Sunday, December 20, 2015

How to Increase the size of a Linux LVM by expanding the virtual machine disk

Hello Guys,
I was working on my virtual machine and suddenly i got this isssue that i dont have disk space left. and then i started increasing the disk sapce from 20G to make the disk space to 30G.

This post will cover how to increase the disk space for a Oracle VirtualBox virtual machine running Linux that is using logical volume manager (LVM). Firstly we will be increasing the size of the actual disk on the Oracle VirtualBox virtual machine, so at the hardware level – this is the VM’s .vmdk file. Once this is complete we will get into the virtual machine and make the necessary changes through the operating system in order to take advantage of the additional space that has been provided by the hard drive being extended. This will involve creating a new partition with the new space, expanding the volume group and logical group, then finally resizing the file system.

Important Note: Be very careful when working with the commands in this article as they have the potential to cause a lot of damage to your data. If you are working with virtual machines make sure you take a snapshot of your virtual machine beforehand, or otherwise have some other form of up to date backup before proceeding. Note that a snapshot must not be taken until after the virtual disk has been increased, otherwise you will not be able to increase it. It could also be worth cloning the virtual machine first and testing out this method on the clone.
Prerequisites: As this method uses the additional space to create a primary partition, you must not already have 4 partitions as you will not be able to create more than 4. If you do not have space for another partition then you will need to consider a different method, there are some others in the above list.
As this method focuses on working with LVM, we will first confirm that our partition type is actually Linux LVM by running the below command.
fdisk -l
As you can see in the above image /dev/sda5 is listed as “Linux LVM” and it has the ID of 8e. The 8e hex code shows that it is a Linux LVM, while 83 shows a Linux native partition. Now that we have confirmed we are working with an LVM we can continue. For increasing the size of a Linux native partition
Below is the disk information showing that our initial setup only has the one 20gb disk currently, which is under the logical volume named /dev/mapper/Mega-root – this is what we will be expanding with the new disk.
disk free
Note that /dev/mapper/Mega-root is the volume made up from /dev/sda5 currently – this is what we will be expanding.
first click on windows button on you workstation and then type "cmd"  in then   it will open a command prompt go to path  "C:\Program Files\Oracle\VirtualBox"
 By using Command

C:\Users\nrathi>cd C:\Program Files\Oracle\VirtualBox

after that locate your vdi file for the vm like in my case the path is "C:\Users\nrathi\VirtualBox VMs\ubuntu\ubuntu.vdi"

Then use the below command in the command prompt to increase the dick space

c:\Users\nrathi> "C:\Program Files\Oracle\VirtualBox\VBoxManage.exe" modifyhd   "C:\Users\nrathi\VirtualBox VMs\ubuntu\ubuntu.vdi" --resize 30G

after using this command your disk space will increase to 30G but your Guest os still can access only 20G bacause of the LVM now we need to fix that too 

so lets start doing that.

Below is an image after performing this and confirming that the new space is displaying.

Partition the new disk space

As outlined in my previous images the disk in my example that I am working with is /dev/sda, so we use fdisk to create a new primary partition to make use of the new expanded disk space. Note that we do not have 4 primary partitions already in place, making this method possible.
fdisk /dev/sda
We are now using fdisk to create a new partition, the inputs I have entered in are shown below in bold. Note that you can press ‘m’ to get a full listing of the fdisk commands.
‘n’ was selected for adding a new partition.
WARNING: DOS-compatible mode is deprecated. It's strongly recommended to
         switch off the mode (command 'c') and change display units to
         sectors (command 'u').

Command (m for help): n
‘p’ is then selected as we are making a primary partition.
Command action
   l   logical (5 or over)
   p   primary partition (1-4)
As I already have /dev/sda1 and /dev/sda2 as shown in previous images, I have gone with using ‘3’ for this new partition which will be created as /dev/sda3
Partition number (1-4): 3
We just press enter twice above as by default the first and last cylinders of the unallocated space should be correct. After this the partition is then ready.
First cylinder (2611-3916, default 2611): "enter"
Using default value 2611
Last cylinder, +cylinders or +size{K,M,G} (2611-3916, default 3916): "enter"
Using default value 3916
‘t’ is selected to change to a partition’s system ID, in this case we change to ‘3’ which is the one we just created.
Command (m for help): t
Partition number (1-5): 3
The hex code ‘8e’ was entered as this is the code for a Linux LVM which is what we want this partition to be, as we will be joining it with the original /dev/sda5 Linux LVM.
Hex code (type L to list codes): 8e
Changed system type of partition 3 to 8e (Linux LVM)
‘w’ is used to write the table to disk and exit, basically all the changes that have been done will be saved and then you will be exited from fdisk.
Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.

WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table. The new table will be used at
the next reboot or after you run partprobe(8) or kpartx(8)
Syncing disks.
You will see a warning which basically means in order to use the new table with the changes a system reboot is required. If you can not see the new partition using “fdisk -l” you may be able to run “partprobe -s” to rescan the partitions. In my test I did not require either of those things at this stage (I do a reboot later on), straight after pressing ‘w’ in fdisk I was able to see the new /dev/sda3 partition of my 10gb of space as displayed in the below image.
For CentOS/RHEL run a “partx -a /dev/sda3” to avoid rebooting later on.
That’s all for partitioning, we now have a new partition which is making use of the previously unallocated disk space from the increase in VMware.

Increasing the logical volume

We use the pvcreate command which creates a physical volume for later use by the logical volume manager (LVM). In this case the physical volume will be our new /dev/sda3 partition.
root@Mega:~# pvcreate /dev/sda3
  Device /dev/sda3 not found (or ignored by filtering).
In order to get around this you can either reboot, or use partprobe/partx as previously mentioned to avoid a reboot, as in this instance the disk does not appear to be there correctly despite showing in “fdisk -l”. After a reboot or partprobe/partx use the same command which will succeed.
root@Mega:~# pvcreate /dev/sda3
  Physical volume "/dev/sda3" successfully created
Next we need to confirm the name of the current volume group using the vgdisplay command. The name will vary depending on your setup, for me it is the name of my test server. vgdisplay provides lots of information on the volume group, I have only shown the name and the current size of it for this example.
root@Mega:~# vgdisplay
  --- Volume group ---
  VG Name               Mega
VG Size               19.76 GiB
Now we extend the ‘Mega’ volume group by adding in the physical volume of /dev/sda3 which we created using the pvcreate command earlier.
root@Mega:~# vgextend Mega /dev/sda3
  Volume group "Mega" successfully extended
Using the pvscan command we scan all disks for physical volumes, this should confirm the original /dev/sda5 partition and the newly created physical volume /dev/sda3
root@Mega:~# pvscan
  PV /dev/sda5   VG Mega   lvm2 [19.76 GiB / 0    free]
  PV /dev/sda3   VG Mega   lvm2 [10.00 GiB / 10.00 GiB free]
  Total: 2 [29.75 GiB] / in use: 2 [29.75 GiB] / in no VG: 0 [0   ]
Next we need to increase the logical volume (rather than the physical volume) which basically means we will be taking our original logical volume and extending it over our new partition/physical volume of /dev/sda3.
Firstly confirm the name of the logical volume using lvdisplay. This name will vary depending on your setup.
root@Mega:~# lvdisplay
  --- Logical volume ---
  LV Name                /dev/Mega/root
The logical volume is then extended using the lvextend command.
root@Mega:~# lvextend /dev/Mega/root /dev/sda3
  Extending logical volume root to 28.90 GiB
  Logical volume root successfully resized
There is then one final step which is to resize the file system so that it can take advantage of this additional space, this is done using the resize2fs command for ext based file systems. Note that this may take some time to complete, it took about 30 seconds for my additional space.
root@Mega:~# resize2fs /dev/Mega/root
resize2fs 1.41.12 (17-May-2010)
Filesystem at /dev/Mega/root is mounted on /; on-line resizing required
old desc_blocks = 2, new_desc_blocks = 2
Performing an on-line resize of /dev/Mega/root to 7576576 (4k) blocks.
The filesystem on /dev/Mega/root is now 7576576 blocks long.
Alternatively if you’re running the XFS file system (default as of RedHat/CentOS 7) you can grow the file system with “xfs_growfs /dev/Mega/root”.
That’s it, now with the ‘df’ command we can see that the total available disk space has been increased.
disk free after expansion

SO We have successfully increase the disk space from 20G to 30G.

Thanks guys.and let me know if you want any help with linux...

Once Again...
Happy To Help You.....