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docs: admin-guide: merge sections for the kernel.modprobe sysctl

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Documentation for the kernel.modprobe sysctl was added both by
commit 0317c5371e ("docs: merge debugging-modules.txt into
sysctl/kernel.rst") and by commit 6e71582506 ("docs: admin-guide:
document the kernel.modprobe sysctl"), resulting in the same sysctl
being documented in two places.  Merge these into one place.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Stephen Kitt <steve@sk2.org>
Link: https://lore.kernel.org/r/20200414172430.230293-1-ebiggers@kernel.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
This commit is contained in:
Eric Biggers 2020-04-14 10:24:30 -07:00 committed by Jonathan Corbet
parent 404e603f1e
commit 52338dfb3c
1 changed files with 19 additions and 28 deletions
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47
Documentation/admin-guide/sysctl/kernel.rst
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@ -390,9 +390,17 @@ When ``kptr_restrict`` is set to 2, kernel pointers printed using
modprobe
========
This gives the full path of the modprobe command which the kernel will
use to load modules. This can be used to debug module loading
requests::
The full path to the usermode helper for autoloading kernel modules,
by default "/sbin/modprobe". This binary is executed when the kernel
requests a module. For example, if userspace passes an unknown
filesystem type to mount(), then the kernel will automatically request
the corresponding filesystem module by executing this usermode helper.
This usermode helper should insert the needed module into the kernel.
This sysctl only affects module autoloading. It has no effect on the
ability to explicitly insert modules.
This sysctl can be used to debug module loading requests::
echo '#! /bin/sh' > /tmp/modprobe
echo 'echo "$@" >> /tmp/modprobe.log' >> /tmp/modprobe
@ -400,10 +408,15 @@ requests::
chmod a+x /tmp/modprobe
echo /tmp/modprobe > /proc/sys/kernel/modprobe
This only applies when the *kernel* is requesting that the module be
loaded; it won't have any effect if the module is being loaded
explicitly using ``modprobe`` from userspace.
Alternatively, if this sysctl is set to the empty string, then module
autoloading is completely disabled. The kernel will not try to
execute a usermode helper at all, nor will it call the
kernel_module_request LSM hook.
If CONFIG_STATIC_USERMODEHELPER=y is set in the kernel configuration,
then the configured static usermode helper overrides this sysctl,
except that the empty string is still accepted to completely disable
module autoloading as described above.
modules_disabled
================
@ -446,28 +459,6 @@ Notes:
successful IPC object allocation. If an IPC object allocation syscall
fails, it is undefined if the value remains unmodified or is reset to -1.
modprobe:
=========
The path to the usermode helper for autoloading kernel modules, by
default "/sbin/modprobe". This binary is executed when the kernel
requests a module. For example, if userspace passes an unknown
filesystem type to mount(), then the kernel will automatically request
the corresponding filesystem module by executing this usermode helper.
This usermode helper should insert the needed module into the kernel.
This sysctl only affects module autoloading. It has no effect on the
ability to explicitly insert modules.
If this sysctl is set to the empty string, then module autoloading is
completely disabled. The kernel will not try to execute a usermode
helper at all, nor will it call the kernel_module_request LSM hook.
If CONFIG_STATIC_USERMODEHELPER=y is set in the kernel configuration,
then the configured static usermode helper overrides this sysctl,
except that the empty string is still accepted to completely disable
module autoloading as described above.
nmi_watchdog
============