Hi Tadas,
Render now supports the use of magic-wormhole in our native environments. You may need to re-deploy your service from the dashboard to upgrade to the latest base image Manual Deploy -> Deploy Latest Commit
Once you verify that magic-wormhole is installed you can go to the Shell tab on your dashboard and run:
tar -zcvf archive-name.tar.gz path/to/disk
wormhole send archive-name.tar.gz
Make note of the code that appears in the output from wormhole. Then from any internet-connected machine, install magic wormhole and run wormhole receive , entering in the code when prompted.
I hope this helps!