Install Java 8 on CentOS/RHEL 7.x

If you have a fresh installation, it is recommended to run the update first
yum update
Usually Java comes installed on CentOS 7 (Everything), for CentOS 7 minimal you may need to install Java for various setups. On a CentOS 7 Everything, you can verify it by simply checking the version:
java -version

The output:

# java -version
openjdk version "1.8.0_111"
OpenJDK Runtime Environment (build 1.8.0_111-b15)
OpenJDK 64-Bit Server VM (build 25.111-b15, mixed mode)
Java 1.8.0_111-b15 is the latest available, ‘1.8.0’ states it is Java 8, ‘u111’ means update 111, and ‘b15’means build 15.
For CentOS 7 minimal, the same command will give a different output:
# java -version
-bash: java: command not found
Which means Java is not installed. The latest Java version currently is Java 8.

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Install Puppet Master-Agent on CentOS 7

Puppet is a configuration management tool for Unix-like and Microsoft Windows systems – which is basically provisioning automation i.e. the steps you want to preform on your freshly spawned virtual machine. Puppet uses declarative language for specification, and these configuration declaration files are termed as “Puppet manifests”. Puppet treats anything configurable as a “resource” i.e. file, service, package, user, cron, etc. The Puppet manifest is about describing the resources and their required states. Puppet gets the dynamic data (i.e. OS dependent) using Facter utility, for example Apache web server package is named ‘apache2’ in Ubunut, and ‘httpd’ for CentOS systems, Puppet allows variables in manifest (.pp file) to get such info on the fly, and set the right installation command.

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Syncing Date and Timezone – Install and configure ntpd

For various cluster or distributed application setups it’s an explicit requirement to have date and timezone (TZ) on each node synced. The difference in date or TZ may result in serious issues, for example in case of Puppet Master/Agent setup it’s a must requirement to have the data and TZ synced across all the nodes, if not, Puppet master server being the certificate authority may issue agent certificate from the distant past or future, which other nodes will treat as expire.
For syncing data and timezone across all the nodes, for whatever reason the tool at hand is ntpd.
The Network Time Protocol daemon (ntpd) is an operating system program that maintains the system time in synchronization with time servers using the Network Time Protocol (NTP).

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Installing open-source standalone Puppet on CentOS 7

Puppet is an open-source configuration management tool – for infrastructure orchestration, or automated provisioning, or configuration automation, and lot more. The simplest use case is for automated provisioning i.e. the tasks we need to perform once our machine/VM comes up for the first time (or even after it), like installing webserver, DB server, etc. Instead of manually performing the tasks/running the tasks we can use any of the available configuration management tools (like Puppet) to automate the boring repetitive tasks, and also making configuration consistent across all the servers.

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What is DevOps and Configuration Management

DevOps

First of all I want to address the biggest confusion here i.e. DevOps is not any tool, or technology, or some product one can use to make and do things better. DevOps is an idea, a management and operations approach – emphasizing on cohesiveness between development and operations teams. In simplest words, it’s about gluing the development and the IT operation hence the name DevOps:
  • Dev – comes from development (developer/software engineers), people who make the system/software, and update it during it’s lifetime.
  • Ops – from IT operations (sysadmins), who take care of the system once it’s developed, i.e. in production.

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