I would like to implement a private cloud-storage on a Linux VPS. For example, I can use ownCloud.
I can do the root login on the VPS by ssh.
My question is if I can securely encrypt the /var/www directory in a way that the service provider cannot (easily) access my files (so I'll have to manually enter a password at every VPS reboot to mount /var/www). I assume that I cannot (easily) modify the existing partitions because I cannot umount them.
The purpose is to implement a cloud-storage that is enough safe for a working team to store very sensitive data (I cannot trust any commercial cloud-storage service that is zero-knowledge, because none of them has a fully open-source client).
Thank you very much for any help.
P.S.: CryFS on the clients seems interesting, but it's restricted on Linux machines, so it's not suitable for sharing files between people using different operating systems.