Logical Volume Manager (LVM) - Santa Monica Collegehomepage.smc.edu/morgan_david/linux/a13-lvm.pdf · 1 © David Morgan 2005-17 Logical Volume Manager (LVM) David Morgan © David

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© David Morgan 2005-17

Logical Volume Manager (LVM)Logical Volume Manager (LVM)

David Morgan

© David Morgan 2005-17

““File systemFile system”” hierarchyhierarchy� A tree structure of directories

� The directory tree is standardized

portions can spread

across

different partitions

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© David Morgan 2005-17

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home bin bootusr varlib etcdev

bin manlib spoollib runlogtom harrydick

Standard file system hierarchyStandard file system hierarchy

© David Morgan 2005-17

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tom harrydick

In some piecesIn some pieces

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spoollib runlog

/

bin manlib

/

home bin bootusr varlib etcdev

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Disks and partitionsDisks and partitions

© David Morgan 2005-17

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tom harrydick

House the piecesHouse the pieces

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spoollib runlog

/

bin manlib

/

home bin bootusr varlib etcdev

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© David Morgan 2005-17

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tom harrydick

Or maybeOr maybe

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spoollib runlog

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bin manlib

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home bin bootusr varlib etcdev

© David Morgan 2005-17

ProblemProblem

� Container (partition) size is rigid

� One partition can fill while another has extra space

� Subtree in filled partition can’t grow into extra space

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tom harrydick

RehouseRehouse the piecesthe pieces

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spoollib runlog

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bin manlib

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home bin bootusr varlib etcdev

“Logical

Volumes”

LV for /

LV for /home

LV for /usr

LV for /var

...functional equivalent of partitions

© David Morgan 2005-17

Reorganize the Reorganize the

housing stockhousing stock

---- into volume groupsinto volume groups

physical

volumes,

grouped:

a.k.a, volume groups

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tom harrydick

Distribute theDistribute the

stockstock

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spoollib runlog

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bin manlib

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home bin bootusr varlib etcdev

“Logical

volumes:”

“Volume

groups:”

© David Morgan 2005-17

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tom harrydick

Later, if /Later, if /usrusr gets gets

““fullfull”” –– out of space/gasout of space/gas

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spoollib runlog

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bin manlib

/

home bin bootusr varlib etcdev

“Logical

volumes:”

“Volume

groups:”

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tom harrydick

Gas in the tankGas in the tank

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spoollib runlog

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bin manlib

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home bin bootusr varlib etcdev

“Logical

volumes:”

“Volume

groups:”

© David Morgan 2005-17

“Logical

volumes:”

“Volume

groups:”

partitions:

disks:

sdb

sda

sdcsdc1

sdb1

sda1

sda2

VGsVGs are like disks, virtuallyare like disks, virtually

LVsLVs are like are like partitonspartitons, virtually, virtually

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© David Morgan 2005-17

An LVM Fedora installationAn LVM Fedora installation

� post-Fedora LVM installation (LVs were auto-created)� disk size is 20GB� partitions occupy 10GB� one is LVM type – what’s inside?

10 GB consumed

© David Morgan 2005-17

2 logical 2 logical volsvols in 1 volume groupin 1 volume group

Symbolic links to them, categorized into

folders by containing volume groups

Global set of logical volumes, as

block devices

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© David Morgan 2005-17

LVMLVM’’ss hierarchy of hierarchy of ““piecespieces””

� Physical volumes

� Volume groups

� Logical volumes

© David Morgan 2005-17

General procedureGeneral procedure

� Acquire more storage units

– install new disks or

– create new partitions

� Turn them into LVM-recognized PVs

� Group them to form new VGs

� Create LVs in the new VGs

� Mount and use the LVs

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© David Morgan 2005-17

Our specific planOur specific plan

� Create 3 new data partitions

� Turn them into PVs

� Put them all in one new VG

� Create an LV 70% the size of the VG

� Favorite beverage

© David Morgan 2005-17

Make more physical volumesMake more physical volumes

� Create partitions from empty space with fdisk

� Set partition type code to 8e with fdisk

� “brand” them with pvcreate command

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© David Morgan 2005-17

Make 3 new data partitionsMake 3 new data partitionsMade another primary partition and a couple logical partitions, with fdisk

Aggregate size is 10GB = 2 + 4 + 4

© David Morgan 2005-17

Set partition type code to 8eSet partition type code to 8e

Tagged them with LVM’s type code 8e, with fdisk

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© David Morgan 2005-17

Brand them with Brand them with pvcreatepvcreate

© David Morgan 2005-17

Group them to form a new VGGroup them to form a new VG

New VG name is “NewVolGrp” size is 10GB

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© David Morgan 2005-17

Make LV, 70% of VGMake LV, 70% of VG

New LV name is “NewLogVol” size is 7GB

© David Morgan 2005-17

3 logical 3 logical volsvols in 2 volume groupsin 2 volume groups

Global set of logical volumes

categorized by their volume groups

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© David Morgan 2005-17

LV is a partitionLV is a partition--equivalentequivalent

Can format (note containing VG’s

constituent partitions are never formatted).

Then can mount.

Characteristic of fresh-formatted partitions

© David Morgan 2005-17

Diagnostic commands for viewingDiagnostic commands for viewing-- physical volumesphysical volumes

-- volume groupsvolume groups

-- logical volumeslogical volumes

� summary output

– pvs

– vgs

– lvs

� more verbose output

– pvdisplay

– vgdisplay

– lvdisplay

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© David Morgan 2005-17

vgdisplayvgdisplay : volume group info: volume group info

© David Morgan 2005-17

lvdisplaylvdisplay: logical volume info: logical volume info

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© David Morgan 2005-17

Practicing on USB storagePracticing on USB storage

� identify the correct name of the device– these activities are data-destructive

– be sure not to mistakenly give the name of your hard disk when manipulating your usb disk

� tools for identifying usb device name after inserting– dmesg

– fdisk -l