WHY PLAN 9?
Why
Plan
9
indeed.
Isn't
Plan
9
just
another
Unix
clone?
Who
cares?
Plan
9
presents
a
consistent
and
easy
to
use
interface.
Once
you've
settled
in,
there
are
very
few
surprises
here.
After
I
switched
to
Linux
from
Windows
3.1,
I
noticed
all
manner
of
inconsistent
behavior
in
Windows
3.1
that
Linux
did
not
have.
Switching
to
Plan
9
from
Linux
highlighted
just
as
much
in
Linux.
One
reason
Plan
9
can
do
this
is
that
the
Plan
9
group
has
had
the
luxury
of
having
an
entire
system,
so
problems
can
be
fixed
and
features
added
where
they
belong,
rather
than
where
they
can
be.
For
example,
there
is
no
tty
driver
in
the
kernel.
The
window
system
handles
the
nuances
of
terminal
input.
If
Plan
9
was
just
a
really
clean
Unix
clone,
it
might
be
worth
using,
or
it
might
not.
The
neat
things
start
happening
with
user-level
file
servers
and
per-process
namespace.
In
Unix,
/dev/tty
refers
to
the
current
window's
output
device,
and
means
different
things
to
different
processes.
This
is
a
special
hack
enabled
by
the
kernel
for
a
single
file.
Plan
9
provides
full-blown
per-process
namespaces.
In
Plan
9
/dev/cons
also
refers
to
the
current
window's
output
device,
and
means
different
things
to
different
processes,
but
the
window
system
(or
telnet
daemon,
or
ssh
daemon,
or
whatever)
arranges
this,
and
does
the
same
for
/dev/mouse,
/dev/text
(the
contents
of
the
current
window),
etc.
Since
pieces
of
file
tree
can
be
provided
by
user-level
servers,
the
kernel
need
not
know
about
things
like
DOS's
FAT
file
system
or
GNU/Linux's
EXT2
file
system
or
NFS,
etc.
Instead,
user-level
servers
provide
this
functionality
when
desired.
In
Plan
9,
even
FTP
is
provided
as
a
file
server:
you
run
ftpfs
and
the
files
on
the
server
appear
in
/n/ftp.
We
need
not
stop
at
physical
file
systems,
though.
Other
file
servers
synthesize
files
that
represent
other
resources.
For
example,
upas/fs
presents
your
mail
box
as
a
file
tree
at
/mail/fs/mbox.
This
models
the
recursive
structure
of
MIME
messages
especially
well.
As
another
example,
cdfs
presents
an
audio
or
data
CD
as
a
file
system,
one
file
per
track.
If
it's
a
writable
CD,
copying
new
files
into
the
/mnt/cd/wa
or
/mnt/cd/wd
directories
does
create
new
audio
or
data
tracks.
Want
to
fixate
the
CD
as
audio
or
data?
Remove
one
of
the
directories.
Plan
9
fits
well
with
a
networked
environment,
files
and
directory
trees
can
be
imported
from
other
machines,
and
all
resources
are
files
or
directory
trees,
it's
easy
to
share
resources.
Want
to
use
a
different
machine's
sound
card?
Import
its
/dev/audio.
Want
to
debug
processes
that
run
on
another
machine?
Import
its
/proc.
Want
to
use
a
network
interface
on
another
machine?
Import
its
/net.
And
so
on.
Russ
Cox
