Linux list module options

modprobe, lsmod, modinfo Command Tutorial With Examples To Load, List Linux Kernel Modules

What makes an Operating system Linux Distribution? All Linux distributions use same kernel named Linux Kernel. Linux kernel provides operating system services, hardware management, process management, memory management etc.

Linux kernel is a monolithic kernel which means single executable all in one. But the operating systems should provide dynamic environments to comply user needs. Linux provides mechanism to load some drivers, features etc. This is called kernel modules. In this tutorial we will look kernel modules operations with modprobe command. Most of the examples in this tutorial requires root privileges.

List Available Kernel Modules

Linux kernel came with a lot of default kernel modules. These modules are loaded according to requirements and kernel config provided by the distribution. There is also an option to add new kernel modules externally to the Linux. We can list all of these modules with lsmod command

List Available Kernel Modules

List Available Kernel Modules

List Loaded Modules

As we know kernel modules are loaded or unloaded. We can list only installed kernel modules by using previous command. but in this command we need some external help. We will use egrep to filter installed kernel modules.

List Loaded Modules

Get Information About Kernel Module

Kernel modules can get different parameter for configuration purposes. Also there are different type of information. Here are some of them which can be listed with modinfo command.

• filename what is modules file name and the path
• license modules license type like GPL,GPL2,Apache,TM
• description short description about the kernel module
• depends specify what other kernel modules are needed to load this module
• intree specify if this kernel module is maintained in kernel git repository
• vermagic specifies the version of the kernel module
• parm specifies parameter that can be used to configure this kernel module.

Get Information About Kernel Module

Load or Install New Kernel Modules

Generally Linux operating system automatically loads related kernel modules. There is no need to load them manually in most situations. But some times manual operation may be needed to load kernel modules. We will install module named ipx by using insmod in this example.

Remove or Unload Loaded Kernel Module

We can remove kernel modules. We will use modprobe command again with -r option by providing the kernel module name. In this example we unload ipx kernel module

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How to list installed Nginx modules and compiled flags

Linux list installed Nginx modules

Make sure you run nginx command as the root user ( sudo nginx -V ), and nginx is in your $PATH.

Open the terminal app and then type the following command:
$ nginx -V

Nginx list installed modules in neat format

The -V option passed to the nginx command. It lists all the configured Nginx modules. However, the output is not easy to read or searchable using the egrep command/grep command. For example, see if Nginx compiled with stub_status_module, run:
$ nginx -V | grep —color stub_status_module
More readable syntax:
$ nginx -V 2>&1 | tr ‘ ‘ ‘\n’
$ nginx -V 2>&1 | tr ‘ ‘ ‘\n’ | grep ‘something’
$ nginx -V 2>&1 | tr ‘ ‘ ‘\n’ | grep ‘ssl’
$ nginx -V 2>&1 | tr ‘ ‘ ‘\n’ | egrep -i ‘ssl|brotli|pagespeed’

Please note that ‘ 2>&1 ‘ will redirect stderr and stdout to the tr command command using shell pipes. See “BASH Shell Redirect stderr To stdout ( redirect stderr to a File )” for detailed explanation.

Find which flags Nginx was compiled with under Unix

The same command lists compiled and dynamic modules under Nginx:
$ nginx -V
$ nginx -V 2>&1 | tr ‘ ‘ ‘\n’

Other nginx command options

Display nginx version and exit:
$ nginx -v # small -v
To see version and configure options, run:
$ nginx -V # CAPITAL -V
Test nginx configuration for errors:
$ nginx -t

Hide non-error messages during configuration testing
$ nginx -t -q
We can test configuration, and dump it on the screen:
$ nginx -T
Send a signal to control the Nginx server:
$ sudo nginx -s signal
Stop the Nginx server:
$ sudo nginx -s stop
Reload the Nginx server after making changes to the config file or when TLS/SSL certificate created/issues/renewed:
$ sudo ngix -s reload
Reopen log files after creating log files stored in /var/log/nginx/:
$ sudo ngix -s reopen

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Conclusion

In this quick tutorial, we learned how to see which flags Nginx compiled with, including listing Nginx modules.

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Kernel module

Kernel modules are pieces of code that can be loaded and unloaded into the kernel upon demand. They extend the functionality of the kernel without the need to reboot the system.

To create a kernel module, you can read The Linux Kernel Module Programming Guide. A module can be configured as built-in or loadable. To dynamically load or remove a module, it has to be configured as a loadable module in the kernel configuration (the line related to the module will therefore display the letter M ).

Contents

Obtaining information

Modules are stored in /usr/lib/modules/kernel_release . You can use the command uname -r to get your current kernel release version.

To show what kernel modules are currently loaded:

To show information about a module:

To list the options that are set for a loaded module:

To display the comprehensive configuration of all the modules:

To display the configuration of a particular module:

List the dependencies of a module (or alias), including the module itself:

Automatic module loading with systemd

Today, all necessary modules loading is handled automatically by udev, so if you do not need to use any out-of-tree kernel modules, there is no need to put modules that should be loaded at boot in any configuration file. However, there are cases where you might want to load an extra module during the boot process, or blacklist another one for your computer to function properly.

