LVM逻辑卷操作（PV、VG、LV及XFS的扩容）－实验笔记
LVM作为操作非常灵活的磁盘操作模式，还是有必要熟练的。
ENV：
[root@centos7 ~]# uname -r
3.10.0-514.el7.x86_64
[root@centos7 ~]# cat /etc/redhat-release
CentOS Linux release 7.3.1611 (Core)
[root@centos7 ~]# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 5G 0 disk
sdb 8:16 0 5G 0 disk
sdc 8:32 0 5G 0 disk
sdd 8:48 0 5G 0 disk
sde 8:64 0 5G 0 disk
sdf 8:80 0 5G 0 disk
sdg 8:96 0 5G 0 disk
sdh 8:112 0 8G 0 disk
├─sdh1 8:113 0 1G 0 part /boot
└─sdh2 8:114 0 7G 0 part
├─cl-root 253:0 0 6.2G 0 lvm /
└─cl-swap 253:1 0 820M 0 lvm [SWAP]
sr0 11:0 1 1024M 0 rom 上面的ENV为系统环境，为了操作LVM，下面还要进行卷操作，以加深操作。
整个过程为PVcreate－>VGcreate—>LVcreate：
[root@centos7 ~]# pvcreate /dev/sda
Physical volume "/dev/sda" successfully created.
[root@centos7 ~]# pvcreate /dev/sdb
Physical volume "/dev/sdb" successfully created.
[root@centos7 ~]# vgcreate vgsys /dev/sda /dev/sdb
Volume group "vgsys" successfully created
[root@centos7 ~]# vgdisplay
--- Volume group ---
VG Name vgsys
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 9.99 GiB
PE Size 4.00 MiB
Total PE 2558
Alloc PE / Size 0 / 0
Free PE / Size 2558 / 9.99 GiB
VG UUID T2eygA-LOhE-zjMo-Ocrc-pnI2-l7as-20WMxA
--- Volume group ---
VG Name cl
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 7.00 GiB
PE Size 4.00 MiB
Total PE 1791
Alloc PE / Size 1791 / 7.00 GiB
Free PE / Size 0 / 0
VG UUID XDjUdW-Lk2W-dLnv-ErFe-YPq4-vPTk-VDrqmH
[root@centos7 ~]# lvcreate -n lvsys -L 500M vgsys
Logical volume "lvsys" created.
[root@centos7 ~]# mkfs.xfs -f /dev/vgsys/lvsys
meta-data=/dev/vgsys/lvsys isize=512 agcount=4, agsize=32000 blks
= sectsz=512 attr=2, projid32bit=1
= crc=1 finobt=0, sparse=0
data = bsize=4096 blocks=128000, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0 ftype=1
log =internal log bsize=4096 blocks=855, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0
[root@centos7 ~]# lvdisplay /dev/vgsys/lvsys
--- Logical volume ---
LV Path /dev/vgsys/lvsys
LV Name lvsys
VG Name vgsys
LV UUID JzBZCe-oLME-GZ29-Xed4-2KOj-xh9l-boYEJN
LV Write Access read/write
LV Creation host, time centos7, 2019-05-09 18:39:47 +0800
LV Status available
# open 0
LV Size 500.00 MiB
Current LE 125
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 8192
Block device 253:2
[root@centos7 ~]# mkdir /mnt/LVM
[root@centos7 ~]# echo "/dev/vgsys/lvsys /mnt/LVM xfs defaults 0 0" >> /etc/fstab
[root@centos7 ~]# mount -a
到此，前期的卷操作完成，任务环境也布置完成。
1.扩展卷：
[root@centos7 ~]# resize2fs /dev/vgsys/lvsys
resize2fs 1.42.9 (28-Dec-2013)
resize2fs: Bad magic number in super-block while trying to open /dev/vgsys/lvsys
Couldn't find valid filesystem superblock.出现错误了，有没有，最高兴的就是看到错误了，这样才有意思^V^.
其实最新的xfs格式分区不能使用resize2fs了，而是有专用的xfs_grows
[root@centos7 ~]# xfs_growfs -h
xfs_growfs: invalid option -- 'h'
Usage: xfs_growfs [options] mountpoint
Options:
-d grow data/metadata section
-l grow log section
-r grow realtime section
-n don't change anything, just show geometry
-i convert log from external to internal format
-t alternate location for mount table (/etc/mtab)
-x convert log from internal to external format
-D size grow data/metadata section to size blks
-L size grow/shrink log section to size blks
-R size grow realtime section to size blks
-e size set realtime extent size to size blks
-m imaxpct set inode max percent to imaxpct
-V print version information换这个命令再操作一次：
[root@centos7 ~]# xfs_growfs /dev/vgsys/lvsys
xfs_growfs: /dev/vgsys/lvsys is not a mounted XFS filesystem还出错，不过这次提示的就明显了，说是没有挂载，那挂载试试：
[root@centos7 ~]# mount /dev/vgsys/lvsys /mnt/LVM/
[root@centos7 ~]# xfs_growfs /dev/vgsys/lvsys
meta-data=/dev/mapper/vgsys-lvsys isize=512 agcount=4, agsize=327680 blks
= sectsz=512 attr=2, projid32bit=1
= crc=1 finobt=0 spinodes=0
data = bsize=4096 blocks=1310720, 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 1310720 to 1835008这次操作成功了，找了下xfs_growfs的man文档，其中写有这个xfs是支持挂载操作的，真的是很方便啊
xfs_growfs(8) System Manager's Manual xfs_growfs(8)
NAME
xfs_growfs, xfs_info - expand an XFS filesystem
SYNOPSIS
xfs_growfs [ -dilnrx ] [ -D size ] [ -e rtextsize ] [ -L size ] [ -m
maxpct ] [ -t mtab ] [ -R size ] mount-point
xfs_growfs -V
xfs_info [ -t mtab ] mount-point
xfs_info -V
DESCRIPTION
xfs_growfs expands an existing XFS filesystem (see xfs(5)). The mount-
point argument is the pathname of the directory where the filesystem is
mounted. The filesystem must be mounted to be grown (see mount(8)).
The existing contents of the filesystem are undisturbed, and the added
space becomes available for additional file storage.学习Linux要善于看man文档，系统命令都可以在这个帮助文档中找到详细的说明和应用。
那有没有缩小呢？？
[root@centos7 ~]# xfs //xfs后直接tab补齐，可以看到下面列的所有xfs命令，可以看到是没有缩小了
xfs_admin xfs_estimate xfsinvutil xfs_mkfile xfs_rtcp
xfs_bmap xfs_freeze xfs_io xfs_ncheck
xfs_copy xfs_fsr xfs_logprint xfs_quota
xfs_db xfs_growfs xfs_mdrestore xfs_repair
xfsdump xfs_info xfs_metadump xfsrestore 没发现有缩小的操作，但不排除其他方法，但可能性可能小些，毕竟以后都是向大容量扩容的，已经不再和以前的文件系统一样支持缩小功能了，就不再找了。
2.删除卷
有安装就有删除了，go on!
[root@centos7 ~]# umount /dev/vgsys/lvsys
[root@centos7 ~]# lvremove /dev/vgsys/lvsys
Do you really want to remove active logical volume vgsys/lvsys? [y/n]: y
Logical volume "lvsys" successfully removed
[root@centos7 ~]# vgremove vgsys
Volume group "vgsys" successfully removed
[root@centos7 ~]# pvremove /dev/sda /dev/sdb
Labels on physical volume "/dev/sda" successfully wiped.
Labels on physical volume "/dev/sdb" successfully wiped.好了，操作完成了。