linux系统里，文件系统需要被挂载后才可以被使用
lvm没有分区限制，分一个物理分区，建立一个物理卷，然后这个物理卷建立一个卷组，我们就可以在这个卷组里面去分无数个逻辑卷,而且逻辑卷可以随意扩大缩小，不会对物理分 区有影响，逻辑卷的功能也和物理分区差不多，一样可以格式化成随意的文件系统，挂载到随意的目录。
lvm的主要功能
从硬盘驱动器中创建物理卷（physical volumes-PV）。
从物理卷中创建卷组（volume groups-VG）。
从卷组中创建逻辑卷（logical volumes-LV），并分派逻辑卷挂载点
其中只有逻辑卷才可以写数据
就像金箍棒，想大就大，想小就小。
使硬盘无限分区，扩容。
物理分区、pv、vg、pE、lvm、/mnt ；
pv 处理后的物理分区,为物理卷，处于lvm最底层，可以是物理硬盘或者分区 ；
vg 物理卷组，建立在pv之上，可以含有一个到多个pv ；
pE 是vg的最小单位 。
[root@localhost ~]# fdisk /dev/vdb ##创建分区
Welcome to fdisk (util-linux 2.23.2).
Command (m for help): p
Disk /dev/vdb: 10.7 GB, 10737418240 bytes, 20971520 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: 0x1a008f30
Device Boot Start End Blocks Id System
/dev/vdb1 2048 2050047 1024000 83 Linux
/dev/vdb2 2050048 4098047 1024000 83 Linux
/dev/vdb3 4098048 6146047 1024000 83 Linux
Command (m for help): t
Partition number (1-3, default 3): 1
Hex code (type L to list all codes): 8e
Changed type of partition 'Linux' to 'Linux LVM'
Command (m for help): t
Partition number (1-3, default 3): 2
Hex code (type L to list all codes): 8e
Changed type of partition 'Linux' to 'Linux LVM'
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): p
Disk /dev/vdb: 10.7 GB, 10737418240 bytes, 20971520 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: 0x1a008f30
Device Boot Start End Blocks Id System
/dev/vdb1 2048 2050047 1024000 8e Linux LVM
/dev/vdb2 2050048 4098047 1024000 8e Linux LVM
/dev/vdb3 4098048 6146047 1024000 8e Linux LVM
Command (m for help): wq
The partition table has been altered!
Calling ioctl() to re-read partition table.
Syncing disks.
[root@localhost ~]# partprobe
重启一个sell插入一个监控命令：
[root@localhost ~]# watch -n 1 'pvs;vgs;lvs;df -h /mnt'在开始操作，就可以看得到了
[root@localhost ~]# pvcreate /dev/vdb1 ##创建物理卷
Physical volume "/dev/vdb1" successfully created
[root@localhost ~]# vgcreate vg0 /dev/vdb1 ##创建物理卷组
Volume group "vg0" successfully created
[root@localhost ~]# lvcreate -L 300M -n lv0 vg0 ##创建逻辑卷
Logical volume "lv0" created
[root@localhost ~]# mkfs.xfs /dev/vg0/lv0 ##格式化
meta-data=/dev/vg0/lv0 isize=256 agcount=4, agsize=19200 blks
= sectsz=512 attr=2, projid32bit=1
= crc=0
data = bsize=4096 blocks=76800, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0 ftype=0
log =internal log bsize=4096 blocks=853, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0
[root@localhost ~]# mount /dev/vg0/lv0 /mnt/ ##挂载
[root@localhost ~]# ll /dev/vg0/lv0
lrwxrwxrwx. 1 root root 7 May 4 22:53 /dev/vg0/lv0 -> ../dm-0
[root@localhost ~]# ll /dev/mapper/vg0-lv0 lv ##查看有关的虚拟设备
ls: cannot access lv: No such file or directory
lrwxrwxrwx. 1 root root 7 May 4 22:53 /dev/mapper/vg0-lv0 -> ../dm-0一、逻辑卷的扩容
（目的使扩大系统的储存容量）
xfs系统：
情况一、vg足够拉伸
[root@localhost ~]# lvextend -L 500M /dev/vg0/lv0 ##扩大系统
Extending logical volume lv0 to 500.00 MiB
Logical volume lv0 successfully resized
[root@localhost ~]# xfs_growfs /dev/vg0/lv0 ##扩展文件系统
meta-data=/dev/mapper/vg0-lv0 isize=256 agcount=4, agsize=19200 blks
