ubuntu@ubuntu:~$ pwd
/home/ubuntu
ubuntu@ubuntu:~$ ls
-bash: ls: command not found
ubuntu@ubuntu:~$ echo *
*
ubuntu@ubuntu:~$ cd ..
cd: error retrieving current directory: getcwd: cannot access parent directories: No such file or directory
ubuntu@ubuntu:~/..$ pwd
/home/ubuntu/..
ubuntu@ubuntu:~/..$ echo *
*
ubuntu@ubuntu:~/..$ cd ..
ubuntu@ubuntu:/$ pwd
/
ubuntu@ubuntu:/$ echo *
dev etc proc sys
ubuntu@ubuntu:/$ echo dev/*
dev/console dev/mqueue dev/pts dev/shm