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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta name="generator" content="HTML Tidy, see www.w3.org" /><title>Groups</title><meta name="GENERATOR" content="Modular DocBook HTML Stylesheet Version 1.7" /><link rel="HOME" title="FreeBSD Handbook" href="index.html" /><link rel="UP" title="Users and Basic Account Management" href="users.html" /><link rel="PREVIOUS" title="Personalizing Users" href="users-personalizing.html" /><link rel="NEXT" title="Security" href="security.html" /><link rel="STYLESHEET" type="text/css" href="docbook.css" /></head><body class="SECT1" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#840084"alink="#0000FF"><div class="NAVHEADER"><table summary="Header navigation table" width="100%" border="0" cellpadding="0"cellspacing="0"><tr><th colspan="3" align="center">FreeBSD Handbook</th></tr><tr><td width="10%" align="left" valign="bottom"><a href="users-personalizing.html"accesskey="P">Prev</a></td><td width="80%" align="center" valign="bottom">Chapter 13 Users and Basic AccountManagement</td><td width="10%" align="right" valign="bottom"><a href="security.html"accesskey="N">Next</a></td></tr></table><hr align="LEFT" width="100%" /></div><div class="SECT1"><h1 class="SECT1"><a id="USERS-GROUPS" name="USERS-GROUPS">13.9 Groups</a></h1><p>A group is simply a list of users. Groups are identified by their group name and GID(Group ID). In FreeBSD (and most other <span class="TRADEMARK">UNIX</span>® likesystems), the two factors the kernel uses to decide whether a process is allowed to dosomething is its user ID and list of groups it belongs to. Unlike a user ID, a processhas a list of groups associated with it. You may hear some things refer to the ``groupID'' of a user or process; most of the time, this just means the first group in thelist.</p><p>The group name to group ID map is in <tt class="FILENAME">/etc/group</tt>. This is aplain text file with four colon-delimited fields. The first field is the group name, thesecond is the encrypted password, the third the group ID, and the fourth thecomma-delimited list of members. It can safely be edited by hand (assuming, of course,that you do not make any syntax errors!). For a more complete description of the syntax,see the <a href="http://www.FreeBSD.org/cgi/man.cgi?query=group&sektion=5"><spanclass="CITEREFENTRY"><span class="REFENTRYTITLE">group</span>(5)</span></a> manualpage.</p><p>If you do not want to edit <tt class="FILENAME">/etc/group</tt> manually, you can usethe <a href="http://www.FreeBSD.org/cgi/man.cgi?query=pw&sektion=8"><spanclass="CITEREFENTRY"><span class="REFENTRYTITLE">pw</span>(8)</span></a> command to addand edit groups. For example, to add a group called <tt class="GROUPNAME">teamtwo</tt>and then confirm that it exists you can use:</p><div class="EXAMPLE"><a id="AEN18583" name="AEN18583"></a><p><b>Example 13-8. Adding a Group Using <span class="CITEREFENTRY"><spanclass="REFENTRYTITLE">pw</span>(8)</span></b></p><pre class="SCREEN"><samp class="PROMPT">#</samp> <kbd class="USERINPUT">pw groupadd teamtwo</kbd><samp class="PROMPT">#</samp> <kbd class="USERINPUT">pw groupshow teamtwo</kbd>teamtwo:*:1100:</pre></div><p>The number <var class="LITERAL">1100</var> above is the group ID of the group <ttclass="GROUPNAME">teamtwo</tt>. Right now, <tt class="GROUPNAME">teamtwo</tt> has nomembers, and is thus rather useless. Let's change that by inviting <ttclass="USERNAME">jru</tt> to the <tt class="GROUPNAME">teamtwo</tt> group.