<s>
In	O
Unix-like	B-Operating_System
systems	I-Operating_System
,	O
multiple	O
users	O
can	O
be	O
put	O
into	O
groups	O
.	O
</s>
<s>
POSIX	O
and	O
conventional	O
Unix	B-Application
file	B-Application
system	I-Application
permissions	O
are	O
organized	O
into	O
three	O
classes	O
,	O
user	O
,	O
group	O
,	O
and	O
others	O
.	O
</s>
<s>
This	O
method	O
,	O
among	O
others	O
,	O
also	O
enables	O
the	O
superuser	B-Application
to	O
delegate	O
some	O
administrative	O
tasks	O
to	O
normal	O
users	O
,	O
similar	O
to	O
the	O
Administrators	O
group	O
on	O
Microsoft	B-Device
Windows	I-Device
NT	I-Device
and	O
its	O
derivatives	O
.	O
</s>
<s>
A	O
group	B-Application
identifier	I-Application
,	O
often	O
abbreviated	O
to	O
GID	O
,	O
is	O
a	O
numeric	O
value	O
used	O
to	O
represent	O
a	O
specific	O
group	O
.	O
</s>
<s>
The	O
range	O
of	O
values	O
for	O
a	O
GID	O
varies	O
amongst	O
different	O
systems	O
;	O
at	O
the	O
very	O
least	O
,	O
a	O
GID	O
can	O
be	O
between	O
0	O
and	O
32	O
,	O
767	O
,	O
with	O
one	O
restriction	O
:	O
the	O
login	O
group	O
for	O
the	O
superuser	B-Application
must	O
have	O
GID	O
0	O
.	O
</s>
<s>
This	O
numeric	O
value	O
is	O
used	O
to	O
refer	O
to	O
groups	O
in	O
the	O
/etc/passwd	O
and	O
/etc/group	B-Application
files	O
or	O
their	O
equivalents	O
.	O
</s>
<s>
Shadow	B-Protocol
password	I-Protocol
files	O
and	O
Network	B-Operating_System
Information	I-Operating_System
Service	I-Operating_System
also	O
refer	O
to	O
numeric	O
GIDs	O
.	O
</s>
<s>
The	O
group	B-Application
identifier	I-Application
is	O
a	O
necessary	O
component	O
of	O
Unix	B-Application
file	B-Application
systems	I-Application
and	O
processes	B-Operating_System
.	O
</s>
<s>
In	O
Unix	B-Application
systems	I-Application
,	O
every	O
user	O
must	O
be	O
a	O
member	O
of	O
at	O
least	O
one	O
group	O
,	O
the	O
primary	O
group	O
,	O
which	O
is	O
identified	O
by	O
the	O
numeric	O
GID	O
of	O
the	O
user	O
's	O
entry	O
in	O
the	O
passwd	B-Protocol
database	O
,	O
which	O
can	O
be	O
viewed	O
with	O
the	O
command	O
getent	O
passwd	B-Protocol
(	O
usually	O
stored	O
in	O
/etc/passwd	O
or	O
LDAP	B-Protocol
)	O
.	O
</s>
<s>
This	O
group	O
is	O
referred	O
to	O
as	O
the	O
primary	O
group	B-Application
ID	I-Application
.	O
</s>
<s>
A	O
user	O
may	O
be	O
listed	O
as	O
member	O
of	O
additional	O
groups	O
in	O
the	O
relevant	O
entries	O
in	O
the	O
group	O
database	O
,	O
which	O
can	O
be	O
viewed	O
with	O
getent	O
group	O
(	O
usually	O
stored	O
in	O
/etc/group	B-Application
or	O
LDAP	B-Protocol
)	O
;	O
the	O
IDs	B-Application
of	O
these	O
groups	O
are	O
referred	O
to	O
as	O
supplementary	O
group	B-Application
IDs	I-Application
.	O
</s>
<s>
Unix	B-Application
processes	B-Operating_System
have	O
an	O
effective	O
(	O
EUID	O
,	O
EGID	O
)	O
,	O
a	O
real	O
(	O
UID	O
,	O
GID	O
)	O
and	O
a	O
saved	O
(	O
SUID	O
,	O
SGID	O
)	O
ID	B-Application
.	O
</s>
<s>
Normally	O
these	O
are	O
identical	O
,	O
but	O
in	O
setuid	O
and	O
setgid	O
processes	B-Operating_System
they	O
are	O
different	O
.	O
</s>
<s>
Since	O
the	O
sign	O
was	O
not	O
necessary	O
–	O
negative	O
numbers	O
do	O
not	O
make	O
valid	O
group	B-Application
IDs	I-Application
–	O
an	O
unsigned	O
integer	O
is	O
now	O
used	O
instead	O
,	O
allowing	O
group	B-Application
IDs	I-Application
between	O
0	O
and	O
65,535	O
.	O
</s>
<s>
Modern	O
operating	O
systems	O
usually	O
use	O
unsigned	O
32-bit	O
integers	O
,	O
which	O
allow	O
for	O
group	B-Application
IDs	I-Application
between	O
0	O
and	O
4,294,967,295	O
.	O
</s>
<s>
0	O
:	O
The	O
superuser	B-Application
normally	O
has	O
a	O
GID	O
of	O
zero	O
(	O
0	O
)	O
.	O
</s>
