Online expansion of Ubuntu LVM disk

LVM overview

lvm

Physical Volume (PV)

Refers to a disk partition, or a device (such as RAID) that has the same function as a disk partition. It is the basic storage logical block of LVM, but compared with basic physical storage media (such as partitions, disks, etc.), it contains LVM-related Management parameters.

Volume Group (VG)

Similar to a physical disk in a non-LVM system, it is composed of one or more physical volumes PV. One or more LVs (logical volumes) can be created on the volume group.

Logical Volume (LV)

Similar to disk partitions in non-LVM systems, logical volumes are built on the volume group VG. A file system (such as /home or /usr, etc.) can be established on the logical volume LV.

LVM expansion operation

Create a new primary partition

If you expanded the hard disk size of the virtual machine, and you are still using one hard disk such as /dev/sda, you can do this:

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sudo fdisk /dev/sda

Enter m to view the help, enter n to create a new partition, select the primary partition, step by step, press w to write and save, and get /dev/sda2.

You can also add a new hard drive to the machine, and the new hard drive may be shown as /dev/sdb. The operation of creating a new partition is similar.

Format the partition as ext4 format

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sudo mkfs -t ext4 /dev/sda2

/dev/sda2 represents the new partition, you can replace it with other paths according to your situation, for example /dev/sdb1.

Find the VG Name

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~# vgdisplay
  --- Volume group ---
  VG Name               ubuntu--vg-root
  System ID
  Format                lvm2
  ......

Add the new partition to the original VG of lvm

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vgextend ubuntu--vg-root /dev/sda2

Check the VG

You should find that there are some free space in the volume group.

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~# vgdisplay
  --- Volume group ---
  VG Name               ubuntu--vg-root
  System ID
  Format                lvm2
  Metadata Areas        2
  Metadata Sequence No  5
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                3
  Open LV               3
  Max PV                0
  Cur PV                2
  Act PV                2
  VG Size               758.99 GiB
  PE Size               4.00 MiB
  Total PE              194302
  Alloc PE / Size       15103 / <59.00 GiB
  Free  PE / Size       179199 / <700.00 GiB

Check the LV

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~# lvdisplay
  --- Logical volume ---
  LV Path                /dev/ubuntu--vg-root/lv-root
  LV Name                lv-root
  VG Name                ubuntu--vg-root
  LV UUID                KiPSR5-XXvZ-JaXz-fyTw-EE0U-NV7E-6ohpCN
  LV Write Access        read/write
  LV Creation host, time ubuntu-server, 2018-11-15 06:06:41 +0000
  LV Status              available
  # open                 1
  LV Size                45.00 GiB
  Current LE             11520
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           253:0

Extend the LV

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~# lvextend -L 700G /dev/ubuntu--vg-root/lv-root
  Size of logical volume ubuntu--vg-root/lv-root changed from 45.00 GiB (11520 extents) to 700.00 GiB (179200 extents).
  Logical volume ubuntu--vg-root/lv-root successfully resized.

Find the root file system name

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~# df -h
Filesystem                       Size  Used Avail Use% Mounted on
udev                              16G     0   16G   0% /dev
tmpfs                            3.2G   19M  3.2G   1% /run
/dev/mapper/ubuntu--vg-root       45G  5.3G   37G  13% /

Resize file system

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~# resize2fs -p /dev/mapper/ubuntu--vg-root
resize2fs 1.44.1 (24-Mar-2018)
Filesystem at /dev/mapper/ubuntu--vg-root is mounted on /; on-line resizing required
old_desc_blocks = 6, new_desc_blocks = 88
The filesystem on /dev/mapper/ubuntu--vg-root is now 183500800 (4k) blocks long.

View the latest hard drive size

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~# df -h
Filesystem                       Size  Used Avail Use% Mounted on
udev                              16G     0   16G   0% /dev
tmpfs                            3.2G   59M  3.1G   2% /run
/dev/mapper/ubuntu--vg-root      689G  5.4G  655G   1% /

How to reduce the LV size

You can use the lvreduce command.

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