Starting two Linux at once

[registereduser]

I have two USB sticks, one has Ubuntu and the other has Mint
so just for fun (no practical purpose) I wanted to run them both at the same time.

after booting into Mint, I opened a virtual terminal and mounted the Mint root inside the Ubuntu /media/Mint folder
mount -t ext4 /dev/sdb1 /media/ubuntudrive/media/mint

then in a virtual terminal I chroot to the Ubuntu USB
chroot /media/ubuntudrive

create a symlink from /media/mint/dev to /dev
ln -s /media/mint/dev /dev
**do i need anything other than dev? please let me know**

then, from the chrooted Ubuntu drive I startx -- :1 (since Mint is already on display :0)
thinking it would run the other Linux OS along side in a different window, but it gives an error

"Fatal server error: No screens found"

I went into the /etc/X11/ and renamed xorg.conf.failsafe to xorg.conf but it didn't help, still no screens found.

any ideas?