Oracle 7 Linux

August 30, 2018 Add Comment Edit

LVM Snapshots of Logical Volume on Rhel 7/Centos 7/Oracle 7 Linux are space productive pointing time duplicates of lvm volumes.

It works just with lvm and expend the space just when changes are made to the source intelligent volume to depiction volume.

If source volume has a huge changes made to sum of 500MB the same changes will be made to the snapshot volume.

Incase the preview comes up short on capacity, we can utilize lvextend to develop.

On the off chance that we have incidentally erased any record in the wake of making a Snapshot we don't need to stress in light of the fact that the preview have the first document which we have erased.

To remove the snapshot we can use lvremove command.

Step 1: Create LVM Snapshot

First, check for free space in volume group to create a new snapshot.For that we are using using following vgs command.

# vgs

VG #PV #LV #SN Attr VSize VFree

VolGroup 1 2 0 wz--n- 7.51g 0

testvg 2 1 0 wz--n- 3.99g 1.99g

# lvs

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

lv_root VolGroup -wi-ao---- 6.71g

lv_swap VolGroup -wi-ao---- 816.00m

testlv testvg -wi-ao---- 2.00g

You see, there is 1.99GB of free space left in above vgs output. So, let’s create a snapshot for one of my volume named testlv.

For an example we are going to create only 1GB snapshot volume using following commands.

# lvcreate -L 1GB -s -n testlv_snap /dev/testvg/testlv

Logical volume "testlv_snap" created

Where

1GB= Size of snapshot Iam creating here.

-s= Creates snapshot.

-n= Creates name for the snapshot.

testlv_snap= New snapshots name.

/dev/testvg/testlv= Volume which we are going to create a snapshot.

create snapshot

We can use the below command to list new created snapshot.

# lvs

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

lv_root VolGroup -wi-ao---- 6.71g

lv_swap VolGroup -wi-ao---- 816.00m

testlv testvg owi-aos--- 2.00g

testlv_snap testvg swi-a-s--- 1.00g testlv 0.00

Snapshot of Logical Volume and Restore in LVM

List snapshot

You see above, a snapshot was created successfully.

# df -Th /dev/mapper/testvg-testlv

Filesystem Type Size Used Avail Use% Mounted on

/dev/mapper/testvg-testlv ext4 2.0G 67M 1.9G 4% /testlvm

Let’s add some new files into testlv.

Now check the volume using the follwing command.

#lvs

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

lv_root VolGroup -wi-ao---- 6.71g

lv_swap VolGroup -wi-ao---- 816.00m

testlv testvg owi-aos--- 2.00g

testlv_snap testvg swi-a-s--- 1.00g testlv 0.13

You see, 0.13% of snapshot volume was used now.

If we copy more than 1GB of files in testlV you will get error message appear On the screen Input/output error, it means out of space in snapshot.

Step 2: Extend Snapshot in LVM

First we check available PE using vgdisplay command

# vgdisplay

--- Volume group ---

VG Name testvg

System ID

Format lvm2

Metadata Areas 2

Metadata Sequence No 4

VG Access read/write

VG Status resizable

MAX LV 0

Cur LV 2

Open LV 1

Max PV 0

Cur PV 2

Act PV 2

VG Size 3.99 GiB

PE Size 4.00 MiB

Total PE 1022

Alloc PE / Size 768 / 3.00 GiB

Free PE / Size 254 / 1016.00 MiB

VG UUID mz7AN3-jsR0-rnsQ-XpvM-2W0N-M8q8-pki2kB

# lvextend -l +254 /dev/testvg/testlv_snap

Extending logical volume testlv_snap to 1.99 GiB

Logical volume testlv_snap successfully resized

Now verify the size using the below command.

# lvdisplay /dev/testvg/testlv_snap

--- Logical volume ---

LV Path /dev/testvg/testlv_snap

LV Name testlv_snap

VG Name testvg

LV UUID eVvo1m-OZhv-PfP2-caja-r67k-W2o6-PD9Fcm

LV Write Access read/write

LV Creation host, time localhost.localdomain, 2018-06-16 08:17:05 +0530

LV snapshot status active destination for testlv

LV Status available

# open 0

LV Size 2.00 GiB

Current LE 512

COW-table size 1.99 GiB

COW-table LE 510

Allocated to snapshot 0.07%

Snapshot chunk size 4.00 KiB

Segments 1

Allocation inherit

Read ahead sectors auto

- currently set to 256

Block device 253:3

# lvs

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

lv_root VolGroup -wi-ao---- 6.71g

lv_swap VolGroup -wi-ao---- 816.00m

testlv testvg owi-aos--- 2.00g

testlv_snap testvg swi-a-s--- 1.99g testlv 0.07

Step 3: Restoring Snapshot or Merging

To restore the snapshot, we need to un-mount the file system first.

