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h1. Resizing an existing disk with LVM

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h2. Synopsis

If an existing disk is resized and you want to add the extra space to an existing LVM logical volume, follow this guide.

Source: https://www.ibm.com/support/pages/how-increase-partition-size-using-existing-disk-rhel-lvm

h2. Procedure

The output of the commands below are from a real situation:

* The disk was resized from 100GB to 300GB

* The extra space was to be added to the root filesystem

* The disk is @/dev/sda@; adapt where necessary for your situation

h3. Rescan the disk

When a disk is resized, the Linux kernel doesn't automatically pick up this change.

To trigger it to rescan a disk, execute this command:

<pre>

root@server:~# </notextile>*echo 1 > /sys/class/block/sda/device/rescan*<notextile>

</pre>

Make sure the disk space is refreshed:

<pre>

root@server:~# </notextile>*fdisk -l*<notextile>

Disk /dev/sda: </notextile>%{background-color: yellow}300 GiB%, 322122547200 bytes, 629145600 sectors<notextile>

Disk model: Virtual disk

Units: sectors of 1 * 512 = 512 bytes

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

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

Disklabel type: dos

Disk identifier: 0xc4a390f9

Device     Boot   Start       End   Sectors  Size Id Type

/dev/sda1  *       2048    999423    997376  487M 83 Linux

/dev/sda2       1001470 104855551 103854082 49.5G  5 Extended

/dev/sda5       1001472 104855551 103854080 49.5G 8e Linux LVM

Disk /dev/mapper/volume-vg-root: 48.56 GiB, 52143587328 bytes, 101842944 sectors

Units: sectors of 1 * 512 = 512 bytes

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

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

Disk /dev/mapper/volume-vg-swap_1: 980 MiB, 1027604480 bytes, 2007040 sectors

Units: sectors of 1 * 512 = 512 bytes

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

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

</pre>

Looks good.

h3. Create a new partition containing the extra disk space

Before disk space can be added to a LVM volume group, it needs to be inside a disk partition.

We create a primary partition (which will become @/dev/sda3@) for the disk space:

<pre>

root@server:~# </notextile>*fdisk /dev/sda*<notextile>

Welcome to fdisk (util-linux 2.36.1).

Changes will remain in memory only, until you decide to write them.

Be careful before using the write command.

Command (m for help): </notextile>*F*<notextile>

Unpartitioned space /dev/sda: 250 GiB, 268436504576 bytes, 524290048 sectors

Units: sectors of 1 * 512 = 512 bytes

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

    Start       End   Sectors  Size

104855552 629145599 524290048  250G

Command (m for help): </notextile>*n*</notextile>

Partition type

   p   primary (1 primary, 1 extended, 2 free)

   l   logical (numbered from 5)

Select (default p): </notextile>*p*<notextile>

Partition number (3,4, default 3): </notextile>*&lt;ENTER&gt;*<notextile>

First sector (104855552-629145599, default 104855552): </notextile>*&lt;ENTER&gt;*<notextile>

Last sector, +/-sectors or +/-size{K,M,G,T,P} (104855552-629145599, default 629145599): </notextile>*&lt;ENTER&gt;*<notextile>

Created a new partition 3 of type 'Linux' and of size 250 GiB.

Command (m for help): </notextile>*p*<notextile>

Disk /dev/sda: 300 GiB, 322122547200 bytes, 629145600 sectors

Disk model: Virtual disk

Units: sectors of 1 * 512 = 512 bytes

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

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

Disklabel type: dos

Disk identifier: 0xc4a390f9

Device     Boot     Start       End   Sectors  Size Id Type

/dev/sda1  *         2048    999423    997376  487M 83 Linux

/dev/sda2         1001470 104855551 103854082 49.5G  5 Extended

/dev/sda3       104855552 629145599 524290048  250G 83 Linux

/dev/sda5         1001472 104855551 103854080 49.5G 8e Linux LVM

Partition table entries are not in disk order.

Command (m for help): </notextile>*w*<notextile>

The partition table has been altered.

Syncing disks.

</pre>

h3. Refresh the partition table

Like we had to trigger the kernel to rescan the disk to pick up on the newly created diskspace, we need to trigger the kernel to reread the partition table to pick up the changes we just made.

<pre>

root@server:~# </notextile>*partprobe -s*<notextile>

/dev/sda: msdos partitions 1 2 <5> 3

/dev/mapper/volume-vg-swap_1: loop partitions 1

/dev/mapper/volume-vg-root: loop partitions 1

</pre>

h3. Create a physical volume (PV) for LVM

In order to use a raw disk partition with LVM, it must be wrapped in a LVM physical volume.

To create such a physical volume with our new partition, execute:

<pre>

root@server:~# </notextile>*pvcreate /dev/sda3*<notextile>

  Physical volume "/dev/sda3" successfully created.

