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1 .TH GNUSERV 1 "" "XEmacs Server"
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2 .UC 4
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3 .SH NAME
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4 gnuserv, gnuclient \- Server and Clients for XEmacs
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5 .SH SYNOPSIS
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6 .B gnuclient
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7 [-q] [-nw] [-l library] [-f function] [-eval form] [[-h hostname]
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8 [-p port] [-r pathname]] [[+line] path] ...
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9 .br
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10 .B gnuserv
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11 .SH DESCRIPTION
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12
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13 .PP
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163
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14 \fIgnuclient\fP allows the user to request a running XEmacs process to
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15 edit the named files or directories in a new frame. Depending on your
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16 environment, it can be an X frame or a TTY frame. One typical use for
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17 this is with a dialup connection to a machine on which an XEmacs
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18 process is currently running.
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19 .PP
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20 \fIgnuserv\fP is the server program that is set running by XEmacs to
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21 handle all incoming and outgoing requests. It is not usually invoked
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22 directly, but is started from XEmacs by loading the \fIgnuserv\fP
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23 package and evaluating the Lisp form (gnuserv-start).
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24 .SH OPTIONS
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25 .TP 8
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26 .BI \-q
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27 This option informs \fIgnuclient\fP to exit once connection has been
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28 made with the XEmacs process. Normally \fIgnuclient\fP waits until
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29 all of the files on the command line have been finished with (their
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30 buffers killed) by the XEmacs process, and all the forms have been
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31 evaluated.
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32 .TP 8
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33 .BI \-h " hostname"
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34 Used only with Internet-domain sockets, this option specifies the host
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35 machine which should be running \fIgnuserv\fP. If this option is not
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36 specified then the value of the environment variable GNU_HOST is used
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37 if set. If no hostname is specified, and the GNU_HOST variable is not
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38 set, an internet connection will not be attempted. N\.B.:
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39 \fIgnuserv\fP does NOT allow internet connections unless the
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40 GNU_SECURE variable has been specified and points at a file listing
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41 all trusted hosts. (See SECURITY below.)
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42
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43 .br
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44 Note that an internet address may be specified instead of a hostname
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45 which can speed up connections to the server by quite a bit,
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46 especially if the client machine is running YP.
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47
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48 .br
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49 Note also that a hostname of \fBunix\fP can be used to specify that
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50 the connection to the server should use a Unix-domain socket (if
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51 supported) rather than an Internet-domain socket.
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52 .TP 8
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53 .BI \-p " port"
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54 Used only with Internet-domain sockets, this option specifies the
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55 service port used to communicate between server and clients. If this
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56 option is not specified, then the value of the environment variable
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57 GNU_PORT is used, if set, otherwise a service called ``gnuserv'' is
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58 looked up in the services database. Finally, if no other value can be
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59 found for the port, then a default port is used which is usually 21490
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60 + uid.
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61 .br
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62 Note that since \fIgnuserv\fP doesn't allow command-line options, the port for
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63 it will have to be specified via one of the alternative methods.
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64 .TP 8
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65 .BI \-r " pathname"
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66 Used only with Internet-domain sockets, the pathname argument may be
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67 needed to inform XEmacs how to reach the root directory of a remote
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68 machine. \fIgnuclient\fP prepends this string to each path argument
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69 given. For example, if you were trying to edit a file on a client
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70 machine called otter, whose root directory was accessible from the
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71 server machine via the path /net/otter, then this argument should be
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72 set to '/net/otter'. If this option is omitted, then the value is
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73 taken from the environment variable GNU_NODE, if set, or the empty
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74 string otherwise.
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75 .TP 8
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76 .BI "path"
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77 This is the path of the file to be edited. If the file is a directory, then
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78 the directory browsers dired or monkey are usually invoked instead.
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79 .TP 8
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80 .BI "sexpr"
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81 This is part of an XEmacs LISP expression to evaluate. All the sexprs
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82 are concatenated together and wrapped in a progn form before sending
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83 to XEmacs.
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84
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85 .PP
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86 .SH SETUP
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87 \fIgnuserv\fP is packaged standardly with recent versions of XEmacs.
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88 Therefore, you should be able to start the server simply by evaluating
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89 the XEmacs Lisp form (gnuserv-start), or equivalently by typing
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90 `M-x gnuserv-start'.
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91 .SH EXAMPLE
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92 .RS 4
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93 gnuclient -q -f mh-smail
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94 .br
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95 gnuclient -h cuckoo -r /ange@otter: /tmp/*
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96 .br
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97 gnuclient -nw ../src/listproc.c
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98 .RE
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99
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163
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100 .SH SYSV IPC
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101 SysV IPC is used to communicate between \fIgnuclient\fP and
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102 \fIgnuserv\fP if the symbol SYSV_IPC is defined at the top of
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103 gnuserv.h. This is incompatible with both Unix-domain and
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104 Internet-domain socket communication as described below. A file called
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105 /tmp/gsrv??? is created as a key for the message queue, and if removed
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106 will cause the communication between server and client to fail until
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107 the server is restarted.
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108 .SH UNIX-DOMAIN SOCKETS
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109 A Unix-domain socket is used to communicate between \fIgnuclient\fP
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110 and \fIgnuserv\fP if the symbol UNIX_DOMAIN_SOCKETS is defined at the
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111 top of gnuserv.h. A file called /tmp/gsrvdir????/gsrv is created for
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112 communication and if deleted will cause communication between server
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113 and client to fail. Only the user running gnuserv will be able to
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114 connect to the socket.
