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// Copyright (c) The Tor Project, Inc.
// See LICENSE for licensing information
// This is an asciidoc file used to generate the manpage/html reference.
// Learn asciidoc on http://www.methods.co.nz/asciidoc/userguide.html
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:man source:   Tor
:man manual:   Tor Manual
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TOR(1)
======

NAME
----
tor - The second-generation onion router


SYNOPSIS
--------
**tor** [__OPTION__ __value__]...

DESCRIPTION
-----------
__tor__ is a connection-oriented anonymizing communication
service. Users choose a source-routed path through a set of nodes, and
negotiate a "virtual circuit" through the network, in which each node
knows its predecessor and successor, but no others. Traffic flowing down
the circuit is unwrapped by a symmetric key at each node, which reveals
the downstream node. +

Basically __tor__ provides a distributed network of servers ("onion routers").
Users bounce their TCP streams -- web traffic, ftp, ssh, etc -- around the
routers, and recipients, observers, and even the routers themselves have
difficulty tracking the source of the stream.

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COMMAND-LINE OPTIONS
--------------------
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**-h**, **-help**::
    Display a short help message and exit.

**-f** __FILE__::
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    Specify a new configuration file to contain further Tor configuration
    options. (Default: $HOME/.torrc, or @CONFDIR@/torrc if that file is not
    found)

**--defaults-torrc** __FILE__::
    Specify a file in which to find default values for Tor options.  The
    contents of this file are overridden by those in the regular
    configuration file, and by those on the command line. (Default:
    @CONFDIR@/torrc-defaults.)
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**--hash-password**::
    Generates a hashed password for control port access.

**--list-fingerprint**::
    Generate your keys and output your nickname and fingerprint.

**--verify-config**::
    Verify the configuration file is valid.

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**--service install** [**--options** __command-line options__]::
    Install an instance of Tor as a Windows service, with the provided
    command-line options. Current instructions can be found at
    https://trac.torproject.org/projects/tor/wiki/doc/TorFAQ#HowdoIrunmyTorrelayasanNTservice

**--service** **remove**|**start**|**stop**::
    Remove, start, or stop a configured Tor Windows service.

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**--nt-service**::
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    Used internally to implement a Windows service.
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**--list-torrc-options**::
    List all valid options.

**--version**::
    Display Tor version and exit.

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**--quiet**|**--hush**::
    Override the default console log.  By default, Tor starts out logging
    messages at level "notice" and higher to the console.  It stops doing so
    after it parses its configuration, if the configuration tells it to log
    anywhere else.  You can override this behavior with the **--hush** option,
    which tells Tor to only send warnings and errors to the console, or with
    the **--quiet** option, which tells Tor not to log to the console at all.
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Other options can be specified on the command-line in the format "--option
value", in the format "option value", or in a configuration file.  For
instance, you can tell Tor to start listening for SOCKS connections on port
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9999 by passing --SOCKSPort 9999 or SOCKSPort 9999 to it on the command line,
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or by putting "SOCKSPort 9999" in the configuration file.  You will need to
quote options with spaces in them: if you want Tor to log all debugging
messages to debug.log, you will probably need to say --Log 'debug file
debug.log'.

Options on the command line override those in configuration files. See the
next section for more information.

THE CONFIGURATION FILE FORMAT
-----------------------------

All configuration options in a configuration are written on a single line by
default.  They take the form of an option name and a value, or an option name
and a quoted value (option value or option "value"). Anything after a #
character is treated as a comment.  Options are
case-insensitive. C-style escaped characters are allowed inside quoted
values. To split one configuration entry into multiple lines, use a single
backslash character (\) before the end of the line.  Comments can be used in
such multiline entries, but they must start at the beginning of a line.

By default, an option on the command line overrides an option found in the
configuration file, and an option in a configuration file overrides one in
the defaults file.

This rule is simple for options that take a single value, but it can become
complicated for options that are allowed to occur more than once: if you
specify four SOCKSPorts in your configuration file, and one more SOCKSPort on
the command line, the option on the command line will replace __all__ of the
SOCKSPorts in the configuration file.  If this isn't what you want, prefix
the option name with a plus sign, and it will be appended to the previous set
of options instead.

Alternatively, you might want to remove every instance of an option in the
configuration file, and not replace it at all: you might want to say on the
command line that you want no SOCKSPorts at all.  To do that, prefix the
option name with a forward slash.

GENERAL OPTIONS
---------------
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**BandwidthRate** __N__ **bytes**|**KB**|**MB**|**GB**::
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    A token bucket limits the average incoming bandwidth usage on this node to
    the specified number of bytes per second, and the average outgoing
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    bandwidth usage to that same value.  If you want to run a relay in the
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    public network, this needs to be _at the very least_ 30 KB (that is,
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    30720 bytes). (Default: 1 GB)
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**BandwidthBurst** __N__ **bytes**|**KB**|**MB**|**GB**::
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    Limit the maximum token bucket size (also known as the burst) to the given
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    number of bytes in each direction. (Default: 1 GB)
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**MaxAdvertisedBandwidth** __N__ **bytes**|**KB**|**MB**|**GB**::
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    If set, we will not advertise more than this amount of bandwidth for our
    BandwidthRate. Server operators who want to reduce the number of clients
    who ask to build circuits through them (since this is proportional to
    advertised bandwidth rate) can thus reduce the CPU demands on their server
    without impacting network performance.

