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Linux in a Nutshell

This directory of Linux commands is from Linux in a Nutshell, 5th Edition.

Click on any of the 687 commands below to get a description and list of available options. All links in the command summaries point to the online version of the book on Safari Bookshelf.

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apmd [options]

System administration command. apmd handles events reported by the Advanced Power Management BIOS driver. The driver reports on battery level and requests to enter sleep or suspend mode. apmd will log any reports it gets via syslogd and take steps to make sure that basic sleep and suspend requests are handled gracefully. You can fine-tune the behavior of apmd by editing the apmd_proxy script, which apmd runs when it receives an event. Note that the APM hardware standard is gradually being replaced by the ACPI (Advanced Configuration and Power Interface) standard, and apmd by acpid. On SUSE Linux, both APM and ACPI hardware are handled by powersave and powersaved.


-c n, --check n

Set the number of seconds to wait for an event before rechecking the power level. Default is to wait indefinitely. Setting this causes the battery levels to be checked more frequently.

-p n, --percentage n

Log information whenever the power changes by n percent. The default is 5. Values greater than 100 will disable logging of power changes.

-P command, --apmd_proxy command

Specify the apmd_proxy command to run when APM driver events are reported. This is generally a shell script. The command will be invoked with parameters indicating what kind of event was received. The parameters are listed in the next section.

-v, --verbose

Verbose mode; all events are logged.

-V, --version

Print version and exit.

-w n, --warn n

Log a warning at ALERT level when the battery charge drops below n percent. The default is 10. Negative values disable low-battery-level warnings.

-W, --wall

Use wall to alert all users of a low battery status.

-q, --quiet

Disable low-battery-level warnings.

-?, --help

Print help summary and exit.


The apmd proxy script is invoked with the following parameters:


Invoked when the daemon starts.


Invoked when the daemon stops.

suspend [ system | user ]

Invoked when the daemon receives a suspend request. The second parameter indicates whether the request was made by the system or by the user. Suspend, also known as "hibernate," effectively powers the system down but has a quicker recovery than a normal boot process.

standby [ system | user ]

Invoked when the daemon receives a standby request. The second parameter indicates whether the request was made by the system or by the user. Standby mode powers off the monitor and disks, but the system continues to run and use power.

resume [ suspend | standby | critical ]

Invoked when the system resumes normal operation. The second parameter indicates the mode the system was in before resuming. critical suspends indicate an emergency shutdown. After a critical suspend, the system may be unstable, and you can use the resume command to help you recover from the suspension.

change power

Invoked when system power is changed from AC to battery or from battery to AC.

change battery

Invoked when the APM BIOS driver reports that the battery is low.

change capability

Invoked when the APM BIOS driver reports that some hardware that affects its capability has been added or removed.

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