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Editor to share with you how to use LVM in RHEL6.5, I believe most people do not know much about it, so share this article for your reference, I hope you can learn a lot after reading this article, let's go to know it!

One of the common problems that Linux users encounter when installing an operating system is how to correctly evaluate the size of each partition in order to allocate the appropriate hard disk space. The ordinary disk partition management method cannot change the size of each partition after it has been partitioned, and when a logical partition cannot hold a file, the file cannot be stored across multiple partitions because of the limitations of the upper file system. So it can't be put on another disk at the same time. Or when a partition is running out of space, the solution is usually to use symbolic links, or to create a new directory plug-in partition and use a tool to resize the partition, but this is only a temporary solution, not a fundamental solution to the problem. In fact, under Linux, using LVM, these problems can be easily solved, and users can easily adjust the size of each partition without downtime.

1. Brief introduction of LVM command

LVM (Logical Volume Manager) is a logical volume manager applied to the kernel of Linux and a mechanism for disk partition management in Linux environment.

Nouns you need to know in LVM:

1. PV (physical volume) can be a disk and a partition. Composed of PE (physical extent), multiple PV can form a VG (volume group).

2. VG (volume group) is a group composed of multiple physical volumes, but the volume group cannot be used directly. You need to create a LV (logical volume) on it before you can use it. Multiple LV can be created on VG.

3. PE (physical extent) is like the block block of the disk we learned earlier, and the default is 4MB.

4. LV (logical volume) is an available space built on top of a volume group. There are two kinds of boundaries: physical boundary and logical boundary.

2. Introduction of related commands

1. Physical volume PV

Pvcreate creates pv example: pvcreate / dev/sda1

Pvs to view pv information example: enter pvs directly on the command line

Pvdisplay View pv details example: pvcreate / dev/sda1

Pvmove moves pv data to another pv example: pvmove / dev/sda1 / dev/sda4

Pvremove deletes pv example: pvremove / dev/sda1

2. Volume group VG

How to create, view, and delete vg

Vgcreate creates vg as an example: vgcreate myvg / dev/sda {mrecom n}

Vgs to view vg information example: enter vgs directly on the command line

Vgdisplay View vg details example: vgdisplay myvg

Vgremove deletes vg example: vgremove myvg

How to extend vg

First of all, prepare a PV.

Then use the vgextend command to complete the extension

Format: vgextend VG_NAME / PATH/TO/PV

Vgextend testvg / dev/sdb2 extends the myvg volume group, adding / dev/sda2

How to reduce vg

1) determine the PV to be removed

2) transfer the data on this PV to another PV

Pvmove / path/ to / pv

3) remove this PV from the volume group

Format: vgreduce VG_NAME / PATH/TO/PV

Vgreduce testvg / dev/sdb2 reduce the myvg volume group and remove / dev/sda2

3. Logical volume LV

How to create, view, and delete lv

Lvcreate creates lv example: lvcreate lv1 / dev/myvg

Lvs to view lv information example: enter lvs directly on the command line

Lvdisplay View lv details example: vgdisplay lv1

Lvremove removes lv example: lvremove / dev/myvg/lv1

How to extend lv

Determine how much space needs to be expanded

Determine whether the volume group in which the current logical volume belongs has enough free space

An example of expansion:

1. Physical boundary

Lvextend-L [+] SIZE / path/to/lv

2. Logical boundary

Resize2fs / path/to/device

How to reduce lv

Determine the size of the reduction, but only if it can accommodate at least all the original data.

Shrink:

1) unmount and forcibly detect the file system

Umount / path

E2fsck-f

2) logical boundary

Resize2fs / path/to/device SIZE

3) physical boundary

Lvreduce-L [-] SIZE / path/to/lv

4. Snapshot Volume

1) the lifecycle is the entire data duration, during which the growth of data cannot exceed the snapshot volume size.

