.TH INTRO 1
.SH NAME
intro \- introduction to the Octopus
.SH DESCRIPTION
The
.I octopus
is a system built to achieve a distributed computing system by using a centralized one. The idea
is that all the applications run at a single, central, computer. Users connect devices found in
the Internet (probably attached to full-fledged computers) to their (remote) central computer, so that
they do not have to carry hardware around, yet they see a single, homogeneous, reliable system.
Even while using a distributed, heterogeneous, and dynamic environment.
.PP
The octopus inherits most ideas from Plan B and therefore from Plan 9 and Inferno.
Thus, it would be appropriate to read the
.IR intro (1)
manual page from Inferno before proceeding with this one. See also
.BR http://lsub.org/octopus .
.PP
The octopus
mounts file systems across network links with
bad latency, that is, links exhibiting RTT times from 50 to 120 milliseconds. Such links
are used to connect devices (found in the Internet) to the central PC.
.PP
A machine providing one or more devices to the central computer is known as a
.IR terminal .
The central computer is known as the
.I "personal computer"
or the
.IR PC ,
and
provides a central name space to
.IR terminals .
Both the
.I PC
and
.I terminals
run
.I "file servers"
to
provide services to be mounted on the other end of the link. Terminals and PCs
cooperate using the
.I Op
file protocol, described in section
.I O
of this manual.
.PP
Usually, two (network) connections are set up between the
.I PC
and a
.I terminal
in the octopus. In one of them, the
.I PC
is a
.I client
(for terminal devices)
and the
.I terminal
is a
.IR server .
In the other, the roles are exchanged.
But note that for the octopus
implementation in Inferno, Styx is used within the central computer, and also within
any terminal using Inferno. However, servers in the terminal speaking to clients in
the central computer do so using
.IR Op ,
and the same happens for exporting the central computer name space to terminal devices.
.PP
The computing environment as seen by the user is that of the central computer. In the
current implementation, it would be an Inferno computing environment or perhaps a Plan B
computing environment. It depends on which machine is designated as the central computer and
which software does it run.
.PP
The central computer is implemented by an Inferno system running the
.B o/pcrc
start-up script, described in
.IR pcrc (1).
This script starts listeners providing network services expected at the PC, and makes the PC
able to import terminal devices and to export a central name space. The central comptuer adapts
to changes in device availability. This way, the central name space changes depending on the
set of devices available and the name space as configured by the user. See
.IR mux (4)
and
.IR netget (1)
for a description of what this means.
.PP
A terminal in the present implementation is an Inferno system running the
.B o/termrc
start-up script. But note that any machine following the conventions for terminals would
be a terminal. In particular, a machine exporting through
.I Op
one or more devices would be a perfect terminal. User I/O happens at terminals, the central
computer runs applications instead.
.PP
In the implementation for Inferno,
.B /dis/o
contains portable (Dis) binaries for the octopus. This manual includes just those manual pages
that must be added to an Inferno user's manual to convert it to an Octopus user's manual. Section
1 describes commands implemented for the octopus, section 2
describes Limbo modules for the octopus, section 4 describes file servers, and section O describes
the file protocol used to glue the system together. But note that usually, all file servers in the octopus
are Styx (i.e., Inferno) file servers. Only
.IR oxport (4)
and
.IR ofs (4)
need to speak Op, when Inferno is being used on both terminals and the PC.
.SH SEE ALSO
.IR intro (O),
.BR http://lsub.org/octopus ,
and various papers mentioned there.
.SH BUGS
Just born, still evolving.