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**RelayBandwidthRate** __N__ **bytes**|**KB**|**MB**|**GB**::
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    If not 0, a separate token bucket limits the average incoming bandwidth
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    usage for \_relayed traffic_ on this node to the specified number of bytes
    per second, and the average outgoing bandwidth usage to that same value.
    Relayed traffic currently is calculated to include answers to directory
    requests, but that may change in future versions. (Default: 0)

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**RelayBandwidthBurst** __N__ **bytes**|**KB**|**MB**|**GB**::
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    If not 0, limit the maximum token bucket size (also known as the burst) for
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    \_relayed traffic_ to the given number of bytes in each direction.
    (Default: 0)

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**PerConnBWRate** __N__ **bytes**|**KB**|**MB**|**GB**::
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    If set, do separate rate limiting for each connection from a non-relay.
    You should never need to change this value, since a network-wide value is
    published in the consensus and your relay will use that value. (Default: 0)

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**PerConnBWBurst** __N__ **bytes**|**KB**|**MB**|**GB**::
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    If set, do separate rate limiting for each connection from a non-relay.
    You should never need to change this value, since a network-wide value is
    published in the consensus and your relay will use that value. (Default: 0)

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**ClientTransportPlugin** __transport__ socks4|socks5 __IP__:__PORT__::
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**ClientTransportPlugin** __transport__ exec __path-to-binary__ [options]::
    In its first form, when set along with a corresponding Bridge line, the Tor
    client forwards its traffic to a SOCKS-speaking proxy on "IP:PORT". It's the
    duty of that proxy to properly forward the traffic to the bridge. +
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    In its second form, when set along with a corresponding Bridge line, the Tor
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    client launches the pluggable transport proxy executable in
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    __path-to-binary__ using __options__ as its command-line options, and
    forwards its traffic to it. It's the duty of that proxy to properly forward
    the traffic to the bridge.

**ServerTransportPlugin** __transport__ exec __path-to-binary__ [options]::
    The Tor relay launches the pluggable transport proxy in __path-to-binary__
    using __options__ as its command-line options, and expects to receive
    proxied client traffic from it.
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**ServerTransportListenAddr** __transport__ __IP__:__PORT__::
    When this option is set, Tor will suggest __IP__:__PORT__ as the
    listening address of any pluggable transport proxy that tries to
    launch __transport__.

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**ConnLimit** __NUM__::
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    The minimum number of file descriptors that must be available to the Tor
    process before it will start. Tor will ask the OS for as many file
    descriptors as the OS will allow (you can find this by "ulimit -H -n").
    If this number is less than ConnLimit, then Tor will refuse to start. +
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    You probably don't need to adjust this. It has no effect on Windows
    since that platform lacks getrlimit(). (Default: 1000)

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**DisableNetwork** **0**|**1**::
    When this option is set, we don't listen for or accept any connections
    other than controller connections, and we don't make any outbound
    connections.  Controllers sometimes use this option to avoid using
    the network until Tor is fully configured. (Default: 0)

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**ConstrainedSockets** **0**|**1**::
    If set, Tor will tell the kernel to attempt to shrink the buffers for all
    sockets to the size specified in **ConstrainedSockSize**. This is useful for
    virtual servers and other environments where system level TCP buffers may
    be limited. If you're on a virtual server, and you encounter the "Error
    creating network socket: No buffer space available" message, you are
    likely experiencing this problem. +
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    The preferred solution is to have the admin increase the buffer pool for
    the host itself via /proc/sys/net/ipv4/tcp_mem or equivalent facility;
    this configuration option is a second-resort. +
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    The DirPort option should also not be used if TCP buffers are scarce. The
    cached directory requests consume additional sockets which exacerbates
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    You should **not** enable this feature unless you encounter the "no buffer
    space available" issue. Reducing the TCP buffers affects window size for
    the TCP stream and will reduce throughput in proportion to round trip
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    time on long paths. (Default: 0)
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**ConstrainedSockSize** __N__ **bytes**|**KB**::
    When **ConstrainedSockets** is enabled the receive and transmit buffers for
    all sockets will be set to this limit. Must be a value between 2048 and
    262144, in 1024 byte increments. Default of 8192 is recommended.

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**ControlPort** __PORT__|**auto**::
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    If set, Tor will accept connections on this port and allow those
    connections to control the Tor process using the Tor Control Protocol
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    (described in control-spec.txt). Note: unless you also specify one or
    more of **HashedControlPassword** or **CookieAuthentication**,
    setting this option will cause Tor to allow any process on the local
    host to control it. (Setting both authentication methods means either
    method is sufficient to authenticate to Tor.) This
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    option is required for many Tor controllers; most use the value of 9051.
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    Set it to "auto" to have Tor pick a port for you. (Default: 0)
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**ControlListenAddress** __IP__[:__PORT__]::
    Bind the controller listener to this address. If you specify a port, bind
    to this port rather than the one specified in ControlPort. We strongly
    recommend that you leave this alone unless you know what you're doing,
    since giving attackers access to your control listener is really
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    dangerous. This directive can be specified multiple
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    times to bind to multiple addresses/ports.  (Default: 127.0.0.1)
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**ControlSocket** __Path__::
    Like ControlPort, but listens on a Unix domain socket, rather than a TCP
    socket. (Unix and Unix-like systems only.)

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**ControlSocketsGroupWritable** **0**|**1**::
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    If this option is set to 0, don't allow the filesystem group to read and
    write unix sockets (e.g. ControlSocket). If the option is set to 1, make
    the control socket readable and writable by the default GID. (Default: 0)

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**HashedControlPassword** __hashed_password__::
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    Allow connections on the control port if they present
    the password whose one-way hash is __hashed_password__. You
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    can compute the hash of a password by running "tor --hash-password
    __password__". You can provide several acceptable passwords by using more
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    than one HashedControlPassword line.
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**CookieAuthentication** **0**|**1**::
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    If this option is set to 1, allow connections on the control port
    when the connecting process knows the contents of a file named
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    "control_auth_cookie", which Tor will create in its data directory. This
    authentication method should only be used on systems with good filesystem
    security. (Default: 0)

**CookieAuthFile** __Path__::
    If set, this option overrides the default location and file name
    for Tor's cookie file. (See CookieAuthentication above.)

