Lab Environment: RHEL7.0
Experimental content:
MBR first 446 bytes corrupted
Grub boot file is missing
Forget the power-on password
1.MBR First 446 bytes damaged
1.1 Damage to MBR
[Email protected] ~]# df-h
/DEV/SDA1 497M 119M 379M 24%/boot
[[email protected] ~]# dd if=/dev/zero OF=/DEV/SDA bs=400 count=1
[email protected] ~]# reboot
1.2 Phenomena
650) this.width=650; "src=" Http://s2.51cto.com/wyfs02/M02/87/D2/wKioL1fid5yz4VgMAADgmtSeArc305.png "title=" Screenshot from 2016-09-21 20:05:01.png "alt=" Wkiol1fid5yz4vgmaadgmtsearc305.png "width=" to "height=" 157 "border=" 0 " Hspace= "0" vspace= "0" style= "width:700px;height:157px;"/>
1.3 Fix
1.3.1 Mount CD, CD Boot
650) this.width=650; "src=" Http://s2.51cto.com/wyfs02/M01/87/D6/wKiom1fieUiR8COYAAEpH4jRa2A757.png "title=" Screenshot from 2016-09-21 20:11:39.png "style=" WIDTH:400PX;HEIGHT:317PX; "width=" "height=" 317 "border=" 0 "hspace= "0" vspace= "0" alt= "wkiom1fieuir8coyaaeph4jra2a757.png"/>
650) this.width=650; "src=" Http://s2.51cto.com/wyfs02/M00/87/D6/wKiom1fieUbBvWdSAAA_bmfLlqo453.png "style=" float: none; "Title=" screenshot from 2016-09-21 20:12:12.png "alt=" Wkiom1fieubbvwdsaaa_bmfllqo453.png "/>
1.3.2 Select troubleshooting, continue to select repair Redhat system
650) this.width=650; "src=" Http://s4.51cto.com/wyfs02/M01/87/D2/wKioL1fiekXTnqjYAAAO3OlIQyM473.png "title=" Screenshot from 2016-09-21 20:14:38.png "style=" Float:none; "alt=" Wkiol1fiekxtnqjyaaao3oliqym473.png "/>
650) this.width=650; "src=" Http://s2.51cto.com/wyfs02/M01/87/D6/wKiom1fiekTCP7rjAAAWNQwf1AY258.png "title=" Screenshot from 2016-09-21 20:15:08.png "style=" Float:none; "alt=" Wkiom1fiektcp7rjaaawnqwf1ay258.png "/>
1.3.3 Important carriage return Knock 3 and then go into the black box interface ready to repair MBR
650) this.width=650; "src=" Http://s2.51cto.com/wyfs02/M00/87/D6/wKiom1fiekTC1MVWAAAehvVoJxc448.png "style=" width : 400px;height:348px; "title=" screenshot from 2016-09-21 20:15:30.png "width=" to "height=" 348 "border=" 0 "hspace=" 0 " Vspace= "0" alt= "wkiom1fiektc1mvwaaaehvvojxc448.png"/>
650) this.width=650; "src=" Http://s3.51cto.com/wyfs02/M00/87/D2/wKioL1fiekOQgPV8AAATNQ44VcI313.png "title=" Screenshot from 2016-09-21 20:15:45.png "style=" Float:none; "alt=" Wkiol1fiekoqgpv8aaatnq44vci313.png "/>
650) this.width=650; "src=" Http://s3.51cto.com/wyfs02/M00/87/D6/wKiom1fiekPA6VSXAAAIDS3FL3s451.png "title=" Screenshot from 2016-09-21 20:15:52.png "style=" Float:none; "alt=" Wkiom1fiekpa6vsxaaaids3fl3s451.png "/>
650) this.width=650; "src=" Http://s3.51cto.com/wyfs02/M02/87/D2/wKioL1fiekPixHMTAAANsUuOSr0090.png "title=" Screenshot from 2016-09-21 20:16:01.png "style=" Float:none; "alt=" Wkiol1fiekpixhmtaaansuuosr0090.png "/>
1.3.4 Switch root file system, repair MBR
650) this.width=650; "src=" Http://s4.51cto.com/wyfs02/M01/87/D6/wKiom1fie7-xm6fUAAAkWhowBk0853.png "title=" Screenshot from 2016-09-21 20:22:58.png "alt=" Wkiom1fie7-xm6fuaaakwhowbk0853.png "/>
1.4 Repair Complete, adjust boot order to hard drive boot, restart view
650) this.width=650; "src=" Http://s1.51cto.com/wyfs02/M01/87/D6/wKiom1fifGqAz25PAABCeUKrVWk346.png "title=" Screenshot from 2016-09-21 20:24:51.png "alt=" Wkiom1fifgqaz25paabceukrvwk346.png "/>
650) this.width=650; "src=" Http://s2.51cto.com/wyfs02/M02/87/D6/wKiom1fifI_ziUAOAAALHHwuRS0866.png "title=" Screenshot from 2016-09-21 20:26:37.png "width=", "height="-"border=" 0 "hspace=" 0 "vspace=" 0 "style=" width:750px; height:128px, "alt=" Wkiom1fifi_ziuaoaaalhhwurs0866.png "/>650" this.width=650; "src=" Http://s5.51cto.com/wyfs02 /m01/87/d2/wkiol1fiflejkoq7aablrpsgkbg496.png "title=" screenshot from 2016-09-21 20:27:14.png "width=" "height=" 397 "border=" 0 "hspace=" 0 "vspace=" 0 "style=" WIDTH:600PX;HEIGHT:397PX; "alt=" wkiol1fiflejkoq7aablrpsgkbg496.png "/ >
Repair complete.
2.GRUB boot file is missing
Grub Boot file is/boot/grub2/grub.cfg
[Email protected] ~]# file/boot/grub2/grub.cfg
/boot/grub2/grub.cfg:ascii text
2.1 Corrupted files
[Email protected] ~]# rm-rf/boot/grub2/grub.cfg
2.2 Phenomena
650) this.width=650; "src=" Http://s3.51cto.com/wyfs02/M00/87/D2/wKioL1fifirxUXWKAAALtIOmsT0751.png "title=" Screenshot from 2016-09-21 20:33:20.png "alt=" Wkiol1fifirxuxwkaaaltiomst0751.png "/>
2.3 Fix
2.3.1 like repairing MBR, mount the disc, CD-ROM, and enter rescue mode.
650) this.width=650; "src=" Http://s2.51cto.com/wyfs02/M02/87/D2/wKioL1fif8CAIWYkAAAlEmpsA5c747.png "title=" Screenshot from 2016-09-21 20:39:29.png "alt=" Wkiol1fif8caiwykaaalempsa5c747.png "/>
2.3.2 Re-start view
650) this.width=650; "src=" Http://s5.51cto.com/wyfs02/M01/87/D2/wKioL1fifLejKoq7AAblRPSGkbg496.png "title=" Screenshot from 2016-09-21 20:27:14.png "width=" "height=" 397 "border=" 0 "hspace=" 0 "vspace=" 0 "style=" width:600px; height:397px; "alt=" Wkiol1fiflejkoq7aablrpsgkbg496.png "/>
3 Boot password forgotten.
I've written about how to change the root password by forgetting the boot password. See links for details.
Linux forgot root password solution
This article from the "Technology life, Simple not simple" blog, please be sure to keep this source http://willis.blog.51cto.com/11907152/1855173
Linux system Recovery "one"