user-access/rootfs/etc/cont-init.d/02-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