**CookieAuthFileGroupReadable** **0**|**1**|__Groupname__::
    If this option is set to 0, don't allow the filesystem group to read the
    cookie file. If the option is set to 1, make the cookie file readable by
    the default GID. [Making the file readable by other groups is not yet
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    implemented; let us know if you need this for some reason.] (Default: 0)
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**ControlPortWriteToFile** __Path__::
    If set, Tor writes the address and port of any control port it opens to
    this address.  Usable by controllers to learn the actual control port
    when ControlPort is set to "auto".

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**ControlPortFileGroupReadable** **0**|**1**::
    If this option is set to 0, don't allow the filesystem group to read the
    control port file. If the option is set to 1, make the control port
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    file readable by the default GID. (Default: 0)
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**DataDirectory** __DIR__::
    Store working data in DIR (Default: @LOCALSTATEDIR@/lib/tor)

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**FallbackDir** __address__:__port__ orport=__port__ id=__fingerprint__ [weight=__num__]::
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    When we're unable to connect to any directory cache for directory info
    (usually because we don't know about any yet) we try a FallbackDir.
    By default, the directory authorities are also FallbackDirs.

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**DirAuthority** [__nickname__] [**flags**] __address__:__port__ __fingerprint__::
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    Use a nonstandard authoritative directory server at the provided address
    and port, with the specified key fingerprint. This option can be repeated
    many times, for multiple authoritative directory servers. Flags are
    separated by spaces, and determine what kind of an authority this directory
    is. By default, every authority is authoritative for current ("v2")-style
    directories, unless the "no-v2" flag is given. If the "v1" flags is
    provided, Tor will use this server as an authority for old-style (v1)
    directories as well. (Only directory mirrors care about this.) Tor will
    use this server as an authority for hidden service information if the "hs"
    flag is set, or if the "v1" flag is set and the "no-hs" flag is **not** set.
    Tor will use this authority as a bridge authoritative directory if the
    "bridge" flag is set. If a flag "orport=**port**" is given, Tor will use the
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    given port when opening encrypted tunnels to the dirserver. If a flag
    "weight=**num**" is given, then the directory server is chosen randomly
    with probability proportional to that weight (default 1.0). Lastly, if a
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    flag "v3ident=**fp**" is given, the dirserver is a v3 directory authority
    whose v3 long-term signing key has the fingerprint **fp**. +
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    If no **DirAuthority** line is given, Tor will use the default directory
    authorities. NOTE: this option is intended for setting up a private Tor
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    network with its own directory authorities. If you use it, you will be
    distinguishable from other users, because you won't believe the same
    authorities they do.

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**DirAuthorityFallbackRate** __NUM__::
    When configured to use both directory authorities and fallback
    directories, the directory authorities also work as fallbacks. They are
    chosen with their regular weights, multiplied by this number, which
    should be 1.0 or less. (Default: 1.0)

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**DynamicDHGroups** **0**|**1**::
    If this option is set to 1, when running as a server, generate our
    own Diffie-Hellman group instead of using the one from Apache's mod_ssl.
    This option may help circumvent censorship based on static
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    Diffie-Hellman parameters. (Default: 0)
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**AlternateDirAuthority** [__nickname__] [**flags**] __address__:__port__ __fingerprint__ +

**AlternateHSAuthority** [__nickname__] [**flags**] __address__:__port__ __fingerprint__ +

**AlternateBridgeAuthority** [__nickname__] [**flags**] __address__:__port__ __ fingerprint__::
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    These options behave as DirAuthority, but they replace fewer of the
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    default directory authorities. Using
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    AlternateDirAuthority replaces the default Tor directory authorities, but
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    leaves the default hidden service authorities and bridge authorities in
    place.  Similarly, AlternateHSAuthority replaces the default hidden
    service authorities, but not the directory or bridge authorities; and
    AlternateBridgeAuthority replaces the default bridge authority,
    but leaves the directory and hidden service authorities alone.
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**DisableAllSwap** **0**|**1**::
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    If set to 1, Tor will attempt to lock all current and future memory pages,
    so that memory cannot be paged out. Windows, OS X and Solaris are currently
    not supported. We believe that this feature works on modern Gnu/Linux
    distributions, and that it should work on *BSD systems (untested). This
    option requires that you start your Tor as root, and you should use the
    **User** option to properly reduce Tor's privileges. (Default: 0)
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**DisableDebuggerAttachment** **0**|**1**::
   If set to 1, Tor will attempt to prevent basic debugging attachment attempts
   by other processes. It has no impact for users who wish to attach if they
   have CAP_SYS_PTRACE or if they are root.  We believe that this feature
   works on modern Gnu/Linux distributions, and that it may also work on *BSD
   systems (untested).  Some modern Gnu/Linux systems such as Ubuntu have the
   kernel.yama.ptrace_scope sysctl and by default enable it as an attempt to
   limit the PTRACE scope for all user processes by default. This feature will
   attempt to limit the PTRACE scope for Tor specifically - it will not attempt
   to alter the system wide ptrace scope as it may not even exist. If you wish
   to attach to Tor with a debugger such as gdb or strace you will want to set
   this to 0 for the duration of your debugging. Normal users should leave it
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   on. Disabling this option while Tor is running is prohibited. (Default: 1)

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**FetchDirInfoEarly** **0**|**1**::
    If set to 1, Tor will always fetch directory information like other
    directory caches, even if you don't meet the normal criteria for fetching
    early. Normal users should leave it off. (Default: 0)

**FetchDirInfoExtraEarly** **0**|**1**::
    If set to 1, Tor will fetch directory information before other directory
    caches. It will attempt to download directory information closer to the
    start of the consensus period. Normal users should leave it off.
    (Default: 0)

