tahoe-lafs/docs/configuration.txt

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= Configuring a Tahoe node =
A Tahoe node is configured by writing to files in 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.
The main file is named 'tahoe.cfg', which is an ".INI"-style configuration
file (parsed by the Python stdlib 'ConfigParser' module: "[name]" section
markers, lines with "key.subkey: value", rfc822-style continuations). There
are other files that contain information which does not easily fit into this
format. The 'tahoe create-client' command will create an initial tahoe.cfg
file for you. After creation, the node will never modify the 'tahoe.cfg'
file: all persistent state is put in other files.
The item descriptions below use the following types:
boolean: one of (True, yes, on, 1, False, off, no, 0), case-insensitive
strports string: a Twisted listening-port specification string, like "tcp:80"
or "tcp:8123:interface=127.0.0.1". For a full scription of
the format, see
http://twistedmatrix.com/documents/current/api/twisted.application.strports.html
FURL string: a Foolscap endpoint identifier, like
pb://soklj4y7eok5c3xkmjeqpw@192.168.69.247:44801/eqpwqtzm
== Overall Node Configuration ==
This section controls the network behavior of the node overall: which ports
and IP addresses are used, when connections are timed out, etc. This
configuration is independent of the services that the node is offering: the
same controls are used for client and introducer nodes.
[node]
nickname = (UTF-8 string, optional)
This value will be displayed in management tools as this node's "nickname".
If not provided, the nickname will be set to "<unspecified>". This string
shall be a UTF-8 encoded unicode string.
web.port = (strports string, optional)
This controls where the node's webserver should listen, providing filesystem
access and node status as defined in webapi.txt . This file contains a
Twisted "strports" specification such as "8123" or
"tcp:8123:interface=127.0.0.1". The 'tahoe create-client' command sets the
web.port to "tcp:8123:interface=127.0.0.1" by default, and is overridable by
the "--webport" option. You can make it use SSL by writing
"ssl:8123:privateKey=mykey.pem:certKey=cert.pem" instead.
If this is not provided, the node will not run a web server.
web.static = (string, optional)
This controls where the /static portion of the URL space is served. The
value is a directory name (~username is allowed, and non-absolute names are
interpreted relative to the node's basedir) which can contain HTML and other
files. This can be used to serve a javascript-based frontend to the Tahoe
node, or other services.
The default value is "public_html", which will serve $BASEDIR/public_html .
With the default settings, http://127.0.0.1:8123/static/foo.html will serve
the contents of $BASEDIR/public_html/foo.html .
tub.port = (integer, optional)
This controls which port the node uses to accept Foolscap connections from
other nodes. If not provided, the node will ask the kernel for any available
port. The port will be written to a separate file (named client.port or
introducer.port), so that subsequent runs will re-use the same port.
tub.location = (string, optional)
In addition to running as a client, each Tahoe node also runs as a server,
listening for connections from other Tahoe clients. The node announces its
location by publishing a "FURL" (a string with some connection hints) to the
Introducer. The string it publishes can be found in
$BASEDIR/private/storage.furl . The "tub.location" configuration controls
what location is published in this announcement.
If you don't provide tub.location, the node will try to figure out a useful
one by itself, by using tools like 'ifconfig' to determine the set of IP
addresses on which it can be reached from nodes both near and far. It will
also include the TCP port number on which it is listening (either the one
specified by tub.port, or whichever port was assigned by the kernel when
tub.port is left unspecified).
You might want to override this value if your node lives behind a firewall
that is doing inbound port forwarding, or if you are using other proxies
such that the local IP address or port number is not the same one that
remote clients should use to connect. You might also want to control this
when using a Tor proxy to avoid revealing your actual IP address through the
Introducer announcement.