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115 .SH INTERNET-DOMAIN SOCKETS
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116 Internet-domain sockets are used to communicate between
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117 \fIgnuclient\fP and \fIgnuserv\fP if the symbol
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118 INTERNET_DOMAIN_SOCKETS is defined at the top of gnuserv.h. Both
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119 Internet-domain and Unix-domain sockets can be used at the same
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120 time. If a hostname is specified via -h or via the GNU_HOST
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121 environment variable, \fIgnuclient\fP establish connections using an
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122 internet domain socket. If not, a local connection is attempted via
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123 either a unix-domain socket or SYSV IPC.
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124 .SH SECURITY
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125 Using Internet-domain sockets, a more robust form of security is
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126 needed that wasn't necessary with either Unix-domain sockets or SysV
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127 IPC. Currently, two authentication protocols are supported to provide
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128 this: MIT-MAGIC-COOKIE-1 (based on the X11 xauth(1) program) and a
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129 simple host-based access control mechanism, hereafter called
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130 GNUSERV-1. The GNUSERV-1 protocol is always available, whereas support
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131 for MIT-MAGIC-COOKIE-1 may or may not have been enabled (via a #define
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132 at the top of gnuserv.h) at compile-time.
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133 .PP
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134 \fIgnuserv\fP, using GNUSERV-1, performs a limited form of access
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135 control at the machine level. By default no internet-domain socket is
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136 opened. If the variable GNU_SECURE can be found in \fIgnuserv\fP's
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137 environment, and it names a readable filename, then this file is
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138 opened and assumed to be a list of hosts, one per line, from which the
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139 server will allow requests. Connections from any other host will be
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140 rejected. Even the machine on which \fIgnuserv\fP is running is not
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141 permitted to make connections via the internet socket unless its
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142 hostname is explicitly specified in this file. Note that a host may
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143 be either a numeric IP address or a hostname, and that
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144 .I any
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145 user on an approved host may connect to your gnuserv and execute arbitrary
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146 elisp (e.g., delete all your files).
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147 If this file contains a lot of
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148 hostnames then the server may take quite a time to start up.
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149 .PP
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150 When the MIT-MAGIC-COOKIE-1 protocol is enabled, an internet socket
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151 \fIis\fP opened by default. \fIgnuserv\fP will accept a connection from
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152 any host, and will wait for a "magic cookie" (essentially, a password)
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153 to be presented by the client. If the client doesn't present the
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154 cookie, or if the cookie is wrong, the authentication of the client is
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155 considered to have failed. At this point. \fIgnuserv\fP falls back to
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156 the GNUSERV-1 protocol; If the client is calling from a host listed in
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157 the GNU_SECURE file, the connection will be accepted, otherwise it
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158 will be rejected.
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159 .TP 4
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160 .I Using MIT-MAGIC-COOKIE-1 authentication
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161 When the \fIgnuserv\fP server is started, it looks for a cookie
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162 defined for display 999 on the machine where it is running. If the
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163 cookie is found, it will be stored for use as the authentication
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164 cookie. These cookies are defined in an authorization file (usually
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165 ~/.Xauthority) that is manipulated by the X11 xauth(1) program. For
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166 example, a machine "kali" which runs an emacs that invokes
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167 \fIgnuserv\fP should respond as follows (at the shell prompt) when set
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168 up correctly.
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169 .PP
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170 .RS 8
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171 kali% xauth list
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172 .br
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173 GS65.SP.CS.CMU.EDU:0 MIT-MAGIC-COOKIE-1 11223344
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174 .br
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175 KALI.FTM.CS.CMU.EDU:999 MIT-MAGIC-COOKIE-1 1234
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176 .RE
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177 .PP
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178 .RS 4
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179 In the above case, the authorization file defines two cookies. The
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180 second one, defined for screen 999 on the server machine, is used for
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181 gnuserv authentication.
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182 .PP
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183 On the client machine's side, the authorization file must contain an
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184 identical line, specifying the
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185 .I server's
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186 cookie. In other words, on a machine "foobar" which wishes to connect
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187 to "kali," the `xauth list' output should contain the line:
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188 .PP
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189 .RS 4
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190 KALI.FTM.CS.CMU.EDU:999 MIT-MAGIC-COOKIE-1 1234
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191 .RE
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192 .PP
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193 For more information on authorization files, take a look at the
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194 xauth(1X11) man page, or invoke xauth interactively (without any
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195 arguments) and type "help" at the prompt. Remember that case in the
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196 name of the authorization protocol (i.e.`MIT-MAGIC-COOKIE-1')
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197 .I is
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198 significant!
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199 .RE
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200
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201 .SH FILES
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202 .PP
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203 .TP 8
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204 .B /tmp/gsrv???
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205 (SYSV_IPC only)
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206 .TP 8
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207 .B /tmp/gsrvdir???/gsrv
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208 (unix domain sockets only)
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209 .TP 8
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210 .B ~/.emacs
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211 XEmacs customization file, see xemacs(1).
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212 .SH SEE ALSO
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213 .PP
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214 .TP 8
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215 xauth(1X11), Xsecurity(1X11)
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216 .SH BUGS
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217 .PP
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218 NULs occurring in result strings don't get passed back to gnudoit properly.
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219
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220 .SH AUTHOR.
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221 Andy Norman (ange@hplb.hpl.hp.com), based heavily upon
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222 etc/emacsclient.c, etc/server.c and lisp/server.el from the GNU Emacs
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223 18.52 distribution. Various modifications from Bob Weiner (weiner@mot.com),
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224 Darrell Kindred (dkindred@cmu.edu), Arup Mukherjee (arup@cmu.edu), Ben
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225 Wing (wing@666.com) and Hrvoje Niksic (hniksic@srce.hr).
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