1 What are kernel parameters?

Kernel parameters are settings that affect how the Linux kernel operates. They can be used to enable or disable features, adjust memory allocation, configure devices, and more. You can view the current kernel parameters by typing cat /proc/cmdline in a terminal. You can also modify them temporarily or permanently using different methods.

2 How to modify kernel parameters temporarily?

To modify kernel parameters temporarily, you can use the sysctl command or the /sys filesystem. The sysctl command allows you to read and write kernel parameters as key-value pairs. For example, to disable IPv6, you can type sudo sysctl -w net.ipv6.conf.all.disable_ipv6=1 . The /sys filesystem exposes kernel parameters as files that you can read and write. For example, to change the CPU frequency scaling governor, you can type echo performance | sudo tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor . These changes will only last until the next reboot.

3 How to modify kernel parameters permanently?

To modify kernel parameters permanently, you can use the /etc/sysctl.conf file or the boot loader. The /etc/sysctl.conf file contains key-value pairs of kernel parameters that are applied at boot time. You can edit this file with your preferred text editor and add or modify the parameters you want. For example, to enable IP forwarding, you can add net.ipv4.ip_forward=1 to the file. Then, you can apply the changes by typing sudo sysctl -p . The boot loader is the program that loads the kernel and passes parameters to it. You can edit the boot loader configuration file, such as /etc/default/grub , and add or modify the parameters you want in the GRUB_CMDLINE_LINUX variable. For example, to disable the splash screen, you can add nosplash to the variable. Then, you can update the boot loader by typing sudo update-grub .

4 What are kernel modules?

Kernel modules are pieces of code that can be loaded and unloaded from the kernel on demand. They can provide drivers, filesystems, network protocols, and other functionality. You can view the loaded kernel modules by typing lsmod in a terminal. You can also load and unload them manually or automatically using different methods.

5 How to load and unload kernel modules manually?

To load and unload kernel modules manually, you can use the modprobe or insmod and rmmod commands. The modprobe command is the preferred way to load and unload kernel modules, as it can handle dependencies and options automatically. For example, to load the snd_hda_intel module, you can type sudo modprobe snd_hda_intel . To unload it, you can type sudo modprobe -r snd_hda_intel . The insmod and rmmod commands are lower-level and require you to specify the full path and name of the module file. For example, to load the snd_hda_intel module, you can type sudo insmod /lib/modules/$(uname -r)/kernel/sound/pci/hda/snd-hda-intel.ko . To unload it, you can type sudo rmmod snd_hda_intel .

6 How to load and unload kernel modules automatically?

To load and unload kernel modules automatically, you can use the /etc/modules file or the modprobe.d directory. The /etc/modules file contains a list of kernel modules that are loaded at boot time. You can edit this file with your preferred text editor and add or remove the modules you want. For example, to load the snd_hda_intel module at boot time, you can add snd_hda_intel to the file. The modprobe.d directory contains configuration files that control the loading and unloading of kernel modules based on various events and conditions. You can create or edit these files with your preferred text editor and add or modify the rules you want. For example, to load the snd_hda_intel module when a sound card is detected, you can create a file named snd_hda_intel.conf in the modprobe.d directory and add install snd_hda_intel /sbin/modprobe --ignore-install snd_hda_intel; /sbin/modprobe snd_hda_codec_generic; /sbin/modprobe snd_hda_codec_realtek to the file.

7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?