在配置时，指定磁盘大小
不管在虚拟磁盘上实际存储多少数据，都将占用相同大小宿主机的磁盘空间

初始空间占用小
随着空间的使用逐渐增长到最大容量，但是只根据需求使用更多的空间

因为创建是差异磁盘，所以只保存变更的数据
例如，将操作系统安装在父盘，然后创建差异化磁盘来执行进一步配置

此为默认磁盘格式,但并是一种真正的磁盘格式，而是代表虚拟机所使用的原始镜像,它并不存储元数据，因此可作为保证虚拟机兼容性的候选方案。然而，也正因为它不存储元数据，因此不支持某些高级特往，比如快照和压缩等格式简单，容易转换为其他的格式。
如果主机文件系统允许，raw 文件可以是预分配（pre-allocated）或 稀疏（sparse）。稀疏文件根据需求分配主机磁盘空间，因此它是一种精简配置形式（thin provisioning）。预分配文件的所有空间需要被预先分配，但它比稀疏文件性能好。当对磁盘 I/O 性能要求非常高，而且通常不需要通过网络传输镜像文件时，可以使用 raw文件
优点 : 性能好
缺点 : 空间占用大,功能较少,生产不推荐使用

copy-on-write格式，昙花一现

QEMU早期的copy-on-write格式，过渡性方案

qcow2 镜像文件提供许多高级磁盘镜像特征，如快照、压缩及加密。它们可以用来代表通过模板镜像创建的虚拟机。因为只有虚拟机写入的扇区部分才会分配在镜像中，所以 qcow2 文件的网络传输效率较高。RHEL 7.0 及更新版本支持 qcow2 v3 镜像文件格式按需进行分配磁盘空间，不管文件系统是否支持
优点 :
空间节约,功能丰富
支持快照
支持zlib的磁盘压缩
支持AES的加密
缺点 : 性能较差,生产推荐使用

案例：查看不同磁盘文件格式支持选项
#raw
[root@ubuntu2204 ~]#qemu-img create -f raw -o ?
Supported raw options:
size=<size> - Virtual disk size

The protocol level may support further options.
Specify the target filename to include those options.

#qcow2
[root@ubuntu2204 ~]#qemu-img create -f qcow2 -o ?
Supported qcow2 options:
backing_file=<str> - File name of a base image
backing_fmt=<str> - Image format of the base image
cluster_size=<size> - qcow2 cluster size
compat=<str> - Compatibility level (v2 [0.10] or v3 [1.1])
compression_type=<str> - Compression method used for image cluster compression
data_file=<str> - File name of an external data file
data_file_raw=<bool (on/off)> - The external data file must stay valid as a raw image
encrypt.cipher-alg=<str> - Name of encryption cipher algorithm
encrypt.cipher-mode=<str> - Name of encryption cipher mode
encrypt.format=<str> - Encrypt the image, format choices: 'aes', 'luks'
encrypt.hash-alg=<str> - Name of encryption hash algorithm
encrypt.iter-time=<num> - Time to spend in PBKDF in milliseconds
encrypt.ivgen-alg=<str> - Name of IV generator algorithm
encrypt.ivgen-hash-alg=<str> - Name of IV generator hash algorithm
encrypt.key-secret=<str> - ID of secret providing qcow AES key or LUKS passphrase
encryption=<bool (on/off)> - Encrypt the image with format 'aes'. (Deprecated in favor of encrypt.format=aes)
extended_l2=<bool (on/off)> - Extended L2 tables
lazy_refcounts=<bool (on/off)> - Postpone refcount updates
preallocation=<str> - Preallocation mode (allowed values: off, metadata, falloc, full)
refcount_bits=<num> - Width of a reference count entry in bits
size=<size> - Virtual disk size

The protocol level may support further options.
Specify the target filename to include those options.

