Cacti
Installing
To install use apt-get install cacti.
On the "libphp-adodb" prompt you can safely select "Ok". During the "Configuring Cacti" prompt, make sure to select "Apache2." You will be presented with an additional "Configuring cacti" prompt that will ask if you'd like to configure your database with dbconfig-common. Select "Yes" and continue. On the MySQL prompt, enter the root password you created earlier. On the next screen, either create your own password for cacti's database access, or leave it blank for it to automatically generate one for you.
From here we'll continue configuring Cacti through the browser. Visit the domain you have pointed at your Linode, or your Linode's IP address, and add /cacti. Follow the instructions shown on each page. Make sure to select RRDTool 1.2.x in the "RRDTool Utility Version" drop down. You should be able to continue through these pages into the login page without alteration.
At the login screen, enter admin/admin for the username/password combination. You'll be prompted to change your password on the next screen. At this point, Cacti is installed and ready to be configured.
At this point Cacti will contain an entry for localhost, which we'll need to modify. Click the "Console" tab in the top left corner, and select "Create Devices for network". Click the "Localhost" entry to begin making the needed changes. Select the Host Template drop down and pick the "ucd/net SNMP Host". Scroll down to SNMP Options and click the drop down box for SNMP Version, picking "Version 1". Enter "Bucknell" (or the community name you created above) in the box for the "SNMP Community" field. The "Associated Graph Templates" section allows you to add additional graphs. Hit "Save" to keep the changes.
Click "Settings" under "Configuration" and set your "SNMP Version" to "Version 1" in the drop down box. Type the name of your community for the "SNMP Community" (in this example, "Bucknell") and save.
Configuring multiple hosts
In Console -> Devices you can create a new device / host by clickin on 'Add' all the way on the right of the blue bar which says 'Devices'. Make sure the SNMP version is set to Version 1 (should be by default) and the SNMP community is filled in properly. Press 'Create'.
In the bottom you can now select the graph templates. In the Associated Graph Templates you can select anything with Linux / Unix in it. In the Associated Data Queries you can select anything with SNMP. Once you Press 'Save' you can then click 'Create graphs for this host'. You only need to select and create them once! If you recreate the Data Query ones with a different graph type selected, you destroy the old data. Only select the interfaces you're interested in, or your graph will become huge.
LVM partition size monitoring
In Associated Data Queries, The ucd/net - Get Monitored Patitions seems to do nothing and Unix - Get Mounted Partitions only gives attached harddrives. The SNMMP - Get Mounted Partitions allows you to select LVM partitions to graph when creating the graphs.
In order to read the whole title you need to go to Settings -> Visual and change maximum title length to 250
Putting all of one type of graph into a tree
In graph trees create a new tree (eg. Traffic). In Graph management select the template you want (eg. Interface - Traffic). Select all the graphs and in 'choose an action' select place on a tree (Traffic) -> Go