No.M55-week5CentOS故障修复RAID简介分区文件系统网络模型实例

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2021-5-27

1.MBR修复

dd命令详解:

[root@centos6 ~]# dd --help
Usage: dd [OPERAND]...
  or:  dd OPTION
Copy a file, converting and formatting according to the operands.

  bs=BYTES        #一次读写块大小
  cbs=BYTES       convert BYTES bytes at a time
  conv=CONVS      convert the file as per the comma separated symbol list
  count=N         copy only N input blocks
  ibs=BYTES       read BYTES bytes at a time (default: 512)
  if=FILE         #输入文件名,缺省为标准输入
  iflag=FLAGS     read as per the comma separated symbol list
  obs=BYTES       write BYTES bytes at a time (default: 512)
  of=FILE         #输出文件名,缺省为标准输出
  oflag=FLAGS     write as per the comma separated symbol list
  seek=BLOCKS     #从输出文件开头跳过blocks个块后再开始复制
  skip=BLOCKS     #从输入文件开头跳过blocks个块后再开始复制
  status=WHICH    WHICH info to suppress outputting to stderr;
                  \'noxfer\' suppresses transfer stats, \'none\' suppresses all
                  
# skip是跳过if中的前多少字节
# seek是跳过of中的前多少字节

一、备份分区文件:

[root@localhost ~]# dd if=/dev/sda of=/data/dpt.img bs=1 count=64 skip=446
[root@localhost ~]# scp /data/dpt.img 10.0.0.6:

二、模拟破坏分区:

索引部分任意地方破导致启动不了,只备份446开始的64字节,破坏这64字节内容

[root@localhost ~]# dd if=/dev/zero of=/dev/sda bs=1 count=64 seek=446

三、救援

reboot
进入光盘救援模式,选择3直接进入shell环境。备注:选1会出错,硬盘挂载不起来
配置临时网络(此时没有网络)
ifconfig ens eth0(看ifconfig中失效网卡) 10.0.0.6/24
scp 10.0.0.16: /root/dpt.img
dd if=dpt.img of=/dev/sda bs=1 seek=446
exit

实战:模拟破坏mbr表并修复

#1.备份MBR分区表
[root@centos6 ~]# lsblk
NAME                          MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sr0                            11:0    1   406M  0 rom  
sda                             8:0    0   200G  0 disk 
├─sda1                          8:1    0   500M  0 part /boot
└─sda2                          8:2    0 199.5G  0 part 
  ├─vg_centos6-lv_root (dm-0) 253:0    0    50G  0 lvm  /
  ├─vg_centos6-lv_swap (dm-1) 253:1    0   3.9G  0 lvm  [SWAP]
  └─vg_centos6-lv_home (dm-2) 253:2    0 145.6G  0 lvm  /home
[root@centos6 ~]# dd if=/dev/sda of=/tmp/dpt.img bs=1 count=64 skip=446
64+0 records in
64+0 records out
64 bytes (64 B) copied, 0.000830782 s, 77.0 kB/s
[root@centos6 ~]# scp /tmp/dpt.img 10.0.0.6:
The authenticity of host \'10.0.0.6 (10.0.0.6)\' can\'t be established.
RSA key fingerprint is ad:ce:fa:ec:a7:6d:0d:d1:90:92:e9:d1:b5:b3:79:46.
Are you sure you want to continue connecting (yes/no)? y
Please type \'yes\' or \'no\': yes
Warning: Permanently added \'10.0.0.6\' (RSA) to the list of known hosts.
root@10.0.0.6\'s password: 
dpt.img                                                                          100%   64     0.1KB/s   00:00  
#2.破坏MBR分区表
[root@centos6 ~]# 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, 0.000832751 s, 76.9 kB/s
[root@centos6 ~]# reboot
#3.之后无法正常启动,进入grub>; 
#重启系统快速按F2键,进入Bios界面,选择Boot选项,将光盘‘CD-ROM Drive’设置为第一个优先启动,F10保存
#4.进入救援模式‘rescue mode’,选择第3项 \'skip to shell\'
sh-4.1# ifconfig eth0 10.0.0.16/24
sh-4.1# scp 10.0.0.6:/root/dpt.img .
sh-4.1# dd if=dpt.img of=/dev/sda bs=1 seek=446
sh-4.1# exit

