Tuesday, November 25, 2014

How to install and Remove Java on Ubuntu

Install Oracle Java in Ubuntu by PPA 

This provides instructions on how to install the Oracle Java JDK (which includes Java JDK, JRE and the Java browser plugin). The PPA provides the full Oracle JDK package. 

To add the PPA and install Oracle Java 7 in Ubuntu use this: 

sudo add-apt-repository ppa:webupd8team/java

sudo apt-get update
sudo apt-get install oracle-java7-installer 

To add the PPA and install Oracle Java 8 in Ubuntu use this: 

sudo add-apt-repository ppa:webupd8team/java
sudo apt-get update
sudo apt-get install oracle-java8-installer 

If you want to see your version of java run the following command in the terminal: 

java -version

It should return something like this 

Java version "1.7.0_51" (version 7) or "1.8.0" (version 8) 
Java(TM) SE Runtime Environment (build 1.7.0_51-b13) - version 7
Java(TM) SE Runtime Environment (build 1.8.0-b132) - version 8
Java HotSpot(TM) 64-Bit Server VM (build 24.51-b03, mixed mode) - version 7
Java HotSpot(TM) 64-Bit Server VM (build 25.0-b70, mixed mode) - version 8 

If the Java version in use is not 1.7.0, you can try to run the following command in the terminal: 

sudo update-java-alternatives -s java-7-oracle 

The installer requires you accept the Oracle license before the installation begins. This is only required once. If you need the installation to be automated, you can run the following command to automatically accept the Oracle license: 

Version 7

echo oracle-java7-installer shared/accepted-oracle-license-v1-1 select true | sudo /usr/bin/debconf-set-selections 

Version 8 

echo oracle-java8-installer shared/accepted-oracle-license-v1-1 select true | sudo /usr/bin/debconf-set-selections 

Setting Java environment variables To automatically set up the Java 7 environment variables, you can install the following package:

sudo apt-get install oracle-java7-set-default 

 If you've already installed oracle-java6-set-default or oracle-java8-set-default, they will be automatically removed when installing oracle-java7-set-default (and the environment variables will be set for Oracle Java 7 instead). Switch back and forth between Java 7 and 8

Switch to Java 7

sudo update-java-alternatives -s java-7-oracle 

 And, switch back to Oracle Java 8 using: 

 sudo update-java-alternatives -s java-8-oracle 

If you get some warnings when running these two commands, ignore them.

How to Remove Oracle Java To remove java on your system and want to go back to OpenJDK or remove java completely, all you have to do is remove the Oracle JDK7 Installer and the previous Java (OpenJDK, etc.) version will be used: 

sudo apt-get remove oracle-java7-installer 

sudo apt-get 
remove oracle-java8-installer    

Special thanks to webupd8.org for their great tutorial for which this is based.

Tuesday, November 18, 2014

Disable Encryption on Ubuntu VNC Server

In Ubuntu starting with 14.04 a change was made in the VINO server (VNC) to have encryption on by default. Of course this breaks many of the VNC Clients on windows, so to allow windows users access to the linux server via VNC there are 2 ways to update the VINO server to disable encryption.

Option 1 - Command Line:

edit ~/.bashrc and on the last line add

dconf write /org/gnome/desktop/remote-access/require-encryption false

save the file and reboot the system

Option 2 - GUI

On the linux server open the terminal and install dconf-editor

sudo apt-get install dconf-editor 

Open the program it Navigate to: 

org  >>  gnome >> desktop >> remote-access and Disable "require encryption"

After doing this your windows VNC client will have no problem connecting to the Ubuntu Server using Screen Sharing.

Troubleshooting Tip:  If your having problems with the screen redraws make sure your using the XORG driver.  Using the proprietary driver can cause redraw issues with VNC

Friday, November 14, 2014

Removing Java Runtime from OS X

Java 8 removes the Medium Security
Setting in OS X

Removing Java From OS X

Since Java 8 came out you no longer have the ability to run self signed java runtimes.  This is a good thing from a security perspective but some devices like iKVM's use java self signed certificates to allow access and if your running Java 8 and OS X you might have a problem.  My solution to this was to uninstall java 8 using the following commands

sudo rm -rf /Library/Java/JavaVirtualMachines/jdk{version}.jdk

sudo rm -rf /Library/PreferencePanes/JavaControlPanel.prefPane

sudo rm -rf /Library/Internet\ Plug-Ins/JavaAppletPlugin.plugin

Then I installed the latest version of Java 7 which will only be available until April 2015, but it will still be made available though the Java Archive.

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