= sectsz=512 attr=2, projid32bit=1
= crc=0
data = bsize=4096 blocks=76800, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0 ftype=0
log =internal bsize=4096 blocks=853, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0
data blocks changed from 76800 to 128000情况二、vg不够拉伸，得先扩大设备，在扩大系统。
[root@localhost ~]# pvcreate /dev/vdb2
Physical volume "/dev/vdb2" successfully created
[root@localhost ~]# vgextend vg0 /dev/vdb2 ##添加物理卷到物理卷组
Volume group "vg0" successfully extended
[root@localhost ~]# lvextend -L 1500M /dev/vg0/lv0 ##划分物理卷 & 扩展逻辑卷大小
Extending logical volume lv0 to 1.46 GiB
Logical volume lv0 successfully resizedefx4系统:
[root@localhost ~]# umount /mnt/ ##先卸载掉之前的xfs系统的/mnt
[root@localhost ~]# mkfs.ext4 /dev/vg0/lv0 ##格式化
mke2fs 1.42.9 (28-Dec-2013)
Filesystem label=
OS type: Linux
Allocating group tables: done
Writing inode tables: done
Creating journal (8192 blocks): done
Writing superblocks and filesystem accounting information: done [root@localhost ~]# mount /dev/vg0/lv0 /mnt/ ##挂载
[root@localhost ~]# df
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/vda1 10473900 3809252 6664648 37% /
devtmpfs 469344 0 469344 0% /dev
tmpfs 484932 140 484792 1% /dev/shm
tmpfs 484932 12840 472092 3% /run
tmpfs 484932 0 484932 0% /sys/fs/cgroup
/dev/mapper/vg0-lv0 1479088 4512 1381392 1% /mnt
[root@localhost ~]# mount
/dev/mapper/vg0-lv0 on /mnt type ext4 (rw,relatime,seclabel,data=ordered)
[root@localhost ~]# lvextend -L 1800M /dev/vg0/lv0 ##扩展逻辑卷大小
Extending logical volume lv0 to 1.76 GiB
Logical volume lv0 successfully resized
[root@localhost ~]# resize2fs /dev/vg0/lv0
##更新逻辑卷信息 二、逻辑卷的缩容
（目的使缩小系统的储存容量）
注意：xfs系统没有缩容。
ext4系统：
[root@localhost ~]# umount /mnt/ ##卸载
[root@localhost ~]# e2fsck -f /dev/vg0/lv0 ##扫描逻辑卷上的空间
e2fsck 1.42.9 (28-Dec-2013)
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/lv0: 11/120000 files (9.1% non-contiguous), 16862/460800 blocks
[root@localhost ~]# resize2fs /dev/vg0/lv0 1000M ##缩系统到1000M
resize2fs 1.42.9 (28-Dec-2013)
Resizing the filesystem on /dev/vg0/lv0 to 256000 (4k) blocks.
The filesystem on /dev/vg0/lv0 is now 256000 blocks long.[root@localhost ~]# mount /dev/vg0/lv0 /mnt/ ##挂载
[root@localhost ~]# lvreduce -L 1000M /dev/vg0/lv0 ##缩设备
WARNING: Reducing active and open logical volume to 1000.00 MiB
THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce lv0? [y/n]: y
Reducing logical volume lv0 to 1000.00 MiB
Logical volume lv0 successfully resized缩减vg：
（迁移到闲置设备）
[root@localhost ~]# pvmove /dev/vdb1 /dev/vdb2 ##将vdb1内的数据移到vdb2中
/dev/vdb1: Moved: 88.0%
/dev/vdb1: Moved: 100.0%
[root@localhost ~]# vgreduce vg0 /dev/vdb1 ##再将vdb1从vg0中取出来
Removed "/dev/vdb1" from volume group "vg0"
[root@localhost ~]# pvremove /dev/vdb1 ##删除vdb1
Labels on physical volume "/dev/vdb1" successfully wiped报错：
[root@localhost ~]# pvmove /dev/vdb1 /dev/vdb2
Insufficient free space: 249 extents needed, but only 248 available
Unable to allocate mirror extents for pvmove0.
