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It is believed that many inexperienced people don't know what to do about how to create logical volume management LVM in Linux. Therefore, this paper summarizes the causes and solutions of the problem. Through this article, I hope you can solve this problem.

LVM explanation:

Image outline:

1) what is LVM and its function:

LVM is called logical volume management, and its purpose is to improve the flexibility of disk partition management and use.

Through logical volume LVM, disk space can be effectively managed and allocated, and scattered small partitions can be combined into a large volume group, and the required space can be separated from the volume group to make logical volumes, which makes disk expansion and reduction easy to use. There is also a backup function, which refers to lvm snapshots.

2) create an instance:

Disk-"partition -" ID modification 8e-"save.

I use a disk to do it through partitions. Each disk can also be divided into a zone to do.

Device Boot Start End Blocks Id System

/ dev/sdb1 1 1306 10490413 + 8e Linux LVM

/ dev/sdb2 1307 2612 10490445 8e Linux LVM

/ dev/sdb3 2613 3918 10490445 8e Linux LVM

3) create a physical volume: through the pvcreate command.

Pvcreate / dev/sdb1

Pvcreate / dev/sdb2

Pvcreate / dev/sdb3

[root@station106 ~] # pvs (view the physical volume created).

PV VG Fmt Attr PSize PFree

/ dev/sda2 vg0 lvm2 a muri-59.99g 7.99g

/ dev/sdb1 lvm2 a muri-10.00g 10.00g

/ dev/sdb2 lvm2 a muri-10.00g 10.00g

/ dev/sdb3 lvm2 a muri-10.00g 10.00g

Pvdisplay to see more details.

[root@station106 ~] # pvdisplay

-Physical volume

PV Name / dev/sdb1

VG Name myvg

PV Size 10.00 GiB / not usable 4.54 MiB

Allocatable yes

PE Size 4.00 MiB

Total PE 2560

Free PE 2560

Allocated PE 0

PV UUID XP8QfA-WQDd-1v9p-QKxk-AztZ-Nr9e-QbN6Gu

-Physical volume

PV Name / dev/sdb2

VG Name myvg

PV Size 10.00 GiB / not usable 4.58 MiB

Allocatable yes

PE Size 4.00 MiB

Total PE 2560

Free PE 2560

Allocated PE 0

PV UUID f8Dtdd-fV9e-1yB7-1B8P-21mU-CU2f-fQDAxe

-Physical volume

PV Name / dev/sdb3

VG Name myvg

PV Size 10.00 GiB / not usable 4.58 MiB

Allocatable yes

PE Size 4.00 MiB

Total PE 2560

Free PE 2560

Allocated PE 0

PV UUID rKNL0x-WXq2-gHYD-T27r-Gf05-a4y3-f4zqzt

4) create a logical volume: through vgcreate.

[root@station106 ~] # vgcreate myvg / dev/sdb {1pm 2pm 3}

Volume group "myvg" successfully created

[root@station106 ~] # vgs

VG # PV # LV # SN Attr VSize VFree

Myvg 30 0 wz--n- 30.00g 30.00g

5) create a logical volume, lvcreate.

[root@station106] # lvcreate-L 10G-n test myvg

Logical volume "test" created

-L: space size.

-n: logical volume name.

[root@station106 ~] # lvdisplay / dev/myvg/test

-Logical volume

LV Path / dev/myvg/test

LV Name test

VG Name myvg

LV UUID wY1YUF-f0o6-jzu1-mtTL-64p0-qvfC-3QfF8y

LV Write Access read/write

LV Creation host, time station106.magelinux.com, 2014-02-10 11:18:43 + 0800

LV Status available

# open 0

LV Size 10.00 GiB

Current LE 2560

Segments 1

Allocation inherit

Read ahead sectors auto

-currently set to 256

Block device 253:4

6) Mount the created logical volume.

Mke2fs-t ext4 / dev/myvg/test format.

Mount / dev/myvg/test / mnt/ is used for mounting.

7) if one day the logical volume is not enough. How do you extend from a volume group? The analysis is as follows.

Rough steps for logical volume expansion:

1, first determine the size of the extension and make sure that the volume group to which you belong has enough remaining space.

