Managing Saved Configurations with kconfig

When you have an HP-UX kernel configuration that satisfies your needs, you may want to save a copy of it to protect yourself against inadvertent configuration changes. Or, you may want to have multiple kernel configurations, so that you can switch between them easily. HP-UX allows you to save as many kernel configurations as you wish (subject to available disk space in /stand), and to modify them and use them at will.

Getting Information about Saved Configurations

When you run kconfig with no options, it shows you the saved configurations on your system. There will always be a saved configuration called backup, which is automatically maintained by the system; any other saved configurations on the system will also be listed. (For more information on the backup configuration, see “Recovering from Errors”.)

The output of kconfig can be varied with several options. The output can be restricted to specific configurations by listing them on the command line.

To control the output format, use the -a (all), -v (verbose), or -P (parse) options.

With No Options With no options, the output looks like this:

# kconfig
Configuration  Title
backup         Automatic Backup
day            Configuration for daytime multiuser processing
last_install   Created by last OS install
night          Configuration for nighttime batch processing

With the -v Option The -v option gives verbose, multiline information about each saved configuration:

# kconfig -v day
Configuration day
Title         Configuration for daytime multiuser processing
Created       Thu Oct 12 01:33:36 2006 by allanp
              as a copy of ’last_install’
Modified      Thu Oct 12 01:37:14 2006 by allanp
Kernel Path   /stand/day/vmunix

With the -a Option The -a option is the equivalent of the command sequence:

# kcmodule -a -v -c config
# kctune -v -c config
# kconfig -v config

for each specified or implied configuration (config). This gives a detailed record of all settings in the configuration. The following output is edited.

# kconfig -a day
Module              DeviceFileSystem  (1.0)
Description         DevFS File System
Timestamp           Mon Sep 11 15:31:18 2006 [4505E3B6]
State               unused 
Capable             static unused
Depends On          module OocCore:0.0.0
                    interface HPUX_11_31_PERF:1.0

...

Tunable             NSTREVENT
Description         Maximum number of concurrent Streams bufcalls
Module              hpstreams
Current Value       50 [Default]
Default Value       50

...

Configuration day
Title         Configuration for daytime multiuser processing
Created       Thu Oct 12 01:33:36 2006 by allanp
              as a copy of ’last_install’
Modified      Thu Oct 12 01:37:14 2006 by allanp
Kernel Path   /stand/day/vmunix

With the -P Option The -P option, which is designed for use by scripts or programs, gives complete control over what information is printed. For more information, see “Parsing Command Output” or the kconfig(5 )manpage.

The special keyword ALL displays all the possible categories. Compare with the -v option.

# kconfig -P ALL day
name    day
title   Configuration for daytime multiuser processing
createtime      Thu Oct 12 01:33:36 2006
createuser      allanp
modifytime      Thu Oct 12 01:37:14 2006
modifyuser      allanp
kernel  /stand/day/vmunix

Use a comma-separated list with the -P option to display the categories you want.

# kconfig -P name,title,modifyuser night
name    night
title   Configuration for nighttime batch processing
modifyuser      allanp

Interpreting Saved Configuration Information

Referring to the examples above, each saved configuration has a name, title, time signatures, user signatures, and kernel location.

The name must start with a letter; contain only letters, digits, and underscores; and be at most 32 characters long. Except for the backup configuration, you choose the name for each saved configuration when you create it, and you can rename it at will.

Each saved configuration can also have a title. The title can be used to provide yourself with a longer description of the configuration’s purpose or settings. It is optional.

Each saved configuration also has a pair of timestamps. The Created/createtime stamp indicates when the configuration was created (kconfig –s). The Modify/modifytime stamp indicates when the configuration was last changed. Each timestamp is associated with the login name of the user who performed the action.

The kernel itself is located in a subdirectory of /stand that has the same name as the configuration.

Associated with each saved configuration is a complete set of module state settings and tunable value settings. These can be seen by using:

# kcmodule –c config

and

# kctune –c config

or by using

# kconfig –a config

Using and Modifying Saved Configurations

Creating Saved Configurations

Saved kernel configurations can be created in three ways: by saving the currently running configuration, by copying an existing saved configuration, or by reading a system file.

To save the currently running configuration, use kconfig -s (save). The resulting saved configuration will include any changes to the currently running configuration that are being held for next boot.

An existing saved configuration can be copied using kconfig -c (copy).

For information on working with system files, see “Managing Configurations with System Files”.

Using Saved Configurations

A saved configuration can be loaded using kconfig -l (load). This changes the configuration of the currently running kernel to match what was saved. If the configuration can be changed without a reboot, the changes will take effect immediately. Otherwise, all of the changes will be held for next boot.

Sometimes you may want to force the configuration change to be held for next boot, instead of applying it immediately. In these cases, you can mark the saved configuration for use at next boot using kconfig -n (next boot). HP recommends that this option be used only when the next boot is expected to be soon. If, for example, the next boot doesn’t happen for months after you make such a change, the system administrator could be unpleasantly surprised at the effect of a pending change that had been forgotten.

To find out which saved configuration is marked for use at next boot, use kconfig -w (which). This command also identifies the saved configuration that was most recently loaded or booted, or the system file that was most recently imported.

Modifying Saved Configurations

To modify the module state settings and tunable value settings in a saved configuration, use the -c (configuration) option of the kcmodule and kctune commands, respectively. Saved configurations can also be changed by changing their system file and then importing it; see “Managing Configurations with System Files”.

Several options of kconfig allow other changes to saved configurations. The -r (rename) option will rename a saved configuration. (The backup configuration cannot be renamed.) The -t option will change the title on a saved configuration. The -d (delete) option will delete a saved configuration.

If a configuration has been marked for use at next boot, and you decide you want to continue using the currently running configuration instead, use kconfig -H (unhold) to discard all changes being held for next boot.