linux基于xfs文件系统实现数据备份和恢复

约定不等于承诺〃 2022-09-10 13:28 178阅读 0赞

# 实战：xfs文件系统的备份和恢复 #

## XFS文件系统 ##

*  centos7选择xfs格式作为默认文件系统，而且不再使用以前的ext，仍然支持ext4，
 *  xfs专为大数据产生，每个单个文件系统最大可以支持8eb，单个文件可以支持16tb，不仅数据量大，而且扩展性高。
 *  还可以通过xfsdump，xfsrestore来备份和恢复。

## XFS备份 恢复工具 ##

*  XFS提供了 xfsdump 和 xfsrestore 工具协助备份XFS文件系统中的数据。xfsdump 按inode顺序备份一个XFS文件系统。
 *  与传统的UNIX文件系统不同，XFS不需要在备份前被卸载；对使用中的XFS文件系统做备份就可以保证镜像的一致性。XFS的备份和恢复的过程是可以被中断然后继续的，无须冻结文件系统。xfsdump 甚至提供了高性能的多线程备份操作——它把一次dump拆分成多个数据流，每个数据流可以被发往不同的目的地

## xfsdump的备份级别 ##

首先了解一下xfsdump的备份级别有以下两种，默认为0（即完全备份）

*  0 级别代表： 完全备份
 *  1 到9级别代表： 增量备份

扩展：

*  完全备份：每次都把指定的备份目录完整的复制一遍，不管目录下的文件有没有变化；
 *  增量备份：每次将之前（第一次、第二次、直到前一次）做过备份之后有变化的文件进行备份；
 *  差异备份：每次都将第一次完整备份以来有变化的文件进行备份。

## 环境准备 ##

### 实验环境 ###

系统CetnOS8 添加一块虚拟硬盘（准备一个测试分区）  
正常使用一块磁盘过程如下：  
添加磁盘大小：2G ->分区->格式化->挂载

1.  虚拟机新增2G硬盘
2.  开机后查看设备  
    使用fdisk -l查看新增硬盘

Last login: Tue Oct 20 04:13:20 2020 from 10.0.0.1
    [root@C8-3 ~]# fdisk -l
    Disk /dev/sda: 20 GiB, 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
    Disklabel type: dos
    Disk identifier: 0xbfcdb101
    
    Device     Boot   Start      End  Sectors Size Id Type
    /dev/sda1  *       2048  2099199  2097152   1G 83 Linux
    /dev/sda2       2099200 41943039 39843840  19G 8e Linux LVM
    
    
    Disk /dev/sdb: 2 GiB, 2147483648 bytes, 4194304 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

1.  给新增硬盘分区

[root@C8-3 ~]# fdisk /dev/sdb #使用fdisk命令分区
    
    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 0x467c42d4.
    
    Command (m for help): m #查看有哪些命令可以用
    
    Help:
    
      DOS (MBR)
       a   toggle a bootable flag
       b   edit nested BSD disklabel
       c   toggle the dos compatibility flag
    
      Generic
       d   delete a partition
       F   list free unpartitioned space
       l   list known partition types
       n   add a new partition
       p   print the partition table
       t   change a partition type
       v   verify the partition table
       i   print information about a partition
    
      Misc
       m   print this menu
       u   change display/entry units
       x   extra functionality (experts only)
    
      Script
       I   load disk layout from sfdisk script file
       O   dump disk layout to sfdisk script file
    
      Save & Exit
       w   write table to disk and exit
       q   quit without saving changes
    
      Create a new label
       g   create a new empty GPT partition table
       G   create a new empty SGI (IRIX) partition table
       o   create a new empty DOS partition table
       s   create a new empty Sun partition table
    
    
    Command (m for help): n #选择新建一个分区
    Partition type
       p   primary (0 primary, 0 extended, 4 free)
       e   extended (container for logical partitions)
    Select (default p): p #创建主分区
    Partition number (1-4, default 1):  #直接回车默认值
    First sector (2048-4194303, default 2048):  #起始扇区，回车默认
    Last sector, +sectors or +size{ K,M,G,T,P} (2048-4194303, default 4194303):  #结束扇区，回车默认分配全部空间
    
    Created a new partition 1 of type 'Linux' and of size 2 GiB.
    
