Linux启动故障排错
Linux启动过程
开机流程、模块管理-CSDN博客
Grub三个阶段
- 1st stage：执行Grub主程序。Grub安装在MBR。由于MBR太小，所以与配置文件分开放
- 1.5 stage：识别不同的文件系统
- 2nd stage：加载Grub配置文件 /boot/grub2/grub.cfg。配置文件在文件系统中。
Centos6
一、grub第1阶段故障
制造故障
查看磁盘分区，仅一块磁盘且第一块磁盘为 sda
[root@localhost ~]# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sr0 11:0 1 1024M 0 rom
sda 8:0 0 20G 0 disk
├─sda1 8:1 0 1G 0 part /boot
├─sda2 8:2 0 2G 0 part [SWAP]
└─sda3 8:3 0 17G 0 part /
以十六进制格式查看grub引导的配置文件
[root@localhost ~]# hexdump -C -n 512 /dev/sda
00000000 eb 48 90 10 8e d0 bc 00 b0 b8 00 00 8e d8 8e c0 |.H..............|
00000010 fb be 00 7c bf 00 06 b9 00 02 f3 a4 ea 21 06 00 |...|.........!..|
00000020 00 be be 07 38 04 75 0b 83 c6 10 81 fe fe 07 75 |....8.u........u|
00000030 f3 eb 16 b4 02 b0 01 bb 00 7c b2 80 8a 74 03 02 |.........|...t..|
00000040 80 00 00 80 00 45 04 00 00 08 fa 90 90 f6 c2 80 |.....E..........|
00000050 75 02 b2 80 ea 59 7c 00 00 31 c0 8e d8 8e d0 bc |u....Y|..1......|
00000060 00 20 fb a0 40 7c 3c ff 74 02 88 c2 52 f6 c2 80 |. ..@|<.t...R...|
00000070 74 54 b4 41 bb aa 55 cd 13 5a 52 72 49 81 fb 55 |tT.A..U..ZRrI..U|
00000080 aa 75 43 a0 41 7c 84 c0 75 05 83 e1 01 74 37 66 |.uC.A|..u....t7f|
00000090 8b 4c 10 be 05 7c c6 44 ff 01 66 8b 1e 44 7c c7 |.L...|.D..f..D|.|
000000a0 04 10 00 c7 44 02 01 00 66 89 5c 08 c7 44 06 00 |....D...f.\..D..|
000000b0 70 66 31 c0 89 44 04 66 89 44 0c b4 42 cd 13 72 |pf1..D.f.D..B..r|
000000c0 05 bb 00 70 eb 7d b4 08 cd 13 73 0a f6 c2 80 0f |...p.}....s.....|
000000d0 84 f0 00 e9 8d 00 be 05 7c c6 44 ff 00 66 31 c0 |........|.D..f1.|
000000e0 88 f0 40 66 89 44 04 31 d2 88 ca c1 e2 02 88 e8 |[email protected]........|
000000f0 88 f4 40 89 44 08 31 c0 88 d0 c0 e8 02 66 89 04 |[email protected]..|
00000100 66 a1 44 7c 66 31 d2 66 f7 34 88 54 0a 66 31 d2 |f.D|f1.f.4.T.f1.|
00000110 66 f7 74 04 88 54 0b 89 44 0c 3b 44 08 7d 3c 8a |f.t..T..D.;D.}<.|
00000120 54 0d c0 e2 06 8a 4c 0a fe c1 08 d1 8a 6c 0c 5a |T.....L......l.Z|
00000130 8a 74 0b bb 00 70 8e c3 31 db b8 01 02 cd 13 72 |.t...p..1......r|
00000140 2a 8c c3 8e 06 48 7c 60 1e b9 00 01 8e db 31 f6 |*....H|`......1.|
00000150 31 ff fc f3 a5 1f 61 ff 26 42 7c be 7f 7d e8 40 |1.....a.&B|..}.@|
00000160 00 eb 0e be 84 7d e8 38 00 eb 06 be 8e 7d e8 30 |.....}.8.....}.0|
00000170 00 be 93 7d e8 2a 00 eb fe 47 52 55 42 20 00 47 |...}.*...GRUB .G|
00000180 65 6f 6d 00 48 61 72 64 20 44 69 73 6b 00 52 65 |eom.Hard Disk.Re|
00000190 61 64 00 20 45 72 72 6f 72 00 bb 01 00 b4 0e cd |ad. Error.......|
000001a0 10 ac 3c 00 75 f4 c3 00 00 00 00 00 00 00 00 00 |..<.u...........|
000001b0 00 00 00 00 00 00 00 00 45 b7 02 00 00 00 80 20 |........E...... |
000001c0 21 00 83 aa 28 82 00 08 00 00 00 00 20 00 00 aa |!...(....... ...|
000001d0 29 82 82 bf 78 87 00 08 20 00 00 00 40 00 00 bf |)...x... ...@...|
000001e0 79 87 83 fe ff ff 00 08 60 00 00 f8 1f 02 00 00 |y.......`.......|
000001f0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 55 aa |..............U.|
00000200
修改前446个字节为0，破坏grub引导
[root@localhost ~]# dd if=/dev/zero of=/dev/sda bs=1 count=446
446+0 records in
446+0 records out
446 bytes (446 B) copied, 0.000820605 s, 544 kB/s
再次查看grub引导的配置，已破坏
[root@localhost ~]# hexdump -C -n 512 /dev/sda -v
