Sun Microsystems Sun Fire V440 Diagnostics And Troubleshooting Manual page 191

After forcing the system into OpenBoot firmware control, be aware that issuing
certain OpenBoot commands (like probe-scsi, probe-scsi-all, or probe-ide)
might hang the system.
L1-A (Stop-A) Keys or Break Key
When it is impossible or impractical to shut down the system gracefully, you can get
to the ok prompt by typing the L1-A (Stop-A) key sequence from a Sun keyboard, or,
if you have an alphanumeric terminal attached to the Sun Fire V440 server, by
pressing the Break key.
Note – These methods of reaching the ok prompt will only work if the system
console has been redirected to the appropriate port. For details, see "Reference for
System Console OpenBoot Configuration Variable Settings" on page 196.
If you use these methods to reach the ok prompt, be aware that issuing certain
OpenBoot commands (like probe-scsi, probe-scsi-all, or probe-ide) might
hang the system.
Externally Initiated Reset (XIR)
Use the ALOM system controller reset -x command to execute an externally
initiated reset (XIR). Forcing an XIR might be effective in breaking the deadlock that
is hanging up the system. However, an XIR also precludes the orderly shutdown of
applications, and so it is not the preferred method of reaching the ok prompt, unless
you are troubleshooting these types of system hangs. Generating an XIR has the
advantage of allowing you to issue the sync command to produce a dump file of the
current system state for diagnostic purposes.
For more information about the reset -x command, see the Sun Advanced Lights
Out Manager (ALOM) Online Help.
Caution – Because an XIR precludes an orderly shutdown of applications, it should
only be attempted if previously described methods do not work.
Manual System Reset
Use the ALOM system controller reset command or poweroff and poweron
commands to reset the server. Reaching the ok prompt by performing a manual
system reset or by power-cycling the system should be the method of last resort.
Appendix A Configuring the System Console 173