What does “sudo -s” actually do?

Question

I am using ubuntu 10.04.

I notice that after I run "sudo -s" in terminal, the prompt changed from

"XXX@XXX"

to

"root@XXX",

seems it changed to root privilege.

But when I check the documentation of "sudo" command here, it explains another story of "sudo -s", can anyone explain to me what is "sudo -s" doing exactly?

Answer 1

The two aren't really inconsistent - the sudo command always changes user, either to root, or to the user you specify with the -u switch. All the -s does is provide a shortcut for starting a shell as that user. It is really equivalent to:

sudo $SHELL

except that it will likely fallback to /bin/sh or something if SHELL is not set.

Answer 2

It sounds like it is creating another instance of the shell on top of the current shell, but with root privileges. I'll bet that after you do sudo -s if you type exit, you will go back to the original shell.

Answer 3

Have a look at this post from superuser:

http://superuser.com/questions/29/difference-between-comands-su-s-and-sudo-s#42

By the way, your post should be moved to superuser (or askubuntu as said in comments)!

Answer 4

RTFM everything is in there.

sudo allows a permitted user to execute a command as the superuser or another user, as specified in the sudoers file.

-s Shell, runs the shell specified by the SHELL environment variable if it is set or the shell as specified in passwd(5).

More seriously, the sudo -s run a shell environment variable. Since you didn't add any variable it run as specified in passwd, and so connect you as root.

Answer 5

sudo -s let you run a command for which you're pre-authorized [see /etc/sudoers], possibly by asking you to confirm your current ID.