Creating containers for Linux targets is busted due to outdated apt
For Linux containers we hardcode 0.9.7.9+deb7u8 as the minimal apt version but that's not available anymore on deb.freexian.com. Rather it's 0.9.7.9+deb7u9 now.
To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information