Why use "su -" rather than "su"

[Rick Stevens]

Mike McCarty wrote:
> Paul Howarth wrote:
> 
>> Mike McCarty wrote:
>>
>>>>
>>> I have a general *NIX admin question. Why does one want to use
>>> su -
>>> as opposed to just su? I think I understand the difference in regards
>>> to "su -" actually changes you to root, as if logged in that way, as
>>> opposed to simply granting root privilege. But why do that? If I do
>>> that, then I lose my path settings, and can't run my normal editor, 
>>> which
>>> is in ~/bin and so on. I just use "su".
>>>
>>> What am I missing?
>>
>>
>>
>> You're missing getting /sbin and /usr/sbin on your PATH, which you 
>> probably want for what you're about to do as root. If you already have 
>> those directories on your regular user's PATH (which is not the 
>> default), "su -" probably doesn't help you much. But it does for most 
>> people.
>>
>> Paul.
>>
> Hmm. So I give up my regular editor in return for not having to type /sbin/
> 
> Well, I think I'll go along the way I am. I'm a pretty good typist.
> 
> I thought there might be a *real* reason, and I had missed something. I
> was wondering if there might be some subtle problems which would bite
> me later.

Actually, "su" will give you root's UID and GID, but not root's
_environment_ (path and such).  "su -" is roughly equivalent to doing
a full-on login as root, and thus getting not only the UID and GID, but
the environment as well.

See "man su" for details.
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- Rick Stevens, Senior Systems Engineer     rstevens at vitalstream.com -
- VitalStream, Inc.                       http://www.vitalstream.com -
-                                                                    -
-         The Navy's a bunch of wimps!  MY job's an adventure!       -
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