Category: Computers

All things computing.

Firewall for Ubuntu 14.04 LTS

Posted on by rchapin

For whatever reason, Ubuntu 14.04 does not seem to come with a firewall.

There are however two packages which provide, both a firewall and a handy GUI front-end for it.  UncomplicatedFireWall is the main package (ufw) and the GUI is gufw.

To install:

apt-get install gufw

This will install the front-end and the dependent packages

To turn it on:

ufw enable

The default is to block all incoming traffic.

To update and add your own firewall rules and allow incoming → Continue reading “Firewall for Ubuntu 14.04 LTS”

Possible Remediation for Stagefright Android Vulnerability

Posted on by rchapin

By now, everyone is aware of the Stagefright vulnerability in Android.  It isn’t as much the name of the vulnerability but a media player library used in Android.

It seems that one of the ways to remediate the vulnerability is to configure your text messaging application to NOT auto-retrieve Multimedia messages (MMS).  On my phone that is under the Advanced Settings, “Auto-retrieve Automatically retrieve messages”.

The other thing that I did was disable Google Hangouts.  I don’t use it on → Continue reading “Possible Remediation for Stagefright Android Vulnerability”

Hadoop Cluster Sizing Wizard by Hortonworks

Posted on by rchapin

Anyone who does any Hadoop development or systems engineering arrives at the “how should I size my cluster” question.

Hortonworks has a very nice cluster sizing calculator that takes into account the basic use-cases and data profile to help get you started with your hardware requirements.→ Continue reading “Hadoop Cluster Sizing Wizard by Hortonworks”

Generate a Random String of a Specified Size with a Shell Script

Posted on by rchapin

The following is a one-liner for generating a random string of a fixed size in bash, where the possible characters to use in the string are any digit, letter, and a newline.

By adding the newline, you are fairly sure to prevent getting one long line of text.

< /dev/urandom tr -dc "[:digit:][:alpha:][\n]" | head -c1000 file.out
→ Continue reading “Generate a Random String of a Specified Size with a Shell Script”

Connecting To a Test Kitchen Instance Via SFTP, SSH, or SCP

Posted on by rchapin

If you are using Chef and Test Kitchen to test your cookbooks you may have need to connect to the Test Kitchen VM in some other fashion other than $ kitchen login instance-name.

To do so:

Do a $ kitchen list to see the running vms

kitchen list
Instance                      Driver   Provisioner  Verifier  Transport  Last Action
default-centos-66             Vagrant  ChefSolo     Busser    Ssh        Converged

Then look in the .kitchen directory from where you ran your $ kitchen command and look for the corresponding → Continue reading “Connecting To a Test Kitchen Instance Via SFTP, SSH, or SCP”

Setting the Compiler Version for Maven from the Command Line

Posted on by rchapin

By default maven sets the compiler version for you.  Of course, you can always set it in the pom, but there are cases where you cannot modify the pom, and/or you might want to test compilation and tests with different versions of java.

Following are the specific arguments to pass the compiler version to maven from the command line:

mvn clean install -Dmaven.compiler.source=1.7 -Dmaven.compiler.target=1.7
→ Continue reading “Setting the Compiler Version for Maven from the Command Line”

Writing a BASH Script to Read from STDIN to a Variable

Posted on by rchapin

Let’s say you have some program that is generating output to STDOUT and you want to write a script to read that output from STDIN and use it as a variable in your script.

To do so:

#!/bin/bash

SOME_VAR=$(cat)
echo "SOME_VAR = $SOME_VAR"

→ Continue reading “Writing a BASH Script to Read from STDIN to a Variable”

How To Publish Artifacts to the Maven Central Repository

Posted on by rchapin

I have just finished releasing my first project to Maven Central Repository and wanted to capture my notes for the setup of the project and all of the steps required.

Resources

Create account on OSSRH

You will need an account to the sonatype JIRA for OSSRH.  From there, you can request the creation of a new project. See http://central.sonatype.org/pages/ossrh-guide.html for details.

Setup of the Project/pom and Pre-requisites:

PGP keys

http://central.sonatype.org/pages/working-with-pgp-signatures.html

Create a set of PGP keys

gpg2
→ Continue reading “How To Publish Artifacts to the Maven Central Repository”

Debugging MapReduce MRv2 Code in Eclipse

Posted on by rchapin

Following is how to set-up your environment to be able to set breakpoints, step-through, and debug your MapReduce code in Eclipse.

All of the this was done on a machine running Linux, but should work just fine for any *nix machine, and perhaps Windows running Cygwin (assuming that you can get Hadoop and its naitive libraries compiled under Windows).

This also assumes that you are building your project with maven.

Install a pseudo-distributed hadooop cluster on your development box.  (Yes, → Continue reading “Debugging MapReduce MRv2 Code in Eclipse”

© 2005 Ryan Chapin