Failed to convert pvmove LV to mirrored
vdb1 缩的不够小，vdb2容不下。所以说，得再重新缩小vdb1.
[root@localhost ~]# umount /mnt/ ##卸载
[root@localhost ~]# lvreduce -L 500M /dev/vg0/lv0
WARNING: Reducing active and open logical volume to 500.00 MiB
THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce lv0? [y/n]: y
Reducing logical volume lv0 to 500.00 MiB
Logical volume lv0 successfully resized
[root@localhost ~]# mount /dev/vg0/lv0 /mnt/ ##挂载
[root@localhost ~]# pvmove /dev/vdb1 /dev/vdb2 ##将vdb1内的数据移到vdb2中
/dev/vdb1: Moved: 88.0%
/dev/vdb1: Moved: 100.0%
[root@localhost ~]# vgreduce vg0 /dev/vdb1 ##再将vdb1从vg0中取出来
Removed "/dev/vdb1" from volume group "vg0"
[root@localhost ~]# pvremove /dev/vdb1 ##删除vdb1
Labels on physical volume "/dev/vdb1" successfully wiped之后再继续对vg缩小，就可以了。
快照
[root@localhost ~]# touch /mnt/file{1..5}
[root@localhost ~]# lvcreate -L 50M -n lv0backup -s /dev/vg0/lv0 ##建立一个50M的快照
[root@localhost ~]# mount /dev/vg0/lv0backup /mnt
[root@localhost ~]# cd /mnt
[root@localhost mnt]# ls
[root@localhost mnt]# rm -fr * ##删除所有文件
[root@localhost mnt]# cd
[root@localhost ~]# umount /mnt
[root@localhost ~]# lvremove /dev/vg0/lv0backup
[root@localhost ~]# lvcreate -L 50M -n lv0backup -s /dev/vg0/lv0
[root@localhost ~]# mount /dev/vg0/lv0backup /mnt ##挂载快照
[root@localhost ~]# ls /mnt ##又可以看到之前建立的文件
file1 file2 file3 file4 file5 lost+found当快照的大小大于所在文件的大小时，则需要再重新建一个vdb1。
[root@localhost ~]# pvcreate /dev/vdb1 ##创建物理卷
Physical volume “/dev/vdb1” successfully created
[root@localhost ~]# vgcreate vg0 /dev/vdb1 ##创建物理卷组
Volume group “vg0” successfully created
删除设备：
[root@localhost ~]# umount /mnt/ ##卸载/mnt
[root@localhost ~]# lvremove /dev/vg0/lv0backup ##删除快照
Do you really want to remove active logical volume lv0backup? [y/n]: y
Logical volume "lv0backup" successfully removed
[root@localhost ~]# lvremove /dev/vg0/lv0 ##删除逻辑卷
Do you really want to remove active logical volume lv0? [y/n]: y
Logical volume "lv0" successfully removed
[root@localhost ~]# vgremove vg0 ##删除物理卷组
Volume group "vg0" successfully removed
[root@localhost ~]# pvremove /dev/vdb2 ##删除物理卷
Labels on physical volume "/dev/vdb2" successfully wiped
报错：
[root@localhost ~]# lvremove /dev/vg0/lv0
Logical volume vg0/lv0 contains a filesystem in use.
[root@localhost ~]# df
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/vda1 10473900 3809236 6664664 37% /
devtmpfs 469344 0 469344 0% /dev
tmpfs 484932 140 484792 1% /dev/shm
tmpfs 484932 12816 472116 3% /run
tmpfs 484932 0 484932 0% /sys/fs/cgroup
/dev/mapper/vg0-lv0 471176 2272 434328 1% /mnt
[root@localhost ~]# umount /mnt/
[root@localhost ~]# df
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/vda1 10473900 3809260 6664640 37% /
devtmpfs 469344 0 469344 0% /dev
tmpfs 484932 140 484792 1% /dev/shm
tmpfs 484932 12816 472116 3% /run
tmpfs 484932 0 484932 0% /sys/fs/cgroup
重新卸载/mnt，再继续操作。