If you have a Chromebook with a fairly meager 16 or 32 GB of storage, Linux through Project Crostini may not be an option due to limited local storage. Back in 2018, Google realized this and started work on allowing Linux to run from an external drive connected to a Chromebook. After a year of silence, the work has recently been returned to this function; in the last few months several code updates have been moved.
Assuming this change goes ahead, it could be that otherwise Chostebooks with Crostini-compatible Chromebooks with limited storage space will run the Linux virtual machine on a USB drive or even an SD memory card. You want fast media in both cases if you get the chance to try this; running a virtual machine with a Linux container on slower media would not be optimal.
While I see the potential need for this on Chromebooks with smaller internal disks, it can benefit all Chromebooks users.
For example, you may have 64 or more GB of storage capacity on your device, but you may just use the majority of it for Chrome OS, Android apps, and file storage. It would be handy to just wipe out a USB drive with your Linux instance, boot up and do whatever you need in the virtual machine.
Or maybe you have set up different Linux containers for different purposes: one for work and one for general purpose. However, having this flexibility can be beneficial.
Given that Google is very focused on keeping Chrome OS secure, implementing Linux and VM support on external disks brings some challenges. There are developers talking about how you can best protect the environment while also bringing this external drive feature.
The last relevant comment on the security aspect was to “allow extra disks only on untrusted VMs”, but that is perhaps not a bad thing.
Recently, we have seen progress in enabling such VMs and these have led to the ability to install Windows 10 in a virtual machine on a Chromebook. In theory, one could run any operating system within such an untrusted VM, with the only caveat being that it might not have full access to all the hardware and software on your Chromebook.
There is currently no target version of Chrome OS for this feature, so if it is implemented, it will probably be several months out.