00000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000010 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000020 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000030 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000040 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000050 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000060 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000070 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000080 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000090 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
000000a0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
000000b0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
000000c0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
000000d0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
000000e0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
000000f0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000100 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000110 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000120 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000130 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000140 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000150 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000160 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000170 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000180 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000190 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
000001a0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
000001b0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 80 20 |............... |
000001c0 21 00 83 aa 28 82 00 08 00 00 00 00 20 00 00 aa |!...(....... ...|
000001d0 29 82 82 bf 78 87 00 08 20 00 00 00 40 00 00 bf |)...x... ...@...|
000001e0 79 87 83 fe ff ff 00 08 60 00 00 f8 1f 02 00 00 |y.......`.......|
000001f0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 55 aa |..............U.|
00000200
重启系统
启动故障
找不到启动项
二、grub第1.5阶段故障
制造故障
跳过第一扇区MBR，损坏第一扇区之后的扇区，seek表示跳过
硬盘一个扇区512字节
[root@wenzi ~]# dd if=/dev/zero of=/dev/sda bs=512 count=10 seek=1
10+0 records in
10+0 records out
5120 bytes (5.1 kB) copied, 0.000132509 s, 38.6 MB/s
查看破坏结果
[root@wenzi ~]# hexdump -C -n 5120 /dev/sda -v
00000000 eb 63 90 10 8e d0 bc 00 b0 b8 00 00 8e d8 8e c0 |.c..............|
00000010 fb be 00 7c bf 00 06 b9 00 02 f3 a4 ea 21 06 00 |...|.........!..|
00000020 00 be be 07 38 04 75 0b 83 c6 10 81 fe fe 07 75 |....8.u........u|
00000030 f3 eb 16 b4 02 b0 01 bb 00 7c b2 80 8a 74 01 8b |.........|...t..|
00000040 4c 02 cd 13 ea 00 7c 00 00 eb fe 00 00 00 00 00 |L.....|.........|
00000050 00 00 00 00 00 00 00 00 00 00 00 80 01 00 00 00 |................|
00000060 00 00 00 00 ff fa 90 90 f6 c2 80 74 05 f6 c2 70 |...........t...p|
00000070 74 02 b2 80 ea 79 7c 00 00 31 c0 8e d8 8e d0 bc |t....y|..1......|
00000080 00 20 fb a0 64 7c 3c ff 74 02 88 c2 52 be 05 7c |. ..d|<.t...R..||
00000090 b4 41 bb aa 55 cd 13 5a 52 72 3d 81 fb 55 aa 75 |.A..U..ZRr=..U.u|
000000a0 37 83 e1 01 74 32 31 c0 89 44 04 40 88 44 ff 89 |[email protected]..|
000000b0 44 02 c7 04 10 00 66 8b 1e 5c 7c 66 89 5c 08 66 |D.....f..\|f.\.f|
000000c0 8b 1e 60 7c 66 89 5c 0c c7 44 06 00 70 b4 42 cd |..`|f.\..D..p.B.|
