It turns out that the script is already in the right place and all the initramfs hooks are in place etc. It is merely necessary to add keyscript=decrypt_keyctl into the relevant places in crypttab.
Unfortunately doing so causes update-initramfs to fail with the cryptkeyctl hook giving error code 1.
It turns out that the script is already in the right place and all the initramfs hooks are in place etc. It is merely necessary to add keyscript= decrypt_ keyctl into the relevant places in crypttab.
Unfortunately doing so causes update-initramfs to fail with the cryptkeyctl hook giving error code 1.
Still investigating.