# unmount /testlvm

Just check for the mount point whether its unmounted or not.

# df -h

Here our mount has been unmounted, so we can continue to restore the snapshot. To restore the snap using command lvconvert.

# lvconvert --merge /dev/testvg/testlv_snap

Merging of volume testlv_snap started.

testlv: Merged: 100.0%

Merge of snapshot into logical volume testlv has finished.

Logical volume "testlv_snap" successfully removed

After the merge is finished, snapshot volume will be expelled naturally. Now we can check partition space using the below command.

# df -Th

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How to Extend Logical Volume in rhel 7/Centos 7/Oracle 7 Linux LVM

August 30, 2018 Add Comment Edit

Extend Logical Volume In rhel 7/CentOS 7/ Oracle 7 |In creating Logical Volume section we create testlv with 5GB

We want to increase the size of the LV from 5GB to 10GB

we can do it two different ways

1. Extend LV Size with new hardDisk

2. Extend LV Size from extra space of existing VG

Extend LV Size with new hardDisk

We add new disk /dev/sde to LVM using ‘fdisk ’ command

To do this activity we need to execute the below command.

# fdisk /dev/sde

Type ‘n’ to create new partition

Afer that type ‘p’ to create the primary partition

After that we need to enter first and last cylinder value.

Then type ‘t’ and we will enter the partition id to create LVM . Now we need to enter 8e and press w to save change.

Now our disk is prepared to add our existing LV. We have to follow the below steps.

Create Physical volume

Now we create a Physical volume by executing the following command

# pvcreate /dev/sde

To Check PV we use ‘pvdisplay’ command,

Extend Volume group ‘testvg’ to add /dev/sde

# vgextend testvg /dev/sde

To Verify new VG Size we execute ‘vgdisplay’ command

Extend Logical volume ‘testlv’ we need to follow below command.

# lvextend –L +5G /dev/testvg/testlv

Extend logical volume

Here, ‘-L +5G’ means that the size of LV’testlv’ will increased by 5GB, we can verify the new size by executing ‘lvdisplay’ command.

But the LV Size is not affected.After execute the resize command the new LV Size will be affected.

To resize the filesystem we need to execute the below command.

# resize2fs /dev/testvg/testlv

To verify new LV Size we execute lvdisplay command.

Extend LV Size from extra space of testvg

Lets take an example we have 2 GB extra space in our existing Volume Group ‘testvg’ . we add that extra space to our lv to inctease the size by following the below process.

Extend Logical volume ‘testlv’ execute the below command.

# lvextend –L +2G /dev/testvg/testlv

To resize the filesystem we need to execute the below command.

# resize2fs /dev/testvg/testlv

To verify new LV Size we execute lvdisplay command.

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How to Configure Linux LVM2 (logical volume manager) on centos7/rhel7/oracle7 step by step tutorial guide

August 30, 2018 Add Comment Edit

How To Configure Linux LVM on Oracle 7 / rhel 7/Centos 7 |Three major steps we have to follow to Setup a Logical Volume Manager (LVM). The Steps are :

Physical Volume : Arrange the Physical Harddisk’s some way so that Linux LVM can recognise the Device and can be used to configure Volume Group and Logical Volumes is called as Physical Volume.

To create Physical volume you can use the command pvcreate.

You can execute pvdisplay command to show all available Physical Volume’s in the system.

To know about the Physical Volume details Summary use the command pvs.

Physical Volume is partitioned in to little bits of size is called as Physical Extent.

Volume Group : Addition of Multiple Physical Volume is made Volume Group.

To create Volume Group you can use the command vgcreate.

To check the details of VGs we can execute the vgdisplay command.

To know the Volume Group Summary use the command vgs.

Logical Volume : We can create Partitions out of Volume Group to store data is called as Logical Volume.

To create Logical Volume you can use the command lvcreate.

To check the details of Logical Volume you can use the command lvdisplay.

