lfs-book/appendixa/sysvinit-desc.xml

<sect2><title>Contents of Sysvinit</title>

<para>Last checked against version &sysvinit-contversion;.</para>

<sect3><title>Program Files</title>
<para>halt, init, killall5, last, lastb (link to last), mesg, pidof
(link to killall5), poweroff (link to halt), reboot (link to halt), 
runlevel, shutdown, sulogin, telinit (link to init), utmpdump and
wall</para></sect3>

<sect3><title>Descriptions</title>

<sect4><title>halt</title>
<para>halt notes that the system is being brought down in the file 
/var/log/wtmp, and then either tells the kernel to halt, reboot or 
poweroff the system. If halt or reboot is called when the system is not 
in runlevel 0 or 6, shutdown will be invoked instead (with 
the flag -h or -r).</para></sect4>

<sect4><title>init</title>
<para>init is the parent of all processes. Its primary role is to create 
processes from a script stored in the file /etc/inittab. This
file usually has entries which cause init to spawn gettys on each line that
users can log in. It also controls autonomous processes required by any 
particular system.</para></sect4>

<sect4><title>killall5</title>
<para>killall5 is the SystemV killall command. It sends a signal to all 
processes except the processes in its own session, so it won't kill the 
shell that is running the script it was called from.</para></sect4>

<sect4><title>last</title>
<para>last searches back through the file /var/log/wtmp (or the file designated 
by the -f flag) and displays a list of all users logged in (and out) 
since that file was created.</para></sect4>

<sect4><title>lastb</title>
<para>lastb is the same as last, except that by default it shows a log of the 
file /var/log/btmp, which contains all the bad login attempts.</para></sect4>

<sect4><title>mesg</title>
<para>mesg controls the access to the user's terminal by others. It's typically
used to allow or disallow other users to write to his terminal.</para></sect4>

<sect4><title>pidof</title>
<para>pidof displays the process identifiers (PIDs) of the named
programs.</para></sect4>

<sect4><title>poweroff</title>
<para>poweroff is equivalent to shutdown -h -p now. It halts the computer and
switches off the computer (when using an APM compliant BIOS and APM is 
enabled in the kernel).</para></sect4>

<sect4><title>reboot</title>
<para>reboot is equivalent to shutdown -r now. It reboots 
the computer.</para></sect4>

<sect4><title>runlevel</title>
<para>runlevel reads the system utmp file (typically /var/run/utmp) to locate 
the runlevel record, and then prints the previous and current system 
runlevel on its standard output, separated by a single space.</para></sect4>

<sect4><title>shutdown</title>
<para>shutdown brings the system down in a secure way. All logged-in users are 
notified that the system is going down, and login is blocked.</para></sect4>

<sect4><title>sulogin</title>
<para>sulogin is invoked by init when the system goes into single user mode 
(this is done through an entry in /etc/inittab). Init also tries to 
execute sulogin when it is passed the -b flag from the boot loader 
(LILO, for example).</para></sect4>

<sect4><title>telinit</title>
<para>telinit sends appropriate signals to init, telling it which runlevel to
change to.</para></sect4>

<sect4><title>utmpdump</title>
<para>utmpdumps prints the content of a file (usually /var/run/utmp) on
standard output in a user friendly format.</para></sect4>

<sect4><title>wall</title>
<para>wall sends a message to everybody logged in with their mesg permission 
set to yes.</para></sect4>

</sect3>

</sect2>