diff options
Diffstat (limited to 'man/man7/boot.7')
| -rw-r--r-- | man/man7/boot.7 | 73 |
1 files changed, 52 insertions, 21 deletions
diff --git a/man/man7/boot.7 b/man/man7/boot.7 index b66f6596e3..2eb4660c16 100644 --- a/man/man7/boot.7 +++ b/man/man7/boot.7 @@ -14,7 +14,11 @@ .SH NAME boot \- System bootup process based on UNIX System V Release 4 .SH DESCRIPTION -The \fBbootup process\fR (or "\fBboot sequence\fR") varies in details +The +.B bootup process +(or +.RB \[dq] boot\~sequence \[dq]) +varies in details among systems, but can be roughly divided into phases controlled by the following components: .IP (1) 5 @@ -24,7 +28,10 @@ operating system (OS) loader .IP (3) kernel .IP (4) -root user-space process (\fIinit\fR and \fIinittab\fR) +root user-space process +.RB ( init (8) +and +.BR inittab (5)) .IP (5) boot scripts .P @@ -33,22 +40,26 @@ Each of these is described below in more detail. After power-on or hard reset, control is given to a program stored in read-only memory (normally PROM); for historical reasons involving the personal -computer, this program is often called "the \fBBIOS\fR". +computer, this program is often called "the +.BR BIOS \[dq]. .P This program normally performs a basic self-test of the machine and accesses nonvolatile memory to read further parameters. This memory in the PC is battery-backed CMOS memory, so most people -refer to it as "the \fBCMOS\fR"; outside -of the PC world, it is usually called "the \fBNVRAM\fR" +refer to it as "the +.BR CMOS \[dq]; +outside +of the PC world, it is usually called "the +.BR NVRAM \[dq] (nonvolatile RAM). .P The parameters stored in the NVRAM vary among systems, but as a minimum, they should specify which device can supply an OS loader, or at least which devices may be probed for one; such a device is known as "the -\fBboot device\fR". +.BR boot\~device \[dq]. The hardware boot stage loads the OS loader from a fixed position on the boot device, and then transfers control to it. .TP @@ -66,7 +77,8 @@ isn't functioning) and to pass optional parameters to the kernel. .P In a traditional PC, the OS loader is located in the initial 512-byte block -of the boot device; this block is known as "the \fBMBR\fR" +of the boot device; this block is known as "the +.BR MBR \[dq] (Master Boot Record). .P In most systems, the OS loader is very @@ -89,8 +101,9 @@ In Linux, the OS loader is often .SS Kernel When the kernel is loaded, it initializes various components of the computer and operating system; each portion of software -responsible for such a task is usually consider "a \fBdriver\fR" for -the applicable component. +responsible for such a task is usually consider "a +.BR driver \[dq] +for the applicable component. The kernel starts the virtual memory swapper (it is a kernel process, called "kswapd" in a modern Linux kernel), and mounts some filesystem at the root path, @@ -169,13 +182,18 @@ Running the script without parameters displays the possible arguments. .SS Sequencing directories To make specific scripts start/stop at specific run levels and in a -specific order, there are \fIsequencing directories\fR, normally -of the form \fI/etc/rc[0\-6S].d\fR. +specific order, there are +.IR sequencing\~directories , +normally of the form +.IR /etc/rc[0\-6S].d . In each of these directories, -there are links (usually symbolic) to the scripts in the \fI/etc/init.d\fR +there are links (usually symbolic) to the scripts in the +.I /etc/init.d directory. .P -A primary script (usually \fI/etc/rc\fR) is called from +A primary script (usually +.IR /etc/rc ) +is called from .BR inittab (5); this primary script calls each service's script via a link in the relevant sequencing directory. @@ -185,36 +203,49 @@ Each link whose name begins with \[aq]K\[aq] is called with the argument "stop" (thereby stopping the service). .P To define the starting or stopping order within the same run level, -the name of a link contains an \fBorder-number\fR. +the name of a link contains an +.BR order-number . Also, for clarity, the name of a link usually ends with the name of the service to which it refers. For example, -the link \fI/etc/rc2.d/S80sendmail\fR starts the +the link +.I /etc/rc2.d/S80sendmail +starts the .BR sendmail (8) service on run level 2. -This happens after \fI/etc/rc2.d/S12syslog\fR is run -but before \fI/etc/rc2.d/S90xfs\fR is run. +This happens after +.I /etc/rc2.d/S12syslog +is run +but before +.I /etc/rc2.d/S90xfs +is run. .P To manage these links is to manage the boot order and run levels; under many systems, there are tools to help with this task (e.g., .BR chkconfig (8)). .SS Boot configuration -A program that provides a service is often called a "\fBdaemon\fR". +A program that provides a service is often called a +.RB \[dq] daemon \[dq]. Usually, a daemon may receive various command-line options and parameters. To allow a system administrator to change these inputs without editing an entire boot script, some separate configuration file is used, and is located in a specific directory where an associated boot script may find it -(\fI/etc/sysconfig\fR on older Red Hat systems). +.RI ( /etc/sysconfig +on older Red Hat systems). .P In older UNIX systems, such a file contained the actual command line options for a daemon, but in modern Linux systems (and also in HP-UX), it just contains shell variables. -A boot script in \fI/etc/init.d\fR reads and includes its configuration -file (that is, it "\fBsources\fR" its configuration file) and then uses +A boot script in +.I /etc/init.d +reads and includes its configuration +file (that is, it +.RB \[dq] sources \[dq] +its configuration file) and then uses the variable values. .SH FILES .IR /etc/init.d/ , |