**FetchHidServDescriptors** **0**|**1**::
    If set to 0, Tor will never fetch any hidden service descriptors from the
    rendezvous directories. This option is only useful if you're using a Tor
    controller that handles hidden service fetches for you. (Default: 1)

**FetchServerDescriptors** **0**|**1**::
    If set to 0, Tor will never fetch any network status summaries or server
    descriptors from the directory servers. This option is only useful if
    you're using a Tor controller that handles directory fetches for you.
    (Default: 1)

**FetchUselessDescriptors** **0**|**1**::
    If set to 1, Tor will fetch every non-obsolete descriptor from the
    authorities that it hears about. Otherwise, it will avoid fetching useless
    descriptors, for example for routers that are not running. This option is
    useful if you're using the contributed "exitlist" script to enumerate Tor
    nodes that exit to certain addresses. (Default: 0)

**HTTPProxy** __host__[:__port__]::
    Tor will make all its directory requests through this host:port (or host:80
    if port is not specified), rather than connecting directly to any directory
    servers.

**HTTPProxyAuthenticator** __username:password__::
    If defined, Tor will use this username:password for Basic HTTP proxy
    authentication, as in RFC 2617. This is currently the only form of HTTP
    proxy authentication that Tor supports; feel free to submit a patch if you
    want it to support others.

**HTTPSProxy** __host__[:__port__]::
    Tor will make all its OR (SSL) connections through this host:port (or
    host:443 if port is not specified), via HTTP CONNECT rather than connecting
    directly to servers. You may want to set **FascistFirewall** to restrict
    the set of ports you might try to connect to, if your HTTPS proxy only
    allows connecting to certain ports.

**HTTPSProxyAuthenticator** __username:password__::
    If defined, Tor will use this username:password for Basic HTTPS proxy
    authentication, as in RFC 2617. This is currently the only form of HTTPS
    proxy authentication that Tor supports; feel free to submit a patch if you
    want it to support others.

**Socks4Proxy** __host__[:__port__]::
    Tor will make all OR connections through the SOCKS 4 proxy at host:port
    (or host:1080 if port is not specified).

**Socks5Proxy** __host__[:__port__]::
    Tor will make all OR connections through the SOCKS 5 proxy at host:port
    (or host:1080 if port is not specified).

**Socks5ProxyUsername** __username__ +

**Socks5ProxyPassword** __password__::
    If defined, authenticate to the SOCKS 5 server using username and password
    in accordance to RFC 1929. Both username and password must be between 1 and
    255 characters.

**KeepalivePeriod** __NUM__::
    To keep firewalls from expiring connections, send a padding keepalive cell
    every NUM seconds on open connections that are in use. If the connection
    has no open circuits, it will instead be closed after NUM seconds of
    idleness. (Default: 5 minutes)

**Log** __minSeverity__[-__maxSeverity__] **stderr**|**stdout**|**syslog**::
    Send all messages between __minSeverity__ and __maxSeverity__ to the standard
    output stream, the standard error stream, or to the system log. (The
    "syslog" value is only supported on Unix.) Recognized severity levels are
    debug, info, notice, warn, and err. We advise using "notice" in most cases,
    since anything more verbose may provide sensitive information to an
    attacker who obtains the logs. If only one severity level is given, all
    messages of that level or higher will be sent to the listed destination.

**Log** __minSeverity__[-__maxSeverity__] **file** __FILENAME__::
    As above, but send log messages to the listed filename. The
    "Log" option may appear more than once in a configuration file.
    Messages are sent to all the logs that match their severity
    level.

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**Log** **[**__domain__,...**]**__minSeverity__[-__maxSeverity__] ... **file** __FILENAME__ +

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**Log** **[**__domain__,...**]**__minSeverity__[-__maxSeverity__] ... **stderr**|**stdout**|**syslog**::
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    As above, but select messages by range of log severity __and__ by a
    set of "logging domains".  Each logging domain corresponds to an area of
    functionality inside Tor.  You can specify any number of severity ranges
    for a single log statement, each of them prefixed by a comma-separated
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    list of logging domains.  You can prefix a domain with $$~$$ to indicate
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    negation, and use * to indicate "all domains".  If you specify a severity
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    This is an advanced feature which is most useful for debugging one or two
    of Tor's subsystems at a time. +
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    The currently recognized domains are: general, crypto, net, config, fs,
    protocol, mm, http, app, control, circ, rend, bug, dir, dirserv, or, edge,
    acct, hist, and handshake.  Domain names are case-insensitive. +
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    For example, "`Log [handshake]debug [~net,~mm]info notice stdout`" sends
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    to stdout: all handshake messages of any severity, all info-and-higher
    messages from domains other than networking and memory management, and all
    messages of severity notice or higher.

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**LogMessageDomains** **0**|**1**::
    If 1, Tor includes message domains with each log message.  Every log
    message currently has at least one domain; most currently have exactly
    one.  This doesn't affect controller log messages. (Default: 0)

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**OutboundBindAddress** __IP__::
    Make all outbound connections originate from the IP address specified. This
    is only useful when you have multiple network interfaces, and you want all
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    of Tor's outgoing connections to use a single one. This option may
    be used twice, once with an IPv4 address and once with an IPv6 address.
    This setting will be ignored for connections to the loopback addresses
    (127.0.0.0/8 and ::1).
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**PidFile** __FILE__::
    On startup, write our PID to FILE. On clean shutdown, remove
    FILE.

