Use GParted to increase disk size of a Linux native partition

In this post we will cover how to increase disk space for a VMware virtual machine that is using a Linux native partition rather than logical volume manager (LVM). Firstly we will increase the size of the virtual disk on the virtual machine at the hardware level and then once this is complete we will boot into a GParted live CD and perform the changes required to make use of the additional disk space so that the operating system is able to use it.

As there are a number of different ways to increase disk space I have also posted some different methods here:

• How to Increase the size of a Linux LVM by expanding the virtual machine disk – In this article the virtual disk that is using LVM is expanded, whereas in this current article we are instead increasing the virtual disk and expanding the Linux native partition.
• How to Increase the size of a Linux LVM by adding a new disk – In this article a new virtual disk is added to the virtual machine, a new partition is created, the volume group and logical volume are both expanded and then the filesystem is resized.
• How to Decrease the size of a Linux LVM – In this article the file system is shrunk followed by the LVM, allowing you to reclaim space in the volume group.

Important Notes: During the time that the GParted ISO is mounted you will be booted into this live CD rather than your normal operating system, basically meaning that during this process there will be down time from normal server operations.

Be very careful when following this article as this process has 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 in the first step below, otherwise you will not be able to increase the disk until it has been removed. It could also be worth cloning the virtual machine first and testing out this method on the clone.

Prerequisites: You will need to download the GParted live CD ISO file so that you can use it later, you can get this here.

Throughout my examples I will be working with a VMware virtual machine running Debian 6, this was set up with a 20gb disk and we will be increasing it by 10gb for a total final size of 30gb.

Below is an image displaying disk information on the server before we begin.

It is important to identify that you are actually using a Linux native partition – as this is what we are extending. As you can see in the above image /dev/sda1 is listed as “Linux” and it has the ID of 83. The 83 hex code shows that it is a Linux native partition, while 8e shows a Linux LVM. For information on increasing a LVM please see the linked posts above.

Note that /dev/sda1 is the partition we will be expanding.

Increasing the virtual hard disk

First off we increase the allocated disk space on the virtual machine itself. This is done by right clicking the virtual machine in vSphere, selecting edit settings, and then selecting the hard disk. In the below image I have changed the previously set hard disk of 20gb to 30gb while the virtual machine is up and running. Once complete click OK, this is all that needs to be done in VMware for this process.

If you are not able to modify the size of the disk, the provisioned size setting is greyed out. This can happen if the virtual machine has a snapshot in place, these will need to be removed prior to making the changes to the disk. Alternatively you may need to shut down the virtual machine if it does not allow you to add or increase disks on the fly, if this is the case shut down and make the change, do not power the virtual machine back on at this stage as next we mount the GParted ISO.

Booting into the GParted Live CD

Now that we have increased the hard disk space of the virtual machines, we need to boot into the GParted live CD to continue, you can download this here.

Right click on the virtual machine in vSphere and select “Edit Settings” to bring up the properties.

Select the CD/DVD Drive and then select your GParted ISO, in this instance I have already uploaded this file to the datastore so I have just clicked the browse button to select it. Make sure that connect at power on is ticked.

I have also selected for the boot options to be presented on the next boot so that I can select to boot into the ISO easier. You can also adjust the time to delay the boot so that you have appropriate time to select that you want to boot from CD, in the below image this is set to 5 seconds, and force to boot into bios is enabled so that I can select to boot from CD on next boot.

Now we are ready to power on the virtual machine (if your virtual machine was still on, shut down and power on), I have done this using some older versions of GParted in the past and it is worth noting that over time the GUI has changed so the following images may look a little different for you. I am using the current latest version of the live CD, version 0.14.1-1.

Once the virtual machine has powered on and you have booted to the CD, you will be presented with the following menu, just press enter to boot into GParted Live (Default Settings).

After some time you will then arrive at the following screen, for this I did not change anything and just accepted the defaults by pressing enter.

You will then be prompted to select a language, pressing enter defaults to English.

Next we select the default option 0 by pressing enter as we will be working with the GUI.

Once complete you will be presented with the GUI with GParted already open, if it is not already open you can select it from the Desktop icon.

