How to use the command 'bmon' (with examples)

bmon is a powerful tool for monitoring bandwidth and capturing network-related statistics on Unix-based systems. It provides users with a real-time interface that visualizes network traffic, offering insights into the data transfer rates and network utilization. This makes bmon particularly useful for diagnosing network issues, optimizing network performance, and ensuring that systems are operating within expected parameters. The command-line tool is highly versatile, supporting various options for specifying network interfaces and defining output formats, which helps users tailor its functionality to their specific needs.

Use case 1: Display the list of all the interfaces

Code:

bmon -a

Motivation:
When managing a networked system, it’s essential to have visibility into all the network interfaces available. Knowing your interfaces helps ensure that you’re monitoring the correct channels for data traffic, useful for troubleshooting, capacity planning, and network configuration. This command helps to provide a thorough overview of all active network interfaces on a machine, making it a valuable starting point for any network-related inspection or audit.

Explanation:
The -a option in the command stands for ‘all’, instructing bmon to display all network interfaces present on the system. Without specifying an interface, you get a global view, which is particularly helpful when unclear about which interfaces are actively used.

Example output:

if0    1500  0.0  0.0k  1.0Kbps  0.0Kbps UP RUNNING
eth0   1500  0.0  0.0k  5.0Kbps  3.0Kbps UP RUNNING
wlan0  1500  0.0  0.0k  0.0Kbps  0.0Kbps DOWN

This sample output lists each interface with its respective status and bandwidth activity, providing a complete view of the machine’s network landscape.

Use case 2: Display data transfer rates in bits per second

Code:

bmon -b

Motivation:
Being able to look at data transfer rates in bits per second can be instrumental in understanding the network load and efficiency. It allows network administrators to evaluate network speeds, identify bottlenecks, and optimize resource allocation, which is crucial for maintaining high performance and reliability in data communication.

Explanation:
The -b option stands for ‘bits’, telling bmon to present the bandwidth usage in bits per second rather than the default bytes per second. This presentation can be more intuitive when aligning with bandwidth measurements commonly discussed in terms of bits.

Example output:

eth0  TX: 12.3Kbps RX: 8.5Kbps
eth1  TX: 100.2Kbps RX: 95.6Kbps

This indicates that the interface eth0 is transmitting at 12.3 kilobits per second and receiving at 8.5 kilobits per second, while eth1 has higher activity with transmission and reception rates exceeding 100 kilobits per second.

Use case 3: Specify the policy to define which network interface(s) is/are displayed

Code:

bmon -p eth0,eth1,wlan0

Motivation:
Sometimes you might only be interested in a subset of interfaces, especially in environments with numerous interfaces, or in cases where only specific interfaces are crucial for analysis. Filtering the processing to a subset of interfaces reduces noise and focuses the monitoring efforts on relevant data, which helps in preventing information overload.

Explanation:
The -p option is used to define policy by specifying which network interfaces need to be displayed. When followed by a list of interfaces (separated by commas, in this case, eth0, eth1, and wlan0), it customizes which interfaces bmon will monitor and report on.

Example output:

eth0  TX: 15.2Kbps  RX: 11.1Kbps
eth1  TX: 9.8Kbps   RX: 7.6Kbps
wlan0 TX: 0.0Kbps   RX: 0.0Kbps

The command filters all interfaces and displays statistics specifically for eth0, eth1, and wlan0, simplifying focus to those relevant interfaces while hiding the others.

Use case 4: Specify the interval (in seconds) in which rate per counter is calculated

Code:

bmon -R 2.0

Motivation:
Setting the rate calculation interval determines how often the tool updates its data metrics, influencing the smoothness or granularity of the captured data. A shorter interval provides more frequent updates, ideal for scenarios that require high responsiveness to changes in network traffic, while longer intervals may be suitable for tracking trends over time with reduced computational overhead.

Explanation:
The -R option allows the user to set the period over which the rate calculations are made, specified in seconds. Here, an interval of 2.0 seconds implies that every two seconds, bmon will compute and update the rates, providing a dynamic view of the network traffic.

Example output:

Time: 0s
eth0 TX: 13.0Kbps RX: 10.1Kbps
Time: 2s
eth0 TX: 14.5Kbps RX: 12.3Kbps

This shows changes from one interval to the next, highlighting how traffic rates evolve over set periods.

Conclusion:

These use cases of the bmon command give a comprehensive look at its utility in network monitoring and management. By choosing specific interfaces, adjusting data-preference formats, and defining calculation intervals, bmon users can tailor the command to meet diverse networking needs, making it a versatile and powerful tool in a sysadmin’s arsenal.