Increasing the User OS disk size

This document builds on the Getting Started and assumes you already have a system with ACRN installed and running correctly. The size of the pre-built Clear Linux User OS (UOS) virtual disk is typically only 8GB and this may not be sufficient for some applications. This guide explains a simple few steps to increase the size of that virtual disk.

This document is largely inspired from Clear Linux’s Increase virtual disk size of a Clear Linux* OS image tutorial. The process can be broken down into three steps:

  1. Increase the virtual disk (uos.img) size
  2. Resize the rootfs partition
  3. Resize the filesystem


These steps are performed directly on the UOS disk image. The UOS VM must be powered off during this operation.

Increase the virtual disk size

We will use the qemu-img tool to increase the size of the virtual disk (uos.img) file. On a Clear Linux system, you can install this tool using:

$ sudo swupd bundle-add clr-installer

As an example, let us add 10GB of storage to our virtual disk image called uos.img.

$ qemu-img resize -f raw uos.img +10G


Replace uos.img by the actual name of your virtual disk file if you deviated from the Getting Started.


You can choose any increment for the additional storage space. Check the qemu-img resize help for more information.

Resize the rootfs partition

The next step is to modify the rootfs partition (in Clear Linux, it is partition 3) to use the additional space available. We will use the parted tool and perform these steps:

  • Enter the parted tool
  • Press p to print the partition tables
  • A warning will be displayed, enter Fix
  • Enter resizepart 3
  • Enter the size of the disk (19.9GB in our example)
  • Enter q to quit the tool

Here is what the sequence looks like:

$ parted uos.img
WARNING: You are not superuser.  Watch out for permissions.
GNU Parted 3.2
Using /home/gvancuts/uos/uos.img
Welcome to GNU Parted! Type 'help' to view a list of commands.
(parted) p
Warning: Not all of the space available to /home/gvancuts/uos/uos.img appears to be used, you can fix the GPT to use all of the space (an extra 20971520 blocks) or continue with the current setting?
Fix/Ignore? Fix
Model:  (file)
Disk /home/gvancuts/uos/uos.img: 19.9GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags:

Number  Start   End     Size    File system     Name     Flags
 1      1049kB  537MB   536MB   fat16           primary  boot, esp
 2      537MB   570MB   33.6MB  linux-swap(v1)  primary
 3      570MB   9160MB  8590MB  ext4            primary

(parted) resizepart 3
End?  [9160MB]? 19.9GB
(parted) q

Resize the filesystem

The final step is to resize the rootfs filesystem to use the entire partition space.

$ LOOP_DEV=`sudo losetup -f -P --show uos.img`
$ PART_DEV+="p3"
$ sudo e2fsck -f $PART_DEV
$ sudo resize2fs -p $PART_DEV
$ sudo losetup -d $LOOP_DEV

Congratulations! You have successfully resized the disk, partition, and filesystem of your User OS.