Panamax can install in Virtual box but can also install directly on CoreOS instances. The main site does not include direct CoreOS installs as part of the standard installation. It is however explained on the wiki.
Here are the commands I used (stealing from my previous sequence of commands for cygwin).
core@coreos$ mkdir ~/.panamax core@coreos$ cd ~/.panamax core@coreos$ curl -O http://download.panamax.io/installer/pmx-installer-latest.zip core@coreos$ unzip pmx-installer-latest.zip core@coreos$ sudo ./coreos install --stable
Panamax is then accessible on port 3000. (There may be a better way, but this worked for me – I have not tried experimenting to see if I can shorten the list of commands.)
Note: I am having more luck running Panamax directly on a CoreOS VM with a bigger slab of memory than the Virtual Box version on my laptop, probably because the containers I am creating are quite memory hungry. Things just stop working at times on my laptop for reasons I have not verified yet.