10.逻辑卷管理器（LVM） - 《linux base》

LVM介绍
实现过程
实现逻辑卷
关于逻辑卷对应的设备名
扩展逻辑卷
缩减逻辑卷
删除/迁移物理卷pv
逻辑卷快照

LVM介绍

LVM: Logical Volume Manager 可以允许对卷进行方便操作的抽象层，包括重新设定文件系统的大小，允许在多个物理设备间重新组织文件系统

LVM可以弹性的更改LVM的容量：

   通过交换PE来进行资料的转换，将原来LV内的PE转移到其他的设备中以降低LV的容量，或将其他设备中的PE加到LV中以加大容量<br />![image.png](https://cdn.nlark.com/yuque/0/2021/png/22154944/1626702564504-adce90a4-2dca-4949-84ab-d39d81838289.png#align=left&display=inline&height=323&margin=%5Bobject%20Object%5D&name=image.png&originHeight=323&originWidth=620&size=60715&status=done&style=none&width=620)

实现过程

将设备指定为物理卷
用一个或者多个物理卷来创建一个卷组，物理卷是用固定大小的物理区域（Physical Extent，PE）来定义的
在物理卷上创建的逻辑卷，是由物理区域（PE）组成
可以在逻辑卷上创建文件系统并挂载

实现逻辑卷

物理卷pv管理工具

#显示pv信息
pvs
pvdisplay
#创建pv
pvcreate /dev/DEVICE
#删除pv
pvremove /dev/DEVICE

卷组vg管理工具

#显示卷组信息
vgs
vgdisplay
#创建卷组
vgcreate [-s #[kKmMgGtTpPeE]] VolumeGroupName PhysicalDevicePath [PhysicalDevicePath...]
#示例
vgcreate -s 16M vg0 /dev/sdb /dev/sdc  # -s指定PE的大小,默认4M
#管理卷组
vgextend VolumeGroupName PhysicalDevicePath [PhysicalDevicePath...]
vgreduce VolumeGroupName PhysicalDevicePath [PhysicalDevicePath...]
#删除卷组
(1)先做pvmove
(2)再做vgremove

逻辑卷lv管理工具

#显示逻辑卷
lvs
Lvdisplay
#创建逻辑卷
lvcreate -L #[mMgGtT] -n NAME VolumeGroup
#删除逻辑卷
lvremove /dev/VG_NAME/LV_NAME

例子：创建逻辑卷

例子：给/dev/sdb 分配一个5G空间做物理卷，和sdc整个块设备做物理卷。两者合成一个逻辑卷

（1）分配5G空间，得到sdb1

[root@centos8 ~]#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.
Command (m for help): n
Partition type
   p   primary (0 primary, 0 extended, 4 free)
   e   extended (container for logical partitions)
Select (default p): p
Partition number (1-4, default 1): 
First sector (2048-41943039, default 2048): 
Last sector, +sectors or +size{K,M,G,T,P} (2048-41943039, default 41943039): +5G
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@centos8 ~]#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  100G  0 part /
├─sda3   8:3    0    2G  0 part [SWAP]
├─sda4   8:4    0    1K  0 part 
└─sda5   8:5    0   50G  0 part /data
sdb      8:16   0   20G  0 disk 
└─sdb1   8:17   0    5G  0 part        #得到sdb1
sdc      8:32   0   10G  0 disk 
sr0     11:0    1  8.6G  0 rom

