LXC allows us to share Linux kernel to run application in something similar to chroot environment. Lets take a look at how to install and manage LXC on CentOS 7. Containers reside in /var/lib/lxc/ directory Installation yum install epel-release yum install debootstrap perl libvirt yum install lxc lxc-templates systemctl start lxc.service systemctl start libvirtd systemctl…

Zimbra Collaboration 8.8 blank screen after install

After installing Zimbra Collaboration 8.8 or upgrading from previous version you may get blank screen in some cases when accessing your management URL or Web interface. In our example we are using mysite.com smtp domain with server named mail.mysite.com Troubleshooting In the nginx log file you will see following entries cat /opt/zimbra/log/nginx.log …………client closed connection…

Bash script to test websites with curl

We will look at very basic script which will make sure multiple websites are up and running. This is very basic script that utilities power of Linux tool called curl. Curl is well know tool used to automate url related tasks and much more. The basic script will use variable called $LIST_OF_WEBSITES which will contain…