柒

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1、破坏mbr表并修复。

答：① 备份mbr分区表。

dd if=/dev/sda of=dpt.img bs=1 count=64 skip=446：生成mbr分区表，到dpt.img文件。

scp /root/dpt.img 10.0.0.27:/data：远程复制dpt.img文件，到10.0.0.27服务器的/data目录中。

[root@centos7mini ~]#dd if=/dev/sda of=dpt.img bs=1 count=64 skip=446
64+0 records in
64+0 records out
64 bytes (64 B) copied, 0.00026209 s, 244 kB/s
[root@centos7mini ~]#ls dpt.img
dpt.img
[root@centos7mini ~]#scp /root/dpt.img 10.0.0.27:/data
The authenticity of host '10.0.0.27 (10.0.0.27)' can't be established.
ECDSA key fingerprint is SHA256:aZ9KspCQ179viUkXhEFYw6EM1GN/ij913jH9ERjZYv0.
ECDSA key fingerprint is MD5:d1:29:63:fd:91:6e:28:cb:a9:4b:0b:9a:b5:8c:56:95.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '10.0.0.27' (ECDSA) to the list of known hosts.
root@10.0.0.27's password: 
dpt.img                                    100%   64     1.1KB/s   00:00    
[root@centos7mini ~]#

② 破坏mbr分区表。

[root@centos7mini ~]#dd if=/dev/zero of=/dev/sda bs=1 count=64 seek=446
64+0 records in
64+0 records out
64 bytes (64 B) copied, 0.000359388 s, 178 kB/s
[root@centos7mini ~]#hexdump -C /dev/sda -n 512 -v
...
000001b0  00 00 00 00 00 00 00 00  19 a6 0b 00 00 00 00 00  |................|
000001c0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000001d0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000001e0  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@centos7mini ~]#

③ reboot：重启系统。

④ 用光盘启动系统，进入"rescue mode"，选择第3项"skip to shell"。

a. 在出现进度条的时候，点击Esc键，弹出对话框。

注：鼠标一定要进入VMware虚拟机，否则无效。

b. 在弹出的对话框中，选择“3. CD-ROM Drive”。

c. 选择“Troubleshooting”。

d. 选择“Rescue a CentOS system”。

e. 选择“Skip to shell”。

⑤ 临时配置网络。

ip a a 10.0.0.17/24 dev ens33：IP地址为10.0.0.17，子网掩码为255.255.255.0，网卡名称为ens33。

⑥ scp 10.0.0.27:/data/dpt.img .：远程复制10.0.0.27服务器的/data/dpt.img文件，到当前目录中。

⑦ 恢复mbr分区表。

dd if=dpt.img of=/dev/sda bs=1 count=64 seek=446：把dpt.img文件，赋值到mbr分区表中。

⑧ reboot：重启系统。

2、总结RAID的各个级别及其组合方式和性能的不同。

答：① RAID-0：

读写性能：提升

可用空间：等于硬盘数。空间利用率：100%

容错能力：无。1块硬盘损坏，导致其它硬盘的数据损坏

最少硬盘数：2块硬盘及以上

② RAID-1：

镜像

读写性能：读性能提升，写性能略有下降

可用空间：等于硬盘数的一半。空间利用率：50%

容错能力：有

最少硬盘数：2的整数倍硬盘

③ RAID-5：

读写性能：提升

可用空间：等于硬盘数减1。空间利用率：（N - 1）/ N

容错能力：有。允许最多1块硬盘损坏

最少硬盘数：3块硬盘及以上

④ RAID-6：

读写性能：提升

可用空间：等于硬盘数减2。空间利用率：（N - 2）/ N

容错能力：有。允许最多2块硬盘损坏

最少硬盘数：4块硬盘及以上

⑤ RAID-10：

多块硬盘先组合成RAID-1，再组合成RAID-0

读写性能：提升

可用空间：等于硬盘数的一半。空间利用率：50%

容错能力：有。每组镜像硬盘最多只能损坏1块

最少硬盘数：4块硬盘及以上

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。

答：① 创建一个2G的分区。

[root@centos7mini ~]#fdisk /dev/sdb
Welcome to fdisk (util-linux 2.23.2).

Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.


Command (m for help): p

Disk /dev/sdb: 21.5 GB, 21474836480 bytes, 41943040 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x3c35ffd8

   Device Boot      Start         End      Blocks   Id  System

Command (m for help): n
Partition type:
   p   primary (0 primary, 0 extended, 4 free)
   e   extended
Select (default p): 
Using default response p
Partition number (1-4, default 1): 
First sector (2048-41943039, default 2048): 
Using default value 2048
Last sector, +sectors or +size{K,M,G} (2048-41943039, default 41943039): +2G
Partition 1 of type Linux and of size 2 GiB is set

Command (m for help): p

Disk /dev/sdb: 21.5 GB, 21474836480 bytes, 41943040 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x3c35ffd8

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1            2048     4196351     2097152   83  Linux