然后将sdb1类型改成“Linux LVM” ，ID为8e

[root@centos8 ~]#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.
Command (m for help): p
Disk /dev/sdb: 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: 0x781c65fc
Device     Boot Start      End  Sectors Size Id Type
/dev/sdb1        2048 10487807 10485760   5G 83 Linux    # 当前sdb1的Id是83， type是“Linux”
Command (m for help): t                   #t修改类型
Selected partition 1
Hex code (type L to list all codes): L     #L查看所有的类型列表
 0  Empty           24  NEC DOS         81  Minix / old Lin bf  Solaris        
 1  FAT12           27  Hidden NTFS Win 82  Linux swap / So c1  DRDOS/sec (FAT-
 2  XENIX root      39  Plan 9          83  Linux           c4  DRDOS/sec (FAT-
 3  XENIX usr       3c  PartitionMagic  84  OS/2 hidden or  c6  DRDOS/sec (FAT-
 4  FAT16 <32M      40  Venix 80286     85  Linux extended  c7  Syrinx         
 5  Extended        41  PPC PReP Boot   86  NTFS volume set da  Non-FS data    
 6  FAT16           42  SFS             87  NTFS volume set db  CP/M / CTOS / .
 7  HPFS/NTFS/exFAT 4d  QNX4.x          88  Linux plaintext de  Dell Utility   
 8  AIX             4e  QNX4.x 2nd part 8e  Linux LVM       df  BootIt         
 9  AIX bootable    4f  QNX4.x 3rd part 93  Amoeba          e1  DOS access     
 a  OS/2 Boot Manag 50  OnTrack DM      94  Amoeba BBT      e3  DOS R/O        
 b  W95 FAT32       51  OnTrack DM6 Aux 9f  BSD/OS          e4  SpeedStor      
 c  W95 FAT32 (LBA) 52  CP/M            a0  IBM Thinkpad hi ea  Rufus alignment
 e  W95 FAT16 (LBA) 53  OnTrack DM6 Aux a5  FreeBSD         eb  BeOS fs        
 f  W95 Extd (LBA)  54  OnTrackDM6      a6  OpenBSD         ee  GPT            
10  OPUS            55  EZ-Drive        a7  NeXTSTEP        ef  EFI (FAT-12/16/
11  Hidden FAT12    56  Golden Bow      a8  Darwin UFS      f0  Linux/PA-RISC b
12  Compaq diagnost 5c  Priam Edisk     a9  NetBSD          f1  SpeedStor      
14  Hidden FAT16 <3 61  SpeedStor       ab  Darwin boot     f4  SpeedStor      
16  Hidden FAT16    63  GNU HURD or Sys af  HFS / HFS+      f2  DOS secondary  
17  Hidden HPFS/NTF 64  Novell Netware  b7  BSDI fs         fb  VMware VMFS    
18  AST SmartSleep  65  Novell Netware  b8  BSDI swap       fc  VMware VMKCORE 
1b  Hidden W95 FAT3 70  DiskSecure Mult bb  Boot Wizard hid fd  Linux raid auto
1c  Hidden W95 FAT3 75  PC/IX           bc  Acronis FAT32 L fe  LANstep        
1e  Hidden W95 FAT1 80  Old Minix       be  Solaris boot    ff  BBT   
Hex code (type L to list all codes): 8e      # 8e  Linux LVM
Changed type of partition 'Linux' to 'Linux LVM'.
Command (m for help): p
Disk /dev/sdb: 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: 0x781c65fc
Device     Boot Start      End  Sectors Size Id Type
/dev/sdb1        2048 10487807 10485760   5G 8e Linux LVM          #成功将类型改成Linux LVM
Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.

（2）创建物理卷

#创建两个物理卷 pvcreate
pvcreate /dev/sdb1 /dev/sdc
#查看物理卷
[root@centos8 ~]#pvs
  PV         VG Fmt  Attr PSize  PFree 
  /dev/sdb1     lvm2 ---   5.00g  5.00g
  /dev/sdc      lvm2 ---  10.00g 10.00g
[root@centos8 ~]#pvdisplay 
  "/dev/sdb1" is a new physical volume of "5.00 GiB"
  --- NEW Physical volume ---
  PV Name               /dev/sdb1
  VG Name               
  PV Size               5.00 GiB
  Allocatable           NO
  PE Size               0   
  Total PE              0
  Free PE               0
  Allocated PE          0
  PV UUID               9AegYM-t6pf-N8DS-UZHe-1A7j-qsPg-PUbYFy
  "/dev/sdc" is a new physical volume of "10.00 GiB"
  --- NEW Physical volume ---
  PV Name               /dev/sdc
  VG Name               
  PV Size               10.00 GiB
  Allocatable           NO
  PE Size               0   
  Total PE              0
  Free PE               0
  Allocated PE          0
  PV UUID               DJNagH-p4H4-YCck-7mZJ-D6t5-TnYz-y7XYEF

