Several years back, we were more accustomed to changing to the root account using the su command. First, we switched to the root account, and then executed those root commands. Now we are more accustomed to using the sudo command.

But we know that the root account is there. We can readily find the home directory of user root.

$ ls -ld /root/
drwx------ 18 root root 4096 Oct 22 17:21 /root/

Now my point is, it is stated that "the root password in Ubuntu is left unset". Please see the answers to this question. Most of the answers have something to this effect in the first paragraph. One or two answers further state that "the account is left disabled".

Now my (primary) questions are,

1. What is meant by an unset password? Is it blank? Is it null? Or something else more cryptic?
2. How does the account becomes enabled once I set password for it? (sudo password root)

In order get a better understanding, I checked the /etc/shadow file. Since I have already set a password for the root account, I can no longer see what is there (encrypted password). So, I created another account and left it disabled. The corresponding entry in the /etc/shadow file is,

testpassword:!:16020:0:99999:7:::

Now perhaps my above queries need to be changed to, what does an ! in password field mean? Other encrypted passwords are those very long cryptic strings. How come this encrypted form is only one character long? And does an account become disabled if I put an ! in the (encrypted) password field?