As you can see the original /dev/sda1 partition that is making use of the 20gb disk is there, as well as the new unallocated 10gb from when we increased the size of the virtual hard disk earlier. The space between the two is the swap space. The total /dev/sda disk size of 30gb is also shown.

What needs to be done now is get /dev/sda1 to take up that unallocated space, this is not currently possible because swap is in the way so we need to move things around. If you do not have swap in between the partition to be extended and the unallocated space then you will be able to skip down a few steps until you arrive at the image where /dev/sda1 and the unallocated space are next to each other.

First we select /dev/sda2 which is the extended partition containing the swap, we want to expand this to include the 10gb of unallocated space.

Select /dev/sda2 and click “Resize/Move” and you will be presented with the following.

Basically you just need to drag the black arrow of /dev/sda2 all the way to the end of the unallocated space and click the Resize/Move button.

After doing this, you should see /dev/sda2 (represented by the blue box) spread out over the unallocated space.

This change and all further changes will not yet be applied, you can see the tasks down the bottom of the GParted interface and these will be applied only once you click the Apply button. Alternatively you can click the Undo button to remove a pending change.

This time we want to select /dev/sda5 which is the swap partition and select Resize/Move, this will result in the following.

This time rather than expanding the partition, we want to just move swap all the way to the end of the /dev/sda2 space that it is in, this is done by just dragging the box to the end which will then look like this.

Click the Resize/Move button and then a warning may appear informing you that moving a partition might cause your operating system to fail to boot. It also warns that performing this move may take a long time to apply, read the warning then click OK to continue.

The GUI should now look something like the below image, where /dev/sda1 is located right next to /dev/sda2 which contains the unallocated space.

Select the /dev/sda2 extended partition and click Resize/Move.

Drag this to the right so that only the swap space is contained and the grey unallocated space is freed, click Resize/Move once complete.

Once this is complete the disk will look like this.

Now we have /dev/sda1 next to the unallocated space so we are finally ready to expand /dev/sda1. Select /dev/sda1 and click the Resize/Move button.

You will be able to perform this action straight away if you did not have swap in between /dev/sda1 and the unallocated space, the previous steps were to get swap out of the way in GParted.

Drag the arrow over so that the unallocated space is then consumed by /dev/sda1 as shown below, then click Resize/Move.

Once this is done the /dev/sda1 partition will now be using the unallocated space that was previously there. All that is left to do is click the apply button which will apply the changes – you will be prompted to confirm with a warning that data loss may occur.

Note that this may take a while depending on how much of the disk is currently in use and the amount of disk space you are increasing, because a file system check (fsck) is run before the expansion and after it to ensure that there are no issues. I have performed this method on a 400gb server in the past and to increase it 100gb took approximately 5 hours. In this example I am only increasing by 10gb and there is only about 1gb of data on the disk so this took approximately 2 minutes to finish applying.

Once complete you will see something similar to the below image, you will be able to click close once finished.

Everything is now finished, you just need to reboot the virtual machine and then boot from disk rather than CD, alternatively shut down the virtual machine and unmount the live CD and then power it back on.

Once the operating system has booted you can confirm that the disk space has expanded correctly. Below you can see that /dev/sda1 is now 30gb in size.

Summary

With this method we have increased the virtual hard disk drive through VMware, booted into a GParted live CD ISO and expanded the primary Linux native partition over the unallocated space, resulting in overall disk space being increased successfully.

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

This post will cover how to increase the disk space for a VMware virtual machine running Linux that is using logical volume manager (LVM). Firstly we will be increasing the size of the actual disk on the VMware 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.

As there are a number of different ways to increase disk space I have also posted some different methods here:

• Use GParted to increase disk size of a Linux native partition – In this article the virtual disk is expanded, however there is no LVM here just a Linux native partition that is expanded with the GParted live CD.
• How to Increase the size of a Linux LVM by adding a new disk – In this article a new virtual disk is added to the virtual machine, a new partition is created, the volume group and logical volume are both expanded and then the filesystem is resized.
• How to Decrease the size of a Linux LVM – In this article the file system is shrunk followed by the LVM, allowing you to reclaim space in the volume group.

Update 18/04/2015: I have added a video guide of this post in CentOS 7 shown below.