（3）创建卷组 vgcreate

[root@centos8 ~]#vgcreate  vg0 /dev/sdc /dev/sdb1
  Volume group "vg0" successfully created
#或者指定PE大小
vgcreate -s 16M vg0 /dev/sdb /dev/sdc  # -s指定PE的大小,默认4M
#查看信息
[root@centos8 ~]#vgs
  VG  #PV #LV #SN Attr   VSize  VFree 
  vg0   2   0   0 wz--n- 14.99g 14.99g
[root@centos8 ~]#vgdisplay 
  --- Volume group ---
  VG Name               vg0
  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               14.99 GiB
  PE Size               4.00 MiB
  Total PE              3838
  Alloc PE / Size       0 / 0   
  Free  PE / Size       3838 / 14.99 GiB
  VG UUID               vjvvb9-RXlU-JdwY-Ajrn-J3Np-zsQb-3XyUKi

（3）创建逻辑卷lv

[root@centos8 ~]#lvcreate -n mysql -L 1G vg0   #-L 指定大小  -l以PE为单位指定大小
  Logical volume "mysql" created.
 #查看
[root@centos8 ~]#lvdisplay 
  --- Logical volume ---
  LV Path                /dev/vg0/mysql
  LV Name                mysql
  VG Name                vg0
  LV UUID                fUcq3s-GhSD-YI1U-lhPv-PZCs-naAJ-UGuqpX
  LV Write Access        read/write
  LV Creation host, time centos8.3.magedu.com, 2021-07-19 21:22:29 +0800
  LV Status              available
  # open                 0
  LV Size                1.00 GiB
  Current LE             256
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:0
[root@centos8 ~]#lvs
  LV    VG  Attr       LSize Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  mysql vg0 -wi-a----- 1.00g

（4）给逻辑卷vg0-mysql创建文件系统，并进行挂着

#创建文件系统
[root@centos8 ~]#mkfs.ext4 /dev/vg0/mysql 
#编辑/etc/fstab块设备文件 增加挂载点
[root@centos8 ~]#vim /etc/fstab

#查看挂载是否成功
[root@centos8 ~]#mount -a              #挂载点/mnt/mysql目录不存在 
mount: /mnt/mysql: mount point does not exist.
[root@centos8 ~]#mkdir /mnt/mysql     #创建 
[root@centos8 ~]#mount -a
[root@centos8 ~]#df    
Filesystem            1K-blocks    Used Available Use% Mounted on
devtmpfs                 886960       0    886960   0% /dev
tmpfs                    916500       0    916500   0% /dev/shm
tmpfs                    916500    9580    906920   2% /run
tmpfs                    916500       0    916500   0% /sys/fs/cgroup
/dev/sda2             104806400 6128280  98678120   6% /
/dev/sda5              52403200  398404  52004796   1% /data
/dev/sda1                999320  203380    727128  22% /boot
tmpfs                    183300    1180    182120   1% /run/user/42
tmpfs                    183300       0    183300   0% /run/user/0
/dev/mapper/vg0-mysql    999320    2564    927944   1% /mnt/mysql            #挂载成功

[root@centos8 ~]#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  100G  0 part /
├─sda3        8:3    0    2G  0 part [SWAP]
├─sda4        8:4    0    1K  0 part 
└─sda5        8:5    0   50G  0 part /data
sdb           8:16   0   20G  0 disk 
└─sdb1        8:17   0    5G  0 part 
sdc           8:32   0   10G  0 disk 
├─vg0-mysql 253:0    0    1G  0 lvm  /mnt/mysql
└─vg0-log   253:1    0    2G  0 lvm  
sr0          11:0    1  8.6G  0 rom

