| 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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