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.

Throughout my examples I will be working with a VMware virtual machine running Debian 6, this was set up with a 20gb disk and we will be increasing it by 10gb for a total final size of 30gb.

Identifying the partition type
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 (hex code 83) see this article.

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.

Note that /dev/mapper/Mega-root is the volume made up from /dev/sda5 currently – this is what we will be expanding.

Increasing the virtual hard disk
First off we increase the allocated disk space on the virtual machine itself. This is done by right clicking the virtual machine in vSphere, selecting edit settings, and then selecting the hard disk. In the below image I have changed the previously set hard disk of 20gb to 30gb while the virtual machine is up and running. Once complete click OK, this is all that needs to be done in VMware for this process.


If you are not able to modify the size of the disk, the provisioned size setting is greyed out. This can happen if the virtual machine has a snapshot in place, these will need to be removed prior to making the changes to the disk. Alternatively you may need to shut down the virtual machine if it does not allow you to add or increase disks on the fly, if this is the case make the change then power it back on.

Detect the new disk space
Once the physical disk has been increased at the hardware level, we need to get into the operating system and create a new partition that makes use of this space to proceed.

Before we can do this we need to check that the new unallocated disk space is detected by the server, you can use “fdisk -l” to list the primary disk. You will most likely see that the disk space is still showing as the same original size, at this point you can either reboot the server and it will detect the changes on boot or you can rescan your devices to avoid rebooting by running the below command. Note you may need to change host0 depending on your setup.

echo "- - -" > /sys/class/scsi_host/host0/scan

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)
p

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 path of the logical volume using lvdisplay. This path name will vary depending on your setup.

root@Mega:~# lvdisplay
  --- Logical volume ---
  LV Path                /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.

Summary
With this method we have increased the virtual disk drive through VMware, created a new partition out of this newly unallocated space within the guest OS, turned it into a physical volume, extended the volume group, and then finally extended the original logical volume over the newer physical volume resulting in overall disk space being increased successfully.

Read More

How to Increase the size of a Linux LVM by adding a new disk

This post will cover how to increase the disk space for a VMware virtual machine running Linux that is using logical volume manager (LVM). Firstly we will add a new disk to the virtual machine and then extend the original LVM over this additional space. Basically we will have two physical disks but just one volume group and one logical group that is using the space on both disks together. With this method there is no down time for the virtual machine.

As there are a number of different ways to increase disk space I have also posted some different methods here:

• How to Increase the size of a Linux LVM by expanding the virtual machine disk – In this article the virtual disk that is using LVM is expanded, whereas in this current article we are instead increasing the virtual disk and expanding the Linux native partition.
• Use GParted to increase disk size of a Linux native partition – In this article the virtual disk is expanded, however there is no LVM here just a Linux native partition that is expanded with the GParted live CD.
• How to Decrease the size of a Linux LVM – In this article the file system is shrunk followed by the LVM, allowing you to reclaim space in the volume group.

Important Notes: 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. It could also be worth cloning the virtual machine first and testing out this method on the clone.
Throughout my examples I will be working with a VMware virtual machine running Debian 6, this was set up with a 20gb disk and we will be adding a new 20gb disk for a total LVM size of 40gb.
Although my examples make use of virtual machines, this method would work with a physical server as well if you have added a new physical disk in and want to use that to expand the LVM.

Identifying the partition type

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 (hex code 83) see this article.

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.

Note that /dev/mapper/Mega-root is the volume made up from /dev/sda5 currently – this is what we will be expanding.

Adding a new virtual hard disk
First off we add a new disk to the virtual machine. This is done by right clicking the virtual machine in vSphere, selecting edit settings and then clicking the “Add…” button which is used to add hardware to the virtual machine.

Select hard disk and click next.

Select create a new virtual disk and click next.


Select the disk size you want to add, I will be using 20gb as previously mentioned. I have also selected to store the disk with the virtual machine, it will store on the same datastore as the virtual machines files, this will be fine for my test purposes. Click next once complete.

Select next on the advanced options page.


Review everything and click finish once you have confirmed the settings.


You will then see the new disk under the hardware devices tab and it will be labelled with (adding) which means it will not apply until you click OK, so click OK to complete the process.


