Date: Fri, 31 Oct 2008 12:17:00 -0700 From: Chuck Swiger <cswiger@mac.com> To: =?ISO-8859-1?Q?Fr=E9d=E9ric_Perrin?= <frederic.perrin@resel.fr> Cc: freebsd-questions@freebsd.org Subject: Re: Behaviour of su(1) Message-ID: <198CF2A0-D783-4B64-AC34-DAAA3B8E8DD7@mac.com> In-Reply-To: <86mygklilz.fsf@chameau.maisel.enst-bretagne.fr> References: <86mygklilz.fsf@chameau.maisel.enst-bretagne.fr>
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Hi--
On Oct 31, 2008, at 11:33 AM, Fr=E9d=E9ric Perrin wrote:
> When I =AB su - =BB to root (after being logged in as my normal user), =
the
> LOGNAME env variable is still set to my previous user, as in :
>
> ,----
> | fred@chameau:~% /usr/bin/su -l
> | Password:
> | root@chameau:~# echo $USER - $LOGNAME
> | root - fred
> `----
>
> As far as I can tell, this contradicts the fine manual that says :
>
> ,----
> | -l Simulate a full login. The environment is discarded =20
> except for
> | HOME, SHELL, PATH, TERM, and USER.
> `----
>
> So I would have expected LOGNAME to be either empty or set by some =20
> shell
> startup script to be root. So, why is LOGNAME still equal to my =20
> previous
> user ? (and where is it set ? =AB grep -r LOGNAME /etc =BB doesn't =
turn up
> anything...)
When you "su -l" it invokes /usr/bin/login, which per "man login" sets =20=
up up $LOGNAME:
The login utility enters information into the environment (see
environ(7)) specifying the user's home directory (HOME), command =20=
inter-
preter (SHELL), search path (PATH), terminal type (TERM) and =20
user name
(both LOGNAME and USER).
I believe it looks up the actual username from the wtmp record =20
associated with your open tty, so $USER corresponds to the effective =20
userid, but $LOGNAME corresponds to the actual username used to login, =20=
aka your "real userid"...?
Regards,
--=20
-Chuck
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