stretch -> buster

stretch → buster

diff --git a/Dockerfile b/Dockerfile
index 9d65db2..17b1ba3 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,7 +1,21 @@
-FROM debian:stretch
-
-RUN apt-get update \
-	&& apt-get -y install --no-install-recommends curl gdb jq less lsof net-tools procps strace tcpdump telnet vim wget \
-	&& apt-get clean \
-	&& rm -rf /var/lib/apt/lists/*
+FROM debian:buster-slim
 
+RUN DEBIAN_FRONTEND=noninteractive apt-get update \
+  && DEBIAN_FRONTEND=noninteractive apt-get dist-upgrade -y \
+  && DEBIAN_FRONTEND=noninteractive apt-get -y install --no-install-recommends \
+    curl \
+    gdb \
+    jq \
+    less \
+    lsof \
+    net-tools \
+    procps \
+    strace \
+    tcpdump \
+    telnet \
+    vim \
+    wget \
+  && DEBIAN_FRONTEND=noninteractive apt-get clean \
+  && ( find /var/lib/apt/lists -mindepth 1 -delete || true ) \
+  && ( find /var/tmp           -mindepth 1 -delete || true ) \
+  && ( find /tmp               -mindepth 1 -delete || true )
diff --git a/build b/build
index eb84c04..0c21066 100755
--- a/build
+++ b/build
@@ -1,7 +1,9 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 set -e
 
-docker pull debian:stretch
-docker build --build-arg=http_proxy=$http_proxy -t discourse/cdebug:latest .
+docker build \
+  --pull \
+  "--build-arg=http_proxy=${http_proxy:-}" \
+  -t discourse/cdebug:latest .
 docker push discourse/cdebug:latest

GitHub sha: 8181afb5deedcc5657c84afec0324edc9f10b959