Segmentation fault on every command line in Ubuntu 16.04

I have started getting segmentation fault (core dumped) error message on every command I enter on this EC2 instance. It is running Ubuntu 16.04. I was preparing the machine with Microsoft RDP via SSH tunnel and the last few steps I executed are below:

sudo sed -i 's/^PasswordAuthentication no/PasswordAuthentication yes/' /etc/ssh/sshd_config 

sudo /etc/init.d/ssh restart 

sudo passwd ubuntu

sudo apt install xrdp xfce4 xfce4-goodies tightvncserver 

echo xfce4-session> /home/ubuntu/.xsession  

sudo cp /home/ubuntu/.xsession /etc/skel 

sudo sed -i '0,/-1/s//ask-1/' /etc/xrdp/xrdp.ini

Now, I am completely stuck. Almost every step produces the "segmentation fault(core dumped) " error. I rebooted the instance as well. What I can do? What are my options? Thanks in advance.