BOOTUP

NAME
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常è§å¯å¨æµç¨
INITRD(INITIAL RAM DISK) å¯å¨æµç¨
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NAME

bootup - ç³»ç»å¯å¨æµç¨

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å¨ç³»ç»å¯å¨è¿ç¨ä¸è¦æ¶åå¤ä¸ªä¸åçç»ä»¶ã æä¸çµæºæé®åï¼é¦åBIOS/UEFIåæåºæ¬ç硬件èªæ£ä¸åå§åï¼ ç¶åå è½½é¢è®¾/æå¨éæ©çç£ç/ç½ç»ä¸çå¼å¯¼å è½½å¨(ä¾å¦GRUB2)ï¼ å¼å¯¼å è½½å¨è¿ä¸æ¥ä»ç£ç/ç½ç»ä¸å è½½æä½ç³»ç»åæ ¸(ä¾å¦Linux)ã 对äºLinuxæ¥è¯´ï¼åæ ¸å°ä¼(å¯éç)解åä¸ä¸ªinitrd(initial RAM disk)éå(å¯ä»¥ç¨ dracut(8) ä¹ç±»çå·¥å·çæ)ï¼ å¹¶æ§è¡ç±"rdinit="åæ ¸å¼å¯¼é项æå®çinitç¨åº(ä¾å¦ systemd(1)) 以寻æ¾å¹¶æ载根æ件系ç»ã å®ææ ¹æ件系ç»çæè½½ä¹åï¼åæ ¸å¯å¨ç±"init="åæ ¸å¼å¯¼é项æå®çinitç¨åº(ä¾å¦ systemd(1)) 以æ¥ç®¡ç³»ç»çæ§å¶æã 该initç¨åºå°ä¼è´è´£æ£æµææå¶ä»ç硬件设å¤ãæè½½å¿è¦çæ件系ç»ãå¯å¨ææå¿è¦çæå¡ï¼ç- çã

å³æºæ¶ï¼ initç¨åºå°ä¼åæ¢æææå¡ã å¸è½½æææ件系ç»ã (å¯éç)è¿åinitrdç¯å¢å¸è½½æ ¹æ件系ç»ï¼ æåå³éçµæºã

å¶ä»æå³ç³»ç»å¯å¨æµç¨çä¿¡æ¯å¯ä»¥åè boot(7) æåã

常è§å¯å¨æµç¨

å½æåæè½½äº"root="åæ ¸å¼å¯¼é项æå®çæ ¹æ件系ç»ä¹åï¼åæ ¸å°å¯å¨ç±"init="åæ ¸å¼å¯¼é项æå®çinitç¨åºï¼ ä»è¿ä¸ªæ¶é´ç¹å¼å§ï¼å³è¿å¥äº"常è§å¯å¨æµç¨"ï¼ æ£æµç¡¬ä»¶è®¾å¤å¹¶å è½½é©±å¨ãæè½½å¿è¦çæ件系ç»ãå¯å¨ææå¿è¦çæå¡ï¼çç- ãå¯¹äº systemd(1) ç³»ç»æ¥è¯´ï¼ä¸è¿°"initç¨åº"å°±æ¯ systemd è¿ç¨ï¼ èæ´ä¸ª"常è§å¯å¨æµç¨"ä¹ä»¥å ä¸ªç¹æ®ç target åå(è¯¦è§ systemd.target(5)) ä½ä¸ºèç¹ï¼è¢«åå为å ä¸ªé¶æ®µæ§æ¥éª¤ã å¨æ¯ä¸ªé¶æ®µæ§æ- ¥éª¤åé¨ï¼ä»»å¡æ¯é«åº¦å¹¶è¡çï¼ æ以æ æ³åç¡®é¢æµåä¸é¶æ®µåååçåå顺åºï¼ ä½æ¯ä¸åé¶æ®µä¹é´çåå顺åºæ»æ¯åºå®çã

å½å¯å¨ç³»ç»æ¶ï¼ systemd å°ä¼ä»¥ default.target 为å¯å¨ç®æ ï¼ åå©ååä¹é´ç¯ç¯ç¸æ£çä¾èµå³ç³»ï¼å³å¯å®æ"常è§å¯å¨æµç¨"ã default.target é常åªæ¯ä¸ä¸ªæå graphical.target(å¾å½¢çé¢) æ multi-user.target(ææ¬æ§å¶å°) ç软è¿æ¥ã 为äºå¼ºå¶å¯å¨æµç¨çè§èæ§ä»¥åæé«ååç并è¡æ§ï¼ é¢åå®ä¹äºä¸äºå·æç¹å®å«ä¹ç target ååãè¯¦è§ systemd.special(7) æåã

ä¸é¢çå¾è¡¨è§£éäº è¿äºå·æç¹å®å«ä¹ç target ååä¹é´çä¾èµå³ç³» 以ååèªå¨å¯å¨æµç¨ä¸çä½ç½®ã å¾ä¸çç®- 头表示äºååä¹é´çä¾èµå³ç³»ä¸åå顺åºï¼ æ´ä¸ªå¾è¡¨æç§èªä¸èä¸çæ¶é´é¡ºåºæ§è¡ã

local-fs-pre.target
|
v
(å个 mounts ä¸ (å个 swap (å个å å¯å设å¤
fsck services...) devices...) devices...) (å个åºå±æå¡: (å个åºå±èæ
| | | udevd, tmpfiles, æä»¶ç³»ç» mounts:
v v v random seed, mqueue, configfs,
local-fs.target swap.target cryptsetup.target sysctl, ...) debugfs, ...)
| | | | |
\__________________|_________________ | ___________________|____________________/
\|/
v
sysinit.target
|
____________________________________/|\________________________________________
/ | | | \
| | | | |
v v | v v
(å个 (å个 | (å个 rescue.service
timers...) paths...) | sockets...) |
| | | | v
v v | v rescue.target
timers.target paths.target | sockets.target
. | | |
. \_________________ | ___________________/
.................................... \|/
v
basic.target
|
____________________________________/| emergency.service
/ | | |
| | | v
v v v emergency.target
display- (å¾å½¢çé¢æå¿é (å个系ç»æå¡)
manager.service çå个系ç»æå¡) |
| | |
| | v
| | multi-user.target
| | |
\_________________ | _________________/
\|/
v
graphical.target