I'm going to expand 5G now, which is the size of 10G itself. The command is as follows:

[root@station106] # lvextend-L + 5G / dev/myvg/test

Extending logical volume test to 15.00 GiB

Logical volume test successfully resized

2. Extend the physical boundary. The physical boundary refers to the physical edge size of itself.

[root@station106 ~] # lvdisplay / dev/myvg/test

-Logical volume

LV Path / dev/myvg/test

LV Name test

VG Name myvg

LV UUID wY1YUF-f0o6-jzu1-mtTL-64p0-qvfC-3QfF8y

LV Write Access read/write

LV Creation host, time station106.magelinux.com, 2014-02-10 11:18:43 + 0800

LV Status available

# open 1

LV Size 15.00 GiB

Current LE 3840

Segments 2

Allocation inherit

Read ahead sectors auto

-currently set to 256

Block device 253:4

When you have extended the physical boundaries, you will find that the logical volume in the mount is still its own size.

[root@station106 ~] # df-hT

Filesystem Type Size Used Avail Use% Mounted on

/ dev/mapper/vg0-root

Ext4 20G 387m 19G 3% /

Tmpfs tmpfs 242m 0 242m 0% / dev/shm

/ dev/sda1 ext4 194M 29M 156M 16% / boot

/ dev/mapper/vg0-usr

Ext4 9.9G 1.9G 7.6G 20% / usr

/ dev/mapper/vg0-var

Ext4 20G 288m 19G 2% / var

/ dev/mapper/myvg-test

Ext4 9.9G 151m 9.2G 2% / mnt

Extend the logical boundary, which means that after mounting, the logical volume in use is also directly identified.

[root@station106 ~] # resize2fs / dev/myvg/test

Resize2fs 1.41.12 (17-May-2010)

Filesystem at / dev/myvg/test is mounted on / mnt; on-line resizing required

Old desc_blocks = 1, new_desc_blocks = 1

Performing an on-line resize of / dev/myvg/test to 3932160 (4k) blocks.

The filesystem on / dev/myvg/test is now 3932160 blocks long.

[root@station106 ~] # df-hT

Filesystem Type Size Used Avail Use% Mounted on

/ dev/mapper/vg0-root

Ext4 20G 387m 19G 3% /

Tmpfs tmpfs 242m 0 242m 0% / dev/shm

/ dev/sda1 ext4 194M 29M 156M 16% / boot

/ dev/mapper/vg0-usr

Ext4 9.9G 1.9G 7.6G 20% / usr

/ dev/mapper/vg0-var

Ext4 20G 288m 19G 2% / var

/ dev/mapper/myvg-test

Ext4 15G 153M 14G 2% / mnt

This is the part of the extended logical volume.

Example demonstration: shrink the logical volume. First of all, in order to test that I went to the previously mounted record to create some files, test whether it will cause the files to disappear after zooming out.

The steps to shrink the logical volume are as follows:

1) uninstall the previous mount first, and perform a forced test.

[root@station106 ~] # umount / mnt/

[root@station106] # e2fsck-f / dev/myvg/test

E2fsck 1.41.12 (17-May-2010)

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/test: 13ram 983040 files (0.0% non-contiguous), 100864amp 3932160 blocks

2) reduce the logical boundary.

[root@station106 ~] # resize2fs / dev/myvg/test 10G

Resize2fs 1.41.12 (17-May-2010)

Resizing the filesystem on / dev/myvg/test to 2621440 (4k) blocks.

The filesystem on / dev/myvg/test is now 2621440 blocks long.

3) reduce the physical boundary.

[root@station106] # lvreduce-L 10G / dev/myvg/test

WARNING: Reducing active logical volume to 10.00 GiB

THIS MAY DESTROY YOUR DATA (filesystem etc.)

Do you really want to reduce test? [y/n]: y

Reducing logical volume test to 10.00 GiB

Logical volume test successfully resized

View after downsizing:

[root@station106 ~] # lvdisplay / dev/myvg/test

-Logical volume

LV Path / dev/myvg/test

LV Name test

VG Name myvg

LV UUID wY1YUF-f0o6-jzu1-mtTL-64p0-qvfC-3QfF8y

LV Write Access read/write

LV Creation host, time station106.magelinux.com, 2014-02-10 11:18:43 + 0800

LV Status available

# open 0

LV Size 10.00 GiB- "here becomes 10G again.

