Initramfs in debootstrap chroot of fully encrypted system

Using /etc/initramfs-tools/conf.d/cryptsetup is deprecated in stretch.

The new preferred method is to set "CRYPTSETUP=y" in /etc/cryptsetup-initramfs/conf-hook.

In buster and later, this configuration parameter appears to be redundant, as the default behaviour seems to be to configure cryptsetup in initramfs IFF the initramfs-cryptsetup package is installed.

This will always work, even with an empty crypttab:

echo 'export CRYPTSETUP=y' > /etc/initramfs-tools/conf.d/cryptsetup

Alternatively, you can add this to /etc/environment:

CRYPTSETUP=y