Detailed explanation of examples of logical volume management lvm

Logical Volume Management LVM

Create a logical volume

##1 Prepare partitions or hard disks

Here we use two hard disks of /dev/sdb and /dev/sdc and two partitions of /dev/sda9 and /dev/sda10, both in size. It's 1G and the disk is limited, so I don't want to be so picky.

Add partitions /dev/sda9, /dev/sda10

[root@centos7 ~]# fdisk /dev/sda

Welcome to fdisk (util-linux 2.23.2).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.

Command (m for help): n
All primary partitions are in use
Adding logical partition 9
First sector (31885312-41943039, default 31885312):
Using default value 31885312
Last sector, +sectors or +size{K,M,G} (31885312-41943039, default 41943039): +1G
Partition 9 of type Linux and of size 1 GiB is set

Note that you need to change the partition type to Linux LVM

Command (m for help): t
Partition number (1-9, default 9): 8e
Partition number (1-9, default 9): 9
Hex code (type L to list all codes): 8e
Changed type of partition 'Linux' to 'Linux LVM'
Command (m for help):

Create /dev/sda10 in the same way.

[root@centos7 ~]# lsblk

NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 20G 0 disk
├─sda9 8:9 0 1G 0 part
└─sda10 8:10 0 1G 0 part
sdb 8:16 0 1G 0 disk
sdc 8:32 0 1G 0 disk

2 Create PV (physical volume)

The command format is: pvcreate DEVICE, you can create one device at a time , you can also create multiple devices at once.

View physical volume commands: pvdisplay (view detailed information), pvs (view simple information)

[root@centos7 ~]# pvcreate /dev/sda9

Physical volume "/dev/sda9" successfully created.
[root@centos7 ~]# pvcreate /dev/sda10 /dev/sdb /dev/sdc
Physical volume "/dev/sda10" successfully created.
Physical volume "/dev/sdb" successfully created.
Physical volume "/dev/sdc" successfully created.

View the physical volume and see that it has been successfully created.

[root@centos7 ~]# pvs
PV VG Fmt Attr PSize PFree
/dev/sda10 lvm2 --- 1.00g 1.00g
/dev/sda9 lvm2 --- 1.00g 1.00g
/dev/sdb lvm2 --- 1.00g 1.00g
/dev/sdc lvm2 --- 1.00g 1.00g

3 Create a volume group (VG)

The command format is: vgcreate -s PE VGNAME (vg name ) DEVICE (device name)

-s: Specify the physical extension block size, which is the size of the PE

View commands: vgs, vgdisplay

[root@centos7 ~]# vgcreate -s 16M vg0 /dev/sda9 /dev/sda10 /dev/sdb /dev/sdc
Volume group "vg0" successfully created

Check it out

[root@centos7 ~]# vgs

VG #PV #LV #SN Attr VSize VFree
vg0 4 0 0 wz--n- 3.94g 3.94g

and then look at the details

[root@centos7 ~]# vgdisplay

--- Volume group ---
VG Name vg0
System ID
Format lvm2
Metadata Areas 4
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 4
Act PV 4
VG Size 3.94 GiB
PE Size 16.00 MiB
Total PE 252
Alloc PE / Size 0 / 0
Free PE / Size 252 / 3.94 GiB
VG UUID qmoIMg-5wQR-GKCS-dpq9-HLrt-zVIi-JBC9ZX

Everything is as expected, the size is about 4G, which is exactly two partitions and two The sum of hard drives.

4 Create a logical volume (LV)

The command format is: lvcreate -n LVNAME (specify LV name) -L SIZE (specify LV size) vg0 (VG to be used)

-l Specify PE size

View command (similar to PV, VG): lvs, lvdisplay

[root@centos7 ~]# lvcreate -n lv0 -L 3G vg0

Logical volume "lv0" created.

Created successfully, check

[root@centos7 ~]# lvs

LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert
lv0 vg0 -wi-a----- 3.00g

and then check the details

[root@centos7 ~]# lvdisplay

--- Logical volume ---
LV Path /dev/vg0/lv0
LV Name lv0
VG Name vg0
LV UUID 622i7m-uy6s-3nZI-8xSb-sxrR-cZzz-C9pwkd
LV Write Access read/write
LV Creation host, time centos7.3.loacl, 2017-04-25 16:25:13 +0800
LV Status available
# open 0
LV Size 3.00 GiB
Current LE 192
Segments 4
Allocation inherit
Read ahead sectors auto
- currently set to 8192
Block device 253:0

You can confirm that it has been successfully created.

Now you can use /dev/vg0/lv0 as a hard disk.

Now look at the disk information, it has changed.

[root@centos7 ~]# lsblk

NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
fd0 2:0 1 4K 0 disk
sda 8:0 0 20G 0 disk
├─sda9 8:9 0 1G 0 part
│ └─vg0-lv0 253:0 0 3G 0 lvm
└─sda10 8:10 0 1G 0 part
└─vg0-lv0 253:0 0 3G 0 lvm
sdb 8:16 0 1G 0 disk
└─vg0-lv0 253:0 0 3G 0 lvm
sdc 8:32 0 1G 0 disk
└─vg0-lv0 253:0 0 3G 0 lvm

You can see that the added partition and hard disk already belong to vg0-lv0.

