Use su-exec instead of sudo

slim/Dockerfile

@@ -19,7 +19,7 @@ RUN set -x \
         ca-certificates \
         cyrus-sasl \
         icu \
-        sudo \
+        su-exec \
         tini \
     && apk add --no-cache --virtual build-dependencies \
         build-base \

slim/docker-entrypoint.sh

@@ -24,4 +24,4 @@ chmod 700 "$DATADIR" || exit 2
 # ZNC itself responds to SIGTERM, and reaps its children, but whatever was
 # started via *shell module is not guaranteed to reap their children.
 # That's why using tini.
-exec /sbin/tini -- sudo --user znc /opt/znc/bin/znc --foreground --datadir "$DATADIR" "$@"
+exec /sbin/tini -- su-exec znc:znc /opt/znc/bin/znc --foreground --datadir "$DATADIR" "$@"