关于逻辑卷对应的设备名

第一个逻辑卷对应设备名：/dev/dm-#
dm: device mapper，将一个或多个底层块设备组织成一个逻辑设备的模块

/dev/vg0/mysql
/dev/dm-0

[root@centos8 ~]#ll /dev/vg0/mysql 
lrwxrwxrwx. 1 root root 7 Jul 19 21:22 /dev/vg0/mysql -> ../dm-0
[root@centos8 ~]#ll /dev/dm-0
brw-rw----. 1 root disk 253, 0 Jul 19 21:22 /dev/dm-0

扩展逻辑卷

实现方法

#两步实现
#第一步实现逻辑卷的空间扩展
lvextend -L [+]#[mMgGtT] /dev/VG_NAME/LV_NAME
#第二步实现文件系统的扩展
#针对ext
resize2fs /dev/VG_NAME/LV_NAME
#针对xfs 
xfs_growfs MOUNTPOINT 
#一步实现容间和文件系统的扩展   使用-r选项 
lvresize -r -l +100%FREE /dev/VG_NAME/LV_NAME

lvextend说明 ```bash lvextend -l +50%free /dev/vg0/mysql #在剩余可用空间里面取 50% 增加到 /dev/vg0/mysql 逻辑卷里

lvextend -l 50%free /dev/vg0/mysql #将/dev/vg0/mysql 逻辑卷扩展到50%

lvextend -L +1G /dev/vg0/log # 给/dev/vg0/log逻辑卷增加 1G 的空间

**例子：拓展逻辑卷： 给/dev/vg0/mysql 增加空间**<br />第一步实现逻辑卷的空间扩展
```bash
[root@centos8 ~]#lvextend -l +50%free  /dev/vg0/mysql 
  Size of logical volume vg0/mysql changed from 1.00 GiB (256 extents) to <7.02 GiB (1797 extents).
  Logical volume vg0/mysql successfully resized.
[root@centos8 ~]#lvdisplay 
  --- Logical volume ---
  LV Path                /dev/vg0/mysql
  LV Name                mysql
  VG Name                vg0
  LV UUID                fUcq3s-GhSD-YI1U-lhPv-PZCs-naAJ-UGuqpX
  LV Write Access        read/write
  LV Creation host, time centos8.3.magedu.com, 2021-07-19 21:22:29 +0800
  LV Status              available
  # open                 1
  LV Size                <7.02 GiB
  Current LE             1797
  Segments               2
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:0
  --- Logical volume ---
  LV Path                /dev/vg0/log
  LV Name                log
  VG Name                vg0
  LV UUID                x4p6C9-4tyu-SPEV-zKIM-oQK0-b7IM-PXnqtP
  LV Write Access        read/write
  LV Creation host, time centos8.3.magedu.com, 2021-07-19 21:27:18 +0800
  LV Status              available
  # open                 1
  LV Size                1.95 GiB
  Current LE             500
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:1
[root@centos8 ~]#vgdisplay 
  --- Volume group ---
  VG Name               vg0
  System ID             
  Format                lvm2
  Metadata Areas        2
  Metadata Sequence No  4
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                2
  Open LV               2
  Max PV                0
  Cur PV                2
  Act PV                2
  VG Size               14.99 GiB
  PE Size               4.00 MiB
  Total PE              3838
  Alloc PE / Size       2297 / 8.97 GiB
  Free  PE / Size       1541 / <6.02 GiB
  VG UUID               vjvvb9-RXlU-JdwY-Ajrn-J3Np-zsQb-3XyUKi

第二步实现文件系统的扩展


[root@centos8 ~]#df -Th
