虚拟机硬盘预设是20G，用着用着发现不够用了，需要扩展根目录磁盘容量，以此文记录扩容过程，方便后续查看，如果哪里有错误，望大家不吝批评指正，谢谢！
1、在VMware上扩展磁盘容量，由20G扩展到40G；
2、开启虚拟机，使用ssh连接服务器；
3、查看磁盘信息，可以看到系统下只有一块硬盘sda；
[root@server1 ~]# df -lh
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/centos-root 17G 17G 647M 97% /
devtmpfs 2.9G 0 2.9G 0% /dev
tmpfs 2.9G 0 2.9G 0% /dev/shm
tmpfs 2.9G 12M 2.9G 1% /run
tmpfs 2.9G 0 2.9G 0% /sys/fs/cgroup
/dev/sda1 1014M 142M 873M 14% /boot
tmpfs 579M 0 579M 0% /run/user/1000
tmpfs 579M 0 579M 0% /run/user/0
[root@server1 ~]# fdisk -l
Disk /dev/sda: 42.9 GB, 42949672960 bytes, 83886080 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: 0x000b20df
Device Boot Start End Blocks Id System
/dev/sda1 * 2048 2099199 1048576 83 Linux
/dev/sda2 2099200 41943039 19921920 8e Linux LVM
Disk /dev/mapper/centos-root: 18.2 GB, 18249416704 bytes, 35643392 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 /dev/mapper/centos-swap: 2147 MB, 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 bytes4、使用fdisk分区工具给sda磁盘分区
其中：
m - 打印目录列表
n - 增加一个新分区
p - 代表主分区
3 - 分区编号
w - 保存分区信息到磁盘并退出
[root@server1 ~]# fdisk /dev/sda
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): n
Partition type:
p primary (2 primary, 0 extended, 2 free)
e extended
Select (default p):
Using default response p
Partition number (3,4, default 3):
First sector (41943040-83886079, default 41943040):
Using default value 41943040
Last sector, +sectors or +size{K,M,G} (41943040-83886079, default 83886079):
Using default value 83886079
Partition 3 of type Linux and of size 20 GiB is set
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.5、再次查看分区信息
其中sda3即为新增加的分区，看最后一列，sda3的System为Linux（Id为83），需要修改为Linux LVM（Id为8e）；
[root@server1 ~]# fdisk -l
Disk /dev/sda: 42.9 GB, 42949672960 bytes, 83886080 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: 0x000b20df
Device Boot Start End Blocks Id System
/dev/sda1 * 2048 2099199 1048576 83 Linux
/dev/sda2 2099200 41943039 19921920 8e Linux LVM
/dev/sda3 41943040 83886079 20971520 83 Linux
Disk /dev/mapper/centos-root: 18.2 GB, 18249416704 bytes, 35643392 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 /dev/mapper/centos-swap: 2147 MB, 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 bytes6、修改sda3为LVM卷文件系统
其中：
m - 打印目录列表
t - 修改分区的System Id
3 - 分区编号
8e - LVM卷文件系统对应的System Id
w - 保存分区信息到磁盘并退出
[root@server1 ~]# fdisk /dev/sda
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): t
Partition number (1-3, default 3): 3
Hex code (type L to list all codes): 8e
Changed type of partition 'Linux' to '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.7、再次查看分区信息，sda3已经改为Linux LVM了；
[root@server1 ~]# fdisk -l
Disk /dev/sda: 42.9 GB, 42949672960 bytes, 83886080 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: 0x000b20df
Device Boot Start End Blocks Id System
/dev/sda1 * 2048 2099199 1048576 83 Linux
/dev/sda2 2099200 41943039 19921920 8e Linux LVM
/dev/sda3 41943040 83886079 20971520 8e Linux LVM
Disk /dev/mapper/centos-root: 18.2 GB, 18249416704 bytes, 35643392 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 /dev/mapper/centos-swap: 2147 MB, 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 bytes8、重启系统；
9、将sda3分区创建为文件系统
[root@server1 ~]# mkfs -t ext4 /dev/sda3
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
1310720 inodes, 5242880 blocks
262144 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=2153775104
160 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, 1605632, 2654208,
4096000
Allocating group tables: done
Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done10、查看当前的物理卷
[root@server1 ~]# pvdiskplay
-bash: pvdiskplay: command not found
[root@server1 ~]# pvdisplay
--- Physical volume ---
PV Name /dev/sda2
VG Name centos
PV Size <19.00 GiB / not usable 3.00 MiB
Allocatable yes (but full)
PE Size 4.00 MiB
Total PE 4863
Free PE 0
Allocated PE 4863
PV UUID 25WUH5-s8di-Cupq-4FJS-JcgU-jv80-d1zcKP11、将物理硬盘分区初始化为物理卷，以便被LVM使用；
只有System Id修改为8e之后，才能使用pvcreat指令将分区初始化为物理卷；
[root@server1 ~]# pvcreate /dev/sda3
WARNING: ext4 signature detected on /dev/sda3 at offset 1080. Wipe it? [y/n]: y
Wiping ext4 signature on /dev/sda3.
