G907 - Appendix 07 ~ Resizing a root LVM volume.md

G907 - Appendix 07 ~ Resizing a root LVM volume

Let's say you happen to have a Debian-based VM with a small single storage drive (hard disk in Proxmox VE) of about 5 GiB, and you need to make it bigger, up to 10 GiB for instance. To do so you'll have to resize the hard disk first, then you'll need to extend the root LVM filesystem inside of it over the new space. The procedure is not hard but, since it manipulates the root filesystem while it's active, you must be careful when going through it.

Resizing the storage drive on Proxmox VE

You can expand any hard disk attached to a VM easily on Proxmox VE.

1. With the VM shutdown, get into the Hardware tab, select the hard disk and then press on Resize disk.

   

   In this case, the hard disk to resize has a 5 GiB size.

2. You'll get to a very simple form.

   

   The Disk field identifies the hard disk you're about to resize, and the Size Increment field is where you indicate by how much you want to increase the size of this particular hard disk.

   BEWARE!
   The Proxmox VE web console only supports INCREASING a hard disk's size, not reducing it.

3. Type the increment, in gigabytes, you want to apply to the hard disk and click on Resize Disk.

   

   In this case, the hard disk will be made 5 GiB bigger.

4. Proxmox VE will apply the resize immediately, so you'll see the new size shown in the hard disk description.

   

   The hard disk now has a total of 10 GiB, from an initial capacity of 5 GiB.

Extending the root LVM filesystem on a live VM

The hard disk is bigger now, but the VM's filesystem is not using that extra space yet. You need to extend it over the newly available space. Assuming the VM is a Debian system installed over a LVM filesystem, here you'll see how to extend it's root filesystem while the VM is running.

BEWARE!
The following procedure, if not applied with care, could make your VM's filesystem (and the VM itself) unusable!

Resizing the related partitions

Before you can extend the root LVM volume, you need to resize the partition in which it's found.

1. Check with fdisk if your system truly sees the full size of the disk.

   $ sudo fdisk -l
   Disk /dev/sda: 10 GiB, 10737418240 bytes, 20971520 sectors
   Disk model: QEMU HARDDISK
   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: 0xf8a21db5
   
   Device     Boot   Start      End Sectors  Size Id Type
   /dev/sda1  *       2048   999423  997376  487M 83 Linux
   /dev/sda2       1001470 10483711 9482242  4.5G  5 Extended
   /dev/sda5       1001472 10483711 9482240  4.5G 8e Linux LVM
   
   
   Disk /dev/mapper/debiandemo--vg-root: 3.56 GiB, 3825205248 bytes, 7471104 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/debiandemo--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

   Notice the Disk /dev/sda line, it says that the sda harddisk has the expected 10 GiB. Also see how inside sda there are three partitions: sda1, sda2 and sda5. The sda5 partition is the one you want to spread over the extra storage space available, since its the one that contains the root LVM volume (and also the swap volume). But this sda5 partition is inside the Extended sda2 one, so you need to expand first the sda2 partition to the end of the sda drive.

2. Now you're going to install another partition tool that will help you resize the sda2 and sda5 partitions easily. The tool is parted.

   $ sudo apt install -y parted

3. Launch parted over the /dev/sda drive.

   $ sudo parted /dev/sda

   Then you'll get in the parted shell.

   GNU Parted 3.4
   Using /dev/sda
   Welcome to GNU Parted! Type 'help' to view a list of commands.
   (parted)

4. Execute print to check how parted sees the sda partitions.

   (parted) print
   Model: QEMU QEMU HARDDISK (scsi)
   Disk /dev/sda: 10.7GB
   Sector size (logical/physical): 512B/512B
   Partition Table: msdos
   Disk Flags:
   
   Number  Start   End     Size    Type      File system  Flags
    1      1049kB  512MB   511MB   primary   ext2         boot
    2      513MB   5368MB  4855MB  extended
    5      513MB   5368MB  4855MB  logical                lvm

   Notice that the Number is what identifies each partition: the sda2 is shown just as number 2, and sda5 as 5.

5. Resize the partition 2 with the following resize command.

   BEWARE!
   The parted program applies the changes in the partition table immediately, unlike fdisk that works first on a temporal table on memory.

   (parted) resizepart 2 -1s

   It won't return any output. Check with print that the resizing has been done.

