<s>
The	O
Environment	B-Device
Modules	I-Device
system	O
is	O
a	O
tool	O
to	O
help	O
users	O
manage	O
their	O
Unix	B-Application
or	O
Linux	B-Application
shell	O
environment	O
,	O
by	O
allowing	O
groups	O
of	O
related	O
environment-variable	O
settings	O
to	O
be	O
made	O
or	O
removed	O
dynamically	O
.	O
</s>
<s>
The	O
National	O
Energy	O
Research	O
Scientific	O
Computing	O
Center	O
(	O
NERSC	O
)	O
reports	O
that	O
they	O
use	O
Environment	B-Device
Modules	I-Device
to	O
manage	O
nearly	O
all	O
software	O
.	O
</s>
<s>
Environment	B-Device
Modules	I-Device
is	O
specified	O
as	O
a	O
Baseline	O
Configuration	O
requirement	O
of	O
the	O
DoD	O
High	O
Performance	O
Computing	O
Modernization	O
Program	O
(	O
HPCMP	O
)	O
Project	O
Baseline	O
Configuration	O
team	O
for	O
participating	O
DoD	O
Supercomputing	O
Resource	O
Centers	O
(	O
DSRCs	O
)	O
.	O
</s>
<s>
Environment	B-Device
Modules	I-Device
modulefiles	O
are	O
written	O
in	O
the	O
Tcl	B-Operating_System
(	O
Tool	B-Operating_System
Command	I-Operating_System
Language	I-Operating_System
)	O
and	O
are	O
interpreted	O
by	O
the	O
modulecmd	O
program	O
via	O
the	O
module	O
user	O
interface	O
.	O
</s>
<s>
The	O
key	O
advantage	O
of	O
Environment	B-Device
Modules	I-Device
is	O
that	O
it	O
is	O
shell	O
independent	O
and	O
supports	O
all	O
major	O
shells	O
such	O
as	O
bash	O
,	O
ksh	O
,	O
zsh	O
,	O
sh	O
,	O
tcsh	O
,	O
and	O
csh	O
.	O
</s>
<s>
Those	O
two	O
advantages	O
were	O
instrumental	O
in	O
making	O
Environment	B-Device
Modules	I-Device
a	O
part	O
of	O
most	O
HPC	O
cluster	O
setups	O
.	O
</s>
<s>
It	O
also	O
inspired	O
several	O
alternative	O
implementation	O
such	O
as	O
lmod	B-Device
from	O
University	O
of	O
Texas	O
,	O
which	O
is	O
written	O
in	O
Lua	B-Language
instead	O
of	O
TCL	B-Operating_System
.	O
</s>
<s>
Environment	B-Device
Modules	I-Device
on	O
Scientific	O
Linux	B-Application
,	O
CentOS	O
,	O
and	O
RHEL	O
distributions	O
in	O
the	O
environment-modules	O
package	O
include	O
and	O
scripts	O
for	O
the	O
directory	O
that	O
make	O
modules	O
initialization	O
part	O
of	O
the	O
default	O
shell	O
initialization	O
.	O
</s>
<s>
One	O
of	O
the	O
advantages	O
of	O
Environment	B-Device
Modules	I-Device
is	O
a	O
single	O
modulefile	O
that	O
supports	O
bash	O
,	O
ksh	O
,	O
zsh	O
,	O
sh	O
as	O
well	O
as	O
tcsh	O
and	O
csh	O
shell	O
users	O
for	O
environment	O
setup	O
and	O
initialization	O
.	O
</s>
<s>
On	O
Scientific	O
Linux	B-Application
,	O
CentOS	O
,	O
and	O
RHEL	O
distributions	O
Environment	B-Device
Modules	I-Device
is	O
in	O
the	O
environment-modules	O
package	O
which	O
can	O
be	O
installed	O
with	O
:	O
</s>
<s>
On	O
Ubuntu	O
or	O
systems	O
using	O
apt-get	O
,	O
Environment	B-Device
Modules	I-Device
can	O
be	O
installed	O
with	O
:	O
</s>
<s>
Although	O
installing	O
from	O
a	O
Linux	B-Application
distributions	O
repository	O
using	O
that	O
distributions	O
update	O
manager	O
is	O
the	O
easiest	O
the	O
software	O
can	O
be	O
installed	O
from	O
source	O
.	O
</s>
<s>
This	O
section	O
includes	O
the	O
steps	O
to	O
install	O
the	O
Environment	B-Device
Modules	I-Device
package	O
on	O
source	O
including	O
compiling	O
the	O
Tcl	B-Operating_System
(	O
Tool	B-Operating_System
Command	I-Operating_System
Language	I-Operating_System
)	O
from	O
source	O
as	O
a	O
dependency	O
.	O
</s>
<s>
Although	O
the	O
PCLinuxOS	O
64-bit	O
repositories	O
include	O
Tcl	B-Operating_System
(	O
Tool	B-Operating_System
Command	I-Operating_System
Language	I-Operating_System
)	O
they	O
do	O
not	O
include	O
a	O
development	O
package	O
with	O
the	O
configuration	O
files	O
required	O
to	O
build	O
Environment	B-Device
Modules	I-Device
on	O
Linux	B-Application
from	O
source	O
.	O
</s>
<s>
Building	O
Tcl	B-Operating_System
from	O
source	O
will	O
make	O
the	O
required	O
files	O
available	O
.	O
</s>
<s>
Tcl	B-Operating_System
Source	O
:	O
</s>
