On: The Meaning of 'su'

[mrb]

To all people who type "sudo su - root": the much simpler "sudo -i" accomplishes the same (-i launches an interactive shell).

[kelnos → mrb]

The "-i" option actually means "simulate Initial login" -- the idea being -i will drop you into a shell as if you'd logged in as the user in a fresh session. -s will also give you an interactive shell, but doesn't mess with the environment.

(And both -i and -s can also not give you an interactive shell, if you give it a command to run. The point is that it will run the command in the shell rather than just fork()ing and exec()ing like a bare sudo invocation would do.)

[etanol → kelnos]

Read carefully: "sudo -i" to replace "sudo su - root". You should check the "su" manpage and look for the -/-l/--login option.

[kelnos → etanol]

I'm not objecting to that. I'm objecting to the (perhaps unintended) assertion that "sudo -i" means "give me an interactive shell". It does happen to give you an interactive shell (assuming you don't specify a command), but as a side effect. "-s" gives you an interactive shell too, but the semantics are different.

[Osiris → mrb]

I thought "sudo -s" was the correct way to drop into a root user shell.

[ralph → Osiris]

No, unless one understands the subtleties, it may be best to use -i.

    $ sudo -s
    $ pwd
    /home/ralph
    $ exit
    $ sudo -i
    root@orac:~# pwd
    /root
    root@orac:~# logout
    $
    $ sudo strace -fe execve sudo -s
    execve("/usr/bin/sudo", ["sudo", "-s"], [/* 16 vars */]) = 0
    execve("/bin/bash", ["/bin/bash"], [/* 16 vars */]) = 0
    ...
    $ exit
    $ sudo strace -fe execve sudo -i
    execve("/usr/bin/sudo", ["sudo", "-i"], [/* 16 vars */]) = 0
    execve("/bin/bash", ["-bash"], [/* 16 vars */]) = 0
    ...
    root@orac:~# logout
    $

[theblazehen → mrb]

What is the difference between that and sudo bash

[alexkus → theblazehen]

One side effect of "sudo bash" is that when you exit that shell your local user's .bash_history file gets overwritten by one owned by root (and un{read/write}able by the local user), and so your local user loses the bash history functionality from that point on.