bmon Command Linux: Complete Guide to Real-Time Bandwidth Monitoring and Network Analysis

The bmon (Bandwidth Monitor) command is a powerful Linux utility designed for real-time network bandwidth monitoring and rate estimation. This comprehensive tool provides system administrators and network engineers with detailed insights into network interface statistics, traffic patterns, and bandwidth utilization across multiple network interfaces simultaneously.

What is bmon Command?

bmon stands for Bandwidth Monitor and serves as an interactive console-based network monitoring tool. It displays real-time statistics for network interfaces, including incoming and outgoing traffic rates, packet counts, error statistics, and historical data visualization through ASCII graphs.

Key features of bmon include:

• Real-time bandwidth monitoring for all network interfaces
• Interactive terminal-based interface with color coding
• Historical data visualization through ASCII graphs
• Support for multiple output formats and modules
• Configurable update intervals and display options
• Network interface filtering and selection capabilities

Installing bmon on Linux

Installation methods vary depending on your Linux distribution:

Ubuntu/Debian Systems

sudo apt update
sudo apt install bmon

CentOS/RHEL/Fedora Systems

# For Fedora
sudo dnf install bmon

# For CentOS/RHEL (Enable EPEL repository first)
sudo yum install epel-release
sudo yum install bmon

Arch Linux

sudo pacman -S bmon

Basic bmon Command Syntax

The basic syntax for the bmon command is:

bmon [OPTIONS] [INTERFACES]

Where:

• OPTIONS – Various command-line flags and parameters
• INTERFACES – Specific network interfaces to monitor (optional)

Essential bmon Command Options

Practical bmon Examples

Basic Network Monitoring

Start bmon with default settings to monitor all available network interfaces:

bmon

Sample Output:

qdisc wan0 root refcnt=2 handle 1: htb default 30
 Qdisc htb 1: root refcnt=2 r2q 10 default 30 direct_packets_stat 0

Interface                   RX Rate      RX #     TX Rate      TX #
lo                          0.00B/s         0      0.00B/s        0
eth0                       45.2KB/s      1247     12.8KB/s      892
wlan0                       2.1MB/s      3421      890KB/s     2156
docker0                     0.00B/s         0      0.00B/s        0

Monitor Specific Interface

Monitor only a specific network interface like eth0:

bmon -i eth0

This command focuses monitoring on the specified interface, providing detailed statistics and historical graphs.

Set Custom Refresh Interval

Configure bmon to update every 2 seconds instead of the default:

bmon -r 2

This increases the monitoring frequency, useful for observing rapid network changes.

Monitor Multiple Specific Interfaces

Monitor multiple interfaces simultaneously:

bmon -i eth0,wlan0,docker0

Expected Output:

                             (RX Bytes/second)
eth0         ||||||||||||||||                                    856KB/s
wlan0        ||||||||||||||||||||||||||||||||||||||||||||||||||  2.1MB/s  
docker0      |                                                   1.2KB/s

                             (TX Bytes/second)  
eth0         ||||||||||||||                                      445KB/s
wlan0        ||||||||||||||||||||||||||||||||||||                1.8MB/s
docker0      |                                                   890B/s

Advanced bmon Usage

Using Different Output Modules

bmon supports various output modules for different display formats:

# ASCII output module
bmon -o ascii

# Curses-based interface (default)
bmon -o curses

# Format output for parsing
bmon -o format

Customizing Units Display

Control how bandwidth and rates are displayed:

# Display bytes in kilobytes
bmon -U k

# Display rates in megabits per second
bmon -R Mbit

# Combine both options
bmon -U M -R Mbit

Interface Selection Policies

Use policies to automatically select interfaces:

# Monitor all interfaces except loopback
bmon -p eth*,wlan*

# Monitor only physical ethernet interfaces
bmon -p eth*

Interactive Controls in bmon

When running bmon interactively, several keyboard shortcuts enhance functionality:

Configuration File Usage

Create a configuration file for persistent bmon settings:

# Create bmon configuration file
nano ~/.bmonrc

Sample Configuration:

interface {
    policy eth*,wlan*
    hide-policy lo,docker*
}

output {
    module curses
    unit bytes
    rate-unit bits
}

timing {
    read-interval 1.0
    lifetime 60
}

Use the configuration file:

bmon -f ~/.bmonrc

Real-World Use Cases

Network Troubleshooting

Monitor network performance during troubleshooting:

# Monitor primary interface with 1-second updates
bmon -i eth0 -r 1

This provides real-time visibility into network traffic patterns, helping identify bandwidth bottlenecks or unusual traffic spikes.

Server Performance Monitoring

For server environments, monitor all network interfaces:

# Monitor all interfaces with ASCII output for logging
bmon -o ascii -p eth*,bond* > network_stats.log

Wireless Network Analysis

Focus on wireless interface monitoring:

bmon -i wlan0 -U M -R Mbit

This configuration displays wireless traffic in megabytes and rates in megabits per second, ideal for wireless network analysis.

Understanding bmon Output

Statistical Information

bmon displays various network statistics:

• RX Rate/TX Rate: Current receive/transmit rates
• RX #/TX #: Total packet counts
• Errors: Network error counters
• Drops: Dropped packet statistics

Graphical Representation

The ASCII graphs show:

• Historical bandwidth usage over time
• Peak usage indicators
• Traffic pattern visualization
• Comparative interface performance

Best Practices and Tips

Performance Considerations

• Use appropriate refresh intervals to balance accuracy with system load
• Filter interfaces when monitoring high-traffic systems
• Consider output redirection for automated monitoring
• Use configuration files for consistent monitoring setups

Monitoring Strategies

• Combine bmon with other tools like iftop and nethogs for comprehensive analysis
• Use different time scales to identify both immediate and long-term trends
• Implement automated alerting based on bmon output
• Regular monitoring helps establish baseline network performance

Common Issues and Solutions

Permission Issues

If bmon cannot access network interface statistics:

# Run with appropriate privileges
sudo bmon

Interface Not Found

List available interfaces first:

# Check available interfaces
ip link show

# Then monitor specific interface
bmon -i interface_name

Integration with System Monitoring

Scripting with bmon

Create automated monitoring scripts:

#!/bin/bash
# Network monitoring script
echo "Starting network monitoring at $(date)"
bmon -o ascii -r 5 -i eth0 | while read line; do
    echo "$(date): $line" >> /var/log/network-monitor.log
done

Combining with Other Tools

Use bmon alongside other monitoring utilities:

# Terminal multiplexer for comprehensive monitoring
tmux new-session -d 'bmon'
tmux split-window -v 'htop'
tmux split-window -h 'iotop'
tmux attach

Conclusion

The bmon command is an essential tool for Linux system administrators and network engineers requiring real-time bandwidth monitoring and network analysis. Its interactive interface, comprehensive statistics, and flexible configuration options make it invaluable for troubleshooting network issues, monitoring server performance, and analyzing traffic patterns.

By mastering bmon’s various options and features, you can gain deep insights into your network infrastructure’s performance and quickly identify potential issues before they impact system performance. Regular use of bmon as part of your monitoring toolkit will enhance your ability to maintain optimal network performance and troubleshoot connectivity problems effectively.

Whether you’re monitoring a single server or managing a complex network infrastructure, bmon provides the real-time visibility needed to make informed decisions about network performance and capacity planning.