7.9 Sending Messages to Virtual Machines

Sending a message to a virtual machine may be useful during certain situations, like developing or starting a virtual machine template. Messages are passed to the virtual machine operating system, and can be of any key/value pair that the operating system or template understands. For example, to set up a virtual machine template to use DHCP, you may want to send the following key/pairs to a virtual machine:

com.oracle.linux.network.device.0       eth0
com.oracle.linux.network.onboot.0       yes
com.oracle.linux.network.bootproto.0    dhcp
com.oracle.linux.root-password          password

The com.oracle.linux.root-password is always required as a parameter and should be sent as the final parameter for any message.

Any messages that are not understood are discarded and ignored by the operating system. You can hide the message for sensitive information such as passwords, so a series of asterisks are displayed in the user interface instead of the sensitive information.

You can optionally keep a log of the message. This feature is especially useful to template or application developers that want to send messages to virtual machines. Message logs are stored by Oracle VM Manager and are not available through any log file or database query. To gain access to these messages, you must use the Oracle VM Web Services API. Messages are limited to 1024 bytes when message logging is selected, or 8192 bytes when logging is not selected. They key is limited to 256 bytes.

Each message sent to a virtual machine is contained within its own job. If you send multiple messages to multiple virtual machines, each one has its own job, so 10 messages to 100 virtual machines produces 1,000 jobs.

To send a virtual machine a message you must have first installed the Oracle VM Guest Additions in the virtual machine. For information on installing the Oracle VM Guest Additions, see Oracle VM Guest Additions in the Oracle VM Administrator's Guide. For information on sending messages to a virtual machine, see Send VM Messages in the Oracle VM Manager User's Guide.