VMware环境当中默认使用的磁盘格式

微软默认采用的文件格式

VirtualBox 采用的文件格式

[root@ubuntu2204 ~]#qemu-img --help|grep Support
Supported formats: blkdebug blklogwrites blkverify bochs cloop compress copy-before-write copy-on-read dmg file ftp ftps gluster host_cdrom host_device http https iscsi iser luks nbd null-aio null-co nvme parallels preallocate qcow qcow2 qed quorum raw rbd replication ssh throttle vdi vhdx vmdk vpc vvfat

#qemu-img 包括以下子命令
check #检查完整性
create #创建镜像
commit #提交更改
compare #比较
convert #转换
info #获得信息
map #映射
snapshot #快照管理
rebase #在已有的镜像的基础上创建新的镜像
resize #调整大小
amend #修订镜像格式选项

#格式：qemu-img create [-q] [--object objectdef] [-f fmt] [-b backing_file] [-F backing_fmt] [-u] [-o options] filename [size]

#案例1：创建raw格式非稀疏文件
[root@ubuntu2204 ~]#dd if=/dev/zero of=/opt/vm2.img bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 6.2694 s, 171 MB/s
[root@ubuntu2204 ~]#qemu-img info /opt/vm2.img
image: /opt/vm2.img
file format: raw
virtual size: 1 GiB (1073741824 bytes) --> 显示1G
disk size: 1 GiB --> 实际占用磁盘1G

#案例2：创建raw格式稀疏文件
[root@ubuntu2204 ~]#dd if=/dev/zero of=/opt/vm3.img bs=1M count=0 seek=1024
0+0 records in
0+0 records out
0 bytes copied, 0.000217691 s, 0.0 kB/s
[root@ubuntu2204 ~]#qemu-img info /opt/vm3.img
image: /opt/vm3.img
file format: raw
virtual size: 1 GiB (1073741824 bytes) --> 显示1G
disk size: 0 B --> 实际占用磁盘1字节

#案例3：指定将非稀疏文件复制为稀疏格式文件
[root@ubuntu2204 ~]#cp --sparse=always /opt/vm2.img /opt/vm2.img.bk
[root@ubuntu2204 ~]#qemu-img info /opt/vm2.img
image: /opt/vm2.img
file format: raw
virtual size: 1 GiB (1073741824 bytes)
disk size: 1 GiB
[root@ubuntu2204 ~]#qemu-img info /opt/vm2.img.bk
image: /opt/vm2.img.bk
file format: raw
virtual size: 1 GiB (1073741824 bytes)
disk size: 0 B

#案例4：指定将稀疏文件复制为非稀疏格式文件
[root@ubuntu2204 ~]#cp --sparse=never /opt/vm3.img /opt/vm3.img.bk
[root@ubuntu2204 ~]#qemu-img info /opt/vm3.img
image: /opt/vm3.img
file format: raw
virtual size: 1 GiB (1073741824 bytes)
disk size: 0 B
[root@ubuntu2204 ~]#qemu-img info /opt/vm3.img.bk
image: /opt/vm3.img.bk
file format: raw
virtual size: 1 GiB (1073741824 bytes)
disk size: 1 GiB

#qcow2 格式选项
backing_file #指定后端镜像文件
backing_fmt #设置后端镜像的镜像格式
cluster_size #设置镜像中的簇大小，取值在512到2M之间，默认值为64K
preallocation #设置镜像文件空间的预分配模式
encryption #用于设置加密

[root@ubuntu2204 ~]#qemu-img create -f qcow2 /opt/vm1.img 2g
Formatting '/opt/vm1.img', fmt=qcow2 cluster_size=65536 extended_l2=off compression_type=zlib size=2147483648 lazy_refcounts=off refcount_bits=16
[root@ubuntu2204 ~]#qemu-img info /opt/vm1.img
image: /opt/vm1.img
file format: qcow2
virtual size: 2 GiB (2147483648 bytes)
disk size: 196 KiB
cluster_size: 65536
Format specific information:
compat: 1.1
compression type: zlib
lazy refcounts: false
refcount bits: 16
corrupt: false
extended l2: false

