notes/technology

Temporarily enable SSH password authentication on RHEL/Centos VMs.

Posted on by Sreekumar Kj

To enable password based authentication on RHEL/Centos machines, login as root to the target host. ( sudo the commands below if you are not logging in as root)

1. Create the password authenticated user if not already created –

  • On console run : adduser [username]
  • Set a password for the new user: passwd [username]

2. Add the user to sudoers and enable remote login –

  • On console run: visudo
  • In the file opened for editing, comment out the line – “Defaults    requiretty“
  • Add the line “[username] ALL=(ALL)       ALL”  below the line “root ALL=(ALL)       ALL“

3. Enable password authentication for SSH.

  • vi /etc/ssh/sshd_config
  • Replace the line “PasswordAuthentication no” with “PasswordAuthentication yes“. (Uncomment this line if commented.) Save and close this file.
  • /etc/init.d/sshd reload

4. To disable password authentication after use, in the above file replace “PasswordAuthentication yes” with “PasswordAuthentication no“; reload sshd as before.

notes/technology

Fix Vim editor on Ubuntu

Posted on by Sreekumar Kj

Problem: The arrow keys insert characters, no status message at the bottom etc.

Reason : The default Vim on Ubuntu is vim-tiny, a skeleton version.

Fix: Install the real stuff – sudo apt-get install vim

Note: vi = Visual, vim = Visual improved. And vim-tiny is vi compatible, kind of Jurassic.

technology

Install Sun (Oracle) Java on Ubuntu without using PPAs

Posted on by Sreekumar Kj

Install JDK on Ubuntu manually without depending on PPAs –

  1. Select the required package from here – http://www.oracle.com/technetwork/java/javase/downloads/index.html. Download the jdk-[version].bin file from the downloads page.
  2. Make the downloaded file runnable; Eg – sudo chmod +x jdk-6u32-linux-x64.bin
  3. Run this file; Eg- sudo ./jdk-6u32-linux-x64.bin
  4. Move the newly created folder to /usr/lib/jvm/. Eg – sudo mv jdk1.6.0_32 /usr/lib/jvm/ (Optionally change the user of this folder to yourselves)
  5. Add the newly added jdk to known java command option – 
    sudo update-alternatives --install "/usr/bin/java" "java" "/usr/lib/jvm/jdk1.6.0_32/bin/java" 1
sudo update-alternatives --install "/usr/bin/javac" "javac" "/usr/lib/jvm/jdk1.6.0_32/bin/javac" 1
sudo update-alternatives --install "/usr/bin/javaws" "javaws" "/usr/lib/jvm/jdk1.6.0_32/bin/javaws" 1
  6. Choose the new java, javac and javaws by running commands- 
    sudo update-alternatives --config java
sudo update-alternatives --config javac
sudo update-alternatives --config javaws

Run java -version to verify installation. Cheers!

notes/technology

Eclipse Compilation error: [function/type] is not accessible due to restriction on required library … rt.jar

Posted on by Sreekumar Kj

Problem : Eclipse gives the error – “[function/type] is not accessible due to restriction on required library … rt.jar” when building a project.

Reason: Project  classpath (in the build path) is refers to JRE in place of the JDK in which the Project is configured to work with.

Fix:  Go to Java Build Path > Libraries, choose JRE System Library, click Edit button. From the dialog choose Alternate JRE and choose the required JDK.

notes/technology

Create Shortcut / launcher on Desktop in Ubuntu 12.04

Posted on by Sreekumar Kj

To create a shortcut to an application or location on the desktop (Ubuntu 12+), on terminal run –

Method 1: Installing Gnome Panel

  1. if a shortcut is being created for the first time, 
    sudo apt-get install gnome-panel

    , else directly do step 2.

  2. gnome-desktop-item-edit ~/Desktop/ --create-new
  3. In the launcher-creation window choose the type and location of the target. Click OK.

Method 2: For application shortcuts only

If shortcut to an installed application is to be created –

  1. Go to Home Folder –> File System –> usr –> share –> applications.
  2. Right click your favourite icon, choose Copy To –> Desktop

(from mhdizam’s comment, verified working)