**ProtocolWarnings** **0**|**1**::
    If 1, Tor will log with severity \'warn' various cases of other parties not
    following the Tor specification. Otherwise, they are logged with severity
    \'info'. (Default: 0)

**RunAsDaemon** **0**|**1**::
    If 1, Tor forks and daemonizes to the background. This option has no effect
    on Windows; instead you should use the --service command-line option.
    (Default: 0)

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**LogTimeGranularity** __NUM__::
    Set the resolution of timestamps in Tor's logs to NUM milliseconds.
    NUM must be positive and either a divisor or a multiple of 1 second.
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    Note that this option only controls the granularity written by Tor to
    a file or console log.  Tor does not (for example) "batch up" log
    messages to affect times logged by a controller, times attached to
    syslog messages, or the mtime fields on log files.  (Default: 1 second)
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**SafeLogging** **0**|**1**|**relay**::
    Tor can scrub potentially sensitive strings from log messages (e.g.
    addresses) by replacing them with the string [scrubbed]. This way logs can
    still be useful, but they don't leave behind personally identifying
    information about what sites a user might have visited. +
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    If this option is set to 0, Tor will not perform any scrubbing, if it is
    set to 1, all potentially sensitive strings are replaced. If it is set to
    relay, all log messages generated when acting as a relay are sanitized, but
    all messages generated when acting as a client are not. (Default: 1)

**User** __UID__::
    On startup, setuid to this user and setgid to their primary group.

**HardwareAccel** **0**|**1**::
    If non-zero, try to use built-in (static) crypto hardware acceleration when
    available. (Default: 0)

**AccelName** __NAME__::
    When using OpenSSL hardware crypto acceleration attempt to load the dynamic
    engine of this name. This must be used for any dynamic hardware engine.
    Names can be verified with the openssl engine command.

**AccelDir** __DIR__::
    Specify this option if using dynamic hardware acceleration and the engine
    implementation library resides somewhere other than the OpenSSL default.

**AvoidDiskWrites** **0**|**1**::
    If non-zero, try to write to disk less frequently than we would otherwise.
    This is useful when running on flash memory or other media that support
    only a limited number of writes. (Default: 0)

**TunnelDirConns** **0**|**1**::
    If non-zero, when a directory server we contact supports it, we will build
    a one-hop circuit and make an encrypted connection via its ORPort.
    (Default: 1)

**PreferTunneledDirConns** **0**|**1**::
    If non-zero, we will avoid directory servers that don't support tunneled
    directory connections, when possible. (Default: 1)

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**CircuitPriorityHalflife** __NUM1__::
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    If this value is set, we override the default algorithm for choosing which
    circuit's cell to deliver or relay next. When the value is 0, we
    round-robin between the active circuits on a connection, delivering one
    cell from each in turn. When the value is positive, we prefer delivering
    cells from whichever connection has the lowest weighted cell count, where
    cells are weighted exponentially according to the supplied
    CircuitPriorityHalflife value (in seconds). If this option is not set at
    all, we use the behavior recommended in the current consensus
    networkstatus. This is an advanced option; you generally shouldn't have
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    to mess with it. (Default: not set)
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**DisableIOCP** **0**|**1**::
    If Tor was built to use the Libevent's "bufferevents" networking code
    and you're running on Windows, setting this option to 1 will tell Libevent
    not to use the Windows IOCP networking API.  (Default: 1)

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**UserspaceIOCPBuffers** **0**|**1**::
    If IOCP is enabled (see DisableIOCP above), setting this option to 1
    will tell Tor to disable kernel-space TCP buffers, in order to avoid
    needless copy operations and try not to run out of non-paged RAM.
    This feature is experimental; don't use it yet unless you're eager to
    help tracking down bugs. (Default: 0)

**_UseFilteringSSLBufferevents** **0**|**1**::
    Tells Tor to do its SSL communication using a chain of
    bufferevents: one for SSL and one for networking.  This option has no
    effect if bufferevents are disabled (in which case it can't turn on), or
    if IOCP bufferevents are enabled (in which case it can't turn off).  This
    option is useful for debugging only; most users shouldn't touch it.
    (Default: 0)

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**CountPrivateBandwidth** **0**|**1**::
    If this option is set, then Tor's rate-limiting applies not only to
    remote connections, but also to connections to private addresses like
    127.0.0.1 or 10.0.0.1.  This is mostly useful for debugging
    rate-limiting.  (Default: 0)

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CLIENT OPTIONS
--------------

The following options are useful only for clients (that is, if
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**SocksPort**, **TransPort**, **DNSPort**, or **NATDPort** is non-zero):
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**AllowInvalidNodes** **entry**|**exit**|**middle**|**introduction**|**rendezvous**|**...**::
    If some Tor servers are obviously not working right, the directory
    authorities can manually mark them as invalid, meaning that it's not
    recommended you use them for entry or exit positions in your circuits. You
    can opt to use them in some circuit positions, though. The default is
    "middle,rendezvous", and other choices are not advised.

**ExcludeSingleHopRelays** **0**|**1**::
    This option controls whether circuits built by Tor will include relays with
    the AllowSingleHopExits flag set to true. If ExcludeSingleHopRelays is set
    to 0, these relays will be included. Note that these relays might be at
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    higher risk of being seized or observed, so they are not normally
    included.  Also note that relatively few clients turn off this option,
    so using these relays might make your client stand out.
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    (Default: 1)

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**Bridge** [__transport__] __IP__:__ORPort__ [__fingerprint__]::
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    When set along with UseBridges, instructs Tor to use the relay at
    "IP:ORPort" as a "bridge" relaying into the Tor network. If "fingerprint"
    is provided (using the same format as for DirServer), we will verify that
    the relay running at that location has the right fingerprint. We also use
    fingerprint to look up the bridge descriptor at the bridge authority, if
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    it's provided and if UpdateBridgesFromAuthority is set too.  +
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    If "transport" is provided, and matches to a ClientTransportPlugin
    line, we use that pluggable transports proxy to transfer data to
    the bridge.
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**LearnCircuitBuildTimeout** **0**|**1**::
    If 0, CircuitBuildTimeout adaptive learning is disabled. (Default: 1)

