boot(7) Miscellaneous Information Manual boot(7) boot - , UNIX System V Release 4 ( << >>) , , : (1) (2) (3) (4) (init inittab) (5) . , , ( PROM). , , BIOS. , , . CMOS , CMOS, -- NVRAM (nonvolatile RAM). , NVRAM, , , ; . , . : , , ; DHCP, TFTP, PXE, Etherboot . . , . , (, ) . 512- -- MBR (Master Boot Record). . , MBR 512 ( ) . , ; , . In Linux, the OS loader is often grub(8) (an alternative is lilo(8)). ; , , , - . ( , Linux <>) (/). , , (, ). Linux bootparam(7). PID ( ) 1. , /sbin/init, , . : UNIX System V Release 4. , , , systemd(1), bootup(7). When /sbin/init starts, it reads /etc/inittab for further instructions. This file defines what should be run when the /sbin/init program is instructed to enter a particular run level, giving the administrator an easy way to establish an environment for some usage; each run level is associated with a set of services (for example, run level S is single-user mode, and run level 2 entails running most network services). The administrator may change the current run level via init(1), and query the current run level via runlevel(8). , , /etc/inittab , / . : , UNIX System V Release 4. (Slackware Linux, FreeBSD, OpenBSD) . (, nfs, cron . .) (/etc/init.d Linux). <> ( ) <> ( ). () (, <> , <> . .). . To make specific scripts start/stop at specific run levels and in a specific order, there are sequencing directories, normally of the form /etc/rc[0-6S].d. In each of these directories, there are links (usually symbolic) to the scripts in the /etc/init.d directory. A primary script (usually /etc/rc) is called from inittab(5); this primary script calls each service's script via a link in the relevant sequencing directory. Each link whose name begins with 'S' is called with the argument "start" (thereby starting the service). Each link whose name begins with 'K' is called with the argument "stop" (thereby stopping the service). To define the starting or stopping order within the same run level, the name of a link contains an 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 /etc/rc2.d/S80sendmail starts the sendmail(8) service on run level 2. This happens after /etc/rc2.d/S12syslog is run but before /etc/rc2.d/S90xfs is run. 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., chkconfig(8)). , , (daemon). , . . (, /etc/sysconfig Red Hat) . UNIX , Linux ( HP-UX) . /etc/init.d ( , sources ) . /etc/init.d/, /etc/rc[S0-6].d/, /etc/sysconfig/ . init(1), systemd(1), inittab(5), bootparam(7), bootup(7), runlevel(8), shutdown(8) Artyom Kunyov , Azamat Hackimov , Dmitriy Ovchinnikov , Dmitry Bolkhovskikh , ITriskTI , Yuri Kozlov ; GNU 3 , . . , , . Linux man-pages 6.06 31 2023 . boot(7)