Current LE 2560

Segments 1

Allocation inherit

Read ahead sectors auto

-currently set to 256

Block device 253:4

Mount to continue to use and see if the file exists.

[root@station106 ~] # mount / dev/myvg/test / mnt/

[root@station106 ~] # cd / mnt/

[root@station106 mnt] # ls

The accp benet lost+found-- view still exists. Not lost.

[root@station106 mnt] # df-hT

Filesystem Type Size Used Avail Use% Mounted on

/ dev/mapper/vg0-root

Ext4 20G 387m 19G 3% /

Tmpfs tmpfs 242m 0 242m 0% / dev/shm

/ dev/sda1 ext4 194M 29M 156M 16% / boot

/ dev/mapper/vg0-usr

Ext4 9.9G 1.9G 7.6G 20% / usr

/ dev/mapper/vg0-var

Ext4 20G 288m 19G 2% / var

/ dev/mapper/myvg-test

Ext4 9.9G 151m 9.2G 2% / mnt

Suppose that one day, the VG volume group is used up by logical volumes, how to continue to expand the volume group?

1) create a physical volume.

[root@station106 mnt] # pvcreate / dev/sdb5

Physical volume "/ dev/sdb5" successfully created

2) add the new physical machine to the volume group.

[root@station106 mnt] # vgextend myvg / dev/sdb5

Volume group "myvg" successfully extended

View the added volume groups.

[root@station106 mnt] # vgextend myvg / dev/sdb5

Volume group "myvg" successfully extended

[root@station106 mnt] # vgdisplay myvg

-Volume group

VG Name myvg

System ID

Format lvm2

Metadata Areas 4

Metadata Sequence No 5

VG Access read/write

VG Status resizable

MAX LV 0

Cur LV 1

Open LV 1

Max PV 0

Cur PV 4

Act PV 4

VG Size 40.00 GiB-- "from 30g to 40g."

PE Size 4.00 MiB

Total PE 10240

Alloc PE / Size 2560 / 10.00 GiB

Free PE / Size 7680 / 30.00 GiB

VG UUID KyFWJg-BU15-KrOA-uef4-Cckf-eoTz-oM38nu

If there is an extended volume group, there must be a reduction. The reduction process is as follows.

[root@station106 mnt] # vgreduce myvg / dev/sdb5

Removed "/ dev/sdb5" from volume group "myvg"

[root@station106 mnt] # vgdisplay myvg

-Volume group

VG Name myvg

System ID

Format lvm2

Metadata Areas 3

Metadata Sequence No 6

VG Access read/write

VG Status resizable

MAX LV 0

Cur LV 1

Open LV 1

Max PV 0

Cur PV 3

Act PV 3

VG Size 30.00 GiB

PE Size 4.00 MiB

Total PE 7680

Alloc PE / Size 2560 / 10.00 GiB

Free PE / Size 5120 / 20.00 GiB

VG UUID KyFWJg-BU15-KrOA-uef4

-Cckf-eoTz-oM38nu

LVM takes a snapshot.

A snapshot is a logical volume, usually read-only. Popular saying: "Snapshot size depends on backup size."

Function, can maintain the operation before the snapshot, if the subsequent operation has an impact, you can restore some of the previous operations, which is equivalent to making a backup before the snapshot, after the creation of the snapshot, there is no impact before the subsequent operation team snapshot.

[root@station106 mnt] # lvcreate-s-L 50m-n snap-p r / dev/myvg/test

Rounding up size to full physical extent 52.00 Mi

The name of the snapshot created is snap.

-L sets the size.

-p:permission, which sets the read and write permissions for generating snapshots. By default, RW;r is read-only.

-s: specifies that lvcreate generates a snapshot.

-n: specify the snapshot name

Mount the snapshot: here are the contents of the backup.

Mount / dev/myvg/snap / me

[root@station106 me] # ls

Accp benet lost+found

Then the files in the snapshot can be backed up, and the snapshot can be deleted in time after the backup.

[root@station106 ~] # lvremove / dev/myvg/snap

Do you really want to remove active logical volume snap? [y/n]: y

Logical volume "snap" successfully removed

After reading the above, have you mastered how to create a logical volume management LVM in Linux? If you want to learn more skills or want to know more about it, you are welcome to follow the industry information channel, thank you for reading!

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