</p><div class="EXAMPLE"><a id="AEN18599" name="AEN18599"></a><p><b>Example 13-9. Adding Somebody to a Group Using <span class="CITEREFENTRY"><spanclass="REFENTRYTITLE">pw</span>(8)</span></b></p><pre class="SCREEN"><samp class="PROMPT">#</samp> <kbd class="USERINPUT">pw groupmod teamtwo -M jru</kbd><samp class="PROMPT">#</samp> <kbd class="USERINPUT">pw groupshow teamtwo</kbd>teamtwo:*:1100:jru</pre></div><p>The argument to the <var class="OPTION">-M</var> option is a comma-delimited list ofusers who are members of the group. From the preceding sections, we know that thepassword file also contains a group for each user. The latter (the user) is automaticallyadded to the group list by the system; the user will not show up as a member when usingthe <var class="OPTION">groupshow</var> command to <ahref="http://www.FreeBSD.org/cgi/man.cgi?query=pw&sektion=8"><spanclass="CITEREFENTRY"><span class="REFENTRYTITLE">pw</span>(8)</span></a>, but will showup when the information is queried via <ahref="http://www.FreeBSD.org/cgi/man.cgi?query=id&sektion=1"><spanclass="CITEREFENTRY"><span class="REFENTRYTITLE">id</span>(1)</span></a> or similar tool.In other words, <a href="http://www.FreeBSD.org/cgi/man.cgi?query=pw&sektion=8"><spanclass="CITEREFENTRY"><span class="REFENTRYTITLE">pw</span>(8)</span></a> only manipulatesthe <tt class="FILENAME">/etc/group</tt> file; it will never attempt to read additionallydata from <tt class="FILENAME">/etc/passwd</tt>.</p><div class="EXAMPLE"><a id="AEN18623" name="AEN18623"></a><p><b>Example 13-10. Using <span class="CITEREFENTRY"><spanclass="REFENTRYTITLE">id</span>(1)</span> to Determine Group Membership</b></p><pre class="SCREEN"><samp class="PROMPT">%</samp> <kbd class="USERINPUT">id jru</kbd>uid=1001(jru) gid=1001(jru) groups=1001(jru), 1100(teamtwo)</pre></div><p>As you can see, <tt class="USERNAME">jru</tt> is a member of the groups <ttclass="GROUPNAME">jru</tt> and <tt class="GROUPNAME">teamtwo</tt>.</p><p>For more information about <ahref="http://www.FreeBSD.org/cgi/man.cgi?query=pw&sektion=8"><spanclass="CITEREFENTRY"><span class="REFENTRYTITLE">pw</span>(8)</span></a>, see its manualpage, and for more information on the format of <tt class="FILENAME">/etc/group</tt>,consult the <a href="http://www.FreeBSD.org/cgi/man.cgi?query=group&sektion=5"><spanclass="CITEREFENTRY"><span class="REFENTRYTITLE">group</span>(5)</span></a> manualpage.</p></div><div class="NAVFOOTER"><hr align="LEFT" width="100%" /><table summary="Footer navigation table" width="100%" border="0" cellpadding="0"cellspacing="0"><tr><td width="33%" align="left" valign="top"><a href="users-personalizing.html"accesskey="P">Prev</a></td><td width="34%" align="center" valign="top"><a href="index.html"accesskey="H">Home</a></td><td width="33%" align="right" valign="top"><a href="security.html"accesskey="N">Next</a></td></tr><tr><td width="33%" align="left" valign="top">Personalizing Users</td><td width="34%" align="center" valign="top"><a href="users.html"accesskey="U">Up</a></td><td width="33%" align="right" valign="top">Security</td></tr></table></div><p align="center"><small>This, and other documents, can be downloaded from <ahref="ftp://ftp.FreeBSD.org/pub/FreeBSD/doc/">ftp://ftp.FreeBSD.org/pub/FreeBSD/doc/</a>.</small></p><p align="center"><small>For questions about FreeBSD, read the <ahref="http://www.FreeBSD.org/docs.html">documentation</a> before contacting <<ahref="mailto:questions@FreeBSD.org">questions@FreeBSD.org</a>>.<br />For questions about this documentation, e-mail <<ahref="mailto:doc@FreeBSD.org">doc@FreeBSD.org</a>>.</small></p></body></html>⌨️ 快捷键说明
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