How To Install and Configure SNMP on CentOS

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Introduction

SNMP, or Simple Network Management Protocol, is widely used to communicate with and monitor network devices, dedicated servers, and more, all via IP. In this case, we’ll be installing an SNMP agent on a CentOS 6.5 server, which will allow for collection of data from our server, and make the information available to a remote SNMP manager.

Pre-Flight Check

  • These instructions are intended for installing SNMP and doing a very basic configuration.
  • I’ll be working from a Liquid Web Core Managed CentOS 6.5 server, and I’ll be logged in as root.

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How to Commit Changes and Create Docker Images

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Pre-Flight Check
  • As of June 2014 Docker has officially released v1.0.0.
  • These instructions are intended for committing changes to Docker containers.
  • I’ll be working from a Liquid Web Core Managed CentOS 6.6 server (or CentOS 7, Ubuntu 14.04 LTS, Fedora 20, Fedora 21), and I’ll be logged in as root.
  • In the previous tutorials in this series we’ve installed Docker and got a container running, and then we listed which containers were running, and attached to a running Fedora container.

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How To List and Attach to Docker Containers

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Preflight Check
  • As of June 2014 Docker has officially released v1.0.0.
  • These instructions are intended for listing and attaching to Docker containers.
  • I’ll be working from a Liquid Web Core Managed CentOS 6.6 server (or CentOS 7, Ubuntu 14.04 LTS, Fedora 20, Fedora 21), and I’ll be logged in as root.
  • I have one Docker container running.

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How To Install Docker on CentOS 6

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Introduction

Docker is a container-based software framework for automating deployment of applications. “Containers” are encapsulated, lightweight, and portable application modules.

Pre-Flight Check
  • As of June 2014 Docker has officially released v1.0.0.
  • These instructions are intended for installing Docker.
  • I’ll be working from a Liquid Web Core Managed CentOS 6.5 server, and I’ll be logged in as root.

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Update and Patch OpenSSL for Heartbleed Vulnerability

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What is OpenSSL?

OpenSSL is a common cryptographic library which provides encryption, specifically SSL/TLS, for popular applications such as Apache (web), MySQL (database), e-mail, virtual private networks (VPNs), and more.

What is “the Heartbleed Bug”?

The Heartbleed Bug is a severe vulnerability in OpenSSL, known formally as “TLS heartbeat read overrun (CVE-2014-0160)“. As of April 07, 2014, a security advisory was released by OpenSSL.org, along with versions of OpenSSL that fix this vulnerability.

What are the risks?

In short, the risks are many. In most circumstances, this flaw allows an attacker to read the memory of servers running vulnerable versions of OpenSSL. This would allow attackers to impersonate users and services, and provide a means for data theft. For example, the exposed memory could include sensitive information such as private keys. If private keys are leaked, then it is possible that SSL certificates are compromised, and in that case should definitely be reissued.

What do I do?
  • Update and reboot your server immediately.
  • After the server has been rebooted, change all passwords associated with the server.
  • Consider getting your SSL certificates reissued.
Pre-Flight Check
  • These instructions are intended for patching OpenSSL on CentOS 6 against the “TLS heartbeat read overrun (CVE-2014-0160)” vulnerability.
  • I’ll be working from a Liquid Web Core Managed CentOS 6.5 server, and I’ll be logged in as root.

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How to Install Git on CentOS 6

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Introduction

Git is an open source, distributed version control system (VCS). It’s commonly used for source code management (SCM), with sites like GitHub offering a social coding experience, and popular projects such as Perl, Ruby on Rails, and the Linux kernel using it.

Pre-Flight Check
  • These instructions are intended for installing Git on CentOS 6.
  • I’ll be working from a Liquid Web Core Managed CentOS 6.5 server, and I’ll be logged in as root.

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Install Dogecoin Wallet on CentOS

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Dogecoin (Ɖ) is one of the many open-source cryptocurrencies that has penetrated the post-Bitcoin marketplace. As of February 2014, Dogecoin rates fifth (5th) in market capitalization among Bitcoin, Litecoin, and all other cryptocurrencies (source). This particular coin’s name is based on the “doge” meme, a slang term for “dog”.

Dogecoin is a fork of LiteCoin (presently third in market capitalization) and is based on the scrypt cryptographic algorithm, instead of being SHA-2-based like Bitcoin. The fact that Dogecoin is scrypt-based means that you can still actually mine Dogecoin with your Graphics Card or CPU (or Liquid Web server).

Without further delay… to the moon!

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How To Install MongoDB on CentOS 6

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MongoDB is a NoSQL database intended for storing large amounts of data in document-oriented storage with dynamic schemas. NoSQL refers to a database with a data model other than the tabular format used in relational databases such as MySQL, PostgreSQL, and Microsoft SQL. MongoDB features include: full index support, replication, high availability, and auto-sharding.

Pre-Flight Check
  • These instructions are intended for installing MongoDB on a single CentOS 6 node.
  • I’ll be working from a Liquid Web Core Managed CentOS 6.5 server, and I’ll be logged in as root.

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Recommended Production Settings for Cassandra on CentOS 6

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If you’ve already followed the tutorial on How To Install Cassandra on CentOS 6, then you’re ready for another step!