    Command (m for help): w #将以上操作写入硬盘分区表，结束分区
    The partition table has been altered.
    Calling ioctl() to re-read partition table.
    Syncing disks.
    [root@C8-3 ~]# lsblk #查看分区是否成功
    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  17G  0 lvm  /
      └─cl-swap 253:1    0   2G  0 lvm  [SWAP]
    sdb           8:16   0   2G  0 disk 
    └─sdb1        8:17   0   2G  0 part  #分区成功但未挂载

1.  将新建分区格式化为xfs格式  
    使用mkfs.xfs格式化新分区

[root@C8-3 ~]# type mkfs.xfs #查看是否有此工具
    mkfs.xfs is /usr/sbin/mkfs.xfs
    [root@C8-3 ~]# mkfs.xfs --help #查看命令的帮助
    mkfs.xfs: invalid option -- '-'
    unknown option -- 
    Usage: mkfs.xfs
    /* blocksize */		[-b size=num]
    /* metadata */		[-m crc=0|1,finobt=0|1,uuid=xxx,rmapbt=0|1,reflink=0|1]
    /* data subvol */	[-d agcount=n,agsize=n,file,name=xxx,size=num,
    			    (sunit=value,swidth=value|su=num,sw=num|noalign),
    			    sectsize=num
    /* force overwrite */	[-f]
    /* inode size */	[-i log=n|perblock=n|size=num,maxpct=n,attr=0|1|2,
    			    projid32bit=0|1,sparse=0|1]
    /* no discard */	[-K]
    /* log subvol */	[-l agnum=n,internal,size=num,logdev=xxx,version=n
    			    sunit=value|su=num,sectsize=num,lazy-count=0|1]
    /* label */		[-L label (maximum 12 characters)]
    /* naming */		[-n size=num,version=2|ci,ftype=0|1]
    /* no-op info only */	[-N]
    /* prototype file */	[-p fname]
    /* quiet */		[-q]
    /* realtime subvol */	[-r extsize=num,size=num,rtdev=xxx]
    /* sectorsize */	[-s size=num]
    /* version */		[-V]
    			devicename
    <devicename> is required unless -d name=xxx is given.
    <num> is xxx (bytes), xxxs (sectors), xxxb (fs blocks), xxxk (xxx KiB),
          xxxm (xxx MiB), xxxg (xxx GiB), xxxt (xxx TiB) or xxxp (xxx PiB).
    <value> is xxx (512 byte blocks).
    [root@C8-3 ~]# mkfs.xfs -V #查看命令版本
    mkfs.xfs version 5.0.0
    [root@C8-3 ~]# mkfs.xfs /dev/sdb1 #格式化新分区
    meta-data=/dev/sdb1              isize=512    agcount=4, agsize=131008 blks
             =                       sectsz=512   attr=2, projid32bit=1
             =                       crc=1        finobt=1, sparse=1, rmapbt=0
             =                       reflink=1
    data     =                       bsize=4096   blocks=524032, imaxpct=25
             =                       sunit=0      swidth=0 blks
    naming   =version 2              bsize=4096   ascii-ci=0, ftype=1
    log      =internal log           bsize=4096   blocks=2560, version=2
             =                       sectsz=512   sunit=0 blks, lazy-count=1
    realtime =none                   extsz=4096   blocks=0, rtextents=0

1.  查看新分区情况  
    使用lsblk及参数-f查看分区情况和文件系统  
    \*`-f, --fs output info about filesystems*`

[root@C8-3 ~]# lsblk -f
    NAME        FSTYPE      LABEL UUID                                   MOUNTPOINT
    sda                                                                  
    ├─sda1      ext4              8df39f81-d4b1-4881-9bb4-51f8f6ee964a   /boot
    └─sda2      LVM2_member       mQQNpB-AMy6-Ad3M-3RNh-NeRf-8tf9-OmosY7 
      ├─cl-root xfs               8dbc40ac-24cf-45c9-8c53-d07ac9cee558   /
      └─cl-swap swap              ffc54438-efdc-45d7-a244-b9e9bfef4930   [SWAP]
    sdb                                                                  
    └─sdb1      xfs               d549d0dd-23a2-4223-abe5-96055a8f737a

1.  创建一个目录并将新分区sdb1挂载到此目录

[root@C8-3 ~]# mkdir /xfsTest
    [root@C8-3 ~]# mount /dev/sdb1 /xfsTest/
    [root@C8-3 ~]# 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  17G  0 lvm  /
      └─cl-swap 253:1    0   2G  0 lvm  [SWAP]
    sdb           8:16   0   2G  0 disk 
    └─sdb1        8:17   0   2G  0 part /xfsTest

