kconfig(5) kconfig(5)
NAME [Toc] [Back]
kconfig - introduction to kernel configuration commands
DESCRIPTION [Toc] [Back]
HP-UX contains a set of commands used to view and modify the
configuration of the HP-UX kernel. The commands are:
kconfig Operations on complete kernel configurations
kcmodule Operations on kernel modules
kctune Operations on kernel tunable parameters
("tunables")
kcpath Retrieves pathnames of kernel files
kclog Searches and displays the kernel configuration log
file
mk_kernel Builds a kernel configuration from a system file
KERNEL CONFIGURATIONS [Toc] [Back]
The set of data that controls the behavior and content of the HP-UX
kernel is called a kernel configuration. System administrators may
save any number of kernel configurations, and may load any one of them
at any time. A kernel configuration consists of module usage choices
made using kcmodul
.
By default, these commands affect the state of the currently running
system. When these commands are given a -c config option, they
instead affect the saved kernel configuration named config.
The currently running kernel configuration can be saved using kconfig
-s. A saved configuration can be loaded using kconfig -l. This
causes the state of the running system to be changed to match the
saved configuration. A saved configuration can be marked for use when
the system is next booted, by using kconfig -n. This makes no change
to the state of the running system, but causes the specified saved
configuration to be loaded when the system is rebooted. (See Boot
Behavior, below.)
Saved kernel configuration names must start with a letter; contain
only letters, digits, and underscores (_); and be at most 32
characters in length. The names are case-distinct.
Backup Configuration [Toc] [Back]
The system maintains a saved configuration called backup, which can be
used to recover from configuration errors. The system automatically
saves the currently running configuration to backup immediately before
making any requested change to the configuration. This behavior can
be disabled using the -K option on the command line when a change is
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requested.
The first update of the backup configuration after the system boots is
treated specially, since it will overwrite the backup of the
configuration that was running before the reboot. Any time the backup
configuration dates to before the time the system booted, the command
making the configuration change will ask for confirmation before
replacing it. (If the command is running non-interactively, the
answer is assumed to be "no".) This behavior can be overridden by
specifying the -B (update the backup) or -K (don't update the backup)
flags on the command line for the change.
Dynamic and Static Changes [Toc] [Back]
By default, the kernel configuration tools will apply configuration
changes to the currently running system, causing an immediate change
in their behavior. System administrators can override this default by
specifying the -h option to any of the commands. This option causes
the change(s) to be held until the system is rebooted. HP recommends
that this option be used only when the next reboot is expected to
happen soon. If the reboot doesn't happen for months after the
change, the change could come as an unwelcome surprise to an
administrator who had forgotten the request.
Some configuration changes cannot be applied without a reboot. These
changes will be held until the system is rebooted even if the -h
option is not specified. In these cases, a warning message will be
printed.
If multiple configuration changes are requested in a single invocation
of one of the kernel configuration commands, and any one of those
changes requires a reboot, all of the requested changes will be held
until the system is rebooted. In particular, if a saved kernel
configuration is loaded using kconfig -l, and that configuration
cannot be used without a reboot, the state of the running system is
not changed and the specified kernel configuration is marked to be
used at next boot.
If a change to a configuration is being held until next boot, and a
subsequent change to the same configuration setting is made with
immediate effect, the immediate change will take precedence. The
first change will not take effect at next boot. A warning will be
printed in these situations.
Changes that replace the entire currently running configuration, such
as kconfig -i (import), kconfig -l (load), or kconfig -n (nextboot),
cause any changes being held for next boot to be discarded.
Changes that are made to the currently running system are retained
when the system is rebooted. They remain in effect until changed, or
until a saved kernel configuration is loaded.
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Boot Behavior [Toc] [Back]
When the system is booted, the administrator may specify the name of a
saved kernel configuration on the boot command line. (See hpux(1M)
and hpux.efi(1M).) If so, that kernel configuration will be loaded
during boot.
If no kernel configuration is specified on the boot command line, the
system will look for any kernel configuration that had been marked for
use at next boot (via a kconfig -n, kconfig -l, or kconfig -i
command). If any such configuration is found, that configuration will
be loaded during boot.
If no kernel configuration is specified on the boot command line, and
none is marked for use at next boot, the system will boot using the
same configuration that was in use before the reboot. If the
configuration had any changes that were being held for reboot, either
because they could not be applied without a reboot or because the -h
option was used, those changes will be applied during the boot
process.
If the kernel configuration fails to boot properly, recovery can be
attempted by booting the backup configuration and/or booting with the
"failsafe boot" flag (-tm on Itanium(R)-based systems, -f0x40000 on
PA-RISC systems). See hpux(1M) and hpux.efi(1M) for details.