2.RAID级别及组合方式和性能

RAID介绍

RAID:Redundant Arrays of Inexpensive Disks,廉价磁盘冗余阵列。
多个磁盘组合成一个阵列提供更好的性能、冗余,或者两者都提供。

RAID级别及组合方式和性能

RAID-0  #以chunk为单位,读写数据,读、写性能提升,最少磁盘数:2,2+,无容错能力
RAID-1  #读性能提升,写性能略有下降,有冗余能力,最少磁盘数:2,2N
RAID-4  #多块数据盘异或运算值存于专用校验盘,有冗余能力,至少3块硬盘实现
RAID-5  #读、写性能提升、有容错能力:允许最多1块磁盘损坏,最少磁盘数:3,3+
RAID-6  #读、写性能提升、有容错能力:允许最多2块磁盘损坏,最少磁盘数:4,4+
RAID-10 #读、写性能提升、有容错能力:每组镜像最多只能坏一块,最少磁盘数:4,4+
RAID-01 #多块磁盘先实现RAID0,再组合成RAID1
RAID-50 #多块磁盘先实现RAID5,再组合成RAID0

3.创建文件系统

磁盘及文件系统基本命令介绍:

#磁盘分区等相关命令:
lsblk:		#列出块设备信息(list block devices) -f输出文件系统信息
blkid:		#打印块设备属性
fdisk:		#操作磁盘分区表
pvcreate: 	#初始化LVM使用的物理卷
mkfs.ext4:  #创建一个ext4文件系统
mount:	    #挂载一个文件系统到分区表
vgcreate:   #创建一个卷组
vgs:        #显示卷组信息
lvcreate:   #创建一个逻辑卷
lvs:        #显示逻辑卷信息

实战: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

#1.新增一个20G大小的sdb硬盘,做实验操作
[root@CentOS7 ~]# lsblk
NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda      8:0    0  200G  0 disk 
├─sda1   8:1    0    1G  0 part /boot
├─sda2   8:2    0    4G  0 part [SWAP]
└─sda3   8:3    0  100G  0 part /
sdb      8:16   0   20G  0 disk 
sr0     11:0    1    4G  0 rom  
#2.在sdb上创建2G分区
[root@centos6 ~]# fdisk /dev/sdb
Command (m for help): m
Command action
   a   toggle a bootable flag
   b   edit bsd disklabel
   c   toggle the dos compatibility flag
   d   delete a partition
   g   create a new empty GPT partition table
   G   create an IRIX (SGI) partition table
   l   list known partition types
   m   print this menu
   n   add a new partition
   o   create a new empty DOS partition table
   p   print the partition table
   q   quit without saving changes
   s   create a new empty Sun disklabel
   t   change a partition\'s system id
   u   change display/entry units
   v   verify the partition table
   w   write table to disk and exit
   x   extra functionality (experts only)
Command (m for help): n
Partition type:
   p   primary (0 primary, 0 extended, 4 free)
   e   extended
Select (default p): 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): w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks. 
#3.在sdb分区上创建文件系统
[root@CentOS7 ~]# 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 
#4.查看分区结果
[root@CentOS7 ~]# blkid
/dev/sda1: UUID="9a8e98ca-f998-4af2-9dae-28a78e2e4838" TYPE="xfs" 
/dev/sda2: UUID="bbb7b1c6-74d0-499b-8d71-7b6240b0fcb5" TYPE="swap" 
/dev/sda3: UUID="14e56b7c-4eff-4c7d-bf27-0d1ec866a3fb" TYPE="xfs" 
/dev/sdb1: LABEL="TEST" UUID="e84464e9-70bb-4c87-869e-7e2e3e8a5c76" TYPE="ext4" 
/dev/sr0: UUID="2015-12-09-23-14-10-00" LABEL="CentOS 7 x86_64" TYPE="iso9660" PTTYPE="dos" 
[root@CentOS7 ~]# lsblk
NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda      8:0    0  200G  0 disk 
├─sda1   8:1    0    1G  0 part /boot
├─sda2   8:2    0    4G  0 part [SWAP]
└─sda3   8:3    0  100G  0 part /
sdb      8:16   0   20G  0 disk 
└─sdb1   8:17   0    2G  0 part 
sr0     11:0    1    4G  0 rom 
#5.将分区挂载到指定文件夹/test
[root@CentOS7 ~]# mkdir /test
[root@CentOS7 ~]# echo \'UUUUID=e84464e9-70bb-4c87-869e-7e2e3e8a5c76 /test ext4 acl 0 0\' >> /etc/fstab 
[root@CentOS7 ~]# cat /etc/fstab 
#
# /etc/fstab
# Created by anaconda on Tue Apr 20 21:28:17 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=14e56b7c-4eff-4c7d-bf27-0d1ec866a3fb /              xfs     defaults        0 0
UUID=9a8e98ca-f998-4af2-9dae-28a78e2e4838 /boot          xfs     defaults        0 0
UUID=bbb7b1c6-74d0-499b-8d71-7b6240b0fcb5 swap           swap    defaults        0 0
UUUUID=e84464e9-70bb-4c87-869e-7e2e3e8a5c76 /test ext4 acl 0 0
#6.使挂载生效
[root@CentOS7 ~]# mount -a
#7.查看挂载文件系统
[root@CentOS7 ~]# lsblk
NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda      8:0    0  200G  0 disk 
├─sda1   8:1    0    1G  0 part /boot
├─sda2   8:2    0    4G  0 part [SWAP]
└─sda3   8:3    0  100G  0 part /
sdb      8:16   0   20G  0 disk 
└─sdb1   8:17   0    2G  0 part /test
sr0     11:0    1    4G  0 rom  