### 创建测试文件和文件夹 ###

[root@C8-3 ~]# rm -rf /xfsTest/*
    [root@C8-3 ~]# ls /xfsTest/
    [root@C8-3 ~]# cp /etc/passwd /xfsTest/
    [root@C8-3 ~]# touch /xfsTest/file{1..3}{a..b}.txt
    [root@C8-3 ~]# mkdir -p /xfsTest/m{1..3}/n{a..b}
    [root@C8-3 ~]# tree /xfsTest/
    /xfsTest/
    ├── file1a.txt
    ├── file1b.txt
    ├── file2a.txt
    ├── file2b.txt
    ├── file3a.txt
    ├── file3b.txt
    ├── m1
    │   ├── na
    │   └── nb
    ├── m2
    │   ├── na
    │   └── nb
    ├── m3
    │   ├── na
    │   └── nb
    └── passwd
    
    9 directories, 7 files

## 备份 ##

### 使用xfsdump命令进行备份 ###

先查看xfsdump帮助

[root@C8-3 ~]# type xfsdump 
    xfsdump is /usr/sbin/xfsdump
    [root@C8-3 ~]# xfsdump --help
    xfsdump: version 3.1.8 (dump format 3.0)
    xfsdump: usage: xfsdump [ -a (dump DMF dualstate files as offline) ]
    ……

### 备份整个分区。 （这个功能就像是虚拟机的快照，服务器被黑后，进行快速恢复） ###

*\[ -f <destination> … \]*  
xfsdump -f *备份存放位置* *要备份路径或设备文件*  
注意：备份的路径这里不能写成/xfsTest/。 可以是/dev/sdb1 或/xfsTest

[root@C8-3 ~]# xfsdump -f /opt/dump_sdb1 /dev/sdb1
    xfsdump: using file dump (drive_simple) strategy
    xfsdump: version 3.1.8 (dump format 3.0) - type ^C for status and control
    
     ============================= dump label dialog ==============================
    
    please enter label for this dump session (timeout in 300 sec)
     -> dump_sdb1 #提示输入，指定备份会话标签
    session label entered: "dump_sdb1"
    
     --------------------------------- end dialog ---------------------------------
    
    xfsdump: level 0 dump of C8-3:/xfsTest
    xfsdump: dump date: Tue Oct 20 08:09:38 2020
    xfsdump: session id: 3fdced05-235f-4926-9409-7c7e4081da84
    xfsdump: session label: "dump_sdb1"
    xfsdump: ino map phase 1: constructing initial dump list
    xfsdump: ino map phase 2: skipping (no pruning necessary)
    xfsdump: ino map phase 3: skipping (only one dump stream)
    xfsdump: ino map construction complete
    xfsdump: estimated dump size: 30016 bytes
    
     ============================= media label dialog =============================
    
    please enter label for media in drive 0 (timeout in 300 sec)
     -> sdb1 #提示输入，指定设备标签，就是对要备份的设备做一个描述
    media label entered: "sdb1"
    
     --------------------------------- end dialog ---------------------------------
    
    xfsdump: creating dump session media file 0 (media 0, file 0)
    xfsdump: dumping ino map
    xfsdump: dumping directories
    xfsdump: dumping non-directory files
    xfsdump: ending media file
    xfsdump: media file size 32936 bytes
    xfsdump: dump size (non-dir files) : 1568 bytes
    xfsdump: dump complete: 70 seconds elapsed
    xfsdump: Dump Summary:
    xfsdump:   stream 0 /opt/dump_sdb1 OK (success)
    xfsdump: Dump Status: SUCCESS

### 免交互自动备份 像虚拟机的快照 ###

*  如果分区很大，数据很多，可能等的时间会很久，才会跳出提示输入的界面，这样不靠谱又没什么太大意义的提示会中断很久。
 *  免交互才是真的自动化。指定备份时免交互操作，方便后期做定时备份