Filesystem            Type      Size  Used Avail Use% Mounted on
devtmpfs              devtmpfs  867M     0  867M   0% /dev
tmpfs                 tmpfs     896M     0  896M   0% /dev/shm
tmpfs                 tmpfs     896M  9.4M  886M   2% /run
tmpfs                 tmpfs     896M     0  896M   0% /sys/fs/cgroup
/dev/sda2             xfs       100G  5.9G   95G   6% /
/dev/sda5             xfs        50G  1.2G   49G   3% /data
/dev/mapper/vg0-mysql ext4      976M  804M  105M  89% /mnt/mysql   #mysql空间未改变
/dev/sda1             ext4      976M  199M  711M  22% /boot
tmpfs                 tmpfs     180M  1.2M  178M   1% /run/user/42
tmpfs                 tmpfs     180M     0  180M   0% /run/user/0
/dev/mapper/vg0-log   xfs       2.0G   47M  1.9G   3% /mnt/log
#第二步实现文件系统的扩展
[root@centos8 ~]#resize2fs /dev/vg0/mysql
resize2fs 1.45.6 (20-Mar-2020)
Filesystem at /dev/vg0/mysql is mounted on /mnt/mysql; on-line resizing required
old_desc_blocks = 1, new_desc_blocks = 1
The filesystem on /dev/vg0/mysql is now 1840128 (4k) blocks long.
[root@centos8 ~]#df -hT
Filesystem            Type      Size  Used Avail Use% Mounted on
devtmpfs              devtmpfs  867M     0  867M   0% /dev
tmpfs                 tmpfs     896M     0  896M   0% /dev/shm
tmpfs                 tmpfs     896M  9.4M  886M   2% /run
tmpfs                 tmpfs     896M     0  896M   0% /sys/fs/cgroup
/dev/sda2             xfs       100G  5.9G   95G   6% /
/dev/sda5             xfs        50G  1.2G   49G   3% /data
/dev/mapper/vg0-mysql ext4      6.9G  806M  5.8G  12% /mnt/mysql   #mysql空间已扩展成功
/dev/sda1             ext4      976M  199M  711M  22% /boot
tmpfs                 tmpfs     180M  1.2M  178M   1% /run/user/42
tmpfs                 tmpfs     180M     0  180M   0% /run/user/0
/dev/mapper/vg0-log   xfs       2.0G   47M  1.9G   3% /mnt/log

例子：拓展逻辑卷：给/dev/vg0/mysql 增加空间：一步实现

#使用-r 选项
[root@centos8 ~]#lvextend -r -l +100%free /dev/vg0/mysql  
  Size of logical volume vg0/mysql changed from <7.02 GiB (1797 extents) to <12.04 GiB (3082 extents).
  Logical volume vg0/mysql successfully resized.
resize2fs 1.45.6 (20-Mar-2020)
Filesystem at /dev/mapper/vg0-mysql is mounted on /mnt/mysql; on-line resizing required
old_desc_blocks = 1, new_desc_blocks = 2
The filesystem on /dev/mapper/vg0-mysql is now 3155968 (4k) blocks long.
[root@centos8 ~]#df -Th
Filesystem            Type      Size  Used Avail Use% Mounted on
devtmpfs              devtmpfs  867M     0  867M   0% /dev
tmpfs                 tmpfs     896M     0  896M   0% /dev/shm
tmpfs                 tmpfs     896M  9.4M  886M   2% /run
tmpfs                 tmpfs     896M     0  896M   0% /sys/fs/cgroup
/dev/sda2             xfs       100G  5.9G   95G   6% /