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**CircuitBuildTimeout** __NUM__::
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    Try for at most NUM seconds when building circuits. If the circuit isn't
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    open in that time, give up on it. If LearnCircuitBuildTimeout is 1, this
    value serves as the initial value to use before a timeout is learned. If
    LearnCircuitBuildTimeout is 0, this value is the only value used.
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    (Default: 60 seconds)
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**CircuitIdleTimeout** __NUM__::
    If we have kept a clean (never used) circuit around for NUM seconds, then
    close it. This way when the Tor client is entirely idle, it can expire all
    of its circuits, and then expire its TLS connections. Also, if we end up
    making a circuit that is not useful for exiting any of the requests we're
    receiving, it won't forever take up a slot in the circuit list. (Default: 1
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    hour)
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**CircuitStreamTimeout** __NUM__::
    If non-zero, this option overrides our internal timeout schedule for how
    many seconds until we detach a stream from a circuit and try a new circuit.
    If your network is particularly slow, you might want to set this to a
    number like 60. (Default: 0)

**ClientOnly** **0**|**1**::
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    If set to 1, Tor will under no circumstances run as a relay or serve
    directory requests. This config option is mostly meaningless: we
    added it back when we were considering having Tor clients auto-promote
    themselves to being relays if they were stable and fast enough. The
    current behavior is simply that Tor is a client unless ORPort or
    DirPort are configured. (Default: 0)
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**ExcludeNodes** __node__,__node__,__...__::
    A list of identity fingerprints, nicknames, country codes and address
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    patterns of nodes to avoid when building a circuit.
    (Example:
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    ExcludeNodes SlowServer, ABCD1234CDEF5678ABCD1234CDEF5678ABCD1234, \{cc}, 255.254.0.0/8) +
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    By default, this option is treated as a preference that Tor is allowed
    to override in order to keep working.
    For example, if you try to connect to a hidden service,
    but you have excluded all of the hidden service's introduction points,
    Tor will connect to one of them anyway.  If you do not want this
    behavior, set the StrictNodes option (documented below).  +
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    Note also that if you are a relay, this (and the other node selection
    options below) only affects your own circuits that Tor builds for you.
    Clients can still build circuits through you to any node.  Controllers
    can tell Tor to build circuits through any node.

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**ExcludeExitNodes** __node__,__node__,__...__::
    A list of identity fingerprints, nicknames, country codes and address
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    patterns of nodes to never use when picking an exit node---that is, a
    node that delivers traffic for you outside the Tor network.   Note that any
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    node listed in ExcludeNodes is automatically considered to be part of this
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    list too.  See also the caveats on the "ExitNodes" option below.
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**ExitNodes** __node__,__node__,__...__::
    A list of identity fingerprints, nicknames, country codes and address
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    patterns of nodes to use as exit node---that is, a
    node that delivers traffic for you outside the Tor network. +
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    Note that if you list too few nodes here, or if you exclude too many exit
    nodes with ExcludeExitNodes, you can degrade functionality.  For example,
    if none of the exits you list allows traffic on port 80 or 443, you won't
    be able to browse the web. +
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    Note also that not every circuit is used to deliver traffic outside of
    the Tor network.  It is normal to see non-exit circuits (such as those
    used to connect to hidden services, those that do directory fetches,
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    those used for relay reachability self-tests, and so on) that end
    at a non-exit node.  To
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    keep a node from being used entirely, see ExcludeNodes and StrictNodes. +
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    The ExcludeNodes option overrides this option: any node listed in both
    ExitNodes and ExcludeNodes is treated as excluded. +
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    The .exit address notation, if enabled via AllowDotExit, overrides
    this option.
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**EntryNodes** __node__,__node__,__...__::
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    A list of identity fingerprints, nicknames, and country codes of nodes
    to use for the first hop in your normal circuits.
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    Normal circuits include all
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    circuits except for direct connections to directory servers.  The Bridge
    option overrides this option; if you have configured bridges and
    UseBridges is 1, the Bridges are used as your entry nodes. +
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    The ExcludeNodes option overrides this option: any node listed in both
    EntryNodes and ExcludeNodes is treated as excluded.
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**StrictNodes** **0**|**1**::
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    If StrictNodes is set to 1, Tor will treat the ExcludeNodes option as a
    requirement to follow for all the circuits you generate, even if doing so
    will break functionality for you.  If StrictNodes is set to 0, Tor will
    still try to avoid nodes in the ExcludeNodes list, but it will err on the
    side of avoiding unexpected errors.  Specifically, StrictNodes 0 tells
    Tor that it is okay to use an excluded node when it is *necessary* to
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    perform relay reachability self-tests, connect to
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    a hidden service, provide a hidden service to a client, fulfill a .exit
    request, upload directory information, or download directory information.
    (Default: 0)
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**FascistFirewall** **0**|**1**::
    If 1, Tor will only create outgoing connections to ORs running on ports
    that your firewall allows (defaults to 80 and 443; see **FirewallPorts**).
    This will allow you to run Tor as a client behind a firewall with
    restrictive policies, but will not allow you to run as a server behind such
    a firewall. If you prefer more fine-grained control, use
    ReachableAddresses instead.

**FirewallPorts** __PORTS__::
    A list of ports that your firewall allows you to connect to. Only used when
    **FascistFirewall** is set. This option is deprecated; use ReachableAddresses
    instead. (Default: 80, 443)

**ReachableAddresses** __ADDR__[/__MASK__][:__PORT__]...::
    A comma-separated list of IP addresses and ports that your firewall allows
    you to connect to. The format is as for the addresses in ExitPolicy, except
    that "accept" is understood unless "reject" is explicitly provided. For
    example, \'ReachableAddresses 99.0.0.0/8, reject 18.0.0.0/8:80, accept
    \*:80' means that your firewall allows connections to everything inside net
    99, rejects port 80 connections to net 18, and accepts connections to port
    80 otherwise. (Default: \'accept \*:*'.)

