HP-UX System Administrator's Guide: Configuration Management

The Automatic Backup Configuration
The system automatically maintains a saved configuration called backup. Generally,
any time you use the kernel configuration tools to make a change to the currently
running configuration, the previous (pre-change) configuration is saved to backup.
Therefore the backup configuration is somewhat like the “undo” command in a word
processor. In these cases, if you load the backup configuration using kconfig -l
backup, it will reverse the last change you made to the currently running configuration
using the kernel configuration commands.
Some changes can be made to the currently running configuration by calling kernel
system calls directly. The backup configuration is not updated when those changes
are made.
There are cases in which you may not want this automatic backup behavior. For
example, if you have made an undesirable change and are trying to fix it, you do not
want the kernel configuration commands to replace a good backup configuration with
the one containing your undesirable change.
The -b off option (keep the existing backup) can be given in any kernel configuration
command to disable the automatic update of the backup configuration. When making
changes using HP SMH, you can clear the back up the current configuration
before applying change check box to disable the automatic backup behavior.
When your system first boots, the backup configuration mirrors the configuration that
was in use before the reboot. You may not want this replaced by the first kernel
configuration change you make, especially since the first kernel configuration change
could be made by a startup script before you even get a login prompt.
For this reason, the first configuration changes after a boot are handled specially. Instead
of automatically replacing the backup configuration, the kernel configuration commands
will ask you whether or not to do so.
3
They will continue to ask, each time you make
a change, until the first time you say Yes. From that point on, until next boot, they will
automatically replace the backup configuration with each change as described above.
If you want to disable the automatic replacement of the backup configuration for a
particular change, specify -b off. If you want to force an automatic replacement of
the backup configuration, specify -b on (backup). These options work with any kernel
configuration command that makes configuration changes.
Booting a Saved Configuration
In extreme circumstances, a mistaken configuration change can result in a kernel
configuration that won’t boot. In these cases, you have two options: boot a different
configuration, such as the automatic backup configuration, and/or boot in fail-safe
mode (described in “Booting in Fail-Safe Mode” (page 199)).
3. If the command is being run noninteractively, such as from a startup script, the answer is assumed to be
No for kcmodule, kctune, and kcdevice, and Yes for kconfig.
198 Configuring the Kernel