/dev/sda5             xfs        50G  1.2G   49G   3% /data
/dev/mapper/vg0-mysql ext4       12G  807M   11G   7% /mnt/mysql
/dev/sda1             ext4      976M  199M  711M  22% /boot
tmpfs                 tmpfs     180M  1.2M  178M   1% /run/user/42
tmpfs                 tmpfs     180M     0  180M   0% /run/user/0
/dev/mapper/vg0-log   xfs       3.0G   54M  2.9G   2% /mnt/log

如果当前卷组vg的可用空间不足，但依然需要给逻辑卷lv扩展空间，就需要先增加pv，进而增加vg，再从vg中给lv增加空间

例子：扩展卷组vg

#pv可用空间不足，造成vg空间不足就需要增加pv进而增加vg
[root@centos8 ~]#pvs
  PV         VG  Fmt  Attr PSize   PFree
  /dev/sdb1  vg0 lvm2 a--   <5.00g    0 
  /dev/sdc   vg0 lvm2 a--  <10.00g    0

   #利用sdb的剩余空间创建一个新的pv 加入到vg0中
[root@centos8 ~]#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  100G  0 part /
├─sda3          8:3    0    2G  0 part [SWAP]
├─sda4          8:4    0    1K  0 part 
└─sda5          8:5    0   50G  0 part /data
sdb             8:16   0   20G  0 disk                #剩余15G                  
└─sdb1          8:17   0    5G  0 part 
  └─vg0-mysql 253:0    0   12G  0 lvm  /mnt/mysql
sdc             8:32   0   10G  0 disk 
├─vg0-mysql   253:0    0   12G  0 lvm  /mnt/mysql
└─vg0-log     253:1    0    3G  0 lvm  /mnt/log
sr0            11:0    1  8.6G  0 rom  
[root@centos8 ~]#fdisk /dev/sdb     #创建分区
Device     Boot    Start      End  Sectors Size Id Type
/dev/sdb1           2048 10487807 10485760   5G 8e Linux LVM
/dev/sdb2       10487808 41943039 31455232  15G 8e Linux LVM   #创建了新的分区  类型是Linux LVM 
#创建新的pv
[root@centos8 ~]#pvcreate /dev/sdb2
  Physical volume "/dev/sdb2" successfully created.
[root@centos8 ~]#pvs
  PV         VG  Fmt  Attr PSize   PFree  
  /dev/sdb1  vg0 lvm2 a--   <5.00g      0 
  /dev/sdb2      lvm2 ---  <15.00g <15.00g
  /dev/sdc   vg0 lvm2 a--  <10.00g      0 
#扩展vg  利用新的pv扩展vg0 
[root@centos8 ~]#vgextend vg0 /dev/sdb2
  Volume group "vg0" successfully extended
[root@centos8 ~]#vgs            #查看空间是否已扩展成功
  VG  #PV #LV #SN Attr   VSize   VFree  
  vg0   3   2   0 wz--n- <29.99g <15.00g
[root@centos8 ~]#vgdisplay 
  --- Volume group ---
  VG Name               vg0
  System ID             
  Format                lvm2
  Metadata Areas        3
  Metadata Sequence No  7
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                2
  Open LV               2
  Max PV                0
  Cur PV                3
  Act PV                3
  VG Size               <29.99 GiB
  PE Size               4.00 MiB
  Total PE              7677
  Alloc PE / Size       3838 / 14.99 GiB
  Free  PE / Size       3839 / <15.00 GiB
  VG UUID               vjvvb9-RXlU-JdwY-Ajrn-J3Np-zsQb-3XyUKi

缩减逻辑卷

注意：缩减有数据损坏的风险，建议先备份再缩减，xfs文件系统不支持缩减

缩减逻辑卷的5个步骤

缩减逻辑卷的5个步骤
（1）取消挂载 ： 
umount /dev/VG_NAME/LV_NAME
