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
, 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
environment variable, on the device
listed in the bootdef_dev
variable. A list of the
recognized SRM devices can be obtained with the command
at the SRM prompt. If the
variable is not set or empty,
will be used by default.
The kernel will be passed the options listed in the
variable. Option letters are case
insensitive. The following option letters are recognized:
- 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.
In case of system crashes, the kernel will usually enter the kernel debugger,
, 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
during the next
multi-user boot cycle. It is also possible to force other behaviours from ddb.
- 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.