Make upstart script more fault tolerant and easier to debug (#824)

* Make Upstart script more fault tolerant and easier to debug

* update readme

dist/init/linux-upstart/README.md

@@ -9,5 +9,6 @@ Short recap:
 
 * Download Caddy in `/usr/bin/caddy` and execute `sudo setcap cap_net_bind_service=+ep /usr/bin/caddy`.
 * Save the upstart config file in `/etc/init/caddy.conf`.
+* Ensure that the folder `/etc/caddy` exists and that the subfolder .caddy is owned by `www-data`.
 * Create a Caddyfile in `/etc/caddy/Caddyfile`.
 * Now you can use `sudo service caddy start|stop|restart`.

dist/init/linux-upstart/caddy.conf

-description "Caddy startup script"
-author "Mathias Beke"
+description "Caddy HTTP/2 web server"
 
 start on runlevel [2345]
 stop on runlevel [016]
 
+console log
 
 setuid www-data
 setgid www-data
@@ -11,8 +11,13 @@ setgid www-data
 respawn
 respawn limit 10 5
 
-limit nofile 4096 4096
+# Let's Encrypt certificates will be written to this directory.
+env HOME=/etc/caddy
+
+limit nofile 1048576 1048576
 
 script
-	exec /usr/bin/caddy -agree=true -conf=/etc/caddy/Caddyfile
+        cd /etc/caddy
+        rootdir="$(mktemp -d -t "caddy-run.XXXXXX")"
+        exec /usr/bin/caddy -agree -log=stdout -conf=/etc/caddy/Caddyfile -root=$rootdir
 end script