2024 Update - I found myself stuck in this situation again, my Ubuntu root partition was completely full to the brim… I’m scrambling to remove apt chache and pruning and and all docker images, but then I run vgdisplay only to reaslise that my LVM LV isn’t even using the full amount of physical disk space (this is a VM and I have just expanded the VMDK file). Thankfully I wrote this blog post 4 years ago as a how-to. Well now I am going to give this post a refresh and this includes some extra details which I needed during the panic of a full disk.

This title has far too many acronyms so I will start by clarifying the problem that this post aims to solve. I have a Ubuntu server instance running LVM (Logical Volume Manager). My primary LV (Logical Volume) was ‘full’ but was only using 4GB of a 29GB PV (Physical Volume). So if you are suffering the same issue, here are the commands you need to fix this problem.

Let’s break down the acronyms and understand why your Logical Volume (LV) might not be using all the available space on your Physical Volume (PV).

  • LVM (Logical Volume Manager): Think of LVM as a flexible way to manage your hard drive space in Linux. It sits on top of your physical disks and lets you carve them up into logical units.
  • PV (Physical Volume): This is the actual hard drive or partition that LVM is managing. It’s the raw storage space.
  • LV (Logical Volume): This is a chunk of space that LVM carves out from the PV. You can think of it as a virtual partition. It’s what your operating system sees and interacts with.

Why not use all the PV space when creating a LV?

When you first set up your LVM, you might not allocate all the space on your PV to your LV. This is often intentional, leaving room for:

  • Future Expansion: You might want to expand your LV later without having to add more physical disks.
  • Creating More LVs: You might want to create additional LVs on the same PV for different purposes (e.g., one for the operating system, one for data).

Key Takeaway: Just because you have free space on your PV doesn’t mean your LV automatically uses it. You need to explicitly tell LVM to extend the LV and then resize the filesystem to make use of that extra space.

Ok Let’s fix this…

Free up some space:

It might be possible to free up some space without the need to start expanding disks and volumes.

We can check free space on our partitions by look at the df -h output:

Filesystem1K-blocksUsedAvailableUse%Mounted on
/dev/mapper/i-hate-lvm516650451501200100%/

df -h Shows the space available in mounted partitions This is fictitious data, but this is reflective of the fact that the root filesystem is full. This caused me a LOT of headaches and I needed to free up some free space on that partition before I could run any of the upcoming commands to expand the LV. Ways to free up space include:

sudo apt clean
sudo apt autoremove -y

If you are running snap, you can use the following command to remove older versions of a snap application:

snap remove "$snapname" --revision="$revision"

Finding the available PV space

Now that we have a tiny bit of space on ‘/’ we cab start to work on expanding the available space in the LV. First, we need to find out the available space in the PV which is where the LV ‘lives’.

vgdisplay

the value we are looking for specifically is:

Free  PE / Size       2319 / 9.06 GiB

As per the example above, we have just over 2GB available. I want to go head and give all of that space to my one and only LV.

Extending LV with lvextend

First we need to find the LV path:

lvdisplay

In my hypothetical example this is:

    --- Logical volume ---
    LV Path                /dev/i-hate-lvm

So now we can extend the LV, consuming the available disk space, this is done with the lvextend command:

sudo lvextend -l +2319 /dev/i-hate-lvm

Adjust the 2319 value and the /dev/ path to suit your required level of expansion and the LVM volume; this is the path shown by df -h.

Extending an LV filesystem with resize2fs

Finally, now that the LV is larger, we need to expand the filesystem on the volume to make the newly acquired space available for use. Fortunately this another really simple command:

resize2fs /dev/mapper/i-hate-lvm

Pay attention to the fact that I am running this command against /dev/mapper/<volume-name>.

Run the df -h command and again and you should now have ALL OF THE FREE SPACE!

Congratulations! You’ve successfully navigated the sometimes-confusing world of LVM and expanded your logical volume. By using lvextend to claim the available space on your physical volume and then resize2fs to make that space usable by your filesystem, you’ve given your Ubuntu system some much-needed breathing room. No more frantic cache cleaning or image pruning – for now, at least! Remember to keep an eye on your disk usage and repeat this process as needed to keep your system running smoothly.

Consider giving this post a bookmark or a share to help out a fellow LVM sufferer in a moment of need.

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