[root@C8-3 ~]# time xfsdump -f /opt/dump_sdb1_3 /dev/sdb1 -L dump_1_3 -M 1_3
    xfsdump: using file dump (drive_simple) strategy
    xfsdump: version 3.1.8 (dump format 3.0) - type ^C for status and control
    xfsdump: level 0 dump of C8-3:/xfsTest
    xfsdump: dump date: Tue Oct 20 08:21:12 2020
    xfsdump: session id: 5308f2ab-6d0e-476f-9160-a72a37e56ca9
    xfsdump: session label: "dump_1_3"
    xfsdump: ino map phase 1: constructing initial dump list
    xfsdump: ino map phase 2: skipping (no pruning necessary)
    xfsdump: ino map phase 3: skipping (only one dump stream)
    xfsdump: ino map construction complete
    xfsdump: estimated dump size: 30016 bytes
    xfsdump: creating dump session media file 0 (media 0, file 0)
    xfsdump: dumping ino map
    xfsdump: dumping directories
    xfsdump: dumping non-directory files
    xfsdump: ending media file
    xfsdump: media file size 32936 bytes
    xfsdump: dump size (non-dir files) : 1568 bytes
    xfsdump: dump complete: 10 seconds elapsed
    xfsdump: Dump Summary:
    xfsdump:   stream 0 /opt/dump_sdb1_3 OK (success)
    xfsdump: Dump Status: SUCCESS
    
    real	0m10.058s
    user	0m0.000s
    sys	0m0.004s

\-L ：xfsdump 记录每次备份的 session 标头，这里可以填写针对此文件系统的简易说明  
\-M ：xfsdump 可以记录储存媒体的标头，这里可以填写此媒体的简易说明

### 备份指定目录 ###

参数：-s 文件路径 只对指定的文件进行备份，-s指定时，路径写的是相对文件系统根的路径(-s可以是文件或目录)  
要对/xfsTest下的m2/nb这个目录（完整路径是/xfsTest/m2/nb 直接写这个不行)进行备份，使用-s 参数

[root@C8-3 ~]# xfsdump -f /opt/dump_m2nb -s m2/nb /xfsTest -L dump_m2nb -M m2nb 
    xfsdump: using file dump (drive_simple) strategy
    xfsdump: version 3.1.8 (dump format 3.0) - type ^C for status and control
    xfsdump: level 0 dump of C8-3:/xfsTest
    xfsdump: dump date: Tue Oct 20 10:04:58 2020
    xfsdump: session id: 4cd18dc2-9a10-4538-b93c-3d4169c13eae
    xfsdump: session label: "dump_m2nb"
    xfsdump: ino map phase 1: constructing initial dump list
    xfsdump: ino map phase 2: skipping (no pruning necessary)
    xfsdump: ino map phase 3: skipping (only one dump stream)
    xfsdump: ino map construction complete
    xfsdump: estimated dump size: 21440 bytes
    xfsdump: creating dump session media file 0 (media 0, file 0)
    xfsdump: dumping ino map
    xfsdump: dumping directories
    xfsdump: dumping non-directory files
    xfsdump: ending media file
    xfsdump: media file size 22592 bytes
    xfsdump: dump size (non-dir files) : 0 bytes
    xfsdump: dump complete: 10 seconds elapsed
    xfsdump: Dump Summary:
    xfsdump:   stream 0 /opt/dump_m2nb OK (success)
    xfsdump: Dump Status: SUCCESS

