Make SSH connection live for long

ssh -o ServerAliveInterval=60 ubuntu@ip

How to set JAVA_HOME for Java permanently on Ubuntu Linux

You can set your JAVA_HOME in /etc/profile. But the preferred location for JAVA_HOME or any system variable is /etc/environment.

Open /etc/environment in any text editor like nano or gedit and add the following line:

JAVA_HOME="/usr/lib/jvm/open-jdk"

(java path could be different)

Use source to load the variables, by running this command:

source /etc/environment

Then check the variable, by running this command:

echo $JAVA_HOME

Update

Usually most linux systems source /etc/environment by default. If your system doesn't do that add the following line to ~/.bashrc

source /etc/environment

After that, run the below command to add the java_home to the path variable. 

export PATH="$PATH:$JAVA_HOME/bin"

If you want it permanent, then add the above line to ~/.profile

Now, running $ java -version would return your version.

Install Node.js with Ubuntu Package Manager

To install Node.js, type the following command in your terminal:

1	sudo apt-get install nodejs

Then install the Node package manager, npm:

1	sudo apt-get install npm

Create a symbolic link for node, as many Node.js tools use this name to execute.

1	sudo ln -s /usr/bin/nodejs /usr/bin/node

Now we should have both the Node and npm commands working:

1 2 3 4

$ node -v v0.10.25 $ npm -v 1.3.10

Fixing “WARNING: UNPROTECTED PRIVATE KEY FILE!” on Linux / OS X Mac

If you are getting this error then you probably reset the permissions on your hidden .ssh directory in your user folder, and your keys aren’t going to work anymore. It’s very important that these files not be writable by just anybody with a login to the box, so openssh will give you an error if you try to use them.

The full error message:

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@         WARNING: UNPROTECTED PRIVATE KEY FILE!          @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
Permissions 0744 for '/home/geek/.ssh/id_rsa' are too open.
It is recommended that your private key files are NOT accessible by others.
This private key will be ignored.
bad permissions: ignore key: /home/geek/.ssh/id_rsa

To fix this, you’ll need to reset the permissions back to default:

sudo chmod 600 ~/.ssh/id_rsa
sudo chmod 600 ~/.ssh/id_rsa.pub

If you are getting another error:

Are you sure you want to continue connecting (yes/no)? yes
Failed to add the host to the list of known hosts (/home/geek/.ssh/known_hosts).

This means that the permissions on that file are also set incorrectly, and can be adjusted with this:

sudo chmod 644 ~/.ssh/known_hosts

Finally, you may need to adjust the directory permissions as well:

sudo chmod 755 ~/.ssh

This should get you back up and running.

Unzip a gz file and see contents even though you do not have write permission

gunzip -c  <file_name.gz> | less