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My dad once told me, "Even if you are holding on a thorn, hold it tightly". Thats what came to mind , as I saw Cacti. I chose Cacti, after considering different options for resource monitoring of our linux servers. This article is all about , how I tightened my grip on the cacti , and made it work in our servers. If you are a newbie network administrator, this writeup would be really useful for a head start on resource and network monitoring using cacti.
Our server was working pretty well, until it went down one day.
Reason , one partition of the harddisk became full. Two days later,
my boss got an invoice from our datacenter. We are being charged
for the extra bandwidth utilisation in our servers. Same week, servers
started acting crazy. The response would become really slow, for
1-2 hours and then as soon as I start checking to see whats wrong,
everything would be back to normal.
That one week, was enough for me, to see the bigger picture. Either
we install a good resource monitoring software or else, look for a
new job. Since there wasn't much of a choice, I went after the
first option.
Searching and researching, took me to the world of RRDtool, which
eluded me till then. Wikipedia defines RRDtool as
RRDtool is a round-robin database tool designed to handle
time-series
data like network bandwidth, temperatures, CPU load etc. The data
is stored in round-robin database so that system storage footprint
remains constant over the time.
If you are still trying to make a head or tail out of the above
technical
jargon, here is my explanation in a very simple sentence. RRDtool
is a software which can store data and present it graphically, without
eating up much space.
Who provides the data to RRDtool ? In our case , its done by SNMP
(The Simple Network Management Protocol). Though the name contains
"simple" , SNMP is not that easy to understand.
This is clearly stated in the FAQ of SNMP.
http://www.snmp.com/FAQs/snmp-faq-part1.txt
"It will take you at least 6 months or so of studying and
usage to comprehend SNMP very well".
For our purpose, ie resource monitoring , we dont have to dwell too
much with SNMP. It is only used to send data to the server having
RRDtool.
Cacti is a resource monitoring software. It uses RRDtool to store
data and the data is used create graphs. Cacti's greatest strength
is in providing complex graphing easily. It also comes with fast poller
to collect data from different resources simultaneously and has many
user management features. The interface and management is very
userfriendly that even a layman can get it working with less effort.
In a single sentence, "Cacti, because its easy".
Installing and using Cacti is a very simple task and does not require
indepth knowledge in networking or resource management. You can install
and configure it in simple steps, which makes it an ideal software
for newbie network administrators. Never-the-less , its so powerful
and scalable that you can use it even in large networks with hundreds
of devices. Now you know , why I went for Cacti.
The easiest part of setting up cacti is the installation. It gets
over in less than 5 minutes. All you need is a webserver with RRDtool
& MySQL installed. Detailed steps for installation in a *nix
server ( henceforth called cacti server) is available at :
http://www.cacti.net/downloads/docs/html/install_unix.html
After installation, login as admin and make sure that you are filling
in all path variables correctly. Confirm that you are selecting
the correct version of RRDtool as installed in the cacti server.
Finally decide how "poller" should work.
Tip: If you are monitoring more than 10 servers , its better
to use "cactid"
instead of cmd.php for polling.
To start viewing the graphs , you need to perform two tasks
- Add the Device/Resource for which graphs need to be generated.
- Create graphs for each device you've added.
These two tasks are explained in detail at
http://www.cacti.net/downloads/docs/html/graph_howto.html
After you've read the above documentation, proceed to configure
resource
monitoring of localhost.
Cacti comes with many device types and graph templates. A newbie
administrator can configure cacti for the network, with the options
available out of the box. First and easiest one is configuring
for localhost or the cacti server.
- After the installation and initial configuration is over, Create
a
device with the hostname of the localhost.
- From the list of "Host Template" select "Local
Linux Machine". That pretty much take cares of all the
settings of the localhost.
- Now click on the "New Graphs" link on the menu and
create graphs for "localhost".
Wait for 10 -15 minutes and you'll be able to view the graphs by
clicking
on "Graphs" tab on top. Simple , right ?
Now comes the challenge, monitoring the resources of a remote
server.Before
creating the device or graph, you will have to setup SNMPD in the
remote server.
Detailed installation instructions are available at
http://netophilia.net/snmpd.html.
Go ahead and install SNMPD in the remote server. Just make sure that
you are changing the "community-string" (by
default it'll be public). This community string is to be
used later while configuring Cacti.
After testing the working of net-snmpd in the remote server, do a
test from cacti server too. For that you can use the command
[root@cacti ~]# snmpwalk -v 2c -c <community-string>
<remote-server-ip>
The above test will come handy, especially if your servers are heavily
secured using firewalls.( I lost over 4 hours because of ignoring
firewalls)
If everything is working fine w.r.t snmpd , move ahead and configure
cacti for the remote server. To add the remote server
- Click on Devices -> "Add" .
- Give hostname and description
- Select "ucd/net snmp host" from Host Template list
- Fill SNMP community with your "community-string"
- Click on "Create"
- Proceed to add "graphs" for the newly added device.
Thats all for one server. Repeat the steps for adding as many servers
as you want.
For better readability, its suggested that you use graph trees in
cacti to organize your graphs. You can read more about graph trees
and its management at
http://www.cacti.net/downloads/docs/html/graph_viewing.html
Cacti also allows addon scripts incase we need to monitor some
special
services . Common addon scripts used in webhosting servers are
Bind9-stats,
Apache stats etc. A complete list of all the addon scripts is available
at
http://forums.cacti.net/about15067.html
There are many other Resource Monitoring Softwares available in the
market. MRTG is another free software, which has RRDtool as its
back-end.
MRTG is not suggested for a newbie, because of its long learning curve
and amount of man hours required to set it up.
Another alternative to Cacti is OpenNMS which is
gaining
popularity amongst the administrators.
If you are looking for a easy to use , plug and play monitoring
software
, then Cacti is the best option currently available. Another strength
of Cacti is its scalability and flexibility which makes it powerful
enough to use in complex networks too. Just go ahead and hold the
Cacti tightly.
About the author: Sojish Krishnan works as Sr. Engineer in Bobcares.com. Sojish has worked in Bobcares for over 4 years and is a passionate advocate of superior Customer support. He graduated Bachelors in Computer Science in 2001.
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