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.
[root@centos7mini ~]#
[root@centos7mini ~]#lsblk /dev/sdb
NAME   MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sdb      8:16   0  20G  0 disk 
└─sdb1   8:17   0   2G  0 part 
[root@centos7mini ~]#

② 创建文件系统，块大小为2048byte，预留1%可用空间，文件系统ext4，卷标为TEST。

[root@centos7mini ~]#mkfs.ext4 -b 2048 -m 1 -L 'TEST' /dev/sdb1
mke2fs 1.42.9 (28-Dec-2013)
Filesystem label=TEST
OS type: Linux
Block size=2048 (log=1)
Fragment size=2048 (log=1)
Stride=0 blocks, Stripe width=0 blocks
131072 inodes, 1048576 blocks
10485 blocks (1.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=269484032
64 block groups
16384 blocks per group, 16384 fragments per group
2048 inodes per group
Superblock backups stored on blocks: 
	16384, 49152, 81920, 114688, 147456, 409600, 442368, 802816

Allocating group tables: done                            
Writing inode tables: done                            
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done 

[root@centos7mini ~]#
[root@centos7mini ~]#lsblk -f /dev/sdb
NAME   FSTYPE LABEL UUID                                 MOUNTPOINT
sdb                                                      
└─sdb1 ext4   TEST  ceb1b037-c69c-40d8-adaa-b3673c21c740 
[root@centos7mini ~]#

③ 此分区开机后自动挂载至/test目录，且默认有acl挂载选项。

[root@centos7mini ~]#mkdir /test
[root@centos7mini ~]#
[root@centos7mini ~]#vim /etc/fstab

/dev/sdb1: LABEL="TEST" UUID="ceb1b037-c69c-40d8-adaa-b3673c21c740" TYPE="ext4" 

Press ENTER or type command to continue
[root@centos7mini ~]#
[root@centos7mini ~]#cat /etc/fstab

#
# /etc/fstab
# Created by anaconda on Thu May 13 20:29:02 2021
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#
UUID=39e66903-b3bb-4664-844e-9cf1e1726ec9 /                       xfs     defaults        0 0
UUID=2a13f5bb-2492-4f2f-a446-c4ce2df5dbd4 /boot                   xfs     defaults        0 0
UUID=84966365-16e6-408f-aff3-92156186ae70 /data                   xfs     defaults        0 0
UUID=0ebd701e-9490-4871-ac93-748168c60cfc swap                    swap    defaults        0 0
UUID=ceb1b037-c69c-40d8-adaa-b3673c21c740 /test                   ext4    defaults,acl    0 0
[root@centos7mini ~]#
[root@centos7mini ~]#mount -a
[root@centos7mini ~]#
[root@centos7mini ~]#df -h
Filesystem      Size  Used Avail Use% Mounted on
devtmpfs        900M     0  900M   0% /dev
tmpfs           910M     0  910M   0% /dev/shm
tmpfs           910M  9.6M  901M   2% /run
tmpfs           910M     0  910M   0% /sys/fs/cgroup
/dev/sda2       100G  2.0G   98G   2% /
/dev/sda3        50G   33M   50G   1% /data
/dev/sda1      1014M  142M  873M  15% /boot
tmpfs           182M     0  182M   0% /run/user/0
/dev/sdb1       2.0G  9.1M  1.9G   1% /test
[root@centos7mini ~]#

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。

答：① 创建两个物理卷，两者组成的空间大小为20G。

[root@centos7mini ~]#fdisk /dev/sdb
Welcome to fdisk (util-linux 2.23.2).

Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.


Command (m for help): n
Partition type:
   p   primary (1 primary, 0 extended, 3 free)
   e   extended
Select (default p): 
Using default response p
Partition number (2-4, default 2): 
First sector (4196352-41943039, default 4196352): 
Using default value 4196352
Last sector, +sectors or +size{K,M,G} (4196352-41943039, default 41943039): 
Using default value 41943039
Partition 2 of type Linux and of size 18 GiB is set

Command (m for help): p

Disk /dev/sdb: 21.5 GB, 21474836480 bytes, 41943040 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x3c35ffd8

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1            2048     4196351     2097152   83  Linux
/dev/sdb2         4196352    41943039    18873344   83  Linux

Command (m for help): t
Partition number (1,2, default 2): 2
Hex code (type L to list all codes): 8e
Changed type of partition 'Linux' to 'Linux LVM'

Command (m for help): p

Disk /dev/sdb: 21.5 GB, 21474836480 bytes, 41943040 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x3c35ffd8

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1            2048     4196351     2097152   83  Linux
/dev/sdb2         4196352    41943039    18873344   8e  Linux LVM

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.

WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table. The new table will be used at
the next reboot or after you run partprobe(8) or kpartx(8)
Syncing disks.
[root@centos7mini ~]#
[root@centos7mini ~]#partprobe
Warning: Unable to open /dev/sr0 read-write (Read-only file system).  /dev/sr0 has been opened read-only.
[root@centos7mini ~]#
[root@centos7mini ~]#lsblk /dev/sdb2 /dev/sdc
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sdb2   8:18   0  18G  0 part 
sdc    8:32   0   2G  0 disk 
[root@centos7mini ~]#
[root@centos7mini ~]#pvcreate /dev/sdb2 /dev/sdc
  Physical volume "/dev/sdb2" successfully created.
  Physical volume "/dev/sdc" successfully created.
[root@centos7mini ~]#
[root@centos7mini ~]#pvs
  PV         VG Fmt  Attr PSize   PFree  
  /dev/sdb2     lvm2 ---  <18.00g <18.00g
  /dev/sdc      lvm2 ---    2.00g   2.00g
[root@centos7mini ~]#

② 创建卷组，名称为testvg，PE大小为16MB。

[root@centos7mini ~]#vgcreate -s 16M testvg /dev/sdb2 /dev/sdc
  Volume group "testvg" successfully created
[root@centos7mini ~]#
[root@centos7mini ~]#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               <19.97 GiB
  PE Size               16.00 MiB
  Total PE              1278
  Alloc PE / Size       0 / 0   
  Free  PE / Size       1278 / <19.97 GiB
  VG UUID               PZsbjt-t8am-IUy0-hwve-515t-dIVP-JT1CRh
   
[root@centos7mini ~]#

③ 创建逻辑卷，名称为testlv，空间大小为5G。

[root@centos7mini ~]#lvcreate -n testlv -L 5G testvg
  Logical volume "testlv" created.                                                  
[root@centos7mini ~]#
[root@centos7mini ~]#lvdisplay
  --- Logical volume ---
  LV Path                /dev/testvg/testlv
  LV Name                testlv
  VG Name                testvg
  LV UUID                oKPlnd-5hI6-Og1T-XYdH-aFEn-YYeB-Ukpihu
  LV Write Access        read/write
  LV Creation host, time centos7mini, 2022-02-21 23:57:01 +0800
  LV Status              available
  # open                 0
  LV Size                5.00 GiB
  Current LE             320
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:0
   
[root@centos7mini ~]#

④ 创建文件系统，类型为ext4。（题目中没有要求类型）

[root@centos7mini ~]#mkfs.ext4 /dev/testvg/testlv
mke2fs 1.42.9 (28-Dec-2013)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
327680 inodes, 1310720 blocks
65536 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=1342177280
40 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks: 
	32768, 98304, 163840, 229376, 294912, 819200, 884736

Allocating group tables: done                            
Writing inode tables: done                            
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done 

[root@centos7mini ~]#
[root@centos7mini ~]#blkid /dev/testvg/testlv
/dev/testvg/testlv: UUID="8e7e8dc4-4e60-486c-baea-de2b44fdef9b" TYPE="ext4" 
[root@centos7mini ~]#

⑤ 挂载至/users目录。

[root@centos7mini ~]#mkdir /users
[root@centos7mini ~]#
[root@centos7mini ~]#vim /etc/fstab

/dev/testvg/testlv: UUID="8e7e8dc4-4e60-486c-baea-de2b44fdef9b" TYPE="ext4" 

Press ENTER or type command to continue
[root@centos7mini ~]#
[root@centos7mini ~]#cat /etc/fstab

#
# /etc/fstab
# Created by anaconda on Thu May 13 20:29:02 2021
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#
UUID=39e66903-b3bb-4664-844e-9cf1e1726ec9 /                       xfs     defaults        0 0
UUID=2a13f5bb-2492-4f2f-a446-c4ce2df5dbd4 /boot                   xfs     defaults        0 0
UUID=84966365-16e6-408f-aff3-92156186ae70 /data                   xfs     defaults        0 0
UUID=0ebd701e-9490-4871-ac93-748168c60cfc swap                    swap    defaults        0 0
UUID=ceb1b037-c69c-40d8-adaa-b3673c21c740 /test                   ext4    defaults,acl    0 0
UUID=8e7e8dc4-4e60-486c-baea-de2b44fdef9b /users                  ext4    defaults        0 0
[root@centos7mini ~]#
[root@centos7mini ~]#mount -a
[root@centos7mini ~]#
[root@centos7mini ~]#df -h
Filesystem                 Size  Used Avail Use% Mounted on
devtmpfs                   900M     0  900M   0% /dev
tmpfs                      910M     0  910M   0% /dev/shm
tmpfs                      910M  9.6M  901M   2% /run
tmpfs                      910M     0  910M   0% /sys/fs/cgroup
/dev/sda2                  100G  2.0G   98G   2% /
/dev/sda3                   50G   33M   50G   1% /data
/dev/sda1                 1014M  142M  873M  15% /boot
tmpfs                      182M     0  182M   0% /run/user/0
/dev/sdb1                  2.0G  9.1M  1.9G   1% /test
/dev/mapper/testvg-testlv  4.8G   20M  4.6G   1% /users
[root@centos7mini ~]#

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