Detect the new disk space

In my test for this example, as soon as I added the additional disk in through VMware it displayed through “fdisk -l” for me, you can see the second disk labelled /dev/sdb (I have cropped out the information on /dev/sda1 to make it less cluttered here). It is also worth noting that it shows as not containing a valid partition table, we are about to set this up.

This may not however be the case for you, to avoid reboot you may need to rescan your devices, you can try this with the below command. Note that you may need to change host0 depending on your setup.

echo "- - -" > /sys/class/scsi_host/host0/scan

If you have issues detecting the new disk, just perform a reboot and it should then display correctly.

Partition the new disk

We now need to partition the new /dev/sdb disk so that it can be used, this is done by using fdisk.

fdisk /dev/sdb

This should provide us with the below prompt, the inputs I have entered in are shown in bold.

‘n’ was selected for adding a new partition.

root@Mega:~# fdisk /dev/sdb
Command (m for help): n

‘p’ is then selected as we are making a primary partition.

Command action
   e   extended
   p   primary partition (1-4)
p

As this is a new disk, we do not yet have any partitions on it so we will use partition 1 here.

Partition number (1-4): 1

Next we press the enter key twice, as by default the first and last cylinders of the unallocated space should be correct.

First cylinder (1-2610, default 1): "enter"
Using default value 1
Last cylinder, +cylinders or +size{K,M,G} (1-2610, default 2610): "enter"
Using default value 2610

‘t’ is selected to change to a partitions system ID, in this case we change to ’1′ automatically as this is currently our only partition.

Command (m for help): t
Selected partition 1

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 Linux LVM which is currently using /dev/sda5.

Hex code (type L to list codes): 8e
Changed system type of partition 1 to 8e (Linux LVM)

‘w’ is used to write the table to disk and exit, all 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.
Syncing disks.

By using “fdisk -l” now you will be able to see that /dev/sdb1 is listed, this is the new partition created on our newly added /dev/sdb disk and it is currently using all 20gb of space.

Increasing the logical volume

Next we will use the pvcreate command to create a physical volume for later use by the LVM. In this case the physical volume will be our new /dev/sdb1 partition.

root@Mega:~# pvcreate /dev/sdb1
  Physical volume "/dev/sdb1" successfully created

Now 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 plenty 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 using the vgextend command, we extend the ‘Mega’ volume group by adding in the physical volume of /dev/sdb1 which we created using the pvcreate command just before.

root@Mega:~# vgextend Mega /dev/sdb1
  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/sdb1

root@Mega:~# pvscan
  PV /dev/sda5   VG Mega   lvm2 [19.76 GiB / 0    free]
  PV /dev/sdb1   VG Mega   lvm2 [19.99 GiB / 19.99 GiB free]
  Total: 2 [39.75 GiB] / in use: 2 [39.75 GiB] / in no VG: 0 [0   ]

Next we need to increase the logical volume with the lvextend command (rather than the physical volume which we have already done). This means we will be taking our original logical volume and extending it over our new disk/partition/physical volume of /dev/sdb1.

Firstly confirm the name of the logical volume using lvdisplay. The name will vary depending on your setup.

root@Mega:~# lvdisplay
  --- Logical volume ---
  LV Name                /dev/Mega/root
  LV Size                18.91 GiB

The logical volume is then extended using the lvextend command. We are extending the original logical volume of /dev/Mega/root over the newer /dev/sdb1

root@Mega:~# lvextend /dev/Mega/root /dev/sdb1
  Extending logical volume root to 38.90 GiB
  Logical volume root successfully resized

If you like you can then run vgdisplay and lvdisplay again to confirm the size of the volume group and logical volume respectively, I have done this and I now have the following.

  LV Size                38.90 GiB
  VG Size                39.75 GiB

However if you run a “df” command to see available disk space it will not have changed yet as there is one final step, we need to resize the file system using the resize2fs command in order to make use of this 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 = 3
Performing an on-line resize of /dev/Mega/root to 10196992 (4k) blocks.
The filesystem on /dev/Mega/root is now 10196992 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”.

