Linux apmd Command with Practical Examples

Introduction

In this lab, you will learn how to use the apmd command, a tool for monitoring and managing the power status of your Linux system, particularly for laptops and other battery-powered devices. You will start by installing the apmd package and running the service, then explore how to monitor the battery status using various apmd commands. Finally, you will learn how to configure apmd for automated power management to optimize battery life.

The apmd command may require additional installation on some systems, as it is not always included by default. Additionally, the apmd command is an older tool, and more modern power management solutions, such as tlp or powertop, may be preferred in some cases.

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Introduction to the apmd Command

In this step, you will learn about the apmd command, which is a tool used to monitor and manage the power status of your system. The apmd command is particularly useful for laptops and other battery-powered devices, as it allows you to monitor the battery level and configure power management settings.

First, let's check if the apmd package is installed on your system. Run the following command:

sudo apt-get update
sudo apt-get install -y apmd

Example output:

Reading package lists... Done
Building dependency tree... Done
The following NEW packages will be installed:
  apmd
0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded.

The apmd package is now installed on your system. You can start the apmd service using the following command:

sudo /etc/init.d/apmd start

Example output:

Starting ACPI Power Management Daemon: apmd.

The apmd service is now running, and you can use the apmd command to monitor and manage the power status of your system.

Monitoring Battery Status with apmd

In this step, you will learn how to use the apmd command to monitor the battery status of your system.

First, let's check the current battery status using the apmd command:

sudo apmd -s

Example output:

ACPI Power Management Daemon version 3.2.2
Battery status:
  Battery 0: charged, 100% remaining

The output shows the current battery status, including the battery percentage and charging/discharging state.

You can also use the apmd command to display more detailed information about the battery:

sudo apmd -d

Example output:

ACPI Power Management Daemon version 3.2.2
Battery status:
  Battery 0: charged, 100% remaining
  Design capacity: 5000 mAh
  Last full capacity: 5000 mAh
  Battery technology: rechargeable
  Battery voltage: 12.6 V
  Battery current: 0 mA
  Battery temperature: 25.0 C

This command provides more detailed information about the battery, including the design capacity, last full capacity, voltage, current, and temperature.

You can also use the apmd command to monitor the battery status in real-time. To do this, run the following command:

sudo apmd -m

This command will continuously monitor the battery status and display any changes in the battery level or charging/discharging state.

Configuring apmd for Automated Power Management

In this step, you will learn how to configure the apmd command to automatically manage the power settings of your system.

The apmd command can be configured by editing the /etc/apm/event.d/default.script file. This file contains a set of scripts that are executed when specific power events occur, such as the battery level reaching a certain threshold or the system entering a low-power state.

Let's start by opening the default script file:

sudo nano /etc/apm/event.d/default.script

Inside the file, you can find various sections that correspond to different power events. For example, the following section handles the low battery event:

## Low battery event
on battery-low
    logger "ACPI event: battery low"
    ## Add your custom actions here
end

You can customize this section to perform actions when the battery level is low, such as suspending the system or triggering a shutdown.

As an example, let's configure the apmd command to automatically suspend the system when the battery level reaches 20%:

## Low battery event
on battery-low
    logger "ACPI event: battery low"
    if [ "$(sudo apmd -s | grep -o -E '[0-9]+%')" = "20%" ]; then
        logger "Suspending system due to low battery"
        sudo systemctl suspend
    fi
end

In this example, the apmd -s command is used to check the current battery level, and if it is 20% or lower, the system is suspended using the systemctl suspend command.

Save the changes to the file and exit the text editor.

Now, the apmd command is configured to automatically manage the power settings of your system based on the battery level.

Summary

In this lab, you learned about the apmd command, which is a tool used to monitor and manage the power status of your system. You started by checking if the apmd package was installed on your system and then learned how to start the apmd service. You then explored how to use the apmd command to monitor the battery status of your system, including checking the current battery percentage and charging/discharging state, as well as more detailed information about the battery's design capacity, last full capacity, voltage, current, and temperature.

Next, you will learn how to configure apmd for automated power management, which will allow you to set up power-saving policies and actions based on the battery status.

Linux Commands Cheat Sheet