1.1破坏mbr表并修复
##1. 添加一块实验用磁盘：/dev/sdb
[root@bogon ~]# fdisk /dev/sdb
Welcome to fdisk (util-linux 2.32.1).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.
Device does not contain a recognized partition table.
Created a new DOS disklabel with disk identifier 0x440d52d3.
Command (m for help): n
Partition type
p primary (0 primary, 0 extended, 4 free)
e extended (container for logical partitions)
Select (default p):
Using default response p.
Partition number (1-4, default 1):
First sector (2048-10485759, default 2048):
Last sector, +sectors or +size{K,M,G,T,P} (2048-10485759, default 10485759):
Created a new partition 1 of type 'Linux' and of size 5 GiB.
Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.
[root@bogon ~]#
[root@bogon ~]#
[root@bogon ~]# partprobe /dev/sdb
[root@bogon ~]# mkfs.ext4 /dev/sdb1
mke2fs 1.45.6 (20-Mar-2020)
Creating filesystem with 1310464 4k blocks and 327680 inodes
Filesystem UUID: ce994dfa-b43a-41ef-a867-de489f359f14
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912, 819200, 884736
Allocating group tables: done
Writing inode tables: done
Creating journal (16384 blocks): done
Writing superblocks and filesystem accounting information: done
[root@bogon ~]# lsblk /dev/sdb
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sdb 8:16 0 5G 0 disk
└─sdb1 8:17 0 5G 0 part
[root@bogon ~]#
## 用hexdump -C /dev/sdb -n 512查看分区表前512字节
通过修改分区表修改如图的64个字节来达到破坏效果
[root@bogon ~]# hexdump -C /dev/sdb -n 512
00000000 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 95 2e a5 86 00 00 00 20 |............... |
000001c0 21 00 83 b4 a8 8c 00 08 00 00 00 f8 9f 00 00 00 |!...............|
000001d0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
000001f0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 55 aa |..............U.|
00000200
[root@bogon ~]#
# #备份 /dev/sdb mrb分区表：
[root@bogon software]# dd if=/dev/sdb of=/root/mbr-bak.img bs=1 count=64 skip=446
64+0 records in
64+0 records out
64 bytes copied, 0.000591286 s, 108 kB/s
[root@bogon software]# ls -lh
-rw-r--r-- 1 root root 64 Jan 10 22:05 mbr-bak.img
[root@bogon software]#
## 破坏/dev/sdb mbr 分区表
[root@bogon software]# dd if=/dev/zero of=/dev/sdb bs=1 count=64 seek=446
64+0 records in
64+0 records out
64 bytes copied, 0.000855001 s, 74.9 kB/s
[root@bogon software]#
## 破坏分区表前：
[root@bogon ~]# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 20G 0 disk
├─sda1 8:1 0 1G 0 part /boot
└─sda2 8:2 0 19G 0 part
└─cl-root 253:0 0 19G 0 lvm /
sdb 8:16 0 5G 0 disk
└─sdb1 8:17 0 5G 0 part
sr0 11:0 1 1.6G 0 rom
## 破坏分区表后：
[root@bogon software]# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 20G 0 disk
├─sda1 8:1 0 1G 0 part /boot
└─sda2 8:2 0 19G 0 part
└─cl-root 253:0 0 19G 0 lvm /
sdb 8:16 0 5G 0 disk
sr0 11:0 1 1.6G 0 rom
## 如果是根分区所在磁盘
#无法重新启动
[root@bogon software]#reboot
1.2修复/dev/sdb mbr分区表：
用光盘启动,进入rescue mode
先确保鼠标在VMware界面里
重启进入进度条时，按一次Esc键
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使用备份的mbr 表恢复：
image.png
2、总结RAID的各个级别及其组合方式和性能的不同。
| Level | Description | Min number of drives |
|---|---|---|