Pre-Flight Check
  • These instructions are intended for Cassandra 2 on a single CentOS 6 server.
  • I’ll be working from a Liquid Web Core Managed CentOS 6.4 server, and I’ll be logged in as root.

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How To Install Cassandra on CentOS 6

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Apache Cassandra is a NoSQL database intended for storing large amounts of data in a decentralized, high availability server cluster. NoSQL refers to a database with a data model other than the tabular relations used in relational databases such as MySQL, PostgreSQL, and Microsoft SQL.

Prerequisites

  • These instructions are intended for installing Cassandra 2 on a single CentOS 6 node.
  • I’ll be working from a Liquid Web Core Managed CentOS 6.4 server, and I’ll be logged in as root.
  • You may be able to skip to Step #2 if you already have a stable version of Java 7 (preferably the Oracle/Sun JVM). Check to see if your server already has Java installed by running the following command: java -version

Step #1: Download Oracle Java SE Runtime Environment 8

Head over to Oracle’s website and download the latest version of Oracle Java SE Runtime Environment 8. Then, transfer the file up to your server into a directory of your choice. (We suggest using /usr/src/java8/ or something to that effect.

Note:
Following a licensing change of Oracle Java on 16 April 2019, Oracle now forbids anyone from downloading Java outside their approved process. That process is currently to log in to an Oracle account, accept the new license, then attempt the download with the authentication cookies in place. There are no known workarounds at this time.

Next, run the installation by using the command rpm -ivh <filename>, or in this case:

root@host [/usr/src/javaSE8]# rpm -ivh jre-8u251-linux-x64.rpm

Note: Your command may be slightly different if you downloaded a different version of Oracle Java SE Runtime Environment. Simply replace jre-xxxx-linux-x64.rpm with the actual filename.

Then install the Java Native Access (JNA) which can improve Cassandra’s memory usage:

yum install jna

Add a symbolic link to the Oracle Java SE Runtime Environment 8 installation so that your server uses the Oracle JRE instead of the OpenJDK JRE:

alternatives --install /usr/bin/java java /usr/java/jre1.8.0_45/bin/java 20000

Note: Your command will be slightly different if you downloaded a different version of Oracle Java SE Runtime Environment 8. Simply replace jrex.x.x_## with the actual version you’ve installed.

Then use the alternatives command to verify that the Oracle Java SE Runtime Environment 8 is selected. If not, simply choose the appropriate Selection after you run the command:

The results of your command should look similar to the information below:

root@host [/usr/src/javaSE8]# alternatives --config java

There is 1 program that provides 'java'.

  Selection    Command
-----------------------------------------------
+ 1           java-1.8.0-openjdk.x86_64 (/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.252.b09-2.el7_8.x86_64/jre/bin/java)
*+ 2           /usr/java/jre-8u251-linux-x64.rpm/bin/java
Enter to keep the current selection[+], or type selection number: 2
root@host [/usr/src/javaSE8]# java -version
java version "1.8.0_55"
Java(TM) SE Runtime Environment (build 1.8.0_55-b13)
Java HotSpot(TM) 64-Bit Server VM (build 24.55-b03, mixed mode)

Utilize the following command to double check the correct version of Oracle Java SE Runtime Environment 7 is being used:

java -version

Step #2: Add the DataStax Community Repository

For a refresher on editing files with vim see: New User Tutorial: Overview of the Vim Text Editor

vim /etc/yum.repos.d/datastax.repo

Add the following information to the file you’ve created, using i to insert:

[datastax]
 name = DataStax Repo for Apache Cassandra
 baseurl = http://rpm.datastax.com/community
 enabled = 1
 gpgcheck = 0
How To Install Cassandra 2 and Run a Single Node Cluster on CentOS 6 - 02 DataStax Repo

Then exit and save the file with the command :wq (see the example below):

Step #3: Install Apache Cassandra 2

At this point, installing Cassandra is as simple as running just one command:

yum install dsc20

Step #4: Configure the Apache Cassandra 2 Environment

Just two more simple environment tweaks that enable Cassandra to run correctly:

export JAVA_HOME=/usr/java/jre1.7.0_45/
 export PATH=$PATH:/usr/java/jre1.7.0_45/bin/

Note: Your commands will be slightly different if you downloaded a different version of Oracle Java SE Runtime Environment 7. Simply replace jre1.7.0_45 with the actual version you’ve installed.

Step #5: Get Cassandra Running

Start-Up Cassandra

service cassandra start

Check Cassandra Service Status

service cassandra status

Enter the Cassandra Command Line

cqlsh

The cqlsh interface should look similar to the image below:

How To Install Cassandra 2 and Run a Single Node Cluster on CentOS 6 - 03 Cassandra Console

Check Cassandra Node Status

nodetool status

Shutdown Cassandra

service cassandra stop

There are many, many more things we could say about Cassandra, but those will be detailed in follow-up articles in the Liquid Web Knowledge Base! Look for articles on: How To Install Cassandra 2 and run a Multi-Node Server Cluster on CentOS 6, Recommended Production Settings for Cassandra on CentOS 6 and more!