Clarify procedure to add new links

From user networkmaster

README.md

@@ -37,6 +37,12 @@ Prerequisites
 - one or more routers than can generate NetFlow v8/v9 AS aggregation records
   or sFlow samples
 
+Considerations
+-------------
+
+Thoughts on a location for RRD files:
+RRD files are small in size, but there are a lot of them. You will see a performance gain on a filesystem like XFS over EXT3/4. Consider what filesystem you put the RRD files on if performance is a factor for your needs.
+
 
 Installation
 ------------
@@ -283,6 +289,43 @@ XML dump/restore feature is provided (add_ds_proc.pl, add_ds.sh). Note that
 asstatd.pl should be stopped while modifying RRD files, to avoid
 breaking them with concurrent modifications.
 
+Before you follow the instructions below:
+
+- Make sure you stop asstatd.pl.
+- Take a backup of your whole RRD folder. That is the only way to roll back from this process.
+- This will only add one data source at a time. If you are adding multiple new links, you will need to follow the instructions below once for each new link you add.
+
+Instructions for adding a new link:
+
+1.	Edit your known links file and add your new link (see above for syntax)  
+	Example:
+
+		10.1.17.10      33      router-newlink  Friendlyname     1F78B4  1
+
+2.	Edit the script tools/add_ds_proc.pl
+
+	Change this line:  
+	`my $newlinkname = 'newlink';`
+
+	To have the same ID in your knownlinks file:  
+	`my $newlinkname = 'router-newlink';`
+
+3.	Edit the script tools/add_ds.sh
+
+	Make sure the path to add_ds_proc.pl is correct.
+
+4.	cd into the rrd folder:  
+	`cd rrd`
+
+5.	Run the script  
+	`/path/to/add_ds.sh`
+
+	This will take a while (around 20 minutes), so go get a cup of coffee.
+
+6.	Start the collector back up again, and watch for new graphs!
+
+You can also read the RRD files with the command `rrdtool info file.rrd`, which will show you the data sourced in each one.
+
 
 Changing the RRAs
 -----------------
@@ -307,3 +350,4 @@ To do
 
 - rrd-extractstats.pl uses a lot of memory and could probably use some
   optimization.
+- Consider adding a command line parameter to add_ds_proc.pl and add_ds.sh for ease of adding new links.

tools/add_ds.sh

@@ -1,5 +1,10 @@
 #!/bin/sh
 
+## YOU NEED TO EDIT add_ds_proc.pl BEFORE YOU RUN THIS!!
+## You need to edit the line:
+## my $newlinkname = 'NEWIDFROMKNOWNLINKSFILE';
+## to reflect the ID in the known links file
+
 A=`ls -1`
 
 for i in $A ; do