*对于关机状态的虚拟机磁盘,可以检查文件错误
[root@centos8 ~]#virsh list
Id Name State
----------------------------------------------------
2 centos8 running
[root@centos8 ~]#qemu-img check /var/lib/libvirt/images/centos8.qcow2
qemu-img: Could not open '/var/lib/libvirt/images/centos8.qcow2': Failed to get
shared "write" lock
Is another process using the image [/var/lib/libvirt/images/centos8.qcow2]?
[root@centos8 ~]#virsh suspend centos8
Domain centos8 suspended
[root@centos8 ~]#virsh list
Id Name State
----------------------------------------------------
2 centos8 paused
[root@centos8 ~]#qemu-img check /var/lib/libvirt/images/centos8.qcow2
qemu-img: Could not open '/var/lib/libvirt/images/centos8.qcow2': Failed to get
shared "write" lock
Is another process using the image [/var/lib/libvirt/images/centos8.qcow2]?
[root@centos8 ~]#qemu-img check /var/lib/libvirt/images/centos7.qcow2
No errors were found on the image.
25572/327680 = 7.80% allocated, 1.44% fragmented, 0.00% compressed clusters
Image end offset: 1676869632

此为缺省策略，即不使用预分配策略,预分配后的虚拟磁盘占用空间很小,不属于稀疏映像类型,生成的磁盘文件占用空间很小

只预分配元数据(metadata)，预分配后的磁盘文件属于稀疏映像类型,相当于vmware中的磁盘置备选项: Thin Provision(精简配置)
生成的磁盘文件为稀疏格式,实际占用的空间比off策略稍大一些

分配文件的块并标识它们的状态为未初始化，即只分配空间,但不置零(不格式化). 预分配后的虚拟磁盘属于非稀疏映像类型,相对full模式来说，创建虚拟磁盘的速度要快很多,相当于vmware中的磁盘置备选项:厚置备延迟置零
生成的磁盘文件实际占用的空间和分配的空间相同大小

分配所有磁盘空间并置零，预分配后的虚拟磁盘属于非稀疏映像类型,创建最慢,相当于vmware中的磁盘置备选项: 厚置备置零
生成的磁盘文件实际占用的空间和分配的空间相同大小

#案例1：默认开启默认预分配策略 - 稀疏格式，根据实际需要自动分配磁盘空间
[root@ubuntu2204 ~]#qemu-img create -f qcow2 /opt/vm1.img 2g
Formatting '/opt/vm1.img', fmt=qcow2 cluster_size=65536 extended_l2=off compression_type=zlib size=2147483648 lazy_refcounts=off refcount_bits=16
[root@ubuntu2204 ~]#qemu-img info /opt/vm1.img
image: /opt/vm1.img
file format: qcow2
virtual size: 2 GiB (2147483648 bytes)
disk size: 196 KiB
cluster_size: 65536
Format specific information:
compat: 1.1
compression type: zlib
lazy refcounts: false
refcount bits: 16
corrupt: false
extended l2: false

#案例2：指定off关闭预分配
[root@ubuntu2204 ~]#qemu-img create -f qcow2 /opt/vm2.img 1g -o preallocatinotallow=off
Formatting '/opt/vm2.img', fmt=qcow2 cluster_size=65536 extended_l2=off preallocation=off compression_type=zlib size=1073741824 lazy_refcounts=off refcount_bits=16
[root@ubuntu2204 ~]#qemu-img info /opt/vm2.img
image: /opt/vm2.img
file format: qcow2
virtual size: 1 GiB (1073741824 bytes)
disk size: 196 KiB
cluster_size: 65536
Format specific information:
compat: 1.1
compression type: zlib
lazy refcounts: false
refcount bits: 16
corrupt: false
extended l2: false

#案例3：指定预分配metadata
[root@ubuntu2204 ~]#qemu-img create -f qcow2 /opt/vm3.img 1g -o preallocatinotallow=metadata
Formatting '/opt/vm3.img', fmt=qcow2 cluster_size=65536 extended_l2=off preallocation=metadata compression_type=zlib size=1073741824 lazy_refcounts=off refcount_bits=16
[root@ubuntu2204 ~]#qemu-img info /opt/vm3.img
image: /opt/vm3.img
file format: qcow2
virtual size: 1 GiB (1073741824 bytes)
disk size: 324 KiB
cluster_size: 65536
Format specific information:
compat: 1.1
compression type: zlib
lazy refcounts: false
refcount bits: 16
corrupt: false
extended l2: false