Physical volume "/dev/sda3" successfully created.12、再次查看当前物理卷
[root@server1 ~]# pvdisplay
--- Physical volume ---
PV Name /dev/sda2
VG Name centos
PV Size <19.00 GiB / not usable 3.00 MiB
Allocatable yes (but full)
PE Size 4.00 MiB
Total PE 4863
Free PE 0
Allocated PE 4863
PV UUID 25WUH5-s8di-Cupq-4FJS-JcgU-jv80-d1zcKP
"/dev/sda3" is a new physical volume of "20.00 GiB"
--- NEW Physical volume ---
PV Name /dev/sda3
VG Name
PV Size 20.00 GiB
Allocatable NO
PE Size 0
Total PE 0
Free PE 0
Allocated PE 0
PV UUID Z9htWg-egxy-cNR0-EBTq-D0U6-a32n-X65URf13、动态扩展VG
通过vgdisplay查看当前需要扩充的lvm组名，本机为centos；
[root@server1 ~]# vgdisplay
--- Volume group ---
VG Name centos
System ID
Format lvm2
Metadata Areas 1
Metadata Sequence No 3
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 2
Open LV 2
Max PV 0
Cur PV 1
Act PV 1
VG Size <19.00 GiB
PE Size 4.00 MiB
Total PE 4863
Alloc PE / Size 4863 / <19.00 GiB
Free PE / Size 0 / 0
VG UUID kn9EEY-Dt0L-cxsh-cmCa-UBBx-2Jah-vmxwsevgextend通过向卷组中添加物理卷来增加卷组的容量；
[root@server1 ~]# vgextend centos /dev/sda3
Volume group "centos" successfully extended再次查看VG信息，发现倒数第2行的Free PE下20G的可扩展容量；
[root@server1 ~]# vgdisplay
--- Volume group ---
VG Name centos
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 38.99 GiB
PE Size 4.00 MiB
Total PE 9982
Alloc PE / Size 4863 / <19.00 GiB
Free PE / Size 5119 / <20.00 GiB
VG UUID kn9EEY-Dt0L-cxsh-cmCa-UBBx-2Jah-vmxwse14、LV扩展
通过lvdisplay查看根目录的LV Path为/dev/centos/root；
[root@server1 ~]# lvdisplay
--- Logical volume ---
LV Path /dev/centos/swap
LV Name swap
VG Name centos
LV UUID QCd4Hj-QHy0-P5TJ-tHGs-TGDr-BBxD-Haf1XY
LV Write Access read/write
LV Creation host, time localhost, 2018-10-17 16:21:31 +0800
LV Status available
# open 2
LV Size 2.00 GiB
Current LE 512
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 8192
Block device 253:1
--- Logical volume ---
LV Path /dev/centos/root
LV Name root
VG Name centos
LV UUID yiZIHh-mPQU-IFS6-kIFa-a1lT-ADkk-9v0o10
LV Write Access read/write
LV Creation host, time localhost, 2018-10-17 16:21:31 +0800
LV Status available
# open 1
LV Size <36.80 GiB
Current LE 9420
Segments 2
Allocation inherit
Read ahead sectors auto
- currently set to 8192
Block device 253:0扩展空间要小于VG 的Free PE的大小，即小于20GB，这里使用19.8G；
[root@server1 ~]# lvextend -L +19.8G /dev/centos/root /dev/sda3
Rounding size to boundary between physical extents: 19.80 GiB.
Size of logical volume centos/root changed from <17.00 GiB (4351 extents) to <36.80 GiB (9420 extents).
Logical volume centos/root successfully resized.15、查看分区文件系统类型
CentOS7默认使用xfs，CentOS6默认使用ext4；
[root@server1 ~]# df -T
Filesystem Type 1K-blocks Used Available Use% Mounted on
/dev/mapper/centos-root xfs 38574080 17151340 21422740 45% /
devtmpfs devtmpfs 2951704 0 2951704 0% /dev
tmpfs tmpfs 2963976 0 2963976 0% /dev/shm
tmpfs tmpfs 2963976 11956 2952020 1% /run
tmpfs tmpfs 2963976 0 2963976 0% /sys/fs/cgroup
/dev/sda1 xfs 1038336 145252 893084 14% /boot
tmpfs tmpfs 592796 0 592796 0% /run/user/016、同步文件系统
文件系统类型是xfs，只能使用xfs_growfs命令同步文件系统，不能使用resize2fs、e2fsck、dumpe2fs；
resize2fs命令，用于扩大或者缩小未挂载的ext2,ext3或者是ext4文件系统；
[root@server1 ~]# xfs_growfs /dev/centos/root
meta-data=/dev/mapper/centos-root isize=512 agcount=4, agsize=1113856 blks
= sectsz=512 attr=2, projid32bit=1
= crc=1 finobt=0 spinodes=0
data = bsize=4096 blocks=4455424, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0 ftype=1
log =internal bsize=4096 blocks=2560, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0
data blocks changed from 4455424 to 964608017、查看磁盘信息，发现根目录已经扩展了20G，由17G变为37G；
[root@server1 ~]# df -lh
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/centos-root 37G 17G 21G 45% /
devtmpfs 2.9G 0 2.9G 0% /dev
tmpfs 2.9G 0 2.9G 0% /dev/shm
tmpfs 2.9G 12M 2.9G 1% /run
tmpfs 2.9G 0 2.9G 0% /sys/fs/cgroup
/dev/sda1 1014M 142M 873M 14% /boot
tmpfs 579M 0 579M 0% /run/user/1000
tmpfs 579M 0 579M 0% /run/user/0