Rather than resizing the file system manually, you could instead use the -r option of the lvextend command which will automatically resize the file system to make use of the additional disk space.

The resize took a minute or so to complete (it will depend on the disk speed and size), running the
“df” command now shows the correct disk space for /dev/mapper/Mega-root

Summary
We have now increased the total disk space on the virtual machine by first adding a new virtual disk through VMware, created a new partition out of this newly unallocated space within the guest OS, turned it into a physical volume, extended the volume group, then finally extended the original logical volume over the newer physical volume resulting in overall disk space being increased successfully. This method allows for disk space upgrade with no down time, my virtual machine was not shut down or rebooted at all during this process. This is a very useful technique for upgrading disk space on production servers that can not go down.

Read More

LVM Resize – How to Decrease an LVM Partition

Here we show you how to shrink an LVM volume or partition in Linux by first resizing the file system followed by resizing the logical volume.

See here if you’re instead trying to do the opposite and expand an LVM volume.

Note: In this example we are working in CentOS 7, some commands may differ in different Linux distributions. As of CentOS 7 the default file system is XFS which is not currently possible to shrink, this example is working with the ext4 file system.

In this example we will work through shrinking logical volume /var/centos/var from 10GB to 5GB.

Overview of Logical Volume Manager (LVM)

Before working through the resizing process it’s important you first understand some basic concepts around physical volumes, volume groups, logical volumes, and the file system.

• Physical Volume (PV): This can be created on a whole physical disk (think /dev/sda) or a Linux partition.
• Volume Group (VG): This is made up of at least one or more physical volumes.
• Logical Volume (LV): This is sometimes referred to as the partition, it sits within a volume group and has a file system written to it.
• File System: A file system such as ext4 will be on the logical volume.

LVM Resize – How to decrease or shrink the logical volume

To decrease the size of an LVM partition you must first decrease the file system within in order to avoid possible data corruption. As there is the potential for this to happen if you enter the command incorrectly, it is strongly recommended that you have a full backup of your data before proceeding. Shrinking a logical volume will give you more space in the volume group, meaning that you could instead extend another logical volume with this new found space.

The first step will depend on if you’re looking to shrink a LVM root volume, or non-root volume.

Shrinking a root volume

The root volume would typically be the logical volume that is mounted to /. You cannot unmount this to shrink it as it’s in use by the running operating system meaning that you will have to first boot from a Live CD to complete this. Once booted into the Live CD, you may first need to run the below command to pick up LVM volumes, however this usually happens during boot so may not be required, if in doubt just run it.

vgchange -a y

Shrinking a non-root volume

Alternatively if the volume you are shrinking is a non-root volume, that is any other volume not mounted to the root of the file system, you can unmount the volume as shown below to proceed. Please note that when you unmount the volume the data will not be available, so you may need to schedule down time and stop running applications that use data from it prior to unmounting. Unmount by specifying either the logical volume or the location it’s currently mounted to, in the below example we specify the logical volume which can be found in /dev/(vg-name)/(lv-name).

umount /dev/centos/var

All following steps now apply to both a root or non-root volume.

Before being able to attempt to shrink the size of an LVM volume, you must first run a file system check on it. If you don’t do this, you will get an error message and will not be able to proceed. This is a required step as resizing a file system in a bad state could cause data corruption. The -f flag makes the check run even if the file system appears clean, while -y assumes yes to all questions and will respond if asked to fix a problem.

e2fsck -fy /dev/centos/var

Next you need to shrink the file system, to be safe we’re going to shrink the file system lower than what the logical volume will shrink to. This is because we don’t want to accidentally shrink the logical volume to a size lower than the file system in the next step, as this can result in corruption and data loss. Don’t worry, we’ll reclaim the space at the end.

The command below will shrink the file system so that it is only 4G in size total, note that what ever size you specify to shrink to you must have in free space within the file system otherwise you must first delete data.

resize2fs /dev/centos/var 4G

Once the file system has been reduced, we can shrink the size of the logical volume with the lvreduce command. Reduce this to the size that you want the volume to be, as specified by the -L flag. Instead if you want to reduce by a specified size, simply put a – in front of the size. Both are shown below for completeness, however you only need to run one.

