What is the difference between sudo su and su?

Question

As far as i know,

sudo su command will give root login but it will ask for user password,

su command will give root login but it is asking different password

What is the difference between this 2?

Answer 1

First lets understand what is sudo
sudo is used to run a command with root privilege.

Now when we run the command "sudo su" it means we are running a single command or we can say

sudo su only changes the current user to root. Environment settings (like PATH) remain the same.
su creates a fresh environment as if root had just logged in (i.e. creates a new shell).

Comments

As you said "sudo" is used to run a single command in root privilege,
So, "sudo su" here we can consider "su" as a command , right?
Then Why different behavior when i run same command ?

So, does it mean "sudo su" is asking user password and "su" is asking root password?

I am still confused with "sudo"
Because if i am executing some command under root privilege then why it is asking user password why not root password?

Right?

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Thanks sir, for always helping

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Hi Chirag,
Your root and user password might be the same. Please check it once.

As Salil said, sudo doesnt load the root environment variables(like PATH, LD_LIBRARY_PATH and others), bash profile(.bashrc) etc.. Once your command executed, no need to do exit to come back to your user shell. You are already in user shell.

"su" will load a new shell over the previous shell(hence giving different environment variable values)..you will need "exit" command(or Ctrl+D) from that shell to come back to user shell.

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Hi Shobhit, Thanks,

When i execute only "su" and enters a password then it is showing wrong password,
Where as in "sudo su" it takes the password(Same as user password)

Any reason behind that?

Answer 2

‘su‘ forces you to share your root password to other users whereas ‘sudo‘ makes it possible to execute system commands without root password. ‘sudo‘ lets you use your own password to execute system commands i.e., delegates system responsibility without root password.