簡介
LVM是 Logical Volume Manager（邏輯卷管理）的簡寫，它是Linux環境下對磁盤分區進行管理的一種機制，它由Heinz Mauelshagen在Linux 2.4內核上實現。
物理存儲介質（PhysicalStorageMedia）
指系統的物理存儲設備：磁盤，如：/dev/hda、/dev/sda等，是存儲系統最底層的存儲單元。
物理卷（Physical Volume，PV）
指磁盤分區或從邏輯上與磁盤分區具有同樣功能的設備（如RAID），是LVM的基本存儲邏輯塊，但和基本的物理存儲介質（如分區、磁盤等）比較，卻包含有與LVM相關的管理參數。
卷組（Volume Group，VG）
類似於非LVM系統中的物理磁盤，其由一個或多個物理卷PV組成。可以在卷組上創建一個或多個LV（邏輯卷）。
邏輯卷（Logical Volume，LV）
類似於非LVM系統中的磁盤分區，邏輯卷建立在卷組VG之上。在邏輯卷LV之上可以建立文件系統（比如/home或者/usr等）。
查看信息命令
pvdisplay #查看PV信息
[root@localhost ~]# pvdisplay
--- Physical volume ---
PV Name /dev/sda3
VG Name VolGroup
PV Size 18.51 GiB / not usable 3.00 MiB
Allocatable yes (but full)
PE Size 4.00 MiB
Total PE 4738
Free PE 0
Allocated PE 4738
PV UUID ARNJxr-gfcH-rW5H-X6I1-c2da-QhM1-BJ7ljo
vgdisplay #查看VG信息
[root@localhost ~]# vgdisplay
--- Volume group ---
VG Name VolGroup
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 18.51 GiB
PE Size 4.00 MiB
Total PE 4738
Alloc PE / Size 4738 / 18.51 GiB
Free PE / Size 0 / 0
VG UUID gFkWoE-8AVZ-kbd5-Clge-6Tq3-gcFh-4iVr1x
lvdisplay #查看LV信息
[root@localhost ~]# lvdisplay
--- Logical volume ---
LV Path /dev/VolGroup/LogVol01
LV Name LogVol01
VG Name VolGroup
LV UUID UeAMMJ-G6Ou-yMlJ-9Igz-pVBU-1HSy-jt6Trt
LV Write Access read/write
LV Creation host, time localhost.localdomain, 2015-07-23 03:42:14 -0400
LV Status available
# open 1
LV Size 4.05 GiB
Current LE 1036
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 253:0
--- Logical volume ---
LV Path /dev/VolGroup/LogVol00
LV Name LogVol00
VG Name VolGroup
LV UUID OF62jU-eVGO-4Rtd-TycU-aoGC-0Rs0-nDRRhE
LV Write Access read/write
LV Creation host, time localhost.localdomain, 2015-07-23 03:42:15 -0400
LV Status available
# open 1
LV Size 14.46 GiB
Current LE 3702
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 253:1
縮減和增加
減少swap分區空間前要取消掛載，使用 swapoff -a
[root@localhost ~]# free -m
total used free shared buffers cached
Mem: 1877 140 1737 0 6 39
-/+ buffers/cache: 93 1783
Swap: 4143 0 4143
[root@localhost ~]# swapoff -a
[root@localhost ~]# free -m
total used free shared buffers cached
Mem: 1877 136 1740 0 6 39
-/+ buffers/cache: 91 1786
Swap: 0 0 0
使用 lvreduce -L -xxx filename 或 lvreduce -L xxx filename 來減少swap分區空間，“-”代表減多少，不加“-”代表減剩多少。下圖表示給swap分區留512M。
使用 mke2fs filename 格式化分區
使用 resize2fs filename 重寫分區空間
[root@localhost ~]# lvreduce -L 512M /dev/VolGroup/LogVol01
WARNING: Reducing active and open logical volume to 512.00 MiB
THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce LogVol01? [y/n]: y
Reducing logical volume LogVol01 to 512.00 MiB
Logical volume LogVol01 successfully resized
[root@localhost ~]# mke2fs /dev/VolGroup/LogVol01
mke2fs 1.41.12 (17-May-2010)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
32768 inodes, 131072 blocks
6553 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=134217728
4 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks:
32768, 98304
Writing inode tables: done
Writing superblocks and filesystem accounting information: done
This filesystem will be automatically checked every 29 mounts or
180 days, whichever comes first. Use tune2fs -c or -i to override.