#案例4：指定预分配falloc
[root@ubuntu2204 ~]#qemu-img create -f qcow2 /opt/vm4.img 1g -o preallocatinotallow=falloc
Formatting '/opt/vm4.img', fmt=qcow2 cluster_size=65536 extended_l2=off preallocation=falloc compression_type=zlib size=1073741824 lazy_refcounts=off refcount_bits=16
[root@ubuntu2204 ~]#qemu-img info /opt/vm4.img
image: /opt/vm4.img
file format: qcow2
virtual size: 1 GiB (1073741824 bytes)
disk size: 1 GiB
cluster_size: 65536
Format specific information:
compat: 1.1
compression type: zlib
lazy refcounts: false
refcount bits: 16
corrupt: false
extended l2: false

#文件系统显示大小
[root@ubuntu2204 ~]#ll -h /opt/vm*
-rw-r--r-- 1 root root 193K Jan 1 17:40 /opt/vm1.img
-rw-r--r-- 1 root root 193K Jan 1 18:04 /opt/vm2.img
-rw-r--r-- 1 root root 1.1G Jan 1 18:08 /opt/vm3.img
-rw-r--r-- 1 root root 1.1G Jan 1 18:08 /opt/vm4.img
#查看真实大小
[root@ubuntu2204 ~]#du -h /opt/vm*
196K /opt/vm1.img
196K /opt/vm2.img
324K /opt/vm3.img
1.1G /opt/vm4.img

#qemu-img 可以将不同格式的虚拟磁盘文件进行格式转化

#案例：将vmdk转化为raw 和qcow2格式
[root@centos8 ~]#qemu-img info CentOS8.2.vmdk
image: CentOS8.2.vmdk
file format: vmdk
virtual size: 200G (214748364800 bytes)
disk size: 1.6G
cluster_size: 65536
Format specific information:
cid: 2898578192
parent cid: 4294967295
create type: monolithicSparse
extents:
[0]:
virtual size: 214748364800
filename: CentOS8.2.vmdk
cluster size: 65536
format:
#默认转化为raw格式
[root@centos8 ~]#qemu-img convert CentOS8.2.vmdk CentOS8.2.img
#比较大小
[root@centos8 ~]#ll -h CentOS8.2.vmdk CentOS8.2.img
-rw-r--r-- 1 root root 1.6G Sep 20 16:00 CentOS8.2.vmdk
-rw-r--r-- 1 root root 200G Sep 20 16:10 CentOS8.2.img
[root@centos8 ~]#du -h CentOS8.2.vmdk CentOS8.2.img
1.6G CentOS8.2.vmdk
1.5G CentOS8.2.img
[root@centos8 ~]#qemu-img info CentOS8.2.img
image: CentOS8.2.img
file format: raw
virtual size: 200G (214748364800 bytes)
disk size: 1.4G
[root@centos8 ~]#mv CentOS8.2.img /var/lib/libvirt/images/
[root@centos8 ~]#virt-install --import --name=centos8-test2 --vcpus=1 --ram=2048
--disk bus=scsi,path=/var/lib/libvirt/images/CentOS8.2.img --network
network=default --graphics vnc,listen=0.0.0.0 --os-type=Linux --osvariant=
centos8 --noautoconsole --boot hd
#转化为qcow2格式
[root@centos8 ~]#qemu-img convert -f vmdk -O qcow2 CentOS8.2.vmdk
CentOS8.2.qcow2
#比较大小
[root@centos8 ~]#ll -h CentOS8.2.vmdk CentOS8.2.qcow2
-rw-r--r-- 1 root root 1.6G Sep 20 16:00 CentOS8.2.vmdk
-rw-r--r-- 1 root root 1.6G Sep 20 16:12 CentOS8.2.qcow2
[root@centos8 ~]#du -h CentOS8.2.vmdk CentOS8.2.qcow2
1.6G CentOS8.2.vmdk
1.6G CentOS8.2.qcow2
[root@centos8 ~]#qemu-img info CentOS8.2.qcow2
image: CentOS8.2.qcow2
file format: qcow2
virtual size: 200G (214748364800 bytes)
disk size: 1.5G
cluster_size: 65536
Format specific information:
compat: 1.1
lazy refcounts: false
refcount bits: 16
corrupt: false
[root@centos8 ~]#mv CentOS8.2.qcow2 /var/lib/libvirt/images/
[root@centos8 ~]#virt-install --import --name=centos8-test3 --vcpus=1 --ram=2048
--disk bus=scsi,path=/var/lib/libvirt/images/CentOS8.2.qcow2 --network
network=default --graphics vnc,listen=0.0.0.0 --os-type=Linux --osvariant=
centos8 --noautoconsole --boot hd

