Debian/Ubuntu Tips and Tricks

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Debian/Ubuntu Tips and Tricks

How-To: monitor network bandwidth usage with vnstat

Posted by chantra on March 11th, 2013

There is many tools out there that help in monitoring network usage, collect statistics and generate graphs so we can view what happened at a given date/time. Anyhow, finding the bandwidth usage over an hour/day/week/month can be really tricky.

vnstat is a suite of daemon and client programs that monitor network bandwidth usage.

A pro of vnStat is that it uses the values from /proc/net/dev to calculate bandwidth usage. Which means that it saves the resources that would be needed if it was sniffing the network and that it can be ran as a unprivileged user.

Installation

To install vnStat on Debian, you can use apt-get:

# apt-get install vnstat

Unfortunately, while the service will be unable after the package had been installed, it will fail with an error similar to:

Starting vnStat daemon: vnstatdZero database found, exiting.
 failed!

To fix this, we will need to create an empty database for vnStat by using:

# vnstat -u -i eth0
Error: Unable to read database “/var/lib/vnstat/eth0″.
Info: -> A new database has been created.

Now that the database is created, you can restart the vnStat daemon vnstatd with:

# /etc/init.d/vnstat restart
Starting vnStat daemon: vnstatd

If you need to configure vnStat you can go and edit /etc/vnstat.conf .

Usage

Now, let's wait a bit for data to be collected and let's run the command:

# vnstat


Database updated: Mon Mar 11 06:49:58 2013

eth0 since 03/11/13

rx: 508.83 MiB tx: 554.87 MiB total: 1.04 GiB

monthly
rx | tx | total | avg. rate
------------------------+-------------+-------------+---------------
Mar '13 508.83 MiB | 554.87 MiB | 1.04 GiB | 9.81 kbit/s
------------------------+-------------+-------------+---------------
estimated 1.50 GiB | 1.63 GiB | 3.12 GiB |

daily
rx | tx | total | avg. rate
------------------------+-------------+-------------+---------------
today 508.83 MiB | 554.87 MiB | 1.04 GiB | 354.25 kbit/s
------------------------+-------------+-------------+---------------
estimated 1.75 GiB | 1.90 GiB | 3.65 GiB |

If the daemon had been running for more than a month, we would have got the summary for the current and the previous day and month.

To see the summary of the hourly usage use:

$ vnstat -h

The daily usage:

$ vnstat -d

The weekly usage:

$ vnstat -w

and the monthly usage:

$ vnstat -m

Some other useful information that we can get out of vnStat are the top 10 days:

$ vnstat -t

usage over X seconds (5 if no value provided):

$ vnstat -tr 10

and finally live bandwidth usage:

$ vnstat -l

vnStat is a useful little tool to get a good overview of how much bandwidth you use on a hourly/daily/weekly/monthly basis and requires almost no resources to do so.

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