### 查看备份信息与内容 ###

[root@C8-3 xfsTest]# xfsdump -I
    file system 0:
    	fs id:		d549d0dd-23a2-4223-abe5-96055a8f737a
    	session 0:
    		mount point:	C8-3:/xfsTest
    		device:		C8-3:/dev/sdb1
    		time:		Tue Oct 20 08:09:38 2020
    		session label:	"dump_sdb1"
    		session id:	3fdced05-235f-4926-9409-7c7e4081da84
    		level:		0
    		resumed:	NO
    		subtree:	NO
    		streams:	1
    		stream 0:
    			pathname:	/opt/dump_sdb1
    			start:		ino 131 offset 0
    			end:		ino 138 offset 0
    			interrupted:	NO
    			media files:	1
    			media file 0:
    				mfile index:	0
    				mfile type:	data
    				mfile size:	32936
    				mfile start:	ino 131 offset 0
    				mfile end:	ino 138 offset 0
    				media label:	"sdb1"
    				media id:	77e98c40-d588-4562-b801-6ba7dd2425bf
    	session 1:
    		mount point:	C8-3:/xfsTest
    		device:		C8-3:/dev/sdb1
    		time:		Tue Oct 20 08:17:18 2020
    		session label:	"dump_passwd"
    		session id:	e9970178-7a24-4c9d-b9c0-7e13f8d43c48
    		level:		0
    		resumed:	NO
    		subtree:	NO
    		streams:	1
    		stream 0:
    			pathname:	/opt/dump_sdb1
    			start:		ino 0 offset 0
    			end:		ino 0 offset 0
    			interrupted:	YES
    			media files:	0
    	session 2:
    		mount point:	C8-3:/xfsTest
    		device:		C8-3:/dev/sdb1
    		time:		Tue Oct 20 08:19:23 2020
    		session label:	"dump_12"
    		session id:	391b7c46-47f6-4760-b454-c7835045db09
    		level:		0
    		resumed:	NO
    		subtree:	NO
    		streams:	1
    		stream 0:
    			pathname:	/opt/dump_sdb1
    			start:		ino 0 offset 0
    			end:		ino 0 offset 0
    			interrupted:	YES
    			media files:	0
    	session 3:
    		mount point:	C8-3:/xfsTest
    		device:		C8-3:/dev/sdb1
    		time:		Tue Oct 20 08:20:12 2020
    		session label:	"dump_12"
    		session id:	d6613e91-8c68-4f40-b68b-e836fdf35568
    		level:		0
    		resumed:	NO
    		subtree:	NO
    		streams:	1
    		stream 0:
    			pathname:	/opt/dump_sdb1_1
    			start:		ino 131 offset 0
    			end:		ino 138 offset 0
    			interrupted:	NO
    			media files:	1
    			media file 0:
    				mfile index:	0
    				mfile type:	data
    				mfile size:	32936
    				mfile start:	ino 131 offset 0
    				mfile end:	ino 138 offset 0
    				media label:	"12"
    				media id:	f85b0aff-d362-429c-9804-0ca1071f812f
    	session 4:
    		mount point:	C8-3:/xfsTest
    		device:		C8-3:/dev/sdb1
    		time:		Tue Oct 20 08:21:12 2020
    		session label:	"dump_1_3"
    		session id:	5308f2ab-6d0e-476f-9160-a72a37e56ca9
    		level:		0
    		resumed:	NO
    		subtree:	NO
    		streams:	1
    		stream 0:
    			pathname:	/opt/dump_sdb1_3
    			start:		ino 131 offset 0
    			end:		ino 138 offset 0
    			interrupted:	NO
    			media files:	1
    			media file 0:
    				mfile index:	0
    				mfile type:	data
    				mfile size:	32936
    				mfile start:	ino 131 offset 0
    				mfile end:	ino 138 offset 0
    				media label:	"1_3"
    				media id:	78304c29-4353-4edc-a3cb-63454d898918
    xfsdump: Dump Status: SUCCESS

## 删除已备份的文件 ##

[root@C8-3 xfsTest]# cd
    [root@C8-3 ~]# rm -rf /xfsTest/*
    [root@C8-3 ~]# ls -a /xfsTest/

