1 | <?xml version="1.0" encoding="ISO-8859-1"?>
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2 | <!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.3//EN"
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3 | "http://www.oasis-open.org/docbook/xml/4.3/docbookx.dtd" [
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4 | <!ENTITY % general-entities SYSTEM "../../general.ent">
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5 | %general-entities;
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6 |
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7 | <!ENTITY openssh-download-http "http://sunsite.ualberta.ca/pub/OpenBSD/OpenSSH/portable/openssh-&openssh-version;.tar.gz">
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8 | <!ENTITY openssh-download-ftp "ftp://ftp.openbsd.org/pub/OpenBSD/OpenSSH/portable/openssh-&openssh-version;.tar.gz">
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9 | <!ENTITY openssh-size "854 KB">
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10 | <!ENTITY openssh-buildsize "13.3 MB">
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11 | <!ENTITY openssh-time "0.40 SBU">
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12 | ]>
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13 |
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14 | <sect1 id="openssh" xreflabel="OpenSSH-&openssh-version;">
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15 | <sect1info>
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16 | <othername>$LastChangedBy$</othername>
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17 | <date>$Date$</date>
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18 | </sect1info>
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19 | <?dbhtml filename="openssh.html"?>
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20 | <title>Open<acronym>SSH</acronym>-&openssh-version;</title>
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21 |
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22 | <sect2>
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23 | <title>Introduction to
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24 | <application>Open<acronym>SSH</acronym></application></title>
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25 |
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26 | <para>The <application>Open<acronym>SSH</acronym></application> package
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27 | contains <command>ssh</command> clients and the <command>sshd</command> daemon.
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28 | This is useful for encrypting authentication and subsequent traffic over a
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29 | network.</para>
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30 |
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31 | <sect3><title>Package information</title>
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32 | <itemizedlist spacing='compact'>
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33 | <listitem><para>Download (HTTP): <ulink url="&openssh-download-http;"/></para></listitem>
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34 | <listitem><para>Download (FTP): <ulink url="&openssh-download-ftp;"/></para></listitem>
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35 | <listitem><para>Download size: &openssh-size;</para></listitem>
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36 | <listitem><para>Estimated Disk space required: &openssh-buildsize;</para></listitem>
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37 | <listitem><para>Estimated build time: &openssh-time;</para></listitem></itemizedlist>
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38 | </sect3>
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39 |
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40 | <sect3><title><application>Open<acronym>SSH</acronym></application>
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41 | dependencies</title>
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42 | <sect4><title>Required</title>
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43 | <para><xref linkend="openssl"/></para>
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44 | </sect4>
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45 | <sect4><title>Optional</title>
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46 | <para><xref linkend="Linux_PAM"/>,
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47 | <xref linkend="tcpwrappers"/>,
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48 | X (<xref linkend="xfree86"/> or <xref linkend="xorg"/>),
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49 | <xref linkend="mitkrb"/> or <xref linkend="heimdal"/>,
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50 | <xref linkend="j2sdk"/>,
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51 | <xref linkend="net-tools"/> and
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52 | <ulink url="http://www.opensc.org/">OpenSC</ulink>
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53 | </para></sect4>
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54 | </sect3>
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55 |
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56 | </sect2>
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57 |
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58 | <sect2>
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59 | <title>Installation of
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60 | <application>Open<acronym>SSH</acronym></application></title>
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61 |
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62 | <para><application>Open<acronym>SSH</acronym></application> runs as two
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63 | processes when connecting to other computers. The first process is a
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64 | privileged process and controls the issuance of privileges as necessary.
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65 | The second process communicates with the network. Additional installation
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66 | steps are necessary to set up the proper environment, which are performed
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67 | by the following commands:</para>
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68 |
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69 | <screen><userinput><command>mkdir /var/empty &&
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70 | chown root:sys /var/empty &&
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71 | groupadd sshd &&
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72 | useradd -c 'sshd privsep' -d /var/empty -g sshd -s /bin/false sshd</command></userinput></screen>
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73 |
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74 | <para><application>OpenSSH</application> is very sensitive to changes in the
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75 | linked <application>OpenSSL</application> libraries. If you recompile
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76 | <application>OpenSSL</application>, <application>OpenSSH</application> may
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77 | fail to startup. An alternative is to link against the static
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78 | <application>OpenSSL</application> library. To link against the static
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79 | library, execute the following command:</para>
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80 |
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81 | <screen><userinput><command>sed -i "s:-lcrypto:/usr/lib/libcrypto.a:g" configure</command></userinput></screen>
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82 |
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83 | <para>Install <application>Open<acronym>SSH</acronym></application> by running
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84 | the following commands:</para>
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85 |
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86 | <screen><userinput><command>./configure --prefix=/usr --sysconfdir=/etc/ssh \
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87 | --libexecdir=/usr/sbin --with-md5-passwords &&
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88 | make &&
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89 | make install</command></userinput></screen>
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90 |
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91 | </sect2>
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92 |
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93 | <sect2>
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94 | <title>Command explanations</title>
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95 |
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96 | <para><parameter>--sysconfdir=/etc/ssh</parameter>: This prevents the
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97 | configuration files from going to
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98 | <filename class="directory">/usr/etc</filename>.</para>
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99 |
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100 | <para><parameter>--with-md5-passwords</parameter>: This is required
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101 | if you made the changes recommended by the shadowpasswd_plus
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102 | <acronym>LFS</acronym> hint on
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103 | your <acronym>SSH</acronym> server when you installed the Shadow Password
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104 | Suite or if you access a <acronym>SSH</acronym> server that authenticates by
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105 | user passwords encrypted with md5. </para>
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106 |
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107 | <para><parameter>--libexecdir=/usr/sbin</parameter>:
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108 | <application>Open<acronym>SSH</acronym></application> installs programs called
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109 | by programs in <filename class="directory">/usr/libexec</filename>.