实战: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

#1.查看磁盘,新增了一个10G盘sdc
[root@CentOS7 ~]# lsblk
NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda      8:0    0  200G  0 disk 
├─sda1   8:1    0    1G  0 part /boot
├─sda2   8:2    0    4G  0 part [SWAP]
└─sda3   8:3    0  100G  0 part /
sdb      8:16   0   20G  0 disk 
└─sdb1   8:17   0    2G  0 part /test
sdc      8:32   0   10G  0 disk 
sr0     11:0    1    4G  0 rom 
#2.在sdc创建10G分区
[root@CentOS7 ~]# fdisk /dev/sdc
Welcome to fdisk (util-linux 2.23.2).
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 (2048-20971519, default 2048): 
Using default value 2048
Last sector, +sectors or +size{K,M,G} (2048-20971519, default 20971519): +10G
Value out of range.
Last sector, +sectors or +size{K,M,G} (2048-20971519, default 20971519): +9G
Partition 1 of type Linux and of size 9 GiB is set

Command (m for help): t
Selected partition 1
Hex code (type L to list all codes): 8e
Changed type of partition \'Linux\' to \'Linux LVM\'

Command (m for help): p

Disk /dev/sdc: 10.7 GB, 10737418240 bytes, 20971520 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: 0x625894bd

   Device Boot      Start         End      Blocks   Id  System
/dev/sdc1            2048    18876415     9437184   8e  Linux LVM

