Linux Kernel

Kernel drivers for webcam

After you plug in your webcame, the output of the following command should not be empty.

# ls /dev/video*
/dev/video0

sys-apps/usbutils provides lsusb.
See if your hardware is detected, e.g.:

# lsusb
Bus 001 Device 009: ID 046d:08d9 Logitech, Inc. QuickCam IM/Connect

For most USB webcame, make sure the following kernel options are enabled:
CONFIG_MEDIA_CAMERA_SUPPORT
CONFIG_USB_VIDEO_CLASS


evice Drivers --->
Multimedia support --->
[*] Cameras/video grabbers support

Could not find a Makefile in the kernel source directory.

When emerging some (gentoo) packages, you might encounter the following error message:

* Could not find a Makefile in the kernel source directory.
* Please ensure that /usr/src/linux points to a complete set of Linux sources
* Unable to calculate Linux Kernel version for build, attempting to use running version

Kernel boot parameters

Official documentation

See: man bootparam.
For up-to-date information, see the kernel source file Documentation/kernel-parameters.txt (usually within /usr/src/linux/).

Getting started

Understanding your system

There are 3 types of boot parameters:
1) linux kernel parameters, e.g. log_buf_len=1M
2) module parameter, with the module name and the parameter separated by a dot, e.g. nvidia-drm.modeset=1

/boot/System.map-*

Regarding the various System.map-* files that you may see in your /boot/ directory, here is a post that very clearly explains what they are and why they may be useful, answering the following two questions:
What Is The Kernel Symbol Table?
What Is The System.map File?
http://www.dirac.org/linux/system.map/

Simply delete the System.map files corresponding to past kernels that you do not use anymore, keep the other ones.

Other resources:
https://en.wikipedia.org/wiki/System.map
https://kernelnewbies.org/FAQ/System.map

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