The value is a comma-separated string of host:port location hints, like
this:
123.45.67.89:8098,tahoe.example.com:8098,127.0.0.1:8098
A few examples:
Emulate default behavior, assuming your host has IP address 123.45.67.89
and the kernel-allocated port number was 8098:
tub.port = 8098
tub.location = 123.45.67.89:8098,127.0.0.1:8098
Use a DNS name so you can change the IP address more easily:
tub.port = 8098
tub.location = tahoe.example.com:8098
Run a node behind a firewall (which has an external IP address) that has
been configured to forward port 7912 to our internal node's port 8098:
tub.port = 8098
tub.location = external-firewall.example.com:7912
Run a node behind a Tor proxy (perhaps via tsocks), in client-only mode
(i.e. we can make outbound connections, but other nodes will not be able to
connect to us). The literal 'unreachable.example.org' will not resolve, but
will serve as a reminder to human observers that this node cannot be
reached. "Don't call us.. we'll call you":
tub.port = 8098
tub.location = unreachable.example.org:0
Run a node behind a Tor proxy, and make the server available as a Tor
"hidden service". (this assumes that other clients are running their node
with tsocks, such that they are prepared to connect to a .onion address).
The hidden service must first be configured in Tor, by giving it a local
port number and then obtaining a .onion name, using something in the torrc
file like:
HiddenServiceDir /var/lib/tor/hidden_services/tahoe
HiddenServicePort 29212 127.0.0.1:8098
once Tor is restarted, the .onion hostname will be in
/var/lib/tor/hidden_services/tahoe/hostname . Then set up your tahoe.cfg
like:
tub.port = 8098
tub.location = ualhejtq2p7ohfbb.onion:29212
Most users will not need to set tub.location .
Note that the old 'advertised_ip_addresses' file from earlier releases is no
longer supported. Tahoe 1.3.0 and later will ignore this file.
log_gatherer.furl = (FURL, optional)
If provided, this contains a single FURL string which is used to contact a
'log gatherer', which will be granted access to the logport. This can be
used by centralized storage meshes to gather operational logs in a single
place. Note that when an old-style BASEDIR/log_gatherer.furl file exists
(see 'Backwards Compatibility Files', below), both are used. (for most other
items, the separate config file overrides the entry in tahoe.cfg)
timeout.keepalive = (integer in seconds, optional)
timeout.disconnect = (integer in seconds, optional)
If timeout.keepalive is provided, it is treated as an integral number of
seconds, and sets the Foolscap "keepalive timer" to that value. For each
connection to another node, if nothing has been heard for a while, we will
attempt to provoke the other end into saying something. The duration of
silence that passes before sending the PING will be between KT and 2*KT.
This is mainly intended to keep NAT boxes from expiring idle TCP sessions,
but also gives TCP's long-duration keepalive/disconnect timers some traffic
to work with. The default value is 240 (i.e. 4 minutes).
If timeout.disconnect is provided, this is treated as an integral number of
seconds, and sets the Foolscap "disconnect timer" to that value. For each
connection to another node, if nothing has been heard for a while, we will
drop the connection. The duration of silence that passes before dropping the
connection will be between DT-2*KT and 2*DT+2*KT (please see ticket #521 for
more details). If we are sending a large amount of data to the other end
(which takes more than DT-2*KT to deliver), we might incorrectly drop the
connection. The default behavior (when this value is not provided) is to
disable the disconnect timer.
See ticket #521 for a discussion of how to pick these timeout values. Using
30 minutes means we'll disconnect after 22 to 68 minutes of inactivity.
Receiving data will reset this timeout, however if we have more than 22min
of data in the outbound queue (such as 800kB in two pipelined segments of 10
shares each) and the far end has no need to contact us, our ping might be
delayed, so we may disconnect them by accident.
ssh.port = (strports string, optional)
ssh.authorized_keys_file = (filename, 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 from the same keys as the rest of your
account, use:
[tub]
ssh.port = 8022
ssh.authorized_keys_file = ~/.ssh/authorized_keys
== Client Configuration ==
[client]
introducer.furl = (FURL string, mandatory)
This FURL tells the client how to connect to the introducer. Each Tahoe grid
is defined by an introducer. The introducer's furl is created by the
introducer node and written into its base directory when it starts,
whereupon it should be published to everyone who wishes to attach a client
to that grid
helper.furl = (FURL string, optional)
If provided, the node will attempt to connect to and use the given helper
for uploads. See docs/helper.txt for details.
key_generator.furl = (FURL string, optional)
If provided, the node will attempt to connect to and use the given
key-generator service, using RSA keys from the external process rather than
generating its own.
stats_gatherer.furl = (FURL string, optional)
If provided, the node will connect to the given stats gatherer and provide
it with operational statistics.