ç¨æä½æ è¯çç®æ ååç»å¸¸è¢«ç¨ä½å¯å¨ç®æ ã æ两ç§æ¹æ³å¯ä»¥æå®å¯å¨ç®æ ï¼ (1)ä½¿ç¨ systemd.unit= åæ ¸å¼å¯¼é项(åè§ systemd(1))ï¼ (2)ä½¿ç¨ default.target 软è¿æ¥ã

å ä¸º timers.target 以å¼æ¥æ¹å¼åå«å¨ basic.target ä¸ï¼ æ以 timer ååå¯ä»¥ä¾èµäºå¨ basic.target ä¹åæå¯å¨çæå¡ã

INITRD(INITIAL RAM DISK) å¯å¨æµç¨

å¨initrdåé¨ï¼ ä¹å¯ä»¥å° systemd ç¨ä½initç¨åº(ç±"rdinit="åæ ¸å¼å¯¼é项æå®)ã

æ¤æ¶ initrd.target å°æ¯é»è®¤ç®æ ã initrdåé¨å¯å¨æµç¨çä¸åé¨åä¸åä¸å°è basic.target ä¹åçé¨åå®å¨ç¸åã éåçå¯å¨æµç¨å°ä»¥ initrd.target 为ç®æ (å¦ä¸å¾æ示)ã å½æ ¹æ件系ç»è®¾å¤å¯ç¨æ¶ï¼å°å°è¾¾ initd-root-device.target ç®æ ã å¦ææåçå°æ ¹æ件系ç»æè½½å° /sysroot ç®å½ï¼é£ä¹ sysroot.mount ååå°è¢«å¯å¨ï¼ç¶åè¿ä¸æ¥å°è¾¾ initrd-root-fs.target ç®æ ã initrd-parse-etc.service å°ä¼åæ /sysroot/etc/fstab æ件以æè½½ /usr (è¥éè¦) ä¸å¸¦æ x-initrd.mount æ è®°çæè½½ç¹ã ææè¿äºæè½½ç¹é½å°è¢«æè½½å° /sysroot ä¹ä¸ï¼ç¶åæµç¨å°è¾¾ initrd-fs.target ç®æ ãåæ¥ä¸æ¥ initrd-cleanup.service å°ä¼ä½¿ç¨ systemctl --no-block isolate å½ä»¤å¯å¨ initrd-switch-root.target ç®æ ã å ä¸º isolate 表示ç«å³åæ¢ææå¨æ°çç®æ ååä¸ä¸éè¦çè¿ç¨ï¼ æ以æ- ¤å¨ä½å®éä¸æ¯ä¸ºæ¥ä¸æ¥åæ¢æ ¹ç®å½åé¢åçåå¤(ä¹å°±æ¯æ¸çç¯å¢)ã æåï¼å¯å¨ initrd-switch-root.service æå¡ï¼å°ç³»ç»çæ ¹ç®å½åæ¢è³ /sysroot ç®å½ã

(ä¹åçæµç¨ä¸ä¸ä¸å°èå®å¨ç¸å)
:
v
basic.target
| emergency.service
______________________/| |
/ | v
| initrd-root-device.target emergency.target
| |
| v
| sysroot.mount
| |
| v
| initrd-root-fs.target
| |
| v
v initrd-parse-etc.service
(å个èªå®ä¹ç |
initrd services...) v
| (sysroot-usr.mount 以å
| fstab ä¸å¸¦æ x-initrd.mount
| æ è®°çå个æè½½ç¹)
| |
| v
| initrd-fs.target
\______________________ |
\|
v
initrd.target
|
v
initrd-cleanup.service
(ä½¿ç¨ isolates å¯å¨ initrd-switch-root.target)
|
v
______________________/|
/ v
| initrd-udevadm-cleanup-db.service
v |
(å个èªå®ä¹ç |
initrd services...) |
\______________________ |
\|
v
initrd-switch-root.target
|
v
initrd-switch-root.service
|
v
åæ¢å°ä¸»æºä¸çæä½ç³»ç»

å³æºæµç¨

systemd ç³»ç»å¨å³æºæ¶åæ ·éµå¾ªåºå®çæµç¨ï¼ å·ä½å¦ä¸å¾æ示ï¼

(ä¸ææç³»ç»æå¡äºæ¥) (ä¸æææä»¶ç³»ç» mounts, swaps, cryptsetup devices äºæ¥)
| |
v v
shutdown.target umount.target
| |
\____________________________________ ______/
\ /
v
(å个åºå± services)
|
v
final.target
|
_____________________________________/ \_________________________________
/ | | \
| | | |
v v v v
systemd-reboot.service systemd-poweroff.service systemd-halt.service systemd-kexec.service
| | | |
v v v v
reboot.target poweroff.target halt.target kexec.target

ç¨æä½æ è¯çç®æ ååç»å¸¸è¢«ç¨ä½å³æºç®æ ã

åè§

systemd(1), boot(7), systemd.special(7), systemd.target(5), dracut(8)

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ç¿»è¯äººåï¼éæ¥å½
éæ¥å½ä½åéï¼http://www.jinbuguo.com
ä¸æ man æå页计åï¼https://github.com/man-pages-zh/manpages-zh

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