Technology and Technology

Introduction Firewalld is a complete firewall solution available by default on CentOS 7 servers. In this guide, we will cover how to set up a firewall for your server and show you the basics of managing the firewall with the firewall-cmd administrative tool. Basic Concepts in Firewalld Before we begin talking about how to actually use the firewall-cmd utility to manage your firewall configuration, we should get familiar with a few basic concepts that the tool introduces. Zones 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. Network interfaces are assigned a zone to dictate the behavior that the firewall should allow. For computers that might move between networks frequently (like laptops), this kind of flexibility provides a good method of changing your ru...

ElasticSearch Installation: The version we want to install is 2.x (latest sub version of 2). First we have to install java on centOS machine with following command: sudo yum install java-1.8.0-openjdk.x86_64 Install Public Signing Key:   rpm --import https://packages.elastic.co/GPG-KEY-elasticsearch Create new repo in your /etc/yum.repos.d/ directory. For example I have created elasticsearch.repo here. /etc/yum.repos.d/elasticsearch.repo -------------------------------------------------------------------------------------------- [elasticsearch-2.x] name=Elasticsearch repository for 2.x packages baseurl=http://packages.elastic.co/elasticsearch/2.x/centos gpgcheck=1 gpgkey=http://packages.elastic.co/GPG-KEY-elasticsearch enabled=1 --------------------------------------------------------------------------------------------- Now Elasticsearch 2.x will avilable for installation using yum   yum install elasticsearch After installation enable the service a...

Network Scenario: LB1: 192.168.10.10 LB2: 192.168.10.11 Virtual IP: 192.168.10.12 APP_Server1: 192.168.10.20 APP_Server2: 192.168.10.21 Load Balancing: STEP 1 - Install HAProxy: HAProxy package is available under default yum repository for CentOS, Redhat systems. Use the following yum package manager command to install HAProxy on your system.   # yum install haproxy   STEP 2 - Configure HAProxy : Update your HAProxy configuration file /etc/haproxy/haproxy.cfg as per your requirement, You may also use below given configuration file as an example of setup and modify it. Keep the config file same of both servers i.e. LB1 and LB2.   ----------------------------------------------------------------------------------------------------------- global         log /dev/log    local0         log /dev/log    local1 notice     ...

HAProxy automatic failover HAProxy is a TCP load balancing tool with some useful features, including ACLs and SSL termination support. I’ve been using it for a while now on a number of load-balanced sites where scalability is key. What I haven’t yet looked at, however, is automated failover capabilities. My aims were simple: If a server fails, stop using it. If said server starts working again (i.e. because the problem is fixed) start using it again. If all servers in the load balancer pool fail, serve a temporary static page from another location. But first: Some basic HAProxy concepts HAProxy as a load balancer is fairly simple, and works on the basis of defined frontends and backends. A frontend is simply an IP and port declaration that you want the load balancer to listen on. A backend is the set of servers that requests to a frontend are sent to. Your HAProxy configuration lists the frontends and their respective backends, as well as the load balancing algorithm ...