2) the snapshot volume should be read-only

3) in the same volume group as the original volume

Lvcreate

-L specifies the size of the snapshot volume

-s create snapshot volum

The snapshot volume created by-p r is read-only

Format:

Lvcreate-L SIZE-s-pr-n LV_NAME / path/to/lv

III. An example of lv

1. Create a partition

[root@test11 ~] # fdisk-l / / View the partition

[root@test11 ~] # fdisk / dev/sda / / to partition

Command (m for help): n / / n to add a partition, p view partition

First cylinder (2898-10443, default 2898): / / Press the [Enter] key to decide

Using default value 2898 / / start cylinder Select default

Last cylinder or + size or + sizeM or + sizeK (289810443, default 10443): + 2G / / give the size of 2G

Command (m for help): t / / change partition type

Partition number (1-5): 5 / / selected partition

Hex code (type L to list codes): l / / list of partition types

Hex code (type L to list codes): 8e / / Mark the newly added partition as lvm

Command (m for help): P / / View partition table

/ dev/sda5 2756 2999 1959898 + 8e Linux LVM

Command (m for help): W / / Save

[root@test11 ~] # partprobe / dev/sda / / is the system identification partition (instead of reboot)

[root@test11 ~] # mkfs.ext4 / dev/sda5 / / format the newly added partition

2. The creation of PV

[root@test11 ~] # pvcreate / dev/sda5 / / create pv

Writing physical volume data to disk "/ dev/sda5"

Physical volume "/ dev/sda5" successfully created

[root@test11 ~] # pvs / / View the current pv information

PV VG Fmt Attr PSize PFree

/ dev/sda5 lvm2 Amuri-1.87G 1.87G

3. The creation of VG

[root@test11 ~] # vgcreate vg0 / dev/sda5 / / vg0 is the name of the current vg

Volume group "vg0" successfully created

[root@test11 ~] # vgs / / View the information of vg

VG # PV # LV # SN Attr VSize VFree

Vg0 1 0 0 wz--n- 1.87G 1.87G

4. The creation of lv

[root@test11] # lvcreate-L 500m-n lv01 vg0

Logical volume "lv01" created

[root@test11 ~] # lvs / / View the information of lv

LV VG Attr LSize Origin Snap% Move Log Copy% Convert

Lv01 vg0-wi-a- 500.00m

[root@test11 ~] # mkfs.ext4 / dev/vg0/lv01 / / format

5. The increase of lv

[root@test11 ~] # lvextend-L + 300m / dev/vg0/lv01 / / (original lv size 500m, stretch partition to 800m) Extending logical volume lv01 to 800.00 MB

Logical volume lv01 successfully resized

[root@test11 ~] # resize2fs / dev/vg0/lv01 / / stretch the file system

[root@test11 ~] # lvs

LV VG Attr LSize Origin Snap% Move Log Copy% Convert

Lv01 vg0-wi-ao 800.00m / / size becomes 800m

6. Reduction of lv

# umount / dev/vg0/lv01 / / unmount logical volumes / dev/vg0/lv01

# df-h / / View

# e2fsck-f / dev/vg0/lv01 / / disk check

# resize2fs / dev/vg0/lv01 500m / / retract the file system to 500m

# lvreduce-L 500m / dev/vg0/lv01 / / retract partition to 500m

WARNING: Reducing active logical volume to 500.00 MB

THIS MAY DESTROY YOUR DATA (filesystem etc.)