== Storage Server Configuration ==
[storage]
enabled = (boolean, optional)
If this is True, the node will run a storage server, offering space to other
clients. If it is False, the node will not run a storage server, meaning
that no shares will be stored on this node. Use False this for clients who
do not wish to provide storage service. The default value is True.
readonly = (boolean, optional)
If True, the node will run a storage server but will not accept any shares,
making it effectively read-only. Use this for storage servers which are
being decommissioned: the storage/ directory could be mounted read-only,
while shares are moved to other servers. Note that this currently only
affects immutable shares. Mutable shares (used for directories) will be
written and modified anyway. See ticket #390 for the current status of this
bug. The default value is False.
sizelimit = (str, optional)
If provided, this value establishes an upper bound (in bytes) on the amount
of storage consumed by share data (data that your node holds on behalf of
clients that are uploading files to the grid). To avoid providing more than
100MB of data to other clients, set this key to "100MB". Note that this is a
fairly loose bound, and the node may occasionally use slightly more storage
than this. To enforce a stronger (and possibly more reliable) limit, use a
symlink to place the 'storage/' directory on a separate size-limited
filesystem, and/or use per-user OS/filesystem quotas. If a size limit is
specified then Tahoe will do a "du" at startup (traversing all the storage
and summing the sizes of the files), which can take a long time if there are
a lot of shares stored.
This string contains a number, with an optional case-insensitive scale
suffix like "K" or "M" or "G", and an optional "B" suffix. So "100MB",
"100M", "100000000B", "100000000", and "100000kb" all mean the same thing.
== Running A Helper ==
A "helper" is a regular client node that also offers the "upload helper"
service.
[helper]
enabled = (boolean, optional)
If True, the node will run a helper (see docs/helper.txt for details). The
helper's contact FURL will be placed in private/helper.furl, from which it
can be copied to any clients which wish to use it. Clearly nodes should not
both run a helper and attempt to use one: do not create both helper.furl and
run_helper in the same node. The default is False.
== Running An Introducer ==
The introducer node uses a different '.tac' file (named introducer.tac), and
pays attention to the "[node]" section, but not the others.
The Introducer node maintains some different state than regular client
nodes.
BASEDIR/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.
== Other Files in BASEDIR ==
Some configuration is not kept in tahoe.cfg, for the following reasons:
* it is generated by the node at startup, e.g. encryption keys. The node
never writes to tahoe.cfg
* it is generated by user action, e.g. the 'tahoe create-alias' command
In addition, non-configuration persistent state is kept in the node's base
directory, next to the configuration knobs.
This section describes these other files.
private/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.
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.
private/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.
private/logport.furl : this file contains a FURL that provides access to a
'log port' on the client node, from which operational logs can be retrieved.
Do not grant logport access to strangers, because occasionally secret
information may be placed in the logs.
private/helper.furl : if the node is running a helper (for use by other
clients), its contact FURL will be placed here. See docs/helper.txt for more
details.
private/root_dir.cap (optional): The command-line tools will read a directory
cap out of this file and use it, if you don't specify a '--dir-cap' option or
if you specify '--dir-cap=root'.
private/convergence (automatically generated): An added secret for encrypting
immutable files. Everyone who has this same string in their
private/convergence file encrypts their immutable files in the same way when
uploading them. This causes identical files to "converge" -- to share the
same storage space since they have identical ciphertext -- which conserves
space and optimizes upload time, but it also exposes files to the possibility
of a brute-force attack by people who know that string. In this attack, if
the attacker can guess most of the contents of a file, then they can use
brute-force to learn the remaining contents.