#思路：扩展分区-扩容物理卷-扩容逻辑卷组-扩容指定逻辑卷
[root@ubuntu2204 ~]#qemu-img info /var/lib/libvirt/images/centos7-mooreyxia.qcow2
image: /var/lib/libvirt/images/centos7-mooreyxia.qcow2
file format: qcow2
virtual size: 10 GiB (10737418240 bytes)
disk size: 1.6 GiB
cluster_size: 65536
Snapshot list:
ID TAG VM SIZE DATE VM CLOCK ICOUNT
1 centos7-s1 0 B 2023-01-01 19:01:27 00:00:00.000 0
Format specific information:
compat: 1.1
compression type: zlib
lazy refcounts: true
refcount bits: 16
corrupt: false
extended l2: false
[root@ubuntu2204 ~]#du -sh /var/lib/libvirt/images/centos7-mooreyxia.qcow2
1.6G /var/lib/libvirt/images/centos7-mooreyxia.qcow2

#扩容 - 增加10G空间
[root@ubuntu2204 ~]#qemu-img info /var/lib/libvirt/images/centos7-mooreyxia.qcow2
image: /var/lib/libvirt/images/centos7-mooreyxia.qcow2
file format: qcow2
virtual size: 20 GiB (21474836480 bytes)
disk size: 1.6 GiB
cluster_size: 65536
Snapshot list:
ID TAG VM SIZE DATE VM CLOCK ICOUNT
1 centos7-s1 0 B 2023-01-01 19:01:27 00:00:00.000 0
Format specific information:
compat: 1.1
compression type: zlib
lazy refcounts: true
refcount bits: 16
corrupt: false
extended l2: false

#qemu-img resize 扩展空间后，在虚拟机内还需执行如下操作才能最终扩容
[root@localhost ~]# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sr0 11:0 1 1024M 0 rom
vda 252:0 0 20G 0 disk
├─vda1 252:1 0 1G 0 part /boot
└─vda2 252:2 0 9G 0 part
├─centos-root 253:0 0 8G 0 lvm /
└─centos-swap 253:1 0 1G 0 lvm [SWAP]

[root@localhost ~]# df -h
Filesystem Size Used Avail Use% Mounted on
devtmpfs 908M 0 908M 0% /dev
tmpfs 919M 0 919M 0% /dev/shm
tmpfs 919M 8.6M 911M 1% /run
tmpfs 919M 0 919M 0% /sys/fs/cgroup
/dev/mapper/centos-root 8.0G 1.3G 6.8G 16% /
/dev/vda1 1014M 153M 862M 15% /boot
tmpfs 184M 0 184M 0% /run/user/0

#重新创建/dev/vda2,容量使用所有空间，/dev/vda2扩容到20G
[root@localhost ~]# fdisk /dev/vda
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): 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): p

Disk /dev/vda: 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: 0x000df5df

Device Boot Start End Blocks Id System
/dev/vda1 * 2048 2099199 1048576 83 Linux
/dev/vda2 2099200 20971519 9436160 8e Linux LVM

Command (m for help): d
Partition number (1,2, default 2):
Partition 2 is deleted

Command (m for help): p

Disk /dev/vda: 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: 0x000df5df

Device Boot Start End Blocks Id System
/dev/vda1 * 2048 2099199 1048576 83 Linux

Command (m for help): p

Disk /dev/vda: 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: 0x000df5df

Device Boot Start End Blocks Id System
/dev/vda1 * 2048 2099199 1048576 83 Linux

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 (2099200-41943039, default 2099200):
Using default value 2099200
Last sector, +sectors or +size{K,M,G} (2099200-41943039, default 41943039):
Using default value 41943039
Partition 2 of type Linux and of size 19 GiB is set

