Updated faqs

doc/Support/FAQ.md

@@ -13,7 +13,9 @@
  - [How do I debug the poller process?](#faq12)
  - [Why do I get a lot apache or rrdtool zombies in my process list?](#faq14)
  - [Why do I see traffic spikes in my graphs?](#faq15)
+ - [Why do I see gaps in my graphs?](#faq17)
  - [How do I change the IP / hostname of a device?](#faq16)
+ - [Things aren't working correctly?](#faq18)
 
 ### Developing
  - [How do I add support for a new OS?](#faq8)
@@ -72,10 +74,7 @@ If the page you are trying to load has a substantial amount of data in it then i
 
 #### <a name="faq10"> Why do I not see any graphs?</a>
 
-This is usually due to there being blank spaces outside of the `<?php ?>` php tags within config.php. Remove these and retry.
-It's also worth removing the final `?>` at the end of config.php as this is not required.
-Another reason why it might not be working is if you disabled functions needed by LibreNMS, which include `allow_url_fopen`
-and `exec,passthru,shell_exec,escapeshellarg,escapeshellcmd,proc_close,proc_open,popen`.
+The easiest way to check if all is well is to run `./validate.php` as root from within your install directory. This should give you info on why things aren't working.
 
 #### <a name="faq7"> How do I debug pages not loading correctly?</a>
 
@@ -105,6 +104,16 @@ Before this all rrd files were set to 100G max values, now you can enable suppor
 
 rrdtool tune will change the max value when the interface speed is detected as being changed (min value will be set for anything 10M or over) or when you run the included script (scripts/tune_port.php).
 
+#### <a name="faq17"> Why do I see gaps in my graphs?</a>
+
+This is most commonly due to the poller not being able to complete it's run within 300 seconds. Check which devices are causing this by going to /poll-log/ within the Web interface.
+
+When you find the device(s) which are taking the longest you can then look at the Polling module graph under Graphs -> Poller -> Poller Modules Performance. Take a look at what modules are taking the longest and disabled un used modules.
+
+If you poll a large number of devices / ports then it's recommended to run a local recurisve dns server such as pdns-recursor.
+
+Running RRDCached is also highly advised in larger installs but has benefits no matter the size.
+
 #### <a name="faq16"> How do I change the IP / hostname of a device?</a>
 
 There is a host rename tool called renamehost.php in your librenms root directory. When renaming you are also changing the device's IP / hostname address for monitoring.
@@ -113,6 +122,14 @@ Usage:
 ./renamehost.php <old hostname> <new hostname>
 ```
 
+#### <a name="faq18"> Things aren't working correctly?</a>
+
+Run `./validate.php` as root from within your install.
+
+Re-run `./validate.php` once you've resolved any issues raised.
+
+You have an odd issue - we'd suggest you join our irc channel to discuss.
+
 #### <a name="faq8"> How do I add support for a new OS?</a>
 
 The easiest way to show you how to do that is to link to an existing pull request that has been merged in on [GitHub](https://github.com/librenms/librenms/pull/352/files)