## 恢复文件系统 ##

语法：xfsrestore -f 指定恢复文件的位置 指定存放恢复后的文件的路径

[root@C8-3 ~]# mkdir /xfsTest-re #在其他分区创建恢复文件夹
    [root@C8-3 ~]# xfsrestore -f /opt/dump_sdb1 /xfsTest-re
    xfsrestore: using file dump (drive_simple) strategy
    xfsrestore: version 3.1.8 (dump format 3.0) - type ^C for status and control
    xfsrestore: searching media for dump
    xfsrestore: examining media file 0
    xfsrestore: dump description: 
    xfsrestore: hostname: C8-3
    xfsrestore: mount point: /xfsTest
    xfsrestore: volume: /dev/sdb1
    xfsrestore: session time: Tue Oct 20 08:09:38 2020
    xfsrestore: level: 0
    xfsrestore: session label: "dump_sdb1"
    xfsrestore: media label: "sdb1"
    xfsrestore: file system id: d549d0dd-23a2-4223-abe5-96055a8f737a
    xfsrestore: session id: 3fdced05-235f-4926-9409-7c7e4081da84
    xfsrestore: media id: 77e98c40-d588-4562-b801-6ba7dd2425bf
    xfsrestore: using online session inventory
    xfsrestore: searching media for directory dump
    xfsrestore: reading directories
    xfsrestore: 10 directories and 16 entries processed
    xfsrestore: directory post-processing
    xfsrestore: restoring non-directory files
    xfsrestore: restore complete: 0 seconds elapsed
    xfsrestore: Restore Summary:
    xfsrestore:   stream 0 /opt/dump_sdb1 OK (success)
    xfsrestore: Restore Status: SUCCESS
    [root@C8-3 ~]# ll /xfsTest-re/ #查看恢复的文件
    total 4
    -rw-r--r--. 1 root root    0 Oct 20 07:58 file1a.txt
    -rw-r--r--. 1 root root    0 Oct 20 07:58 file1b.txt
    -rw-r--r--. 1 root root    0 Oct 20 07:58 file2a.txt
    -rw-r--r--. 1 root root    0 Oct 20 07:58 file2b.txt
    -rw-r--r--. 1 root root    0 Oct 20 07:58 file3a.txt
    -rw-r--r--. 1 root root    0 Oct 20 07:58 file3b.txt
    drwxr-xr-x. 4 root root   26 Oct 20 07:59 m1
    drwxr-xr-x. 4 root root   26 Oct 20 07:59 m2
    drwxr-xr-x. 4 root root   26 Oct 20 07:59 m3
    -rw-r--r--. 1 root root 1469 Oct 20 07:58 passwd
    [root@C8-3 ~]# tree /xfsTest #对比源目录啥也没有了
    /xfsTest
    
    0 directories, 0 files
    [root@C8-3 ~]# tree /xfsTest-re/ #在恢复的目录中重建了目录结构
    /xfsTest-re/
    ├── file1a.txt
    ├── file1b.txt
    ├── file2a.txt
    ├── file2b.txt
    ├── file3a.txt
    ├── file3b.txt
    ├── m1
    │   ├── na
    │   └── nb
    ├── m2
    │   ├── na
    │   └── nb
    ├── m3
    │   ├── na
    │   └── nb
    └── passwd
    
    9 directories, 7 files

## 注： ##

使用 xfsdump 时，请注意下面下面的几个限制：

1.  xfsdump 不支持没有挂载的文件系统备份！所以只能备份已挂载的！
2.  xfsdump 必须使用 root 的权限才能操作 (涉及文件系统的关系)
3.  xfsdump 只能备份 XFS 文件系统
4.  xfsdump 备份下来的数据 (档案或储存媒体) 只能让 xfsrestore 解析
5.  xfsdump 是透过文件系统的 UUID 来分辨各个备份档的，因此不能备份两个具有相同 UUID 的文件系统

## 增量备份 ##

### 概念 ###

增量备份是指在一次全备份或上一次增量备份后，以后每次的备份只需备份与前一次相比增加或者被修改的文件。这就意味着，第一次增量备份的对象是进行全备后所产生的增加和修改的文件；第二次增量备份的对象是进行第一次增量备份后所产生的增加和修改的文件，以此类推。

### 优缺点 ###

*  优点：没有重复的备份数据，因此备份的数据量不大，备份所需的时间很短。
 *  缺点：数据恢复相对比较麻烦，它需要上一次全备份和所有增量备份的内容才能够完全恢复成功，并且它们必须沿着从全备份到依次增量备份的时间顺序逐个反推恢复，因此可能会延长的恢复时间

### 准备一个需要备份的目录 ###

[root@C8-3 ~]# tree /xfsTest
    /xfsTest
    ├── m1
    │   ├── na
    │   └── nb
    ├── m2
    │   ├── na
    │   └── nb
    ├── m3
    │   ├── na
    │   └── nb
    └── passwd

### 进行一次全面备份 ###

[root@C8-3 ~]# xfsdump -f /opt/xFull /xfsTest -L xF1 -M x1
    xfsdump: using file dump (drive_simple) strategy
    xfsdump: version 3.1.8 (dump format 3.0) - type ^C for status and control
    xfsdump: level 0 dump of C8-3:/xfsTest
    xfsdump: dump date: Tue Oct 20 10:43:59 2020
    xfsdump: session id: 4bc4262b-afa1-493f-8b21-33428325961d
    xfsdump: session label: "xF1"
    xfsdump: ino map phase 1: constructing initial dump list
    xfsdump: ino map phase 2: skipping (no pruning necessary)
    xfsdump: ino map phase 3: skipping (only one dump stream)
    xfsdump: ino map construction complete
    xfsdump: estimated dump size: 28096 bytes
    xfsdump: creating dump session media file 0 (media 0, file 0)
    xfsdump: dumping ino map
    xfsdump: dumping directories
    xfsdump: dumping non-directory files
    xfsdump: ending media file
    xfsdump: media file size 29000 bytes
    xfsdump: dump size (non-dir files) : 1568 bytes
    xfsdump: dump complete: 10 seconds elapsed
    xfsdump: Dump Summary:
    xfsdump:   stream 0 /opt/xFull OK (success)
    xfsdump: Dump Status: SUCCESS