[root@localhost ~]# resize2fs /dev/VolGroup/LogVol01
resize2fs 1.41.12 (17-May-2010)
The filesystem is already 131072 blocks long. Nothing to do!
使用 lvextend -L +1G filename 為根分區增加空閒空間，用法同上。空閒空間可以使用vgdisplay查看，增加空間不需要格式化。
[root@localhost ~]# lvextend -L +3.54G /dev/VolGroup/LogVol00
Rounding size to boundary between physical extents: 3.54 GiB
Extending logical volume LogVol00 to 18.00 GiB
Logical volume LogVol00 successfully resized
[root@localhost ~]# resize2fs /dev/VolGroup/LogVol00
resize2fs 1.41.12 (17-May-2010)
Filesystem at /dev/VolGroup/LogVol00 is mounted on /; on-line resizing required
old desc_blocks = 1, new_desc_blocks = 2
Performing an on-line resize of /dev/VolGroup/LogVol00 to 4719616 (4k) blocks.
The filesystem on /dev/VolGroup/LogVol00 is now 4719616 blocks long.
swap文件
新建2G的swap文件，掛載到swap,添加到開機啟動項。
[root@localhost ~]# dd if=/dev/zero of=/www/swap bs=1024 count=2048000
2048000+0 records in
2048000+0 records out
2097152000 bytes (2.1 GB) copied, 12.0018 s, 175 MB/s
[root@localhost ~]# mkswap /www/swap
mkswap: /www/swap: warning: don't erase bootbits sectors
on whole disk. Use -f to force.
Setting up swapspace version 1, size = 2047996 KiB
no label, UUID=92ab4ed5-f301-4ba4-970f-9e5600610522
[root@localhost ~]# swapon /www/swap
[root@localhost ~]# free -m
total used free shared buffers cached
Mem: 1877 1796 80 0 7 1647
-/+ buffers/cache: 142 1735
Swap: 1999 0 1999
[root@localhost ~]# swapon -s
Filename Type Size Used Priority
/www/swap file 2047992 0 -1
修改啟動項
編輯 /etc/fstab文件，去掉之前的swap分區掛載，在最末行增加swap文件的掛載
[root@localhost ~]# cat /etc/fstab
#
# /etc/fstab
# Created by anaconda on Thu Jul 23 03:45:08 2015
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#
/dev/mapper/VolGroup-LogVol00 / ext4 defaults 1 1
UUID=4221a802-6ce2-4638-a3a5-7c17b961f291 /boot ext4 defaults 1 2
UUID=b720b68f-37b7-45ce-b4a2-40deeb9fa90f /www ext3 defaults 1 2
tmpfs /dev/shm tmpfs defaults 0 0
devpts /dev/pts devpts gid=5,mode=620 0 0
sysfs /sys sysfs defaults 0 0
proc /proc proc defaults 0 0
/www/swap swap swap defaults 0 0
重啟後可以看到，根分區空間有增加， swap使用的是swap文件
[root@localhost ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/VolGroup-LogVol00
18G 716M 17G 5% /
tmpfs 939M 0 939M 0% /dev/shm
/dev/sda1 485M 32M 429M 7% /boot
/dev/sda2 61G 2.2G 55G 4% /www
[root@localhost ~]# free -m
total used free shared buffers cached
Mem: 1877 135 1741 0 7 36
-/+ buffers/cache: 91 1786
Swap: 1999 0 1999
[root@localhost ~]# swapon -s
Filename Type Size Used Priority
/www/swap file 2047992 0 -1
注：之前有實驗過直接刪掉swap的LV，用文件代替，但是，刪除swap的LV後,重啟報錯如圖
按網上的解決辦法，開機按“e”加“enforcing=0”神馬的不管用。這個問題暫時木有解決，有解決過的老師，請告訴下學生。
