From 01238ae5f78dfb9fdf50a069f23205067dcbd165 Mon Sep 17 00:00:00 2001
From: Joseph Hale <me@jhale.dev>
Date: Tue, 17 Feb 2026 16:39:59 -0700
Subject: [PATCH] Replace dcron with supercronic for non-root cron support

The container was failing to start on Ubuntu with Permission denied when
trying to launch crond, because the container runs as the nginx user
(non-root) and dcron requires root privileges.

Key Decisions:
- Supercronic over a sleep loop to preserve full cron expression support
- Supercronic over sudo because sudo defeats non-root security model
- Grouped crontab setup with supercronic startup for better code organization

Supercronic was chosen because it's designed specifically for containers,
runs without root, handles signals gracefully, and adds only ~2MB to image.
---
 Dockerfile    | 11 +++++++++--
 entrypoint.sh | 24 ++++++++++--------------
 2 files changed, 19 insertions(+), 16 deletions(-)

diff --git a/Dockerfile b/Dockerfile
index 5616726..e1ee212 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -9,8 +9,15 @@ RUN apk add --no-cache \
     bash \
     jq \
     coreutils \
-    bc \
-    dcron
+    bc
+
+# Install Supercronic (cron for containers)
+ENV SUPERCRONIC_URL=https://github.com/aptible/supercronic/releases/download/v0.2.43/supercronic-linux-amd64 \
+    SUPERCRONIC_SHA1SUM=f97b92132b61a8f827c3faf67106dc0e4467ccf2
+RUN curl -fsSLO "$SUPERCRONIC_URL" \
+    && echo "${SUPERCRONIC_SHA1SUM}  supercronic-linux-amd64" | sha1sum -c - \
+    && chmod +x supercronic-linux-amd64 \
+    && mv supercronic-linux-amd64 /usr/local/bin/supercronic
 
 # Install Ookla Speedtest CLI
 RUN ARCH=$(uname -m) && \
diff --git a/entrypoint.sh b/entrypoint.sh
index 500c017..33e5c4b 100644
--- a/entrypoint.sh
+++ b/entrypoint.sh
@@ -6,17 +6,6 @@ export HOME=${HOME:-/tmp}
 mkdir -p "$HOME/.config/ookla"
 cp "$HOME/speedtest-cli.json" "$HOME/.config/ookla/"
 
-# Setup cron job
-CRON_SCHEDULE="${CRON_SCHEDULE:-*/30 * * * *}"
-echo "Setting up speedtest cron job with schedule: $CRON_SCHEDULE"
-
-# Create crontab file for current user
-mkdir -p /tmp/crontabs
-echo "$CRON_SCHEDULE /app/speedtest_runner.sh >> $HOME/speedtest.log 2>&1" > /tmp/crontabs/speedtest
-
-# Create log file
-touch "$HOME/speedtest.log"
-
 # Generate initial HTML page (before nginx starts)
 /app/generate_html.sh
 
@@ -27,6 +16,13 @@ NGINX_PID=$!
 # Run initial speedtest
 /app/speedtest_runner.sh
 
-# Start cron in foreground (using busybox crond with user crontab)
-echo "Starting cron daemon..."
-crond -f -l 8 -L "$HOME/cron.log" -c /tmp/crontabs
+# Setup and start supercronic (cron for containers, runs as non-root)
+CRON_SCHEDULE="${CRON_SCHEDULE:-*/30 * * * *}"
+echo "Setting up speedtest cron job with schedule: $CRON_SCHEDULE"
+
+mkdir -p /tmp/crontabs
+echo "$CRON_SCHEDULE /app/speedtest_runner.sh >> $HOME/speedtest.log 2>&1" > /tmp/crontabs/speedtest
+touch "$HOME/speedtest.log"
+
+echo "Starting supercronic..."
+exec supercronic -passthrough-logs /tmp/crontabs/speedtest
-- 
2.51.2