Qubes Live USB (alpha)

Qubes Live USB allows you to run and try Qubes OS without having to install it anywhere. Qubes Live USB is currently in alpha. If you use it, please consider running the HCL reporting tool and sending us the results so that we can continue to improve it. If would like to contribute to the Qubes OS Project by improving Qubes Live USB and integrating it with the installer, please consider applying for a Google Summer of Code scholarship (if you are eligible) and choosing the QubesOS Project as a mentor organization. You can find our list of project ideas here.


When making this Live USB edition of Qubes OS, we faced several challenges which traditional Linux distros don’t have to bother with:

  1. We needed to ensure Xen is properly started when booting the stick. In fact we still don’t support UEFI boot for the stick for this reason, even though the Fedora liveusb creator we used does support it. Only legacy boot for this version, sorry.
  2. We discovered that the Fedora liveusb-create does not verify signatures on downloaded packages. We have temporarily fixed that by creating a local repo, verifying the signatures manually (ok, with a script ;) and then building from there. Sigh.
  3. We had to solve the problem of Qubes too easily triggering an Out Of Memory condition in Dom0 when running as Live OS.

This last problem has been a result of Qubes using the copy-on-write backing for the VMs’ root filesystems, which is used to implement our cool Template-based scheme. Normally these are backed by regular files on disk. Even though these files are discardable upon VM reboots, they must be preserved during the VM’s life span, and they can easily grow to a few tens of MBs per VM, sometimes even more. Also, each VM’s private image, which essentially holds just the user home directory, typically starts with a few tens of MBs for an “empty VM”. Now, while these represent rather insignificant numbers on a disk-basked system, in the case of a live USB all these files must be stored in RAM, which is a scarce resource on any OS, but especially on Qubes.

We have implemented some quick optimizations in order to minimize the above problem, but this is still far from a proper solution. We’re planning to work more on this next.

There are three directions in which we want to do further work on this Qubes Live USB variant:

  1. Introduce an easy, clickable “install to disk” option, merging this with the Qubes installation ISO. So, e.g. make it possible to first see if the given hardware is compatible with Qubes (by running the HCL reporting tool) and only then install on the main disk. Also, ensure UEFI boot works well.

  2. Introduce options for persistence while still running this out of a USB stick. This would be achieved by allowing (select) VMs’ private images to be stored on the r/w partition (or on another stick).

    A nice variant of this persistence option, especially for frequent travelers, would be to augment our backup tools so that it was possible to create a LiveUSB-hosted backups of select VMs. One could then pick a few of their VMs, necessary for a specific travel, back them to a LiveUSB stick, and take this stick when traveling to a hostile country (not risking taking other, more sensitive ones for the travel). This should make life a bit simpler for some.

  3. Introduce more useful preconfigured VMs setup, especially including Whonix/Tor VMs.

Current limitations

(Remember that Qubes Live USB is currently in alpha, so please meter your expectations accordingly.)

  1. Currently just the 3 example VMs (untrusted, personal, work), plus the default net and firewall VMs are created automatically.
  2. The user has an option to manually (i.e. via command line) create an additional partition, e.g. for storing GPG keyring, and then mounting it to select VMs. This is to add poor-man’s persistence. We will be working on improving/automating that, of course.
  3. Currently there is no “install to disk” option. We will be adding this in the future.
  4. The amount of “disk” space is limited by the amount of RAM the laptop has. This has a side effect of e.g. not being able to restore (even few) VMs from a large Qubes backup blob.
  5. It’s easy to generate Out Of Memory (OOM) in Dom0 by creating lots of VMs which are writing a lot into the VMs filesystem.
  6. There is no DispVM savefile, so if you start a DispVM the savefile must be regenerated, which takes about 1-2 minutes.
  7. UEFI boot doesn’t work, and if you try booting Qubes Live USB via UEFI, Xen will not be started, rendering the whole experiment unusable.

Downloading and burning

  1. Download the ISO (and its signature for verification) from the downloads page.
  2. “Burn” (copy) the ISO onto a USB drive (replace /dev/sdX with your USB drive device):

     $ sudo dd if=Qubes-R3.0-rc2-x86_64-LIVE.iso of=/dev/sdX

    Note that you should specify the whole device, (e.g. /dev/sdc, not a single partition, e.g. /dev/sdc1).

    Caution: It is very easy to misuse the dd command. If you mix up if and of or specify an incorrect device, you could accidentally overwrite your primary system drive. Please be careful!