<s>
The	O
Unix	B-Application
command	I-Application
,	O
which	O
stands	O
for	O
'	O
substitute	O
user	O
 '	O
(	O
or	O
historically	O
'	O
superuser	B-Application
 '	O
)	O
,	O
is	O
used	O
by	O
a	O
computer	O
user	O
to	O
execute	O
commands	O
with	O
the	O
privileges	O
of	O
another	O
user	O
account	O
.	O
</s>
<s>
When	O
executed	O
it	O
invokes	O
a	O
shell	B-Application
without	O
changing	O
the	O
current	O
working	O
directory	O
or	O
the	O
user	O
environment	O
.	O
</s>
<s>
When	O
the	O
command	B-Application
is	O
used	O
without	O
specifying	O
the	O
new	O
user	O
id	B-Application
as	O
a	O
command	B-Application
line	O
argument	O
,	O
it	O
defaults	O
to	O
using	O
the	O
superuser	B-Application
account	O
(	O
user	O
id	B-Application
0	O
)	O
of	O
the	O
system	O
.	O
</s>
<s>
The	O
command	B-Application
,	O
including	O
the	O
Unix	B-Application
permissions	O
system	O
and	O
the	O
setuid	O
system	O
call	O
,	O
was	O
part	O
of	O
Version	B-Operating_System
1	I-Operating_System
Unix	I-Operating_System
.	O
</s>
<s>
Encrypted	O
passwords	O
appeared	O
in	O
Version	B-Operating_System
3	I-Operating_System
.	O
</s>
<s>
The	O
command	B-Application
is	O
available	O
as	O
a	O
separate	O
package	O
for	O
Microsoft	B-Application
Windows	I-Application
as	O
part	O
of	O
the	O
UnxUtils	B-Application
collection	O
of	O
native	B-Language
Win32	B-Library
ports	O
of	O
common	O
GNU	B-Operating_System
Unix-like	B-Operating_System
utilities	O
.	O
</s>
<s>
The	O
command	B-Application
was	O
removed	O
from	O
GNU	B-Application
coreutils	I-Application
as	O
of	O
release	O
8.18	O
(	O
2012-08-12	O
)	O
and	O
is	O
currently	O
included	O
in	O
the	O
util-linux	B-Application
package	O
.	O
</s>
<s>
When	O
run	O
from	O
the	O
command	B-Application
line	O
,	O
su	B-Device
asks	O
for	O
the	O
target	O
user	O
's	O
password	O
,	O
and	O
if	O
authenticated	O
,	O
grants	O
the	O
operator	O
access	O
to	O
that	O
account	O
and	O
the	O
files	O
and	O
directories	O
that	O
account	O
is	O
permitted	O
to	O
access	O
.	O
</s>
<s>
When	O
used	O
with	O
a	O
hyphen	O
(	O
)	O
it	O
can	O
be	O
used	O
to	O
start	O
a	O
login	O
shell	B-Application
.	O
</s>
<s>
The	O
command	B-Application
sudo	B-Device
is	O
related	O
,	O
and	O
executes	O
a	O
command	B-Application
as	O
another	O
user	O
but	O
observes	O
a	O
set	O
of	O
constraints	O
about	O
which	O
users	O
can	O
execute	O
which	O
commands	O
as	O
which	O
other	O
users	O
(	O
generally	O
in	O
a	O
configuration	O
file	O
named	O
,	O
best	O
editable	O
by	O
the	O
command	B-Application
)	O
.	O
</s>
<s>
Some	O
Unix-like	B-Operating_System
systems	I-Operating_System
implement	O
the	O
user	O
group	O
wheel	B-Operating_System
,	O
and	O
only	O
allow	O
members	O
to	O
become	O
root	O
with	O
.	O
</s>
<s>
GNU	B-Operating_System
,	O
however	O
,	O
does	O
not	O
support	O
the	O
group	O
wheel	B-Operating_System
for	O
philosophical	O
reasons	O
.	O
</s>
<s>
Richard	O
Stallman	O
argues	O
that	O
because	O
the	O
group	O
would	O
prevent	O
users	O
from	O
utilizing	O
root	B-Application
passwords	I-Application
leaked	O
to	O
them	O
,	O
the	O
group	O
would	O
allow	O
existing	O
admins	O
to	O
ride	O
roughshod	O
over	O
ordinary	O
users	O
.	O
</s>
