diff options
Diffstat (limited to '')
| -rw-r--r-- | man7/boot.7 | 36 |
1 files changed, 18 insertions, 18 deletions
diff --git a/man7/boot.7 b/man7/boot.7 index f69e8c1..3aa0341 100644 --- a/man7/boot.7 +++ b/man7/boot.7 @@ -10,7 +10,7 @@ .\" .\" Modified 2004-11-03 patch from Martin Schulze <joey@infodrom.org> .\" -.TH boot 7 2023-07-08 "Linux man-pages 6.05.01" +.TH boot 7 2023-10-31 "Linux man-pages 6.7" .SH NAME boot \- System bootup process based on UNIX System V Release 4 .SH DESCRIPTION @@ -27,14 +27,14 @@ kernel root user-space process (\fIinit\fR and \fIinittab\fR) .IP (5) boot scripts -.PP +.P Each of these is described below in more detail. .SS Hardware 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". -.PP +.P This program normally performs a basic self-test of the machine and accesses nonvolatile memory to read further parameters. @@ -43,7 +43,7 @@ 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" (nonvolatile RAM). -.PP +.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 @@ -64,11 +64,11 @@ interactive use, in order to enable specification of an alternative kernel (maybe a backup in case the one last compiled isn't functioning) and to pass optional parameters to the kernel. -.PP +.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" (Master Boot Record). -.PP +.P In most systems, the OS loader is very limited due to various constraints. Even on non-PC systems, @@ -76,12 +76,12 @@ there are some limitations on the size and complexity of this loader, but the size limitation of the PC MBR (512 bytes, including the partition table) makes it almost impossible to squeeze much functionality into it. -.PP +.P Therefore, most systems split the role of loading the OS between a primary OS loader and a secondary OS loader; this secondary OS loader may be located within a larger portion of persistent storage, such as a disk partition. -.PP +.P In Linux, the OS loader is often .BR grub (8) (an alternative is @@ -95,13 +95,13 @@ 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, .IR / . -.PP +.P Some of the parameters that may be passed to the kernel relate to these activities (for example, the default root filesystem can be overridden); for further information on Linux kernel parameters, read .BR bootparam (7). -.PP +.P Only then does the kernel create the initial userland process, which is given the number 1 as its .B PID @@ -120,7 +120,7 @@ fundamentally different approach known as .BR systemd (1), for which the bootup process is detailed in its associated .BR bootup (7). -.PP +.P When .I /sbin/init starts, it reads @@ -137,12 +137,12 @@ is single-user mode, and run level .B 2 entails running most network services). -.PP +.P The administrator may change the current run level via .BR init (1), and query the current run level via .BR runlevel (8). -.PP +.P However, since it is not convenient to manage individual services by editing this file, .I /etc/inittab @@ -154,7 +154,7 @@ Note: The following description applies to an OS based on UNIX System V Release 4. However, a number of widely used systems (Slackware Linux, FreeBSD, OpenBSD) have a somewhat different scheme for boot scripts. -.PP +.P For each managed service (mail, nfs server, cron, etc.), there is a single startup script located in a specific directory .RI ( /etc/init.d @@ -174,7 +174,7 @@ of the form \fI/etc/rc[0\-6S].d\fR. In each of these directories, there are links (usually symbolic) to the scripts in the \fI/etc/init.d\fR directory. -.PP +.P A primary script (usually \fI/etc/rc\fR) is called from .BR inittab (5); this primary script calls each service's script via a link in the @@ -183,7 +183,7 @@ Each link whose name begins with \[aq]S\[aq] is called with the argument "start" (thereby starting the service). Each link whose name begins with \[aq]K\[aq] is called with the argument "stop" (thereby stopping the service). -.PP +.P To define the starting or stopping order within the same run level, the name of a link contains an \fBorder-number\fR. Also, for clarity, the name of a link usually @@ -195,7 +195,7 @@ 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. -.PP +.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., @@ -209,7 +209,7 @@ 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). -.PP +.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. |