Command (m for help): p

Disk /dev/vda: 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: 0x000df5df

Device Boot Start End Blocks Id System
/dev/vda1 * 2048 2099199 1048576 83 Linux
/dev/vda2 2099200 41943039 19921920 83 Linux

Command (m for help): t
Partition number (1,2, default 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/vda: 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: 0x000df5df

Device Boot Start End Blocks Id System
/dev/vda1 * 2048 2099199 1048576 83 Linux
/dev/vda2 2099200 41943039 19921920 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.

#同步文件系统，扩展逻辑卷
[root@localhost ~]# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sr0 11:0 1 1024M 0 rom
vda 252:0 0 20G 0 disk
├─vda1 252:1 0 1G 0 part /boot
└─vda2 252:2 0 19G 0 part
├─centos-root 253:0 0 8G 0 lvm /
└─centos-swap 253:1 0 1G 0 lvm [SWAP]

[root@localhost ~]# lsblk -f
NAME FSTYPE LABEL UUID MOUNTPOINT
sr0
vda
├─vda1 xfs 1a55b4e7-3e79-4319-8fd0-7ceb3d1ab505 /boot
└─vda2 LVM2_member 0Sybbx-w3aS-ZdSN-1zQO-eXpw-0zqz-YcYT4V
├─centos-root xfs f1205cb4-8a06-44a8-bece-89e8610e5a77 /
└─centos-swap swap 7ccb94cc-3909-4af8-9abf-e1b63d627f52 [SWAP]

#当前物理卷空间并没有扩容，需要执行下面操作扩容PV
[root@localhost ~]# pvs
PV VG Fmt Attr PSize PFree
/dev/vda2 centos lvm2 a-- <9.00g 0

[root@localhost ~]# pvresize --setphysicalvolumesize 19G /dev/vda2
WARNING: /dev/vda2: Overriding real size <19.00 GiB. You could lose data.
/dev/vda2: Requested size 19.00 GiB exceeds real size <19.00 GiB. Proceed? [y/n]: y
WARNING: /dev/vda2: Pretending size is 39845888 not 39843840 sectors.
Physical volume "/dev/vda2" changed
1 physical volume(s) resized or updated / 0 physical volume(s) not resized

[root@localhost ~]# pvs
PV VG Fmt Attr PSize PFree
/dev/vda2 centos lvm2 a-- <19.00g 10.00g

#逻辑卷组被自动扩容
[root@localhost ~]# vgs -a
VG #PV #LV #SN Attr VSize VFree
centos 1 2 0 wz--n- <19.00g 0

#扩容指定逻辑卷
[root@localhost ~]# lvextend -r -l +100%free /dev/centos/root
Size of logical volume centos/root changed from <8.00 GiB (2047 extents) to <18.00 GiB (4607 extents).
Logical volume centos/root successfully resized.
meta-data=/dev/mapper/centos-root isize=512 agcount=4, agsize=524032 blks
= sectsz=512 attr=2, projid32bit=1
= crc=1 finobt=0 spinodes=0
data = bsize=4096 blocks=2096128, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0 ftype=1
log =internal bsize=4096 blocks=2560, versinotallow=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0
data blocks changed from 2096128 to 4717568
[root@localhost ~]# lvs
LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert
root centos -wi-ao---- <18.00g
swap centos -wi-ao---- 1.00g
[root@localhost ~]# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sr0 11:0 1 1024M 0 rom
vda 252:0 0 20G 0 disk
├─vda1 252:1 0 1G 0 part /boot
└─vda2 252:2 0 19G 0 part
├─centos-root 253:0 0 18G 0 lvm /
└─centos-swap 253:1 0 1G 0 lvm [SWAP]

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#如果是分区不是逻辑卷，则执行如下操作
#如果是xfs文件系统
xfs_growfs /
#如果是ext
resize2fs /dev/vda2
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