
= Configuring a Tahoe node =

A Tahoe node is configured by writing files to its base directory. These
files are read by the node when it starts, so each time you change them, you
need to restart the node.

The node also writes state to its base directory, so it will create files on
its own.

This document contains a complete list of the config files that are examined
by the client node, as well as the state files that you'll observe in its
base directory.

== Client Configuration ==

introducer.furl and vdrive.furl (mandatory): These FURLs tell the client how
to connect to the introducer/vdrive server. Each Tahoe grid is defined by
this pair. They are created by the introducer/vdrive-server node and written
into its base directory when it starts, whereupon they should be published to
everyone who wishes to attach a client to that grid

webport (optional): This controls where the client's webserver should listen,
providing vdrive access as defined in webapi.txt . This file should contain a
Twisted "strports" specification, such as "8123" or
"tcp:8123:interface=127.0.0.1".  The 'tahoe create-client' command sets the
webport to "tcp:8123:interface=127.0.0.1" by default, and is overridable by
the "--webport" option.

client.port (optional): This controls which port the node listens on. If not
provided, the node will ask the kernel for any available port, and write it
to this file so that subsequent runs will re-use the same port.

advertised_ip_addresses (optional): The node normally uses tools like
'ifconfig' to determine the set of IP addresses on which it can be reached
from nodes both near and far. The node introduces itself to the rest of the
grid with a FURL that contains a series of (ipaddr, port) pairs which other
nodes will use to contact this one. By providing this file, you can add to
this list. This can be useful if your node is running behind a firewall, but
you have created a port-forwarding to allow the outside world to access it.
Each line must have a dotted-quad IP address and an optional :portnum
specification:

 123.45.67.89
 44.55.66.77:8098

Lines that do not provide a port number will use the same client.port as the
automatically-discovered addresses.

authorized_keys.SSHPORT (optional): This enables an SSH-based interactive
Python shell, which can be used to inspect the internal state of the node,
for debugging.  To cause the node to accept SSH connections on port 8022,
symlink "authorized_keys.8022" to your ~/.ssh/authorized_keys file, and it
will accept the same keys as the rest of your account.


== Node State ==

node.pem : This contains an SSL private-key certificate. The node generates
this the first time it is started, and re-uses it on subsequent runs. This
certificate allows the node to have a cryptographically-strong identifier
(the Foolscap "TubID"), and to establish secure connections to other nodes.

global_root.uri: The first time the client contacts the vdrive-server, it
retrieves the dirnode URI of the global root directory, and writes it into
this file. On subsequent runs, this URI is used each time the user accesses
the global vdrive.

my_vdrive.uri: The first time the client contacts the vdrive-server, it will
create a brand new directory to use as the non-shared private vdrive root,
and it stores the dirnode URI of this directory in this file. On subsequent
runs, it will read the URI from this file to provide access to the private
vdrive.

storage/ : Nodes which host StorageServers will create this directory to hold
shares of files on behalf of other clients. There will be a directory
underneath it for each StorageIndex for which this node is holding shares.
There is also an "incoming" directory where partially-completed shares are
held while they are being received.

client.tac : this file defines the client, by constructing the actual Client
instance each time the node is started. It is used by the 'twistd'
daemonization program (in the "-y" mode), which is run internally by the
"tahoe start" command. This file is created by the "tahoe create-client"
command.

control.furl : this file contains a FURL that provides access to a control
port on the client node, from which files can be uploaded and downloaded.
This file is created with permissions that prevent anyone else from reading
it (on operating systems that support such a concept), to insure that only
the owner of the client node can use this feature.  This port is intended for
debugging and testing use.

== Introducer/vdrive-server configuration ==

Introducer/vdrive-server nodes use the same 'advertised_ip_addresses' file
as client nodes. They also use 'authorized_keys.SSHPORT'.

encoding_parameters (optional): This file sets the encoding parameters that
will be distributed to all client nodes and used when they encode files
(unless locally overridden). It should contain three numbers, separated by
whitespace, called "needed", "desired", and "total".

 "needed": this is the number of shares that will be needed to reconstruct
           the file. Each share that is pushed to a StorageServer will be
           the size of the original file divided by this number.
 "desired": the encoding/upload process will be happy if it can push
            this many shares to StorageServers. If it cannot, it will
            report failure.
 "total": this is the total number of shares that will be produced. The
          expansion factor (i.e. the amount of space consumed on the whole
          grid divided by the size of the file) will be total/needed. It does
          not make a lot of sense to have "total" be much larger than the
          maximum number of storage nodes you expect to ever have.

The default value of encoding_parameters is "3 7 10".


== Introducer/vdrive-server state ==

The Introducer / Virtual-Drive Server node maintains some different state
than regular client nodes. Both of these services are currently hosted inside
the same node, although keeping the FURLs in separate files will make it
easier to split these services in the future.

introducer.furl : This is generated the first time the introducer node is
started, and used again on subsequent runs, to give the introduction service
a persistent long-term identity. This file should be published and copied
into new client nodes before they are started for the first time.

vdrive.furl : This is also generated the first time the node is started, and
re-used on later runs. This FURL provides access to the vdrive service, used
both to create+access all dirnodes and to learn about the global shared root
vdrive.

introducer.port : this serves exactly the same purpose as 'client.port', but
has a different name to make it clear what kind of node is being run.

vdrive/ : this directory is created by the vdrive service to hold the
encrypted contents of dirnodes on behalf of all clients. It contains one file
per dirnode, plus a file named 'root' which contains the binary storage index
of the global shared root vdrive.

introducer.tac : this file is like client.tac but defines an
introducer/vdrive-server node instead of a client node.

== Other files ==

logs/ : Each Tahoe node creates a directory to hold the log messages produced
as the node runs. These logfiles are created and rotated by the "twistd"
daemonization program, so logs/twistd.log will contain the most recent
messages, logs/twistd.log.1 will contain the previous ones, logs/twistd.log.2
will be older still, and so on. twistd rotates logfiles after they grow
beyond 1MB in size. If the space consumed by logfiles becomes troublesome,
they should be pruned: a cron job to delete all files that were created more
than a month ago in this logs/ directory should be sufficient.

my_nodeid : this is written by all nodes after startup, and contains a
base32-encoded (i.e. human-readable) NodeID that identifies this specific
node. This NodeID is the same string that gets displayed on the web page (in
the "which peers am I connected to" list), and the shortened form (the first
characters) is recorded in various log messages.