Do you really want to reduce lv01? [y/n]: y

# lvs

LV VG Attr LSize Origin Snap% Move Log Copy% Convert

Lv01 vg0-wi-a- 500.00m / / now 500m size

# mount / dev/vg0/lv01 / mnt/lv01 / / remount the partition

# df-h / / View

# ls / mnt/lv01 / / View files

IV. Shutdown of lvm

[root@test11 ~] # umount / mnt/lv01

[root@test11 ~] # lvremove / dev/vg0/lv01 / / Delete lv

Do you really want to remove active logical volume lv01? [y/n]: y

Logical volume "lv01" successfully removed

[root@test11 ~] # vgchange-an vg0 / / makes vg0 without the active flag

0 logical volume (s) in volume group "vg0" now active

[root@test11 ~] # vgremove vg0 / / Delete vg

Volume group "vg0" successfully removed

[root@test11 ~] # pvremove / dev/sda5 / / Delete pv

Labels on physical volume "/ dev/sda5" successfully wiped

Expand the root partition and SWAP

[root@zkdb1 ~] # pvs

PV VG Fmt Attr PSize PFree

/ dev/sda3 vg_zkdb1 lvm2 a muri-557.46g 521.46g

[root@zkdb1 ~] # lvs

LV VG Attr LSize Pool Origin Data% Move Log Cpy%Sync Convert

Root vg_zkdb1-wi-ao---- 20.00g

Swap vg_zkdb1-wi-ao---- 16.00g

[root@zkdb1] # lvcreate-L 30720m vg_zkdb1

Logical volume "lvol0" created

[root@zkdb1 ~] # lvs

LV VG Attr LSize Pool Origin Data% Move Log Cpy%Sync Convert

Lvol0 vg_zkdb1-wi-a- 30.00g

Root vg_zkdb1-wi-ao---- 20.00g

Swap vg_zkdb1-wi-ao---- 16.00g

[root@zkdb1] # lvextend-L + 30g / dev/mapper/vg_zkdb1-root

Extending logical volume root to 50.00 GiB

Logical volume root successfully resized

[root@zkdb1] # e2fsck-f / dev/mapper/vg_zkdb1-root

E2fsck 1.41.12 (17-May-2010)

/ dev/mapper/vg_zkdb1-root is mounted.

E2fsck: Cannot continue, aborting.

[root@zkdb1 ~] # lvs

LV VG Attr LSize Pool Origin Data% Move Log Cpy%Sync Convert

Lvol0 vg_zkdb1-wi-a- 30.00g

Root vg_zkdb1-wi-ao---- 50.00g

Swap vg_zkdb1-wi-ao---- 16.00g

[root@zkdb1 ~] # resize2fs / dev/mapper/vg_zkdb1-root

Resize2fs 1.41.12 (17-May-2010)

Filesystem at / dev/mapper/vg_zkdb1-root is mounted on /; on-line resizing required

Old desc_blocks = 2, new_desc_blocks = 4

Performing an on-line resize of / dev/mapper/vg_zkdb1-root to 13107200 (4k) blocks.

The filesystem on / dev/mapper/vg_zkdb1-root is now 13107200 blocks long.

Extended SWAP

[root@zkdb1 ~] # lvs

LV VG Attr LSize Pool Origin Data% Move Log Cpy%Sync Convert

Lvol0 vg_zkdb1-wi-a- 30.00g

Root vg_zkdb1-wi-ao---- 50.00g

Swap vg_zkdb1-wi-ao---- 16.00g

[root@zkdb1] # lvextend-L + 16G / dev/mapper/vg_zkdb1-swap

Extending logical volume swap to 32.00 GiB

Logical volume swap successfully resized

[root@zkdb1] # e2fsck-f / dev/mapper/vg_zkdb1-swap

E2fsck 1.41.12 (17-May-2010)

/ dev/mapper/vg_zkdb1-swap is mounted.

E2fsck: Cannot continue, aborting.

[root@zkdb1 ~] # resize2fs / dev/mapper/vg_zkdb1-swap

Resize2fs 1.41.12 (17-May-2010)

Resize2fs: Bad magic number in super-block while trying to open / dev/mapper/vg_zkdb1-swap

Couldn't find valid filesystem superblock.

[root@zkdb1 ~] # lvs

LV VG Attr LSize Pool Origin Data% Move Log Cpy%Sync Convert

Lvol0 vg_zkdb1-wi-a- 30.00g

Root vg_zkdb1-wi-ao---- 50.00g

Swap vg_zkdb1-wi-ao---- 32.00g

Attached: the solution of changing root partition to read-only

1 single user mode

Enter the command to repair the file system: fsck-C-y

Enter the command to restart after the repair is complete: reboot

2 remount

Mount-o remount,rw partition name can be read and written

Mount-o remount,rw /

If prompted for file system type

Mount-t ext3-o remount,rw /

The above is all the contents of the article "how to use LVM in RHEL6.5". Thank you for reading! I believe we all have a certain understanding, hope to share the content to help you, if you want to learn more knowledge, welcome to follow the industry information channel!

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