To reduce to 5G

lvreduce -L 5G /dev/vg/disk-name

To reduce by 5G

lvreduce -L -5G /dev/vg/disk-name

Once you execute the lvreduce command you will get a warning advising the size you have chosen to reduce to so use this as a chance to confirm you’re shrinking the logical volume to a size that is NOT smaller than the size you previously shrunk the file system to. Once you have confirmed it’s fine to proceed enter ‘y’ and press enter.

After the logical volume has been lowered to the required size, run resize2fs on the volume as this will extend the file system to use all available space within the logical volume. This makes use of all remaining free space so that none is wasted from when we previously shrunk the file system to a lower size than the logical volume.

resize2fs /dev/centos/var

At this point all that’s left to do is mount the volume. If this was a root volume and you’re working within a Live CD, simply boot back into your primary Linux operating system.

If this was a non-root volume and you unmounted it to complete the reduction, simply mount it back. You can do this with ‘mount -a’ assuming you have the configuration already set in /etc/fstab, otherwise specify the logical volume and where it should mount to. Here we’re manually mounting to /mnt just for testing.

mount /dev/centos/var /mnt

After you’ve either booted back to primary operating system or completed the mount, check the space shown with the ‘df’ command to confirm it has been decreased as expected.

[root@CentOS7 /]# df -h
Filesystem               Size  Used Avail Use% Mounted on
/dev/mapper/centos-root  9.8G  1.4G  8.5G  14% /
devtmpfs                 908M     0  908M   0% /dev
tmpfs                    914M     0  914M   0% /dev/shm
tmpfs                    914M  8.6M  905M   1% /run
tmpfs                    914M     0  914M   0% /sys/fs/cgroup
/dev/sda1                497M   96M  402M  20% /boot
/dev/mapper/centos-var  4.8G   20M  4.6G   1% /mnt

In this example /dev/centos/var is correctly showing as shrunk down from the original 10G.

Summary
We have now successfully shrunk a file system and corresponding LVM logical volume. Root volumes can only be shrunk by unmounting the file system which requires booting into a Live CD to complete the work. For non-root volumes the file system must first be unmounted so that you can shrink the volume. First the file system was checked, then reduced. The logical volume itself was then reduced. It is strongly recommended to have a backup before attempting this to avoid data loss through mistakes.

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LVM Resize – How to Increase an LVM Partition

Here we show you how to expand an LVM volume or partition in Linux by first resizing logical volume followed by resizing the file system to take advantage of the additional space.

See here if you’re instead trying to do the opposite and shrink an LVM volume.

Note: In this example we are working in CentOS 7, some commands may differ in different Linux distributions.

In this example we will work through expanding logical volume /var/centos/var from 5GB to 10GB. We currently have this logical volume mounted to /mnt.

Overview of Logical Volume Manager (LVM)

Before working through the resizing process it’s important you first understand some basic concepts around physical volumes, volume groups, logical volumes, and the file system.

• Physical Volume (PV): This can be created on a whole physical disk (think /dev/sda) or a Linux partition.
• Volume Group (VG): This is made up of at least one or more physical volumes.
• Logical Volume (LV): This is sometimes referred to as the partition, it sits within a volume group and has a file system written to it.
• File System: A file system such as ext4 will be on the logical volume.

LVM Resize – How to increase or expand the logical volume

This process is extremely easy to do with LVM as it can be done on the fly with no downtime needed, you can perform it on a mounted volume without interruption. In order to increase the size of a logical volume, the volume group that it is in must have free space available.

To view the free space of your volume group, run vgdisplay command as shown below and look at the “Free PE / Size” field.

[root@CentOS7 ~]# vgdisplay
  --- Volume group ---
  VG Name               centos
  System ID
  Format                lvm2
  Metadata Areas        2
  Metadata Sequence No  6
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                3
  Open LV               2
  Max PV                0
  Cur PV                2
  Act PV                2
  VG Size               20.74 GiB
  PE Size               4.00 MiB
  Total PE              5309
  Alloc PE / Size       4030 / 15.74 GiB
  Free  PE / Size       1280 / 5.00 GiB
  VG UUID               VvG6Sp-wIgb-LTh0-szdU-s9R1-a6K9-qHassI

In this example we have 5GB of free space in the volume group, as shown by “Free PE / Size 1279 / 5.00 GiB”.

