原博转载：linux centos7 增加内存
注意事项：亲测有效。但是分区不能超过4个，所以，扩展内存的时候，要计算好，不要拓展一次内存依旧不够，再来一次。
################直接扩展原有硬盘#################
#1.初始容量20G，查看磁盘空间大小，使用df -h命令，发现挂载根目录节点的/dev/mapper/centos-root剩余空间太小
#2.关闭客户机，选中原来20G硬盘，点击扩展，直接加大到需要的值30G，确定保存后，重启客户机
#3.使用fdisk -l命令查看磁盘信息。第一行显示的数据值Disk /dev/sda: 32.2 GB，与初始容量不同时则磁盘增加成功
#4.使用fdisk /dev/sda 创建新分区,输入m回车
#5.输入n回车（选中add a new partition创建新分区）
Partition type:
p primary (2 primary, 0 extended, 2 free)
e extended
Select (default p):
#6.直接回车
Partition number (3,4, default 3):
#7.直接回车
First sector (41943040-62914559, default 41943040):
#8.直接回车
Using default value 41943040
Last sector, +sectors or +size{K,M,G} (41943040-62914559, default 62914559):
#9.直接回车
Using default value 62914559
Partition 3 of type Linux and of size 10 GiB is set
Command (m for help):
#10.输入t回车(修改分区格式)
Partition number (1-3, default 3):
#11.直接回车
Hex code (type L to list all codes):
#12.输入L，就可以查看分区类型的id
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 C: 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 eb BeOS fs
e W95 FAT16 (LBA) 53 OnTrack DM6 Aux a5 FreeBSD ee GPT
f W95 Ext'd (LBA) 54 OnTrackDM6 a6 OpenBSD ef EFI (FAT-12/16/
10 OPUS 55 EZ-Drive a7 NeXTSTEP f0 Linux/PA-RISC b
11 Hidden FAT12 56 Golden Bow a8 Darwin UFS f1 SpeedStor
12 Compaq diagnost 5c Priam Edisk a9 NetBSD f4 SpeedStor
14 Hidden FAT16 <3 61 SpeedStor ab Darwin boot f2 DOS secondary
16 Hidden FAT16 63 GNU HURD or Sys af HFS / HFS+ fb VMware VMFS
17 Hidden HPFS/NTF 64 Novell Netware b7 BSDI fs fc VMware VMKCORE
18 AST SmartSleep 65 Novell Netware b8 BSDI swap fd Linux raid auto
1b Hidden W95 FAT3 70 DiskSecure Mult bb Boot Wizard hid fe LANstep
1c Hidden W95 FAT3 75 PC/IX be Solaris boot ff BBT
1e Hidden W95 FAT1 80 Old Minix
Hex code (type L to list all codes):
#13.输入8e回车(选择Linux LVM)
Changed type of partition 'Linux' to 'Linux LVM'
Command (m for help):
#14.输入p回车（显示分区信息）
Disk /dev/sda: 32.2 GB, 32212254720 bytes, 62914560 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: 0x000c7036
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 62914559 10485760 8e Linux LVM
Command (m for help):
#15.输入w后回车，再reboot命令重启
#16.pvcreate /dev/sda3命令创建物理卷,sda3就是14步查询的分区信息 10G的 /dev/sda3 41943040 62914559 10485760 8e Linux LVM
Physical volume "/dev/sda3" successfully created.
#17.pvdisplay 命令查看新建的物理卷和大小
--- 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 mJ091L-x7tT-B1oT-GtHS-gzYX-tsnN-TsUNoN
"/dev/sda3" is a new physical volume of "10.00 GiB"
--- NEW Physical volume ---
PV Name /dev/sda3
VG Name
PV Size 10.00 GiB
Allocatable NO
PE Size 0
Total PE 0
Free PE 0
Allocated PE 0
PV UUID zbMucY-IuSe-MCek-MKD5-WAqI-qRoc-DtKow5
#18.输入 vgextend centos /dev/sda3 （添加新的物理卷，加载到centos卷组）
Volume group "centos" successfully extended
#19.vgdisplay命令，查看卷组信息
--- 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 28.99 GiB
PE Size 4.00 MiB
Total PE 7422
Alloc PE / Size 4863 / <19.00 GiB
Free PE / Size 2559 / <10.00 GiB
VG UUID JesaeJ-WN31-iY8G-GjZ1-bF2h-hDqz-7aEHxl
#20.使用命令 lvresize -L +9.99G /dev/mapper/centos-root （增加centos卷组大小，直接输入10G，报了内存不够，所以这里略微减少了一点）
Rounding size to boundary between physical extents: 9.99 GiB.
Size of logical volume centos/root changed from <17.00 GiB (4351 extents) to <26.99 GiB (6909 extents).
Logical volume centos/root successfully resized.
#21.使用 xfs_growfs /dev/mapper/centos-root 命令重新识别卷组大小
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 7074816
#22.使用 df -h 命令查看可以看见增加成功