</pre>

h3. Add the PV to the volume group (VG)

First we need to get the name of the VG where we want to add the disk space:

<pre>

root@server:~# </notextile>*vgdisplay*<notextile>

  --- Volume group ---

  VG Name               </notextile>%{background-color: yellow}volume-vg%<notextile>

  System ID

  Format                lvm2

  Metadata Areas        1

  Metadata Sequence No  3

  VG Access             read/write

  VG Status             resizable

  MAX LV                0

  Cur LV                2

  Open LV               2

  Max PV                0

  Cur PV                1

  Act PV                1

  VG Size               <49.52 GiB

  PE Size               4.00 MiB

  Total PE              12677

  Alloc PE / Size       12677 / <49.52 GiB

  Free  PE / Size       0 / 0

  VG UUID               qE7Xrc-ePAK-B6vq-eGHt-qRCw-M6K9-TR9YlL

</pre>

Now we'll extend the volume group by adding the physical volume @/dev/sda3@:

<pre>

root@server:~# </notextile>*vgextend volume-vg /dev/sda3*<notextile>

  Volume group "volume-vg" successfully extended

</pre>

List the PVs on the system to verify:

<pre>

root@server:~# </notextile>*pvscan*<notextile>

  PV /dev/sda5   VG volume-vg   lvm2 [<49.52 GiB / 0    free]

</notextile>%{background-color: yellow}  PV /dev/sda3   VG volume-vg   lvm2 [250.00 GiB / 250.00 GiB free]%<notextile>

  Total: 2 [<299.52 GiB] / in use: 2 [<299.52 GiB] / in no VG: 0 [0   ]

</pre>

Check the VG to verify that the free space is added:

<pre>

root@server:~# </notextile>*vgdisplay*<notextile>

  --- Volume group ---

  VG Name               volume-vg

  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               2

  Max PV                0

  Cur PV                2

  Act PV                2

  VG Size               <299.52 GiB

  PE Size               4.00 MiB

  Total PE              76677

  Alloc PE / Size       12677 / <49.52 GiB

</notextile>%{background-color: yellow}  Free  PE / Size       64000 / 250.00 GiB%<notextile>

  VG UUID               qE7Xrc-ePAK-B6vq-eGHt-qRCw-M6K9-TR9YlL

</pre>

h3. Extend the logical volume (LV) with the new disk space

First, display the LV so we can get the path:

<pre>

root@server:~# </notextile>*lvdisplay*<notextile>

  --- Logical volume ---

</notextile>%{background-color: yellow}  LV Path                /dev/volume-vg/root%<notextile>

  LV Name                root

  VG Name                volume-vg

  LV UUID                cH0jGQ-qF4y-aoMg-2mXp-qM6g-FOIu-2vH7sr

  LV Write Access        read/write

  LV Creation host, time volume, 2023-05-24 09:13:41 +0200

  LV Status              available

  # open                 1

  LV Size                48.56 GiB

  Current LE             12432

  Segments               1

  Allocation             inherit

  Read ahead sectors     auto

  - currently set to     256

  Block device           254:0

  --- Logical volume ---

  LV Path                /dev/volume-vg/swap_1

  LV Name                swap_1

  VG Name                volume-vg

  LV UUID                nt3bJn-w6lN-RSnY-iEFQ-uWd7-f3ve-jkj2jw

  LV Write Access        read/write

  LV Creation host, time volume, 2023-05-24 09:13:41 +0200

  LV Status              available

  # open                 2

  LV Size                980.00 MiB

  Current LE             245

  Segments               1

  Allocation             inherit

  Read ahead sectors     auto

  - currently set to     256

  Block device           254:1

</pre>

Extend the LV, giving it all the free space.

By using the @--resizefs@ parameter, @lvresize@ will automatically resize the underlying filesystem to accomodate for the change in available diskspace. Without this parameter, resizing the filesystem must be done manually (using @resize2fs@, @xfs_growfs@, …).

Execute:

<pre>

root@server:~# </notextile>*lvresize --resizefs --extents +100%FREE /dev/volume-vg/root*<notextile>

  Size of logical volume volume-vg/root changed from 48.56 GiB (12432 extents) to 298.56 GiB (76432 extents).

  Logical volume volume-vg/root successfully resized.

resize2fs 1.46.2 (28-Feb-2021)

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

old_desc_blocks = 7, new_desc_blocks = 38

The filesystem on /dev/mapper/volume-vg-root is now 78266368 (4k) blocks long.

</pre>

Finally, use @df@ to verify the disk space is actually available on the filesystem:

<pre>

root@server:~# </notextile>*df -h*<notextile>

Filesystem                            Size  Used Avail Use% Mounted on

udev                                   16G     0   16G   0% /dev

tmpfs                                 3.2G  604K  3.2G   1% /run

</notextile>%{background-color: yellow}/dev/mapper/volume-vg-root            294G  1.4G  280G   1&percnt; /%<notextile>

tmpfs                                  16G     0   16G   0% /dev/shm

tmpfs                                 5.0M     0  5.0M   0% /run/lock

/dev/sda1                             470M   87M  359M  20% /boot

tmpfs                                 3.2G     0  3.2G   0% /run/user/1000

</pre>