Note: If you do not have any or enough free space in the volume group, you will first need to expand the volume group to complete the resize. Alternatively if you have multiple LVM partitions, you could shrink a different logical volume first to create space within the volume group.

Now that we have confirmed there is space free within the volume group, confirm the name of the logical volume you want to increase as well as how much space you plan on adding. The below lvdisplay command will show all logical volumes and their current size. It will also show the volume group that the logical volume is a member of, so ensure that the correct volume group has been checked for enough space with vgdisplay as previously mentioned to prevent trying to increase a logical volume that is inside some other volume group.

As shown in the example below, we are going to be working with the logical volume “var” which is in volume group “centos”, the volume group we saw in vgdisplay. In this example we only have just the one volume group, but you may have more so you need to check.

[root@CentOS7 ~]# lvdisplay
  --- Logical volume ---
  LV Path                /dev/centos/var
  LV Name                var
  VG Name                centos
  LV UUID                7PNgg2-ZmnG-a26g-zRoT-PRVM-RDc1-oq6J4M
  LV Write Access        read/write
  LV Creation host, time CentOS7, 2015-04-16 07:50:25 +1000
  LV Status              available
  # open                 0
  LV Size                5.00 GiB
  Current LE             1280
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           253:2

Now it’s time to expand the logical volume. In the below example we are using the -L flag to increase by a size specified (M for Megabytes, G for Gigabytes, T for Terabytes). You can alternatively remove the + to increase to the amount specified rather than by the amount specified.

lvextend -L+5G /dev/centos/var
  Rounding size to boundary between physical extents: 4.90 GiB
  Size of logical volume centos/var changed from 5.00 GiB (1280 extents) to 10.00 GiB (2560 extents).
  Logical volume var successfully resized

The above command will increase the logical volume /dev/centos/var by 5GB, currently it is already 5GB so this will increase it to a total of 10GB. You could achieve the same with “lvextend -L 10G /dev/centos/var” which will increase the logical volume to 10GB as well, as this is what was specified with no +. Alternatively if you instead want to just use all free space in the volume group rather than specifying a size to increase to, run “lvextend -l +100%FREE /dev/centos/var”.

We can run the below lvdisplay command shown below to check that the extend completed as expected.

[root@CentOS7 ~]# vgdisplay
  --- Logical volume ---
  LV Path                /dev/centos/var
  LV Name                var
  VG Name                centos
  LV UUID                7PNgg2-ZmnG-a26g-zRoT-PRVM-RDc1-oq6J4M
  LV Write Access        read/write
  LV Creation host, time CentOS7, 2015-04-16 07:50:25 +1000
  LV Status              available
  # open                 0
  LV Size                10.00 GiB
  Current LE             2560
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:2

Now that the logical volume has been extended, we can resize the file system. This will extend the file system so that it takes up the newly created space inside the logical volume. The command may differ depending on the type of file system you are using.

Use this for ext3/4 based file systems

resize2fs /dev/centos/var

Alternatively, use this for xfs based file systems

xfs_growfs /dev/centos/var

After the file system has been resized the space should be ready to use. If you run a ‘df’ command to view the disk space you should see that it’s been increased successfully.

[root@CentOS7 mnt]# df -h
Filesystem               Size  Used Avail Use% Mounted on
/dev/mapper/centos-root  9.8G  1.4G  8.5G  14% /
devtmpfs                 908M     0  908M   0% /dev
tmpfs                    914M     0  914M   0% /dev/shm
tmpfs                    914M  8.6M  905M   1% /run
tmpfs                    914M     0  914M   0% /sys/fs/cgroup
/dev/sda1                497M   96M  402M  20% /boot
/dev/mapper/centos-var    10G   33M   10G   1% /mnt

In this example I have run a ‘mount /dev/centos/var /mnt’ to mount the logical volume to /mnt, as shown above /mnt is correctly reporting a size of 10G.

Summary

We have now successfully expanded a file system and corresponding LVM logical volume without any down time. This was done by first expanding the logical volume, and then performing an on-line resize of the file system.

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