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System Management Guide:
Operating System and Devices

Changing System Environment Variables

The system environment is primarily the set of variables that define or control certain aspects of process execution. They are set or reset each time a shell is started. From the system-management point of view, it is important to ensure the user is set up with the correct values at login. Most of these variables are set during system initialization. Their definitions are read from the /etc/profile file or set by default.

Testing the System Battery

If your system is losing track of time, the cause might be a depleted or disconnected battery. To determine the status of your system battery, type the following diag command:

diag -B -c

When the Diagnostics main menu appears, select the Problem Determination option. If the battery is disconnected or depleted, a problem menu will be displayed with a service request number (SRN). Record the SRN on Item 4 of the Problem Summary Form and report the problem to your hardware service organization.

If your system battery is operational, your system time might have been reset incorrectly because either the date or setclock command was run incorrectly or unsuccessfully. Refer to Resetting the System Clock to correct the problem.

Resetting the System Clock

The system clock records the time of system events, allows you to schedule system events (such as running hardware diagnostics at 3:00 a.m.), and tells when you first created or last saved files. Use the date command to set your system clock. Use the setclock command to set the time and date by contacting a time server.

Using the date Command

The date command displays or sets the date and time. Enter the following command to determine what your system recognizes as the current date and time:

Attention: Do not change the date when the system is running with more than one user.

The following formats can be used when setting the date with the Date parameter:

The variables to the Date parameter are defined as follows:

mm Specifies the number of the month.
dd Specifies the number of the day in the month.
HH Specifies the hour in the day (using a 24-hour clock).
MM Specifies the minute number.
YY Specifies the first two digits of a four-digit year.
yy Specifies the last two numbers of the year.

With root authority, you can use the date command to set the current date and time. For example:

date 021714252002

Sets the date to Feb. 17, 2002, and time to 14:25. For more information about the date command, see its description in AIX 5L Version 5.2 Commands Reference.

Using the setclock Command

The setclock command displays or sets the time and date by requesting the current time from a time server on a network. To display your system's date and time, enter:


The setclock command takes the first response from the time server, converts the calendar clock reading found there, and shows the local date and time. If no time server responds, or if the network is not operational, the setclock command displays a message to that effect and leaves the date and time settings unchanged.

Any host running the inetd daemon can act as a time server.

With root authority, you can use the setclock command to send an Internet TIME service request to a time server host and sets the local date and time accordingly. For example:

setclock TimeHost 

Where TimeHost is the host name or IP address of the time server.

Changing the Message of the Day

The message of the day is displayed every time a user logs in to the system. It is a convenient way to communicate information to all users, such as installed software version numbers or current system news. To change the message of the day, use your favorite editor to edit the /etc/motd file.

Enabling Dynamic Processor Deallocation

If your machine supports Dynamic Processor Deallocation, you can use SMIT or system commands to turn the feature on or off. Beginning with AIX 5.2, Dynamic Processor Deallocation is enabled by default during installation, provided the machine has the correct hardware and firmware to support it. In previous versions of AIX, the feature is disabled by default, and if you try to enable it, a message alerts you when your machine cannot support this feature.

For additional information, see Enabling Dynamic Processor Deallocation in the AIX 5L Version 5.2 System Management Concepts: Operating System and Devices.

SMIT Fastpath Procedure

  1. With root authority, type smit system at the system prompt, then press Enter.
  2. In the Systems Environment window, select Change / Show Characteristics of Operating System.
  3. Use the SMIT dialogs to complete the task.

To obtain additional information for completing the task, you can select the F1 Help key in the SMIT dialogs.

Commands Procedure

With root authority, you can use the following commands to work with the Dynamic Processor Deallocation:

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