   (parted) print
   Model: QEMU QEMU HARDDISK (scsi)
   Disk /dev/sda: 10.7GB
   Sector size (logical/physical): 512B/512B
   Partition Table: msdos
   Disk Flags:
   
   Number  Start   End     Size    Type      File system  Flags
    1      1049kB  512MB   511MB   primary   ext2         boot
    2      513MB   10.7GB  10.2GB  extended
    5      513MB   5368MB  4855MB  logical                lvm

6. Now, apply the resizing to partition 5.

   (parted) resizepart 5 -1s

   Again, use print to verify the resizing.

   (parted) print
   Model: QEMU QEMU HARDDISK (scsi)
   Disk /dev/sda: 10.7GB
   Sector size (logical/physical): 512B/512B
   Partition Table: msdos
   Disk Flags:
   
   Number  Start   End     Size    Type      File system  Flags
    1      1049kB  512MB   511MB   primary   ext2         boot
    2      513MB   10.7GB  10.2GB  extended
    5      513MB   10.7GB  10.2GB  logical                lvm

7. Type quit or just use Ctrl+C to exit parted.

   (parted) quit
   Information: You may need to update /etc/fstab.

   Notice that, when exiting, parted will warn you about updating the /etc/fstab file. In this case it won't be necessary.

Extending the root LVM volume

With the real partitions updated, now you can extend the LVM filesystem in the newly available space.

1. First you must extend the physical volume that corresponds to the sda5 partition. Check with pvs its current state.

   $ sudo pvs
     PV         VG            Fmt  Attr PSize  PFree
     /dev/sda5  debiandemo-vg lvm2 a--  <4.52g    0

   Notice that its PSize is only around 4.5 GiB.

2. Use pvresize to expand the sda5 PV.

   $ sudo pvresize /dev/sda5
     Physical volume "/dev/sda5" changed
     1 physical volume(s) resized or updated / 0 physical volume(s) not resized

   Then verify with pvs that the resizing has been done.

   $ sudo pvs
     PV         VG            Fmt  Attr PSize  PFree
     /dev/sda5  debiandemo-vg lvm2 a--  <9.52g 5.00g

   Above you can see that PSize is now 9.52 GiB, from which 5 GiB are free (PFree column).

3. Now you can resize the root LV itself. First, check it's current status.

   $ sudo lvs
     LV     VG            Attr       LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
     root   debiandemo-vg -wi-ao----   3.56g
     swap_1 debiandemo-vg -wi-ao---- 980.00m

   It's LSize is 3.56 GiB and, below it, you can see the swap volume (swap_1) taking up a bit less than 1 GiB.

4. Use the following lvextend command to extend the root volume over all the available free space in the sda5 PV.

   $ sudo lvextend -r -l +100%FREE debiandemo-vg/root
     Size of logical volume debiandemo-vg/root changed from 3.56 GiB (912 extents) to 8.56 GiB (2192 extents).
     Logical volume debiandemo-vg/root successfully resized.
   resize2fs 1.46.2 (28-Feb-2021)
   Filesystem at /dev/mapper/debiandemo--vg-root is mounted on /; on-line resizing required
   old_desc_blocks = 1, new_desc_blocks = 2
   The filesystem on /dev/mapper/debiandemo--vg-root is now 2244608 (4k) blocks long.

   The command not only has resized the LV, but also has resized the ext4 filesystem inside (the -r option called the resize2fs command). Check again with lvs the new status of the root LV.

   $ sudo lvs
     LV     VG            Attr       LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
     root   debiandemo-vg -wi-ao----   8.56g
     swap_1 debiandemo-vg -wi-ao---- 980.00m

   Now it's LSize is 8.56 GiB, and the swap volume has been unaffected by the whole procedure.

5. As a final test, reboot the VM to verify that the changes have not messed up with the system in a bad way. This is something you may detect in the VM's boot sequence, sequence which you can see only through a noVNC shell, never remotely through ssh.

   $ sudo reboot

Final note

This procedure is, as it is, also valid to extend any non-root LVM volumes.

References

About resizing LVM storage

• How to resize LVM disk in Debian 8.6 without losing data
• Expanding LVM Partitions in VMware, on the fly
• How to extend a Linux PV partition online after virtual disk growth
• Extend a LVM partition after increasing its virtual disk on VirtualBox
• How do I extend a partition with a LVM and the contained physical volume and logical volume?
• CentOS / RHEL : How to extend Physical Volume in LVM by extending the Disk Partition used
• How to Increase the size of a Linux LVM by expanding the virtual machine disk
• LVM Resize – How to Increase an LVM Partition

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