000000d0 13 72 05 bb 00 70 eb 76 b4 08 cd 13 73 0d 5a 84 |.r...p.v....s.Z.|
000000e0 d2 0f 83 de 00 be 85 7d e9 82 00 66 0f b6 c6 88 |.......}...f....|
000000f0 64 ff 40 66 89 44 04 0f b6 d1 c1 e2 02 88 e8 88 |[email protected]..........|
00000100 f4 40 89 44 08 0f b6 c2 c0 e8 02 66 89 04 66 a1 |[email protected].|
00000110 60 7c 66 09 c0 75 4e 66 a1 5c 7c 66 31 d2 66 f7 |`|f..uNf.\|f1.f.|
00000120 34 88 d1 31 d2 66 f7 74 04 3b 44 08 7d 37 fe c1 |4..1.f.t.;D.}7..|
00000130 88 c5 30 c0 c1 e8 02 08 c1 88 d0 5a 88 c6 bb 00 |..0........Z....|
00000140 70 8e c3 31 db b8 01 02 cd 13 72 1e 8c c3 60 1e |p..1......r...`.|
00000150 b9 00 01 8e db 31 f6 bf 00 80 8e c6 fc f3 a5 1f |.....1..........|
00000160 61 ff 26 5a 7c be 80 7d eb 03 be 8f 7d e8 34 00 |a.&Z|..}....}.4.|
00000170 be 94 7d e8 2e 00 cd 18 eb fe 47 52 55 42 20 00 |..}.......GRUB .|
00000180 47 65 6f 6d 00 48 61 72 64 20 44 69 73 6b 00 52 |Geom.Hard Disk.R|
00000190 65 61 64 00 20 45 72 72 6f 72 0d 0a 00 bb 01 00 |ead. Error......|
000001a0 b4 0e cd 10 ac 3c 00 75 f4 c3 00 00 00 00 00 00 |.....<.u........|
000001b0 00 00 00 00 00 00 00 00 33 24 0a 00 00 00 80 20 |........3$..... |
000001c0 21 00 83 aa 28 82 00 08 00 00 00 00 20 00 00 aa |!...(....... ...|
000001d0 29 82 82 bf 78 87 00 08 20 00 00 00 40 00 00 bf |)...x... ...@...|
000001e0 79 87 83 fe ff ff 00 08 60 00 00 f8 1f 02 00 00 |y.......`.......|
000001f0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 55 aa |..............U.|
00000200 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000210 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000220 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000230 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000240 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000250 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000260 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000270 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000280 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000290 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
000002a0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
000002b0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
000002c0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
000002d0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
000002e0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
...重启系统
启动故障
找到启动项后，加载文件系统，但是已被破坏，加载失败，所以光标一致闪烁
修复故障
grub三个阶段故障通用方法：进入救援系统，利用 grub-install 可将三个阶段一次性修复完毕
在虚拟机中启用centos6光盘，再次重启。
界面选择第三个： Rescue installed system，进入救援模式
English > OK
us > OK
无需联网，No
继续，Continue
您的系统已被挂载在 /mnt/sysimage，按
然后自动进到shell命令行模式 bash-4.1#
命令如下，最后三次sync，通过ctrl + alt + delete 重启或者输入两遍exit。
三、误删除 /boot/initramfs-2.6.32-642.el6.x86_64.img 文件
制造故障
[root@localhost ~]# rm -f /boot/initramfs-2.6.32-642.el6.x86_64.img启动故障
光标一致闪烁
修复故障
进救援模式，方法如上。手动重新生成 initramfs 文件
chroot /mnt/sysimage
mkinitrd /boot/initramfs-`uname -r`.img `uname -r`
sync
sync
sync
exit
exit四、误删除内核文件 /boot/vmlinuz-2.6.32-642.el6.x86_64
制造故障
[root@localhost ~]# rm -f /boot/vmlinuz-2.6.32-642.el6.x86_64启动故障
修复故障
进救援模式，从同版本的光盘系统复制内核文件
chroot /mnt/sysimage
mkdir /mnt 创建光盘挂载目录
mount /dev/sr0 /mnt
cp /mnt/isolinux/vmlinuz /boot/vmlinuz-`uname -r`
sync
sync
sync
exit
exit