| RAID0 | 缺点：没有数据冗余。 优点：性能提升（写入和读取速度) |
最小磁盘数： 2 |
| RAID1 | 优点：容错和简单的数据恢复。提高了读取性能 缺点：可用容量较低。每兆字节的成本更高（达到所需容量所需的驱动器数量的两倍） |
最小磁盘数： 2 |
| RAID5 | 优点：容错和IO性能提升（低于RAID 0 缺点：由于奇偶校验开销导致服务器执行大量写操作，性能降低 |
最小磁盘数： 3 |
| RAID6 | 优点：比RAID 5更高的冗余。提高了读取性能。 缺点：由于奇偶校验开销，服务器执行大量写操作会降低性能 |
最小磁盘数： 4 |
| RAID10 | 优点：性能非常高。容错 缺点：可用容量较低/成本较高。有限的可扩展性 |
最小磁盘数： 4 |
3、创建一个2G的文件系统，块大小为2048byte，预留1%可用空间,文件系统 ext4，卷标为TEST，要求此分区开机后自动挂载至/test目录，且默认有acl挂载选项
## 热添加磁盘
[root@bogon ~]# ls /sys/class/scsi_host/ # 查看主机scsi 总线号
host0 host1 host2
[root@bogon ~]# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 20G 0 disk
├─sda1 8:1 0 1G 0 part /boot
└─sda2 8:2 0 19G 0 part
└─cl-root 253:0 0 19G 0 lvm /
sdb 8:16 0 5G 0 disk
└─sdb1 8:17 0 5G 0 part
sr0 11:0 1 1.6G 0 rom
[root@bogon ~]#
[root@bogon ~]# echo "- - -" > /sys/class/scsi_host/host0/scan
[root@bogon ~]# echo "- - -" > /sys/class/scsi_host/host1/scan
[root@bogon ~]# echo "- - -" > /sys/class/scsi_host/host2/scan
[root@bogon ~]# lsblk ## 成功热添加 sdc
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 20G 0 disk
├─sda1 8:1 0 1G 0 part /boot
└─sda2 8:2 0 19G 0 part
└─cl-root 253:0 0 19G 0 lvm /
sdb 8:16 0 5G 0 disk
└─sdb1 8:17 0 5G 0 part
sdc 8:32 0 2G 0 disk
sr0 11:0 1 1.6G 0 rom
[root@bogon ~]#
[root@bogon ~]# fdisk /dev/sdc
Welcome to fdisk (util-linux 2.32.1).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.
Device does not contain a recognized partition table.
Created a new DOS disklabel with disk identifier 0xa00230c2.
Command (m for help): n
Partition type
p primary (0 primary, 0 extended, 4 free)
e extended (container for logical partitions)
Select (default p):
Using default response p.
Partition number (1-4, default 1):
First sector (2048-10485759, default 2048):
Last sector, +sectors or +size{K,M,G,T,P} (2048-10485759, default 10485759): +2G
Created a new partition 1 of type 'Linux' and of size 2 GiB.
Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.
[root@bogon ~]# mkfs.ext4 -t ext4 -b 2048 -L TEST -m 1 /dev/sdc1 ##格式化
mke2fs 1.45.6 (20-Mar-2020)
Creating filesystem with 1048576 2k blocks and 131072 inodes
Filesystem UUID: d4822e63-ea0f-4e37-9d9c-2bd7ed120980
Superblock backups stored on blocks:
16384, 49152, 81920, 114688, 147456, 409600, 442368, 802816
Allocating group tables: done
Writing inode tables: done
Creating journal (16384 blocks): done
Writing superblocks and filesystem accounting information: done
[root@bogon ~]# blkid /dev/sdb1
/dev/sdb1: UUID="ce994dfa-b43a-41ef-a867-de489f359f14" TYPE="ext4" PARTUUID="440d52d3-01"
[root@bogon ~]#
[root@bogon /]# cat /etc/fstab |grep acl
UUID=0e342325-5312-444f-ad7a-6f6237bfac47 /test ext4 acl 0 0
[root@bogon /]#
[root@bogon /]# dumpe2fs -h /dev/sdc1
dumpe2fs 1.45.6 (20-Mar-2020)
Filesystem volume name: TEST
Last mounted on:
Filesystem UUID: d4822e63-ea0f-4e37-9d9c-2bd7ed120980
Filesystem magic number: 0xEF53
Filesystem revision #: 1 (dynamic)
Filesystem features: has_journal ext_attr resize_inode dir_index filetype extent 64bit flex_bg sparse_super large_file huge_file dir_nlink extra_isize metadata_csum