**ReachableDirAddresses** __ADDR__[/__MASK__][:__PORT__]...::
    Like **ReachableAddresses**, a list of addresses and ports. Tor will obey
    these restrictions when fetching directory information, using standard HTTP
    GET requests. If not set explicitly then the value of
    **ReachableAddresses** is used. If **HTTPProxy** is set then these
    connections will go through that proxy.

**ReachableORAddresses** __ADDR__[/__MASK__][:__PORT__]...::
    Like **ReachableAddresses**, a list of addresses and ports. Tor will obey
    these restrictions when connecting to Onion Routers, using TLS/SSL. If not
    set explicitly then the value of **ReachableAddresses** is used. If
    **HTTPSProxy** is set then these connections will go through that proxy. +
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    The separation between **ReachableORAddresses** and
    **ReachableDirAddresses** is only interesting when you are connecting
    through proxies (see **HTTPProxy** and **HTTPSProxy**). Most proxies limit
    TLS connections (which Tor uses to connect to Onion Routers) to port 443,
    and some limit HTTP GET requests (which Tor uses for fetching directory
    information) to port 80.

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**HidServAuth** __onion-address__ __auth-cookie__ [__service-name__]::
    Client authorization for a hidden service. Valid onion addresses contain 16
    characters in a-z2-7 plus ".onion", and valid auth cookies contain 22
    characters in A-Za-z0-9+/. The service name is only used for internal
    purposes, e.g., for Tor controllers. This option may be used multiple times
    for different hidden services. If a hidden service uses authorization and
    this option is not set, the hidden service is not accessible. Hidden
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    services can be configured to require authorization using the
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    **HiddenServiceAuthorizeClient** option.

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**CloseHSClientCircuitsImmediatelyOnTimeout** **0**|**1**::
    If 1, Tor will close unfinished hidden service client circuits
    which have not moved closer to connecting to their destination
    hidden service when their internal state has not changed for the
    duration of the current circuit-build timeout.  Otherwise, such
    circuits will be left open, in the hope that they will finish
    connecting to their destination hidden services.  In either case,
    another set of introduction and rendezvous circuits for the same
    destination hidden service will be launched. (Default: 0)

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**CloseHSServiceRendCircuitsImmediatelyOnTimeout** **0**|**1**::
    If 1, Tor will close unfinished hidden-service-side rendezvous
    circuits after the current circuit-build timeout.  Otherwise, such
    circuits will be left open, in the hope that they will finish
    connecting to their destinations.  In either case, another
    rendezvous circuit for the same destination client will be
    launched. (Default: 0)

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**LongLivedPorts** __PORTS__::
    A list of ports for services that tend to have long-running connections
    (e.g. chat and interactive shells). Circuits for streams that use these
    ports will contain only high-uptime nodes, to reduce the chance that a node
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    will go down before the stream is finished. Note that the list is also
    honored for circuits (both client and service side) involving hidden
    services whose virtual port is in this list. (Default: 21, 22, 706,
    1863, 5050, 5190, 5222, 5223, 6523, 6667, 6697, 8300)
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**MapAddress** __address__ __newaddress__::
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    When a request for address arrives to Tor, it will transform to newaddress
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    before processing it. For example, if you always want connections to
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    www.example.com to exit via __torserver__ (where __torserver__ is the
    nickname of the server), use "MapAddress www.example.com
    www.example.com.torserver.exit". If the value is prefixed with a
    "\*.", matches an entire domain. For example, if you
    always want connections to example.com and any if its subdomains
    to exit via
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    __torserver__ (where __torserver__ is the nickname of the server), use
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    "MapAddress \*.example.com \*.example.com.torserver.exit". (Note the
    leading "*." in each part of the directive.) You can also redirect all
    subdomains of a domain to a single address. For example, "MapAddress
    *.example.com www.example.com". +
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 +
    NOTES:

    1. When evaluating MapAddress expressions Tor stops when it hits the most
    recently added expression that matches the requested address. So if you
    have the following in your torrc, www.torproject.org will map to 1.1.1.1:

     MapAddress www.torproject.org 2.2.2.2
     MapAddress www.torproject.org 1.1.1.1

    2. Tor evaluates the MapAddress configuration until it finds no matches. So
    if you have the following in your torrc, www.torproject.org will map to
    2.2.2.2:

      MapAddress 1.1.1.1 2.2.2.2
      MapAddress www.torproject.org 1.1.1.1

    3. The following MapAddress expression is invalid (and will be
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    ignored) because you cannot map from a specific address to a wildcard
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    address:

      MapAddress www.torproject.org *.torproject.org.torserver.exit

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    4. Using a wildcard to match only part of a string (as in *ample.com) is
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    also invalid.
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**NewCircuitPeriod** __NUM__::
    Every NUM seconds consider whether to build a new circuit. (Default: 30
    seconds)

**MaxCircuitDirtiness** __NUM__::
    Feel free to reuse a circuit that was first used at most NUM seconds ago,
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    but never attach a new stream to a circuit that is too old.  For hidden
    services, this applies to the __last__ time a circuit was used, not the
    first.  (Default: 10 minutes)
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**MaxClientCircuitsPending** __NUM__::
    Do not allow more than NUM circuits to be pending at a time for handling
    client streams. A circuit is pending if we have begun constructing it,
    but it has not yet been completely constructed.  (Default: 32)

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**NodeFamily** __node__,__node__,__...__::
    The Tor servers, defined by their identity fingerprints or nicknames,
    constitute a "family" of similar or co-administered servers, so never use
    any two of them in the same circuit. Defining a NodeFamily is only needed
    when a server doesn't list the family itself (with MyFamily). This option
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    can be used multiple times.  In addition to nodes, you can also list
    IP address and ranges and country codes in {curly braces}.
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**EnforceDistinctSubnets** **0**|**1**::
    If 1, Tor will not put two servers whose IP addresses are "too close" on
    the same circuit. Currently, two addresses are "too close" if they lie in
    the same /16 range. (Default: 1)

