1 | <sect2><title>Short descriptions</title>
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2 |
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3 | <para><command>halt</command> normally invokes shutdown with the -h flag,
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4 | except when already in runlevel 0, then it tells the kernel to halt the system.
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5 | But first it notes in the file <filename>/var/log/wtmp</filename> that the
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6 | system is being brought down.</para>
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7 |
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8 | <para><command>init</command> is the mother of all processes. It reads its
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9 | commands from <filename>/etc/inittab</filename>, which normally tell it which
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10 | scripts to run for which runlevel, and how many gettys to spawn.</para>
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11 |
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12 | <para><command>killall5</command> sends a signal to all processes, except
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13 | the processes in its own session -- so it won't kill the shell running the
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14 | script that called it.</para>
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15 |
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16 | <para><command>last</command> shows which users last logged in (and out),
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17 | searching back through the file <filename>/var/log/wtmp</filename>. It can
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18 | also show system boots and shutdowns, and runlevel changes.</para>
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19 |
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20 | <para><command>lastb</command> shows the failed login attempts, as logged
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21 | in <filename>/var/log/btmp</filename>.</para>
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22 |
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23 | <para><command>mesg</command> controls whether other users can send
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24 | messages to the current user's terminal.</para>
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25 |
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26 | <para><command>pidof</command> reports the PIDs of the given programs.</para>
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27 |
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28 | <para><command>poweroff</command> tells the kernel to halt the system and
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29 | switch off the computer. But see halt.</para>
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30 |
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31 | <para><command>reboot</command> tells the kernel to reboot the system.
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32 | But see halt.</para>
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33 |
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34 | <para><command>runlevel</command> reports the previous and the current
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35 | runlevel, as noted in the last runlevel record in
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36 | <filename>/var/run/utmp</filename>.</para>
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37 |
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38 | <para><command>shutdown</command> brings the system down in a secure way,
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39 | signaling all processes and notifying all logged-in users.</para>
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40 |
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41 | <para><command>sulogin</command> allows the superuser to log in. It is
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42 | normally invoked by init when the system goes into single user mode.</para>
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43 |
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44 | <para><command>telinit</command> tells init which runlevel to enter.</para>
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45 |
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46 | <para><command>utmpdump</command> displays the content of the given login
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47 | file in a friendlier format.</para>
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48 |
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49 | <para><command>wall</command> writes a message to all logged-in users.</para>
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50 |
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51 | </sect2>
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52 |
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