Kernel modules can be explicitly listed in files under /etc/modules-load.d/ for systemd to load them during boot. Each configuration file is named in the style of /etc/modules-load.d/program.conf . Configuration files simply contain a list of kernel modules names to load, separated by newlines. Empty lines and lines whose first non-whitespace character is # or ; are ignored.

See modules-load.d(5) for more details.

Manual module handling

Kernel modules are handled by tools provided by kmod package. You can use these tools manually.

To load a module:

To load a module by filename (i.e. one that is not installed in /usr/lib/modules/$(uname -r)/ ):

To unload a module:

Setting module options

To pass a parameter to a kernel module, you can pass them manually with modprobe or assure certain parameters are always applied using a modprobe configuration file or by using the kernel command line.

Manually at load time using modprobe

The basic way to pass parameters to a module is using the modprobe command. Parameters are specified on command line using simple key=value assignments:

Using files in /etc/modprobe.d/

Files in /etc/modprobe.d/ directory can be used to pass module settings to udev, which will use modprobe to manage the loading of the modules during system boot. Configuration files in this directory can have any name, given that they end with the .conf extension. The syntax is:

Using kernel command line

If the module is built into the kernel, you can also pass options to the module using the kernel command line. For all common bootloaders, the following syntax is correct:

Simply add this to your bootloader’s kernel-line, as described in Kernel Parameters.

Aliasing

Aliases are alternate names for a module. For example: alias my-mod really_long_modulename means you can use modprobe my-mod instead of modprobe really_long_modulename . You can also use shell-style wildcards, so alias my-mod* really_long_modulename means that modprobe my-mod-something has the same effect. Create an alias:

Some modules have aliases which are used to automatically load them when they are needed by an application. Disabling these aliases can prevent automatic loading but will still allow the modules to be manually loaded.

Blacklisting

Blacklisting, in the context of kernel modules, is a mechanism to prevent the kernel module from loading. This could be useful if, for example, the associated hardware is not needed, or if loading that module causes problems: for instance there may be two kernel modules that try to control the same piece of hardware, and loading them together would result in a conflict.

Some modules are loaded as part of the initramfs. mkinitcpio -M will print out all automatically detected modules: to prevent the initramfs from loading some of those modules, blacklist them in a .conf file under /etc/modprobe.d and it shall be added in by the modconf hook during image generation. Running mkinitcpio -v will list all modules pulled in by the various hooks (e.g. filesystems hook, block hook, etc.). Remember to add that .conf file to the FILES array in /etc/mkinitcpio.conf if you do not have the modconf hook in your HOOKS array (e.g. you have deviated from the default configuration), and once you have blacklisted the modules regenerate the initramfs, and reboot afterwards.

Using files in /etc/modprobe.d/

Create a .conf file inside /etc/modprobe.d/ and append a line for each module you want to blacklist, using the blacklist keyword. If for example you want to prevent the pcspkr module from loading:

However, there is a workaround for this behaviour; the install command instructs modprobe to run a custom command instead of inserting the module in the kernel as normal, so you can force the module to always fail loading with:

This will effectively blacklist that module and any other that depends on it.

Using kernel command line

You can also blacklist modules from the bootloader.

Simply add module_blacklist=modname1,modname2,modname3 to your bootloader’s kernel line, as described in Kernel parameters.

Troubleshooting

Modules do not load

In case a specific module does not load and the boot log (accessible by running journalctl -b as root) says that the module is blacklisted, but the directory /etc/modprobe.d/ does not show a corresponding entry, check another modprobe source folder at /usr/lib/modprobe.d/ for blacklisting entries.

A module will not be loaded if the «vermagic» string contained within the kernel module does not match the value of the currently running kernel. If it is known that the module is compatible with the current running kernel the «vermagic» check can be ignored with modprobe —force-vermagic .

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Howto: Display List of Modules or Device Drivers In the Linux Kernel

H ow do I display the list of loaded Linux Kernel modules or device drivers on Linux operating systems?

You need to use lsmod program which show the status of loaded modules in the Linux Kernel. Linux kernel use a term modules for all hardware device drivers.

Tutorial details
Difficulty level	Easy
Root privileges	Yes
Requirements	lsmod
Est. reading time	Less than a one minute

Please note hat lsmod is a trivial program which nicely formats the contents of the /proc/modules , showing what kernel modules are currently loaded.

This is an important task. With lsmod you can verify that device driver is loaded for particular hardware. Any hardware device will only work if device driver is loaded.

Task: List or display loaded modules

Open a terminal or login over the ssh session and type the following command
$ less /proc/modules
Sample outputs:

To see nicely formatted output, type:
$ lsmod
Sample outputs:

First column is Module name and second column is the size of the modules i..e the output format is module name, size, use count, list of referring modules.

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Finding more info about any module or driver

Type the following command:
# modinfo driver-Name-Here
# modinfo thermal_sys
# modinfo e1000e
Sample outputs:

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