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**SOCKSPort** \['address':]__port__|**auto** [_flags_] [_isolation flags_]::
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    Open this port to listen for connections from SOCKS-speaking
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    applications. Set this to 0 if you don't want to allow application
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    connections via SOCKS. Set it to "auto" to have Tor pick a port for
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    you. This directive can be specified multiple times to bind
    to multiple addresses/ports. (Default: 9050) +
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    The _isolation flags_ arguments give Tor rules for which streams
    received on this SOCKSPort are allowed to share circuits with one
    another.  Recognized isolation flags are:
    **IsolateClientAddr**;;
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        Don't share circuits with streams from a different
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        client address.  (On by default and strongly recommended;
        you can disable it with **NoIsolateClientAddr**.)
    **IsolateSOCKSAuth**;;
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        Don't share circuits with streams for which different
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        SOCKS authentication was provided. (On by default;
        you can disable it with **NoIsolateSOCKSAuth**.)
    **IsolateClientProtocol**;;
        Don't share circuits with streams using a different protocol.
        (SOCKS 4, SOCKS 5, TransPort connections, NATDPort connections,
        and DNSPort requests are all considered to be different protocols.)
    **IsolateDestPort**;;
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        Don't share circuits with streams targetting a different
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        destination port.
    **IsolateDestAddr**;;
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        Don't share circuits with streams targetting a different
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        destination address.
    **SessionGroup=**__INT__;;
        If no other isolation rules would prevent it, allow streams
        on this port to share circuits with streams from every other
        port with the same session group.  (By default, streams received
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        another. This option overrides that behavior.) +
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    Other recognized _flags_ for a SOCKSPort are:
    **NoIPv4Traffic**;;
        Tell exits to not connect to IPv4 addresses in response to SOCKS
        requests on this connection.
    **IPv6Traffic**;;
        Tell exits to allow IPv6 addresses in response to SOCKS requests on
        this connection, so long as SOCKS5 is in use.  (SOCKS4 can't handle
        IPv6.)
    **PreferIPv6**;;
        Tells exits that, if a host has both an IPv4 and an IPv6 address,
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        we would prefer to connect to it via IPv6. (IPv4 is the default.) +
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       NOTE: Although this option allows you to specify an IP address
       other than localhost, you should do so only with extreme caution.
       The SOCKS protocol is unencrypted and (as we use it)
       unauthenticated, so exposing it in this way could leak your
       information to anybody watching your network, and allow anybody
       to use your computer as an open proxy.
    **CacheIPv4DNS**;;
        Tells the client to remember IPv4 DNS answers we receive from exit
        nodes via this connection. (On by default.)
    **CacheIPv6DNS**;;
        Tells the client to remember IPv6 DNS answers we receive from exit
        nodes via this connection.
    **CacheDNS**;;
        Tells the client to remember all DNS answers we receive from exit
        nodes via this connection.
    **UseIPv4Cache**;;
        Tells the client to use any cached IPv4 DNS answers we have when making
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        requests via this connection. (NOTE: This option, along UseIPv6Cache
        and UseDNSCache, can harm your anonymity, and probably
        won't help performance as much as you might expect. Use with care!)
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    **UseIPv6Cache**;;
        Tells the client to use any cached IPv6 DNS answers we have when making
        requests via this connection.
    **UseDNSCache**;;
        Tells the client to use any cached DNS answers we have when making
        requests via this connection.
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    **PreferIPv6Automap**;;
        When serving a hostname lookup request on this port that
        should get automapped (according to AutomapHostsOnResove),
        if we could return either an IPv4 or an IPv6 answer, prefer
        an IPv6 answer. (On by default.)
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**SOCKSListenAddress** __IP__[:__PORT__]::
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    Bind to this address to listen for connections from Socks-speaking
    applications. (Default: 127.0.0.1) You can also specify a port (e.g.
    192.168.0.1:9100). This directive can be specified multiple times to bind
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    to multiple addresses/ports.  (DEPRECATED: As of 0.2.3.x-alpha, you can
    now use multiple SOCKSPort entries, and provide addresses for SOCKSPort
    entries, so SOCKSListenAddress no longer has a purpose.  For backward
    compatibility, SOCKSListenAddress is only allowed when SOCKSPort is just
    a port number.)
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**SocksPolicy** __policy__,__policy__,__...__::
    Set an entrance policy for this server, to limit who can connect to the
    SocksPort and DNSPort ports. The policies have the same form as exit
    policies below.

**SocksTimeout** __NUM__::
    Let a socks connection wait NUM seconds handshaking, and NUM seconds
    unattached waiting for an appropriate circuit, before we fail it. (Default:
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    2 minutes)
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**TokenBucketRefillInterval** __NUM__ [**msec**|**second**]::
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    Set the refill interval of Tor's token bucket to NUM milliseconds.
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    NUM must be between 1 and 1000, inclusive.  Note that the configured
    bandwidth limits are still expressed in bytes per second: this
    option only affects the frequency with which Tor checks to see whether
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    previously exhausted connections may read again. (Default: 100 msec)
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**TrackHostExits** __host__,__.domain__,__...__::
    For each value in the comma separated list, Tor will track recent
    connections to hosts that match this value and attempt to reuse the same
    exit node for each. If the value is prepended with a \'.\', it is treated as
    matching an entire domain. If one of the values is just a \'.', it means
    match everything. This option is useful if you frequently connect to sites
    that will expire all your authentication cookies (i.e. log you out) if
    your IP address changes. Note that this option does have the disadvantage
    of making it more clear that a given history is associated with a single
    user. However, most people who would wish to observe this will observe it
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