Technical data

4-26 Fault Isolation
4.5 Online Level
At the online level of operation, several diagnostic tools are available. This section
describes the boot shell, the system error log, and the System Acceptance Exerciser
(SAX). We document the remainder of the online tools (the /systest/ssr_util directory,
Storage Subsystem Tests (SST), Graphics Exerciser (GRTEST), and more extensive
information about SAX) in Using Domain Diagnostics, Volume 1
.
4.5.1 Boot Shell
The boot shell is the first user-space program executed by Domain/OS. The boot
shell runs as Process 1 with log-in rights of user.none.none. In Service mode, control
stops in the boot shell, and there is a small command environment available to you. In
Normal mode, the boot shell does nothing more than an internal go command, which
results in the loading of the Display Manager (DM) or Server Process Manager (SPM).
Type help at the boot shell prompt “)” to see a list of available commands.
If you are waiting for a response from the boot shell, always press < RETURN >
before assuming that the shell is dead. Once you have acquired the boot shell, try some
commands (help, wd, ld). Try to load and execute the commands in /bscom. Use
the sh command to bring up a single-user shell. If there are problems bringing up the
DM, a shell, or SPM, you can try specifying debug 1. This causes information about
each library to display as it loads. (Turn this mode off with debug 0.) At this point,
Domain/OS is fully functional, so any forms of remote access that don’t require helper
processes to be running should be possible.
4.5.2 System Error Log
A system error log is automatically created at boot time. The error log is a file in which
the system stores error information (for example, disk errors and parity errors). The
file sys_error_log is actually a 1-block (1024-byte) ring buffer. The oldest entries are
overwritten first, and the file never exceeds one block in length. The error logging pro
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cess consumes minimal system resources. It requires one wired page of memory and
whatever disk I/O is needed to log errors to the file.
This error information is valuable to you during troubleshooting. To read this file in a
shell, type the following at the prompt:
/systest/ssr_util/lsyserr < RETURN >