So the set of people who know your private/convergence string is the set of
people who converge their storage space with you when you and they upload
identical immutable files, and it is also the set of people who could mount
such an attack.
The content of the private/convergence file is a base-32 encoded string. If
the file doesn't exist, then when the Tahoe client starts up it will generate
a random 256-bit string and write the base-32 encoding of this string into
the file. If you want to converge your immutable files with as many people as
possible, put the empty string (so that private/convergence is a zero-length
file).
== 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.
== Backwards Compatibility Files ==
Tahoe releases before 1.3.0 had no 'tahoe.cfg' file, and used distinct files
for each item listed below. For each configuration knob, if the distinct file
exists, it will take precedence over the corresponding item in tahoe.cfg .
[node]nickname : BASEDIR/nickname
[node]web.port : BASEDIR/webport
[node]tub.port : BASEDIR/client.port (for Clients, not Introducers)
[node]tub.port : BASEDIR/introducer.port (for Introducers, not Clients)
(note that, unlike other keys, tahoe.cfg overrides the *.port file)
[node]tub.location : replaces BASEDIR/advertised_ip_addresses
[node]log_gatherer.furl : BASEDIR/log_gatherer.furl (one per line)
[node]timeout.keepalive : BASEDIR/keepalive_timeout
[node]timeout.disconnect : BASEDIR/disconnect_timeout
[client]introducer.furl : BASEDIR/introducer.furl
[client]helper.furl : BASEDIR/helper.furl
[client]key_generator.furl : BASEDIR/key_generator.furl
[client]stats_gatherer.furl : BASEDIR/stats_gatherer.furl
[storage]enabled : BASEDIR/no_storage (False if no_storage exists)
[storage]readonly : BASEDIR/readonly_storage (True if readonly_storage exists)
[storage]sizelimit : BASEDIR/sizelimit
[storage]debug_discard : BASEDIR/debug_discard_storage
[helper]enabled : BASEDIR/run_helper (True if run_helper exists)
Note: the functionality of [node]ssh.port and [node]ssh.authorized_keys_file
were previously combined, controlled by the presence of a
BASEDIR/authorized_keys.SSHPORT file, in which the suffix of the filename
indicated which port the ssh server should listen on, and the contents of the
file provided the ssh public keys to accept. Support for these files has been
removed completely. To ssh into your Tahoe node, add [node]ssh.port and
[node].ssh_authorized_keys_file statements to your tahoe.cfg .
Likewise, the functionality of [node]tub.location is a variant of the
now-unsupported BASEDIR/advertised_ip_addresses . The old file was additive
(the addresses specified in advertised_ip_addresses were used in addition to
any that were automatically discovered), whereas the new tahoe.cfg directive
is not (tub.location is used verbatim).
== Example ==
The following is a sample tahoe.cfg file, containing values for all keys
described above. Note that this is not a recommended configuration (most of
these are not the default values), merely a legal one.
[node]
nickname = Bob's Tahoe Node
tub.port = 34912
tub.location = 123.45.67.89:8098,44.55.66.77:8098
web.port = 8123
log_gatherer.furl = pb://soklj4y7eok5c3xkmjeqpw@192.168.69.247:44801/eqpwqtzm
timeout.keepalive = 240
timeout.disconnect = 1800
ssh.port = 8022
ssh.authorized_keys_file = ~/.ssh/authorized_keys
[client]
introducer.furl = pb://ok45ssoklj4y7eok5c3xkmj@tahoe.example:44801/ii3uumo
helper.furl = pb://ggti5ssoklj4y7eok5c3xkmj@helper.tahoe.example:7054/kk8lhr
[storage]
no_storage = False
readonly_storage = True
sizelimit = 10000000000
[helper]
run_helper = True