cbm Command Linux: Monitor Network Bandwidth in Real-Time with Color Display

The cbm (Color Bandwidth Meter) command is a powerful Linux utility that provides real-time monitoring of network bandwidth usage with an intuitive, colorful display. This tool helps system administrators and users track network traffic across different interfaces, making it easier to identify bandwidth bottlenecks and monitor network performance.

What is cbm Command?

CBM stands for Color Bandwidth Meter, a command-line network monitoring tool that displays bandwidth usage statistics in real-time. Unlike traditional text-based monitoring tools, cbm presents data using colors and graphical elements, making it more visually appealing and easier to interpret network traffic patterns.

Key Features of cbm

• Real-time monitoring: Displays live bandwidth usage statistics
• Colorful interface: Uses colors to differentiate between different types of traffic
• Multiple interfaces: Monitors multiple network interfaces simultaneously
• Customizable display: Adjustable refresh rates and display options
• Lightweight: Minimal system resource usage

Installing cbm Command

Before using cbm, you need to install it on your Linux system. The installation method varies depending on your distribution:

Ubuntu/Debian Systems

sudo apt update
sudo apt install cbm

Red Hat/CentOS/Fedora Systems

# For RHEL/CentOS with EPEL repository
sudo yum install epel-release
sudo yum install cbm

# For Fedora
sudo dnf install cbm

Arch Linux

sudo pacman -S cbm

Compiling from Source

If cbm isn’t available in your distribution’s repository, you can compile it from source:

wget http://www.isotton.com/utils/cbm/cbm-0.1.tar.gz
tar -xzf cbm-0.1.tar.gz
cd cbm-0.1
make
sudo make install

Basic cbm Syntax

The basic syntax for the cbm command is:

cbm [options] [interface]

Common Options

Practical Examples

Example 1: Basic Usage

Monitor bandwidth on the default network interface:

cbm

Expected Output:

Interface: eth0
    RX:    1.2 MB/s ████████████
    TX:  512.3 KB/s ████████
Total RX: 156.7 MB
Total TX:  89.2 MB
Uptime: 2h 15m 30s

Example 2: Monitor Specific Interface

Monitor bandwidth on a specific network interface (e.g., wlan0 for wireless):

cbm wlan0

Expected Output:

Interface: wlan0
    RX:  856.4 KB/s ██████████
    TX:  234.1 KB/s ████
Total RX:  89.3 MB
Total TX:  45.7 MB
Uptime: 1h 42m 18s

Example 3: Monitor All Interfaces

Display bandwidth statistics for all available network interfaces:

cbm -a

Expected Output:

Interface: eth0
    RX:    2.1 MB/s ████████████████
    TX:  768.9 KB/s ██████████

Interface: wlan0
    RX:    0.0  B/s 
    TX:    0.0  B/s 

Interface: lo
    RX:   45.2 KB/s ██
    TX:   45.2 KB/s ██

Example 4: Custom Refresh Rate

Set a custom refresh rate of 5 seconds:

cbm -r 5 eth0

This command updates the display every 5 seconds instead of the default 1 second interval.

Example 5: Display with Units

Show bandwidth with explicit units:

cbm -u -c eth0

Expected Output:

Interface: eth0 [Color Mode]
    RX:    1.47 MB/s ████████████████ (Megabytes per second)
    TX:  623.81 KB/s ██████████       (Kilobytes per second)
Total RX: 234.56 MB
Total TX: 156.78 MB
Peak RX:   2.34 MB/s
Peak TX:   1.12 MB/s

Advanced Usage Scenarios

Monitoring Multiple Interfaces Simultaneously

You can run multiple cbm instances in different terminal windows to monitor various interfaces:

# Terminal 1 - Monitor ethernet
cbm -c eth0

# Terminal 2 - Monitor wireless
cbm -c wlan0

# Terminal 3 - Monitor all interfaces
cbm -a -r 2

Logging Bandwidth Data

While cbm doesn’t have built-in logging, you can combine it with other commands for data collection:

# Redirect output to a log file
cbm eth0 | tee bandwidth.log

# Create timestamped logs
while true; do
    echo "$(date): $(cbm -a | head -n 5)" >> daily_bandwidth.log
    sleep 60
done

Understanding cbm Output

Color Coding

When using the -c option, cbm displays different colors for various metrics:

• Green: Normal bandwidth usage
• Yellow: Medium traffic load
• Red: High bandwidth utilization
• Blue: Download traffic (RX)
• Magenta: Upload traffic (TX)

Graph Interpretation

The horizontal bars represent relative bandwidth usage:

• Bar length: Proportional to current bandwidth usage
• Real-time updates: Bars change dynamically based on network activity
• Scale adjustment: Automatically adjusts to show meaningful comparisons

Troubleshooting Common Issues

Permission Errors

If you encounter permission errors, run cbm with sudo:

sudo cbm eth0

Interface Not Found

List available network interfaces first:

# List all network interfaces
ip link show

# Or use the traditional command
ifconfig -a

# Then use cbm with the correct interface name
cbm enp0s3

No Data Displayed

If cbm shows no data, check if the interface is active:

# Check interface status
ip addr show eth0

# Ensure interface is up
sudo ip link set eth0 up

Alternatives to cbm

While cbm is excellent for colorful bandwidth monitoring, consider these alternatives:

• iftop: Interactive bandwidth usage monitor
• nload: Console application for monitoring network traffic
• vnstat: Network statistics utility
• bmon: Bandwidth monitor and rate estimator
• nethogs: Process-specific network usage monitor

Best Practices

Monitoring Strategy

• Regular monitoring: Check bandwidth usage during different times of day
• Interface selection: Monitor the primary active interface
• Baseline establishment: Understand normal usage patterns
• Alert thresholds: Know when bandwidth usage becomes concerning

Performance Considerations

• Refresh rate: Balance between real-time updates and system load
• Multiple instances: Avoid running too many cbm instances simultaneously
• Resource usage: Monitor cbm’s own impact on system performance

Integration with System Monitoring

CBM can be integrated into broader system monitoring workflows:

Scripting with cbm

#!/bin/bash
# Simple bandwidth monitoring script

INTERFACE="eth0"
LOG_FILE="/var/log/bandwidth.log"

while true; do
    TIMESTAMP=$(date "+%Y-%m-%d %H:%M:%S")
    STATS=$(cbm $INTERFACE | head -n 3)
    echo "$TIMESTAMP - $STATS" >> $LOG_FILE
    sleep 300  # Log every 5 minutes
done

Combining with System Alerts

#!/bin/bash
# Alert script for high bandwidth usage

THRESHOLD=1000000  # 1 MB/s in bytes
CURRENT_RX=$(cat /sys/class/net/eth0/statistics/rx_bytes)
sleep 1
NEW_RX=$(cat /sys/class/net/eth0/statistics/rx_bytes)
RATE=$((NEW_RX - CURRENT_RX))

if [ $RATE -gt $THRESHOLD ]; then
    echo "High bandwidth usage detected: $RATE bytes/s"
    # Send alert or notification
fi

Conclusion

The cbm command is an invaluable tool for Linux system administrators and users who need to monitor network bandwidth usage with a visual, colorful interface. Its real-time monitoring capabilities, combined with customizable display options, make it an excellent choice for understanding network traffic patterns and identifying performance issues.

Whether you’re troubleshooting network problems, monitoring server performance, or simply keeping track of your system’s bandwidth usage, cbm provides the visual feedback needed to make informed decisions about network management. By mastering its various options and understanding how to interpret its output, you can effectively monitor and optimize your network performance.

Remember to combine cbm with other monitoring tools and scripts to create a comprehensive network monitoring solution that meets your specific requirements. Regular monitoring and understanding of your network’s baseline performance will help you quickly identify and address any bandwidth-related issues that may arise.