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110 | <command>sftp-server</command> is a <command>sshd</command>
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111 | utility and <command>ssh-askpass</command> is a <command>ssh-add</command>
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112 | utility that is installed as a link to <command>X11-ssh-askpass</command>.
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113 | Both of these should go in <filename class="directory">/usr/sbin</filename>
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114 | not <filename class="directory">/usr/libexec</filename>.</para>
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115 |
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116 | </sect2>
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117 |
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118 | <sect2>
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119 | <title>Configuring <application>Open<acronym>SSH</acronym></application></title>
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120 |
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121 | <sect3><title>Config files</title>
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122 |
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123 | <para><filename>/etc/ssh/ssh_config</filename> and
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124 | <filename>/etc/ssh/sshd_config </filename></para>
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125 |
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126 | <para>There are no required changes to either of these files. However,
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127 | you may wish to view them to make changes for appropriate security to
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128 | your system. One recomended change is that you disable root login via
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129 | ssh. Execute the following command to disable root login via ssh:</para>
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130 |
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131 | <screen><userinput><command>echo "PermitRootLogin no" >> /etc/ssh/sshd_config</command></userinput></screen>
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132 |
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133 | <para>Additional configuration information can be found in the man pages for
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134 | <command>sshd</command>, <command>ssh</command> and
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135 | <command>ssh-agent</command></para>
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136 |
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137 | </sect3>
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138 |
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139 | <sect3><title>sshd init.d script</title>
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140 |
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141 | <para>To start the <acronym>SSH</acronym> server at system boot, install the
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142 | <filename>/etc/rc.d/init.d/sshd</filename> init script included in the
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143 | <xref linkend="intro-important-bootscripts"/> package.</para>
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144 |
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145 | <screen><userinput><command>make install-sshd</command></userinput></screen>
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146 |
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147 | </sect3>
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148 |
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149 | </sect2>
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150 |
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151 | <sect2>
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152 | <title>Contents</title>
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153 |
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154 | <para>The <application>Open<acronym>SSH</acronym></application> package
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155 | contains <command>ssh</command>, <command>sshd</command>,
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156 | <command>ssh-agent</command>, <command>ssh-add</command>,
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157 | <command>sftp</command>, <command>scp</command>,
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158 | <command>ssh-keygen</command>, <command>sftp-server</command> and
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159 | <command>ssh-keyscan</command>.</para>
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160 |
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161 | </sect2>
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162 |
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163 | <sect2><title>Description</title>
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164 |
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165 | <sect3><title>ssh</title>
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166 | <para>The basic <command>rlogin</command>/<command>rsh</command>-like
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167 | client program.</para></sect3>
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168 |
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169 | <sect3><title>sshd</title>
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170 | <para>The daemon that listens for <command>ssh</command> login
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171 | requests.</para></sect3>
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172 |
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173 | <sect3><title>ssh-agent</title>
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174 | <para>An authentication agent that can store private keys.</para></sect3>
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175 |
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176 | <sect3><title>ssh-add</title>
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177 | <para>Tool which adds keys to the <command>ssh-agent</command>.</para></sect3>
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178 |
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179 | <sect3><title>sftp</title>
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180 | <para><acronym>FTP</acronym>-like program that works over
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181 | <acronym>SSH</acronym>1 and <acronym>SSH</acronym>2 protocols.</para></sect3>
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182 |
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183 | <sect3><title>scp</title>
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184 | <para>File copy program that acts like <command>rcp</command>.</para></sect3>
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185 |
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186 | <sect3><title>ssh-keygen</title>
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187 | <para>Key generation tool.</para></sect3>
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188 |
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189 | <sect3><title>sftp-server</title>
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190 | <para><acronym>SFTP</acronym> server subsystem.</para></sect3>
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191 |
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192 | <sect3><title>ssh-keyscan</title>
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193 | <para>Utility for gathering public host keys from a number of
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194 | hosts.</para></sect3>
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195 |
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196 | </sect2>
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197 |
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198 | </sect1>
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199 |
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