linux 缩减 物理分区,Lvm基本应用，扩展及缩减实现
什么是LVM
LVM是Logical Volume Manager的简写。其是Linux环境下对磁盘分区进行管理的一种机制。LVM由Heinz Mauelshagen在Linux 2.4内核上实现。其主要作用是在不损坏磁盘数据的情况下对磁盘空间进行增加，缩减。LVM的做法是将几块物理硬盘通过软件的方式组合成一块空间相对大的Volume Group，简称VG，然后将这块大磁盘通过Physical Extend组成可以使用的分区Logical Volume，简称LV。将LV格式化之后挂载既能使用
LVM的几个名词介绍
PV：Physical Volume，物理卷
PE：Physical Extend，物理块
VG：Volume Group，卷组
LV：Logical Volume，逻辑卷
LVM常用命令介绍
PV常用命令：
pvcreate [device]：创建PV
pvs：显示pv的简要信息
pvdisplay /dev/sd[abcd]#：显示PV的详细信息。如果不指定设备，则显示所有PV详细信息
pvremove /dev/sd[abcd]#：删除PV
VG常用命令：
vgcreate [–s #[mMgGtT]] VG_NAME PhysicalDevicePath…：创建VG
-s：指定PE的大小，PE默认大小是4MB
vgs [VG_NAME]：显示简要VG信息
vgdisplay [VG_NAME]：显示指定VG的详细信息，不指定VG则默认显示全部VG的详细信息
LV常用命令
lvcreate –L [+]#[mMgGtT] –n LV_NAME VG_NAME：创建LV
-L：指定LV的大小
-n：指定LV的名字
lvs [LV_NAME]：显示制指定v的简要信息，不指定lv默认显示全部lv的简要信息
lvdisplay [LV_NAME]：显示指定lv的详细信息，不指定lv默认显示全部lv的详细信息
lvextend -L [+]#[mMgGtT] LV_NAME：扩展LV到指定大小
lvreduce -L [+]#[mMgGtT] LV_NAME：缩减LV到指定大小
lvremove /dev/VG_NAME/LV_NAME:：删除LV
LV的抽象表示
示例：LV的创建，扩展和缩减。此处以一块120G的硬盘为例，其设备文件是/dev/sda
LV的创建
1. 使用fdisk内建命令创建分区。注意，分区完毕后要将分区文件的System ID 改为8e: Linux LVM。此处以/dev/sda5, /dev/sda6,/dev/sda7作为LVM示例
[root@localhost ~]# fdisk -l /dev/sda
Disk /dev/sda: 128.8 GB, 128849018880 bytes, 251658240 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: 0x000c744b
Device Boot Start End Blocks Id System
/dev/sda1 * 2048 1026047 512000 83 Linux
/dev/sda2 1026048 89120767 44047360 8e Linux LVM
/dev/sda3 89120768 110092287 10485760 83 Linux
/dev/sda4 110092288 251658239 70782976 5 Extended
/dev/sda5 110094336 120580095 5242880 8e Linux LVM
/dev/sda6 120582144 141553663 10485760 8e Linux LVM
/dev/sda7 141555712 173012991 15728640 8e Linux LVM
2. 创建pv
[root@localhost ~]# pvs
PV VG Fmt Attr PSize PFree
/dev/sda2 centos lvm2 a-- 42.00g 4.00m
[root@localhost ~]# pvcreate /dev/{sda5,sda6,sda7}
Physical volume "/dev/sda5" successfully created
Physical volume "/dev/sda6" successfully created
Physical volume "/dev/sda7" successfully created
[root@localhost ~]# pvs
PV VG Fmt Attr PSize PFree
/dev/sda2 centos lvm2 a-- 42.00g 4.00m
/dev/sda5 lvm2 --- 10.00g 10.00g
/dev/sda6 lvm2 --- 10.00g 10.00g
/dev/sda7 lvm2 --- 5.00g 5.00g
3. 创建VG，指定PE大小为16MB
[root@localhost ~]# vgcreate -s 16M myvg /dev/sda5 /dev/sda6 /dev/sda7
Volume group "myvg" successfully created
[root@localhost ~]# vgs
VG #PV #LV #SN Attr VSize VFree
centos 1 3 0 wz--n- 42.00g 4.00m
myvg 3 0 0 wz--n- 24.95g 24.95g
[root@localhost ~]# vgdisplay myvg
--- Volume group ---
VG Name myvg
System ID
Format lvm2
Metadata Areas 3
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 3
Act PV 3
VG Size 24.95 GiB
PE Size 16.00 MiB
Total PE 1597
Alloc PE / Size 0 / 0
Free PE / Size 1597 / 24.95 GiB
VG UUID b2OW0g-eCXR-0oxI-Z8Ft-Jemk-zXON-fnpSb1
4. 创建LV
[root@localhost ~]# lvcreate -L 10G -n mylv myvg
WARNING: ext4 signature detected on /dev/myvg/mylv at offset 1080. Wipe it? [y/n]: y
Wiping ext4 signature on /dev/myvg/mylv.
