Posted by: Eric Schrader | January 18, 2017

Azure Linux Ubuntu disk space full

I noticed our dev team had some issues with our disk space on an Azure VM saying the disk was full. I saw something in Linux called dev/sba1 that was taking up all my space and my disk was full. Why was my Linux storage space low?

Our website is only 5-6GB in size, so I knew something was wrong. Our VM in Azure is a DS12v2 with 56GB ram and 128GB SSD.

We are running the Ubuntu 14 OS image from Azure and are using it as an Apache web host.

When I ran a “df” (Disk Filesystem) command to check the free space, one of the volumes was huge and at 97%

$ sudo df -h

Filesystem Size Used Avail Use% Mounted on

udev 28G 12K 28G 1% /dev

tmpfs 5.6G 432K 5.6G 1% /run

/dev/sda1 29G 27G 1.1G 97% /

none 4.0K 0 4.0K 0% /sys/fs/cgroup

none 5.0M 0 5.0M 0% /run/lock

none 28G 0 28G 0% /run/shm

none 100M 0 100M 0% /run/user

none 64K 0 64K 0% /etc/network/interfaces.dynamic.d

/dev/sdb1 111G 60M 105G 1% /mnt


Run a sudo df -h (h stands for human readable)

I am still not 100% clear on this, but some of these above results are different disk partitions that are mounted via symbolic names, similar to how a disk in Windows can be partitioned into C, D drives, etc.

The Azure VM had one OS VHD assigned to it, which should be 128GB.

So, I focused in on the /dev/sda1 filesystem. I had no clue what this was at first, but after looking into it, it might be my VHD mounted to my VM’s primary root drive (/). (Please correct me if I am wrong). In “sda1“, The “sd” stands for SCSI device (which is now any attached device, could be USB, SATA, IDE, etc.), the “a” stands for the attached device order (a is first, b is the second device, etc.) and the “1” indicates the partition on that device (think of a hard drive partitioned into 1, 2, 3 different partitions.) (thanks to this article for the explanation

For me, I only have one sd device and one partition, so I assume that’s my Azure VM OS VHD that should have been 128GB. But why was it only 29GB?

WELL! All Linux OS vm partitions come as 30GB allocated.

How do I get all my GB’s? Add a second drive for my data? No, just resize the primary partition.

I read this article ( about resizing an Azure VHD and thought “ooh God, I am going to scrap my entire OS partitions data if this goes wrong or if I get stuck in these steps…” but after reading the top, UBUNTU automatically resizes the Linux partition on boot! YES! All I have to do is reboot! But, I just rebooted and that didn’t resize the partition….

The Problem: When browsing the Azure portal, I noticed my VM disk size was blank, and where I could select 128/256 or 512GB, none were selected. So, I thought “maybe Azure doesn’t automatically define a default OS disk size of 128GB since machine sizes can go up or down dynamically.”

These machines will have 128GB OS disks allocated to them, so I wanted to set them to the full 128GB (I can go up in size, but not down).

Problem: my OS disk size is not selected, so Ubuntu cannot automatically resize the partition (I think the VHD is dynamically allocated at this point)

Solution: How to add more space in the Azure Portal easily with a Linux Ubuntu VM

  1. Turn off the VM
  2. Select the disk size for the OS disk (I used 128GB)
  3. Turn it on.

BAM! You now have more space.

Run the “df -h” command again after the VM comes back online and see a 126GB of space at the root! Done!

$ sudo df -h

Filesystem Size Used Avail Use% Mounted on

udev 28G 12K 28G 1% /dev

tmpfs 5.6G 416K 5.6G 1% /run

/dev/sda1 126G 5.8G 116G 5% /

none 4.0K 0 4.0K 0% /sys/fs/cgroup

none 5.0M 0 5.0M 0% /run/lock

none 28G 0 28G 0% /run/shm

none 100M 0 100M 0% /run/user

none 64K 0 64K 0% /etc/network/interfaces.dynamic.d

/dev/sdb1 111G 60M 105G 1% /mnt


If you don’t have Ubuntu, you have more steps to do to resize the Linux OS partition. I haven’t done it, but this seems like a good place to start:


Please leave any comments if you know more about the df command results, the sda1, Azure VM OS disk sizes, Linux partitions, etc. I am always learning.

References that helped me get here:




  1. still in full effect HUH! NICE

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