（2）检查文件系统完整性
e2fsck -f /dev/VG_NAME/LV_NAME
（3）缩减文件系统 指定缩减大小
resize2fs /dev/VG_NAME/LV_NAME #[mMgGtT]
（4）缩减逻辑卷  指定大小需要与第3步一致
lvreduce -L [-]#[mMgGtT] /dev/VG_NAME/LV_NAME
（5）重新挂载
mount /dev/VG_NAME/LV_NAME mountpoint

例子：

（1）取消挂载

[root@centos8 ~]#umount /mnt/mysql

（2）检查文件系统完整性

[root@centos8 ~]#e2fsck -f /dev/vg0/mysql 
e2fsck 1.45.6 (20-Mar-2020)
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
/dev/vg0/mysql: 137/794624 files (0.0% non-contiguous), 264494/3155968 blocks

（3）缩减文件系统指定缩减大小

[root@centos8 ~]#resize2fs /dev/vg0/mysql 2G
resize2fs 1.45.6 (20-Mar-2020)
Resizing the filesystem on /dev/vg0/mysql to 524288 (4k) blocks.
The filesystem on /dev/vg0/mysql is now 524288 (4k) blocks long.

（4）缩减逻辑卷指定大小需要与第3步一致

[root@centos8 ~]#lvreduce -L 2G /dev/vg0/mysql 
  WARNING: Reducing active logical volume to 2.00 GiB.
  THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce vg0/mysql? [y/n]: y
  Size of logical volume vg0/mysql changed from <12.04 GiB (3082 extents) to 2.00 GiB (512 extents).
  Logical volume vg0/mysql successfully resized.

（5）重新挂载

[root@centos8 ~]#mount -a

删除/迁移物理卷pv

#查看当前的pv  目前需要迁移/dev/sdc 
[root@centos8 ~]#pvs 
  PV         VG  Fmt  Attr PSize   PFree  
  /dev/sdb1  vg0 lvm2 a--   <5.00g  <5.00g
  /dev/sdb2  vg0 lvm2 a--  <15.00g <15.00g
  /dev/sdc   vg0 lvm2 a--  <10.00g   5.04g

(1)空间移动（释放）

注意：pvmove移动的是空间。空间移动了，数据也会移动

（2）然后从组卷vg中删除 /dev/sdc ;
（3）再从pv中删除

# 从组卷vg0 删除  /dev/sdc
[root@centos8 ~]#vgreduce vg0 /dev/sdc
  Removed "/dev/sdc" from volume group "vg0"
[root@centos8 ~]#pvs
  PV         VG  Fmt  Attr PSize   PFree  
  /dev/sdb1  vg0 lvm2 a--   <5.00g  44.00m
  /dev/sdb2  vg0 lvm2 a--  <15.00g <15.00g
  /dev/sdc       lvm2 ---   10.00g  10.00g    # 可以看到不再是vg0 
[root@centos8 ~]#vgs
  VG  #PV #LV #SN Attr   VSize  VFree  
  vg0   2   2   0 wz--n- 19.99g <15.04g
 #从pvs中删除 /dev/sdc
[root@centos8 ~]#pvremove /dev/sdc 
  Labels on physical volume "/dev/sdc" successfully wiped.
[root@centos8 ~]#pvs        
  PV         VG  Fmt  Attr PSize   PFree  
  /dev/sdb1  vg0 lvm2 a--   <5.00g  44.00m
  /dev/sdb2  vg0 lvm2 a--  <15.00g <15.00g
[root@centos8 ~]#

逻辑卷快照

逻辑卷快照工作原理

在生成快照时会分配给它一定的空间，但只有在原来的逻辑卷或者快照有所改变才会使用这些空间
当原来的逻辑卷中有所改变时，会将旧的数据复制到快照中
快照中只含有原来的逻辑卷中更改的数据或者自生成快照后的快照中更改的数据

实现方法

mkfs.xfs /dev/vg0/data
mount /dev/vg0/data/ /mnt/data
#为现有逻辑卷创建快照,注意ext4必须使用-p r 实现只读
lvcreate -l 64 -s -n data-snapshot /dev/vg0/data
#挂载快照,xfs注意要使用-o ro实现只读,访止快照被修改
mkdir  -p /mnt/snap
mount -o ro,nouuid /dev/vg0/data-snapshot   /mnt/snap    # xfs必须添加nouuid，否则无法挂载成功
#恢复快照
umount /dev/vg0/data-snapshot
umount /dev/vg0/data
lvconvert --merge /dev/vg0/data-snapshot 
#删除快照
umount /mnt/snap
lvremove /dev/vg0/data-snapshot