Problem Solving Guide and Reference

Chapter 13. Remote Reboot Facility

The remote reboot facility allows the system to be rebooted through a native (integrated) serial port. The system is rebooted when the reboot string is received at the port, followed by a confirmation response of 1. This facility is useful when the system does not otherwise respond but is capable of servicing serial port interrupts. Remote reboot can be enabled on only one native serial port at a time. The user is expected to provide their own external security for the port. This facility runs at the highest device interrupt class and a failure of the UART to clear the transmit buffer quickly may have the effect of causing other devices to lose data if their buffers overflow during this time. It is suggested that this facility only be used to reboot a machine that is otherwise "hung" and cannot be remotely logged into. File systems will NOT be sync'd, and a potential for some loss of data which has not been flushed exists. It is strongly suggested that when remote reboot is enabled that the port not be used for any other purpose, especially file transfer, to prevent an inadvertent reboot.

Two native serial port attributes control the operation of remote reboot.

reboot_enable

Indicates whether this port is enabled to reboot the machine on receipt of the REMOTE reboot STRING, and if so, whether or not to take a system dump prior to rebooting.

no        - Indicates remote reboot is disabled
reboot    - Indicates remote reboot is enabled
dump      - Indicates remote reboot is enabled, and prior to rebooting a system dump will be taken on the primary dump device.

reboot_string

Specifies the remote reboot string that the serial port will scan for when the remote reboot feature is enabled. When the remote reboot feature is enabled and the reboot_string is received on the port, a '>' character is transmitted and the system is ready to reboot. If a '1' character is recieved the system is rebooted; any character other than '1' aborts the reboot process. The reboot string has a maximum length of 16 characters and must not contain a space, colon, equal sign, null, new line, or cntrl-\ character.

Remote reboot can be enabled through SMIT, or via the command line. For SMIT the path System Environments -> Manage Remote Reboot Facility may be used for a configured TTY. Alternatively, when configuring a new TTY, remote reboot may be enabled from the Add a TTY or Change/Show Characteristics of a TTY menus. These menus are accessed through the path Devices -> TTY.

From the command line, the mkdev or chdev commands are used to enable remote reboot. For example, the following command enables remote reboot (with the dump option) and sets the reboot string to ReBoOtMe on tty1.

chdev -l tty1 -a remreboot=dump -a reboot_string=ReBoOtMe

This example enables remote reboot on tty0 with the current reboot string in the database only (will take effect on the next reboot).

chdev -P -l tty0 -a remreboot=reboot

If the tty is being used as a normal port, then you will have to use the pdisable command before enabling remote reboot. You may use penable to reenable the port afterwards.