Alpha system bootstrapping procedures
When powered on, the SRM firmware will proceed to its initialization, and will
boot an operating system if the auto_action variable is set
to “boot” or “restart”, or will wait for
interactive commands if set to “halt”.
After a panic, or if the system is rebooted via
shutdown(8), the SRM console
will only restart the system if the auto_action variable is
set to “boot”.
The SRM console will attempt to boot a kernel named from the
boot_file environment variable, on the device listed in the
bootdef_dev variable. A list of the recognized SRM devices
can be obtained with the command
show dev at the SRM
prompt. If the boot_file variable is not set or empty,
/bsd will be used by default.
The kernel will be passed the options listed in the
boot_osflags variable. Option letters are case
insensitive. The following option letters are recognized:
In case of system crashes, the kernel will usually enter the kernel debugger,
ddb(4), unless it is not present
in the kernel, or it is disabled via the ddb.panic sysctl.
Upon leaving ddb, or if ddb was not entered, the kernel will halt the system
if it was still in device configuration phase, or attempt a dump to the
configured dump device, if possible. The crash dump will then be recovered by
savecore(8) during the next
multi-user boot cycle. It is also possible to force other behaviours from ddb.
- Boot the system multi-user. This is the default behaviour of the kernel if
no flags are specified.
- Enter the debugger, ddb(4), as
soon as the kernel console has been initialized.
- Enter the “User Kernel Configuration” mode upon startup
- Create a kernel crash dump immediately after the devices have been
configured. This option is only available on kernels compiled with
- On the next system reboot, always halt the system, even if a reboot is
- Prompt for the root filesystem device after the devices have been
- Boot the system single-user.
- default system kernel
- standalone installation kernel, suitable for disaster recovery
- primary bootstrap for “ffs” file system
- secondary bootstrap (usually also installed as
- network bootstrap
Alpha Architecture Reference
Manual Third Edition, Digital Press,
Alpha Architecture Committee,
The device names used by OpenBSD/alpha and the SRM
Console often have no relation to each other.