user-access/rootfs/etc/cont-init.d/04-static-user

#!/usr/bin/with-contenv sh

if [ ! -z ${STATIC_USER+x} ]; then
    echo ${STATIC_PASSWORD} | ftpasswd \
        --sha512 \
        --passwd \
        --home /var/lib/ftp/data \
        --uid ${STATIC_UID} \
        --gid ${STATIC_GID} \
        --name ${STATIC_USER} \
        --shell /bin/sh \
        --file /etc/proftpd/passwd \
        --stdin
fi