Filesystem flags: signed_directory_hash
Default mount options: user_xattr acl
Filesystem state: clean
Errors behavior: Continue
Filesystem OS type: Linux
Inode count: 131072
Block count: 1048576
Reserved block count: 10485
Free blocks: 1011035
Free inodes: 131061
First block: 0
Block size: 2048
Fragment size: 2048
Group descriptor size: 64
Reserved GDT blocks: 512
Blocks per group: 16384
Fragments per group: 16384
Inodes per group: 2048
Inode blocks per group: 256
Flex block group size: 16
Filesystem created: Mon Jan 11 00:13:41 2021
Last mount time: n/a
Last write time: Mon Jan 11 00:13:41 2021
Mount count: 0
Maximum mount count: -1
Last checked: Mon Jan 11 00:13:41 2021
Check interval: 0 ()
Lifetime writes: 1058 kB
Reserved blocks uid: 0 (user root)
Reserved blocks gid: 0 (group root)
First inode: 11
Inode size: 256
Required extra isize: 32
Desired extra isize: 32
Journal inode: 8
Default directory hash: half_md4
Directory Hash Seed: 03893215-8699-427e-9856-8ccb079b3099
Journal backup: inode blocks
Checksum type: crc32c
Checksum: 0x1c68f744
Journal features: (none)
Journal size: 32M
Journal length: 16384
Journal sequence: 0x00000001
Journal start: 0
[root@bogon /]#
4、创建一个至少有两个PV组成的大小为20G的名为testvg的VG;要求PE大小 为16MB, 而后在卷组中创建大小为5G的逻辑卷testlv;挂载至/users目录
[root@bogon ~]# vgcreate -s 16m testvg /dev/sdb1 /dev/sdc1 ## 创建VG
WARNING: ext4 signature detected on /dev/sdb1 at offset 1080. Wipe it? [y/n]: y
Wiping ext4 signature on /dev/sdb1.
WARNING: ext4 signature detected on /dev/sdc1 at offset 1080. Wipe it? [y/n]: y
Wiping ext4 signature on /dev/sdc1.
Physical volume "/dev/sdb1" successfully created.
Physical volume "/dev/sdc1" successfully created.
Volume group "testvg" successfully created
[root@bogon ~]# vgdisplay
--- Volume group ---
VG Name testvg
System ID
Format lvm2
Metadata Areas 2
Metadata Sequence No 1
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 0
Open LV 0
Max PV 0
Cur PV 2
Act PV 2
VG Size <6.97 GiB
PE Size 16.00 MiB
Total PE 446
Alloc PE / Size 0 / 0
Free PE / Size 446 / <6.97 GiB
VG UUID U8E23g-ljdX-X1Ga-aDkd-7ouo-wby9-Rg424D
[root@bogon ~]# lvcreate -L 5G -n testlv testvg ## 创建lv
Logical volume "testlv" created.
[root@bogon ~]# mkfs.ext4 /dev/testvg/testlv ##格式化lv 为ext4格式
mke2fs 1.45.6 (20-Mar-2020)
Creating filesystem with 1310720 4k blocks and 327680 inodes
Filesystem UUID: 76031543-4f71-4730-a8f1-88494b6aa290
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912, 819200, 884736
Allocating group tables: done
Writing inode tables: done
Creating journal (16384 blocks): done
Writing superblocks and filesystem accounting information: done
[root@bogon ~]# mkdir /users
[root@bogon ~]# mount /dev/testvg/testlv /users ## 挂载lv 到文件夹
[root@bogon ~]# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 20G 0 disk
├─sda1 8:1 0 1G 0 part /boot
└─sda2 8:2 0 19G 0 part
└─cl-root 253:0 0 19G 0 lvm /
sdb 8:16 0 5G 0 disk
└─sdb1 8:17 0 5G 0 part
└─testvg-testlv 253:1 0 5G 0 lvm /users
sdc 8:32 0 5G 0 disk
└─sdc1 8:33 0 2G 0 part
└─testvg-testlv 253:1 0 5G 0 lvm /users
sr0 11:0 1 1.6G 0 rom
[root@bogon ~]#