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

Calling ioctl() to re-read partition table.
Syncing disks.
#3.在sdc1分区和sdb上分别创建物理卷(PV)
#pvcreate依赖包lvm2-2.02.180-10.el7_6.8.x86_64 
[root@CentOS7 ~]# yum provides pvcreate
7:lvm2-2.02.180-10.el7_6.8.x86_64 : Userland logical volume management tools
Repo        : update
Matched from:
Filename    : /usr/sbin/pvcreate
[root@CentOS7 ~]# yum -y install lvm2-2.02.180-10.el7_6.8.x86_64
#4.在sdc1分区和sdb上分别创建物理卷(pv)
[root@CentOS7 ~]# pvcreate /dev/sdc1
  Physical volume "/dev/sdc1" successfully created.
[root@CentOS7 ~]# pvcreate /dev/sdb
WARNING: dos signature detected on /dev/sdb at offset 510. Wipe it? [y/n]: y
  Wiping dos signature on /dev/sdb.
  Physical volume "/dev/sdb" successfully created.
[root@CentOS7 ~]# pvs
  PV         VG Fmt  Attr PSize  PFree 
  /dev/sdb      lvm2 ---  20.00g 20.00g
  /dev/sdc1     lvm2 ---   9.00g  9.00g
#5.创建物理卷组testvg(vg),并将创建的pv加入其中
[root@CentOS7 ~]# vgcreate -s 16M testvg /dev/sdb /dev/sdc1
  Volume group "testvg" successfully created
[root@CentOS7 ~]# vgs
  VG     #PV #LV #SN Attr   VSize   VFree  
  testvg   2   0   0 wz--n- <28.97g <28.97g
#6.在testvg中创建大小为5G的逻辑卷(LV)
[root@CentOS7 ~]# lvcreate -n testlv -L 5G testvg
WARNING: ext4 signature detected on /dev/testvg/testlv at offset 1080. Wipe it? [y/n]: y
  Wiping ext4 signature on /dev/testvg/testlv.
  Logical volume "testlv" created.
[root@CentOS7 ~]# lvs
  LV     VG     Attr       LSize Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  testlv testvg -wi-a----- 5.00g        
#6.创建文件系统
[root@CentOS7 ~]# 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 
#7.确认BLKID并加入/etc/fstab
[root@CentOS7 ~]# blkid
/dev/sda1: UUID="9a8e98ca-f998-4af2-9dae-28a78e2e4838" TYPE="xfs" 
/dev/sda2: UUID="bbb7b1c6-74d0-499b-8d71-7b6240b0fcb5" TYPE="swap" 
/dev/sda3: UUID="14e56b7c-4eff-4c7d-bf27-0d1ec866a3fb" TYPE="xfs" 
/dev/sdb: UUID="nQf48z-QM6T-QTXA-MwWj-G44h-XQbq-x9wMie" TYPE="LVM2_member" 
/dev/sdc1: UUID="WqmKbk-4Ka4-1OQO-JoHt-iHY3-A7RO-ke9Y7U" TYPE="LVM2_member" 
/dev/sr0: UUID="2015-12-09-23-14-10-00" LABEL="CentOS 7 x86_64" TYPE="iso9660" PTTYPE="dos" 
/dev/mapper/testvg-testlv: UUID="9e33092d-7dd0-41b8-b576-337cc13c6ee8" TYPE="ext4" 
[root@CentOS7 ~]# echo \'UUID=9e33092d-7dd0-41b8-b576-337cc13c6ee8 /users ext4 defaults 0 0\' >> /etc/fstab
[root@CentOS7 ~]# cat /etc/fstab
#
# /etc/fstab
# Created by anaconda on Tue Apr 20 21:28:17 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=14e56b7c-4eff-4c7d-bf27-0d1ec866a3fb /                 xfs     defaults        0 0
UUID=9a8e98ca-f998-4af2-9dae-28a78e2e4838 /boot             xfs     defaults        0 0
UUID=bbb7b1c6-74d0-499b-8d71-7b6240b0fcb5 swap              swap    defaults        0 0
UUID=9e33092d-7dd0-41b8-b576-337cc13c6ee8 /users ext4 defaults 0 0
#8.创建文件夹,并让其生效
[root@CentOS7 ~]# mkdir /users
[root@CentOS7 ~]# mount -a

4.网络模型

实战:简述osi七层模型和TCP/IP五层模型

#OSI七层网络模型
1.应用层		#提供网络服务和接口,协议有HTTP,FTP等
2.表示层		#数据的表示、安全、压缩,格式有JPEG,ASCII、加密格式等
3.会话层		#建立、管理、终止会话,对应主机进程正在进行的会话
4.传输层		#定义传输数据的协议端口号,以及流控和差错校验,协议有TCP,UDP等
5.网络层		#进行逻辑地址寻址,实现不同网络间路径选择,协议有ICMP,IP等
6.数据链路层    #建立逻辑连接,进行硬件寻址,差错校验,如用MAC访问介质
7.物理层		#建立、维护、断开物理连接

#TCP/IP五层模型
1.应用层		#对应OSI的应用层,表示层,会话层
2.传输层		#对应OSI的传输层
3.网络层		#对应OSI的网络层
4.数据链路层    #对应OSI的数据链路层
5.物理层		#对应OSI的物理层

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