Logical volume "mylv" created.
[root@localhost ~]# lvdisplay /dev/myvg/mylv
--- Logical volume ---
LV Path /dev/myvg/mylv
LV Name mylv
VG Name myvg
LV UUID 669CDR-JifV-bCou-1QfU-q7VH-0b07-orShqW
LV Write Access read/write
LV Creation host, time localhost.localdomain, 2016-09-07 14:33:17 +0800
LV Status available
# open 0
LV Size 10.00 GiB
Current LE 640
Segments 2
Allocation inherit
Read ahead sectors auto
- currently set to 8192
Block device 253:2
5.格式化LV文件系统
[root@localhost ~]# mke2fs -t ext3 /dev/myvg/mylv
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
655360 inodes, 2621440 blocks
131072 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=2684354560
80 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
Allocating group tables: done
Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done
[root@localhost ~]# blkid /dev/myvg/mylv
/dev/myvg/mylv: UUID="4eb1b6ce-3777-4c69-9be1-522ca486d936" SEC_TYPE="ext2" TYPE="ext3"
6. Mount LV并测试
[root@localhost ~]# mount /dev/myvg/mylv /test_lv/
[root@localhost ~]# cp /var/log/*.log /test_lv/
[root@localhost ~]# ls /test_lv
boot.log lost+found wpa_supplicant.log Xorg.0.log
[root@localhost ~]# umount /testlv
umount: /testlv: mountpoint not found
[root@localhost ~]# umount /dev/myvg/mylv
[root@localhost ~]# mount /dev/myvg//mylv /users
[root@localhost ~]# ls /users
boot.log lost+found wpa_supplicant.log Xorg.0.log
LVM的扩展
扩展LV
[root@localhost ~]# lvextend -L 15G /dev/myvg/mylv
Size of logical volume myvg/mylv changed from 10.00 GiB (640 extents) to 15.00 GiB (960 extents).
Logical volume mylv successfully resized.
2. 扩展文件系统，填充LV的空间
[root@localhost ~]# resize2fs /dev/myvg/mylv 15G
resize2fs 1.42.9 (28-Dec-2013)
Filesystem at /dev/myvg/mylv is mounted on /users; on-line resizing required
old_desc_blocks = 1, new_desc_blocks = 1
The filesystem on /dev/myvg/mylv is now 3932160 blocks long.
[root@localhost ~]# df -lh
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/centos-root 20G 3.7G 17G 19% /
devtmpfs 480M 0 480M 0% /dev
tmpfs 495M 152K 495M 1% /dev/shm
tmpfs 495M 7.2M 488M 2% /run
tmpfs 495M 0 495M 0% /sys/fs/cgroup
/dev/mapper/centos-home 20G 36M 20G 1% /home
/dev/sda1 497M 159M 339M 32% /boot
tmpfs 99M 12K 99M 1% /run/user/1000
/dev/sr0 4.1G 4.1G 0 100% /run/media/max/CentOS 7 x86_64
/dev/mapper/myvg-mylv 15G 26M 14G 1% /users
Lvm的缩减：先缩减文件空间，再缩减物理空间
卸载LV
[root@localhost ~]# umount /dev/myvg/mylv
2. 强制检测文件系统
[root@localhost ~]# e2fsck -f /dev/myvg/mylv
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/myvg/mylv: 14/983040 files (7.1% non-contiguous), 100917/3932160 blocks
3. 缩减文件系统空间到7G
[root@localhost ~]# resize2fs /dev/myvg/mylv 7G
resize2fs 1.42.9 (28-Dec-2013)
Resizing the filesystem on /dev/myvg/mylv to 1835008 (4k) blocks.
The filesystem on /dev/myvg/mylv is now 1835008 blocks long.
4. 缩减LV空间至7G
[root@localhost ~]# lvs /dev/myvg/mylv
LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert
mylv myvg -wi-a----- 15.00g
[root@localhost ~]# lvreduce -L 7G mylv
Path required for Logical Volume "mylv".
Please provide a volume group name
Run `lvreduce --help' for more information.
[root@localhost ~]# lvreduce -L 7G /dev/myvg/mylv
WARNING: Reducing active logical volume to 7.00 GiB
[root@localhost ~]# lvs /dev/myvg/mylv
LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert
mylv myvg -wi-a----- 7.00g
5. 挂载并测试
[root@localhost ~]# mount /dev/myvg/mylv /users
[root@localhost ~]# ls /users
boot.log lost+found wpa_supplicant.log Xorg.0.log
[root@localhost ~]# cat /users/Xorg.0.log
[ 30.065]
X.Org X Server 1.17.2
Release Date: 2015-06-16
原创文章，作者：mxb93，如若转载，请注明出处：http://www.178linux.com/44303