SYSTEM FILES [Toc] [Back]
Users of past releases of HP-UX may be used to keeping kernel
configuration choices in a text file called /stand/system. Such a
file is known as a "system file". A system file is automatically
maintained for the currently running kernel configuration. This file
can be found at /stand/system. System files are also automatically
maintained for each saved kernel configuration. These files can be
found at /stand/config/system, where config is the name of the saved
configuration. Any time a kernel configuration (saved or current) is
changed using one of the kernel configuration commands, the
corresponding system file automatically gets rewritten to reflect the
change. System files can also be generated on demand for any
configuration set using kconfig -e. The format of a system file is
described in system(4).
It is possible to make configuration changes by modifying a system
file in a text editor and then running kconfig -i. This command will
read the system file and modify the appropriate kernel configuration
to match the contents of the system file. (mk_kernel(1M) can also
read a system file and modify a kernel configuration. It is retained
for compatibility with previous releases of HP-UX.)
Note: Some configuration changes can be made without using one of
the kernel configuration commands (for example, by calling the
settune(2) or modload(2) system calls directly). In these
cases, the system files are not automatically updated. Be
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sure to update them manually, or re-create them using kconfig
-e, before using them.
Note: Avoid putting comments in a system file. System files get
re-created every time a kernel configuration change is made,
and comments are not preserved in this process.
System files can be useful for propagating kernel configurations to
other systems. To do so, use kconfig -e to export a configuration set
to a system file on a source machine. Move the file to one or more
target machines and use kconfig -i to import the system file into a
configuration set on the target. The target machines must have the
same kernel filesets installed, or the import operation may fail. The
-V flag can be used to ensure that the target machine has exactly the
same versions of kernel filesets installed.
If there are changes to the currently running kernel configuration
that are being held for reboot, those changes are reflected in the
system file /stand/system.
LOG FILE [Toc] [Back]
The kernel configuration commands maintain a log file that describes
all kernel configuration changes. This log file is located at
/var/adm/kc.log. The kclog command can be used to search and view the
log file, or to make entries that don't correspond to configuration
changes.
When making a configuration change using any of the commands, you can
specify a -C comment option. The commands will include the specified
comment in the log file entry describing the change. Note that the
comment usually must be quoted to avoid interpretation by the shell.
kconfig -i and mk_kernel will include in the log file any comments
that they remove from a system file.
Some configuration changes can be made without using the kernel
configuration commands. No log file entries are made for such
changes.
The format of the log file may be changed without notice. Programs
must use the kclog command to retrieve entries from the file rather
than attempting to parse the file format.
PARSING OUTPUT [Toc] [Back]
Most of the kernel configuration commands produce tabular output
describing the details of a configuration. Such output may be
attractive for humans, but can be difficult for scripts and
applications to parse. Also, the tabular output format can change at
any time: for example, between different types of systems or between
releases of HP-UX.
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For these reasons, each of the kernel configuration commands that
produce such output accept a -P option, which changes the output
format. The -P format is designed to be easy to parse, and is
guaranteed not to change. HP will not support applications and
scripts which parse the output of the kernel configuration commands
unless they use the -P option.
The -P option must be followed by a comma-separated list of field
names. Each kernel configuration command supports a different set of
field names; refer to the man page for the command for a list. The
field names must appear in a single argument, so there should be no
spaces anywhere in the list. For example,
kcmodule -P name,state,desc
The kernel configuration command will produce output that consists of
a series of lines describing one object, a blank line, a series of
lines describing the next object, a blank line, and so on until all
objects are described. Each line in the series consists of a field
name, a single tab character (ASCII 9), and the value of that field
for the object being described. The lines occur in the same order as
requested. So the above command might produce this output:
name module1
state loaded
desc This is the first sample module.
name module2
state unused
desc This is a different sample module.
Some fields may occur multiple times within an object, or may not
occur at all. This will be noted in the description of the field.
For example, the command
kcmodule -P name,state,depend
might produce this output:
name module1
state loaded
name module2
state unused
depend module1
depend module4
This shows that module1 has no dependencies, but module2 is dependent
on two other modules.
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New fields may be added at any time, but they will not be included in
the output unless specified in a -P option. Fields will not be
removed. In rare cases, future developments may render a field
meaningless. In these cases, the field name will still be accepted
but the corresponding lines will be omitted from the output.
SEE ALSO [Toc] [Back]
hpux(1M), hpux.efi(1M), kclog(1M), kcmodule(1M), kconfig(1M),
kcpath(1M), kctune(1M), mk_kernel(1M), system(4).
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