5 Create the file system and format it

mkfs.ext4 /dev/vg0/lv0

[root@centos7 ~]# mkfs.ext4 /dev/vg0/lv0

6 Mount using

[root@centos7 ~]# mkdir /mnt/lv0

[root@centos7 ~]# mount /dev/vg0/lv0 /mnt/lv0

Second expansion LV

Extension command format:

lvextend -L 100G /dev/vg0/lv0

lvextend -l +100G /dev/vg0/lv0

lvextend -l +100%FREE /dev/vg0/lv0

Note –L is how much to extend, -l is how much to extend (increase), +100%FREE is to extend 100% of the remaining vg, which can be adjusted according to personal circumstances Make your selection.

Since vg0 still reserves nearly 1G space, now expand lv0

1 Let’s check the original LV first

[root@centos7 ~]# vgs

VG #PV #LV #SN Attr VSize VFree
vg0 4 1 0 wz--n- 3.94g 960.00m

2 Extend LV

[root@centos7 ~]# lvextend -r -l +100%FREE /dev/vg0/lv0

-r is resizefs. It’s so convenient to do it in one step

Or It's a little troublesome, step by step

[root@centos7 ~]# lvextend -l +100%FREE /dev/vg0/lv0

Size of logical volume vg0/lv0 changed from 3.00 GiB (192 extents) to 3.94 GiB (252 extents).
Logical volume vg0/lv0 successfully resized.

3 Come down and redefine the file system size

ext series file system redefinition : resize2fs /dev/vg0/lv0

xfs series file system redefinition: xfs_growfs /dev/vg0/lv0

[root@centos7 ~]# resize2fs /dev/vg0/lv0

resize2fs 1.42.9 (28-Dec-2013)
Filesystem at /dev/vg0/lv0 is mounted on /mnt/lv0; on-line resizing required
old_desc_blocks = 1, new_desc_blocks = 1
The filesystem on /dev/vg0/lv0 is now 1032192 blocks long.

4 Check the file System completion (optional)

[root@centos7 ~]# fsck.ext4 /dev/vg0/lv0

e2fsck 1.42.9 (28-Dec-2013)
/dev/vg0/lv0: clean, 20/262144 files, 35918/1032192 blocks

5 Confirm the logical volume size

[root@centos7 ~]# df -h /dev/vg0/lv0

Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg0-lv0 3.9G 12M 3.6G 1% /mnt/lv0

It is obvious that the expansion has been successful.

6 Mount using

[root@centos7 ~]# mount -o remount /dev/vg0/lv0

Three reduced LV

1 Backup data

Although there is generally no loss of data, for the sake of safety . It's better to back up first.

Look at the existing data in the /mnt/lv0 directory

[root@centos7 ~]# ls /mnt/lv0/

lost+found myfile2 myfile4 myfile6 myfile8

myfile1 myfile3 myfile5 myfile7 myfile9

[root@centos7 ~]# mkdir /backup

[root@centos7 ~]# cp -a /mnt/lv0/* /backup/

##2 Uninstall /dev/vg0/lv0

[root@centos7 ~]# umount /mnt/lv0/

3 Check the file systeme2fsck -f /dev/vg0/lv0 Redefining the file system Disk completion must be checked before size

[root@centos7 ~]# e2fsck -f /dev/vg0/lv0

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: 20/262144 files (0.0% non-contiguous), 35918/1032192 blocks

4下来重定义文件系统大小

resize2fs /dev/vg0/lv0 2G #2G位缩减后的LV 大小。

[root@centos7 ~]# resize2fs /dev/vg0/lv0 2G
resize2fs 1.42.9 (28-Dec-2013)
Resizing the filesystem on /dev/vg0/lv0 to 524288 (4k) blocks.
The filesystem on /dev/vg0/lv0 is now 524288 blocks long.

5 缩减LV

lvreduce -L 2G /dev/vg0/lv0 #缩减到2G

[root@centos7 ~]# lvreduce -L 2G /dev/vg0/lv0

WARNING: Reducing active logical volume to 2.00 GiB.
THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce vg0/lv0? [y/n]: y
Size of logical volume vg0/lv0 changed from 3.94 GiB (252 extents) to 2.00 GiB (128 extents).
Logical volume vg0/lv0 successfully resized.

6 挂载使用

mount /dev/vg0/lv0 /mnt/lv0

[root@centos7 ~]# mount /dev/vg0/lv0 /mnt/lv0/

查看磁盘挂载情况

[root@centos7 ~]# df -h /dev/vg0/lv0

Filesystem Size Used Avail Use% Mounted on

/dev/mapper/vg0-lv0 2.0G 9.0M 1.8G 1% /mnt/lv0

7 确认数据是否丢失

现在再来开心目录/mnt/lv0 的内容

[root@centos7 ~]# ls /mnt/lv0/

lost+found myfile2 myfile4 myfile6 myfile8
myfile1 myfile3 myfile5 myfile7 myfile9

 

很完美，数据并没有丢失！

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