To know the Logical Volume Summary use the command lvs.

To configure Linux LVM we need at least a Physical Harddisk . Here I have 3 Harddisk’s i.e : /dev/sdb, /dev/sdc, /dev/sdd with size 2 GB each.

You can check harddisk and partition using the below command

# fdisk -l

Disk /dev/sdb: 2147 MB, 2147483648 bytes

255 heads, 63 sectors/track, 261 cylinders

Units = cylinders of 16065 * 512 = 8225280 bytes

Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 512 bytes / 512 bytes

Disk identifier: 0x00000000

Disk /dev/sdc: 2147 MB, 2147483648 bytes

255 heads, 63 sectors/track, 261 cylinders

Units = cylinders of 16065 * 512 = 8225280 bytes

Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 512 bytes / 512 bytes

Disk identifier: 0x00000000

Disk /dev/sdd: 2147 MB, 2147483648 bytes

255 heads, 63 sectors/track, 261 cylinders

Units = cylinders of 16065 * 512 = 8225280 bytes

Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 512 bytes / 512 bytes

Disk identifier: 0x00000000

Create Physical Volume

To create Physical volume you can use the command pvcreate.

Syntax: pvcreate[disk]

Now we are creating Physical Volume by the given three physical harddisk

# pvcreate /dev/sdb

Physical volume "/dev/sdb" successfully created

# pvcreate /dev/sdc

Physical volume "/dev/sdc" successfully created

# pvcreate /dev/sdd

Physical volume "/dev/sdd" successfully created

create physical volume

You can use pvdisplay command to show all available Physical Volume’s in the system.

# pvdisplay /dev/sdc

"/dev/sdc" is a new physical volume of "2.00 GiB"

--- NEW Physical volume ---

PV Name /dev/sdc

VG Name

PV Size 2.00 GiB

Allocatable NO

PE Size 0

Total PE 0

Free PE 0

Allocated PE 0

PV UUID Joqlch-yWSj-kuEn-IdwM-01S9-XO8M-mcpsVe

PV Name : Physical disk Name

VG Name : Volume Group Name

PV Size : Physical Volume Size

Allocatable : The amount of Space we can allocate

PE Size : PE stands for Physical Extent.

Total PE : Total available Physical Extents.

Free PE : Remaining Physical Extents.

You can use pvs command to check the quick short summary of all available Physical Volumes.

# pvs

PV VG Fmt Attr PSize PFree

/dev/sdb lvm2 a-- 2.00g 2.00g

/dev/sdc lvm2 a-- 2.00g 2.00g

/dev/sdd lvm2 a-- 2.00g 2.00g

Create Volume Group

To create volume Group you can use the command vgcreate.

Syntax: vgcreate [Name of Volume Group] [Physical Volumes]

# vgcreate testvg /dev/sdb /dev/sdc /dev/sdd

Volume group "testvg" successfully created

create volume group

We use vgdisplay command to check the details of Volume Group.

# vgdisplay

--- Volume group ---

VG Name testvg

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 5.99 GiB

PE Size 4.00 MiB

Total PE 1533

Alloc PE / Size 0 / 0

Free PE / Size 1533 / 5.99 GiB

To know the Volume Group Summary use the command vgs.

# vgs

VG #PV #LV #SN Attr VSize VFree

testvg 3 0 0 wz--n- 5.99g 5.99g

Create Logical Volume

We can create Partitions out of Volume Group to store data is called as Logical Volume.

To create Logical Volume you can use the command lvcreate.

To check the details of Logical Volume you can use the command lvdisplay.

To know the Logical Volume Summary use the command lvs.

syntax:lvcreate -L [Size] -n [Name of the LV] VG

We are creating Logical Volume with name testlv

# lvcreate -L 5G -n testlv testvg

Logical volume "testlv" created

logical volume create

To check the details of Logical Volume you can use the command lvdisplay.

To know the Logical Volume Summary use the command lvs.

# lvdisplay

Display logical volume

Now we are ready to store data on logical volumes. we need to create file system in Logical Volume by formatting it .

# mkfs.ext4 /dev/testvg/testlv

Now we needownload to create a directory to mount Logical Volume.

# mkdir /testlvm

we can mount it manually by using this below command

# mount /dev/testvg/testlv /testlvm/

For automatic mount you must need entry in fstab

After successfully enter in fstab do the following command

#mount -a

Finally check it by the below command

#df -h

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