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diff --git a/sag-0.6.1-www/sag-0.6.1.html/x1956.html b/sag-0.6.1-www/sag-0.6.1.html/x1956.html new file mode 100644 index 0000000..6996cc7 --- /dev/null +++ b/sag-0.6.1-www/sag-0.6.1.html/x1956.html @@ -0,0 +1,274 @@ +<!DOCTYPE HTML PUBLIC "-//Norman Walsh//DTD DocBook HTML 1.0//EN"> +<HTML +><HEAD +><TITLE +>What login does</TITLE +><META +NAME="GENERATOR" +CONTENT="Modular DocBook HTML Stylesheet"><LINK +REL="HOME" +TITLE="The Linux System Administrators' Guide" +HREF="book1.html"><LINK +REL="UP" +TITLE="Logging In And Out" +HREF="c1905.html"><LINK +REL="PREVIOUS" +TITLE="Logins via the network" +HREF="x1944.html"><LINK +REL="NEXT" +TITLE="X and xdm" +HREF="x1988.html"></HEAD +><BODY +BGCOLOR="#FFFFFF" +TEXT="#000000" +><DIV +CLASS="NAVHEADER" +><TABLE +WIDTH="100%" +BORDER="0" +CELLPADDING="0" +CELLSPACING="0" +><TR +><TH +COLSPAN="3" +ALIGN="center" +>The Linux System Administrators' Guide</TH +></TR +><TR +><TD +WIDTH="10%" +ALIGN="left" +VALIGN="bottom" +><A +HREF="x1944.html" +>Prev</A +></TD +><TD +WIDTH="80%" +ALIGN="center" +VALIGN="bottom" +>Chapter 8. Logging In And Out</TD +><TD +WIDTH="10%" +ALIGN="right" +VALIGN="bottom" +><A +HREF="x1988.html" +>Next</A +></TD +></TR +></TABLE +><HR +ALIGN="LEFT" +WIDTH="100%"></DIV +><DIV +CLASS="SECT1" +><H1 +CLASS="SECT1" +><A +NAME="AEN1956" +>What <B +CLASS="COMMAND" +>login</B +> does</A +></H1 +><P +>The <B +CLASS="COMMAND" +>login</B +> program takes care of + authenticating the user (making sure that the username and + password match), and of setting up an initial environment for + the user by setting permissions for the serial line and starting + the shell. </P +><P +> Part of the initial setup is outputting the contents of + the file <TT +CLASS="FILENAME" +>/etc/motd</TT +> (short for message of the + day) and checking for electronic mail. These can be disabled + by creating a file called <TT +CLASS="FILENAME" +>.hushlogin</TT +> in + the user's home directory. </P +><P +> If the file <TT +CLASS="FILENAME" +>/etc/nologin</TT +> + exists, logins are disabled. That file is typically + created by <B +CLASS="COMMAND" +>shutdown</B +> and relatives. + <B +CLASS="COMMAND" +>login</B +> checks for this file, and will + refuse to accept a login if it exists. If it does exist, + <B +CLASS="COMMAND" +>login</B +> outputs its contents to the terminal + before it quits. </P +><P +> <B +CLASS="COMMAND" +>login</B +> logs all failed login attempts in + a system log file (via <B +CLASS="COMMAND" +>syslog</B +>). It also logs + all logins by root. Both of these can be useful when tracking + down intruders. </P +><P +> Currently logged in people are listed in + <TT +CLASS="FILENAME" +>/var/run/utmp</TT +>. This file is valid only + until the system is next rebooted or shut down; it is cleared + when the system is booted. It lists each user and the terminal + (or network connection) he is using, along with some other useful + information. The <B +CLASS="COMMAND" +>who</B +>, <B +CLASS="COMMAND" +>w</B +>, + and other similar commands look in <TT +CLASS="FILENAME" +>utmp</TT +> + to see who are logged in. </P +><P +> All successful logins are recorded into + <TT +CLASS="FILENAME" +>/var/log/wtmp</TT +>. This file will grow without + limit, so it must be cleaned regularly, for example by having + a weekly <B +CLASS="COMMAND" +>cron</B +> job to clear it. + + <A +NAME="AEN1980" +HREF="#FTN.AEN1980" +>[1]</A +> + + The <B +CLASS="COMMAND" +>last</B +> command browses + <TT +CLASS="FILENAME" +>wtmp</TT +>. </P +><P +> Both <TT +CLASS="FILENAME" +>utmp</TT +> and + <TT +CLASS="FILENAME" +>wtmp</TT +> are in a binary format (see the + <TT +CLASS="FILENAME" +>utmp</TT +> manual page); it is unfortunately not + convenient to examine them without special programs. </P +></DIV +><H3 +>Notes</H3 +><TABLE +BORDER="0" +CLASS="FOOTNOTES" +WIDTH="100%" +><TR +><TD +ALIGN="LEFT" +VALIGN="TOP" +WIDTH="5%" +><A +NAME="FTN.AEN1980" +HREF="x1956.html#AEN1980" +>[1]</A +></TD +><TD +ALIGN="LEFT" +VALIGN="TOP" +WIDTH="95%" +><P +>Good Linux distributions do this out + of the box.</P +></TD +></TR +></TABLE +><DIV +CLASS="NAVFOOTER" +><HR +ALIGN="LEFT" +WIDTH="100%"><TABLE +WIDTH="100%" +BORDER="0" +CELLPADDING="0" +CELLSPACING="0" +><TR +><TD +WIDTH="33%" +ALIGN="left" +VALIGN="top" +><A +HREF="x1944.html" +>Prev</A +></TD +><TD +WIDTH="34%" +ALIGN="center" +VALIGN="top" +><A +HREF="book1.html" +>Home</A +></TD +><TD +WIDTH="33%" +ALIGN="right" +VALIGN="top" +><A +HREF="x1988.html" +>Next</A +></TD +></TR +><TR +><TD +WIDTH="33%" +ALIGN="left" +VALIGN="top" +>Logins via the network</TD +><TD +WIDTH="34%" +ALIGN="center" +VALIGN="top" +><A +HREF="c1905.html" +>Up</A +></TD +><TD +WIDTH="33%" +ALIGN="right" +VALIGN="top" +>X and xdm</TD +></TR +></TABLE +></DIV +></BODY +></HTML +>
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