### 添加一些东西进去 ###

[root@C8-3 ~]# echo hellow >> /xfsTest/passwd
    [root@C8-3 ~]# touch /xfsTest/nb3.txt

### 删掉一些东西 ###

[root@C8-3 ~]# rm -rf /xfsTest/m2
    [root@C8-3 ~]# ls /xfsTest
    m1  m3  nb3.txt  passwd
    [root@C8-3 ~]# ll /xfsTest
    total 4
    drwxr-xr-x. 4 root root   26 Oct 20 07:59 m1
    drwxr-xr-x. 4 root root   26 Oct 20 07:59 m3
    -rw-r--r--. 1 root root    0 Oct 20 10:47 nb3.txt
    -rw-r--r--. 1 root root 1476 Oct 20 10:46 passwd

### 进行第一次增量备份 ###

[root@C8-3 ~]# xfsdump -l 1 -f /opt/xBL1 /xfsTest -L xBL1 -M xB1

### 进行第二次增量备份 ###

添加点东西、再删点东西

[root@C8-3 ~]# mkdir /xfsTest/xBl2
    [root@C8-3 ~]# rm -rf /xfsTest/m3

然后接茬进行一次2级增量备份

[root@C8-3 ~]# xfsdump -l 2 -f /opt/xBL2 /xfsTest -L xBL2 -M xB2

### 删除已备份的所有数据 ###

[root@C8-3 ~]# rm -rf /xfsTest/*
    [root@C8-3 ~]# ll /xfsTest
    total 0

### 恢复数据 ###

现在进行恢复，要想恢复全部全部数据，包括新添加的文件，如何恢复？  
步骤：  
1、先恢复完全备份  
2、情况1: 恢复最后一次增量备份（如果两次增量备份都是1级的，所以只需要恢复最后一个增量就可以了。  
3、情况2：如果你做的是第一次是1级备，第二次是2级备，那么你在恢复的时候就需要先恢复完全备份，然后是1级备，最后是2级备）

\#\#\#\#直接恢复最后一次增量备份

[root@C8-3 ~]# xfsrestore -f /opt/xBL2 /xfsTest
    [root@C8-3 ~]# tree /xfsTest
    /xfsTest
    └── xBl2

发现只恢复了最后一次建立的文件夹

#### 直接恢复第一次增量备份 ####

[root@C8-3 ~]# rm -rf /xfsTest/*
    [root@C8-3 ~]# ll /xfsTest
    total 0
    [root@C8-3 ~]# xfsrestore -f /opt/xBL1 /xfsTest
    [root@C8-3 ~]# tree /xfsTest
    /xfsTest
    ├── nb3.txt
    └── passwd

发现只恢复了第一次增量备份前添加和修改的文件、文件夹

#### 直接恢复第一次全备份 ####

[root@C8-3 ~]# xfsrestore -f /opt/xFull /xfsTest
    [root@C8-3 ~]# tree /xfsTest
    /xfsTest
    ├── m1
    │   ├── na
    │   └── nb
    ├── m2
    │   ├── na
    │   └── nb
    ├── m3
    │   ├── na
    │   └── nb
    └── passwd
    
    9 directories, 1 file
    [root@C8-3 ~]# ll /xfsTest
    total 4
    drwxr-xr-x. 4 root root   26 Oct 20 07:59 m1
    drwxr-xr-x. 4 root root   26 Oct 20 07:59 m2
    drwxr-xr-x. 4 root root   26 Oct 20 07:59 m3
    -rw-r--r--. 1 root root 1469 Oct 20 07:58 passwd

这时候就恢复到了第一次增量备份之前的状态

如果要恢复到最后删除所有文件时候的状态，就需要按顺序依次恢复增量一和增量二的备份内容。

到此，数据恢复成功了。