Modules

1 Main commands

• Check if it's already there: lsmod | grep <module>

• Get info about the module: modinfo <module>

• Load the module: sudo modprobe <module>

• Verify it created a device: Check /proc/modules first. Then if you want to double check, verify that this created entries in /sys/module/<module>

• Remove it cleanly: sudo modprobe -r <module>

2 Commands mainly used by developers

• insmode: loads a module using the full path and the file ending in .ko. It does not handle dependencies.

• rmmode: it is also a "dummy" command, it removes a module but not its dependencies.

Warning: forcing a rmmode command, is something you could do, but it can cause a "kernel panic". The author is not responsible of the damage to your system with this command or any command listed.

3 Making a change permanent

modprobe is a temporary change (it disappears after reboot). To make it permanent you need to create a .conf file under /etc/modprobe.d/ .

4 Location of modules

There are three different locations where you will find the modules, each one has a different purpose:

1. /lib/modules/$(uname -r): This is the "warehouse". The files are stored in the hard drive. It shows what modules could be loaded.

2. /proc/modules: this is a file with a list of all the modules. This is where lsmod looks to get its information. Like everything in /proc, this lives in memory only. This, with the lsmod command, is the place where you look to verify a module is loaded.

3. /sys/module/: under this directory there are more directories with the modules and its parameters. Parameters can be modified instantly. No need to reload the module. Changes made in /sys are volatile, they are wiped after reboot.

   Example: echo 1 | sudo tee /sys/module/usbcore/parameters/usbfs_memory_mb

5 Checking the logs

dmesg | grep -i <module_name>

6 My short summary

lsmod | grep <module>: /proc/modules, volatile FS

modinfo <module>

sudo modprobe <module> / sudo modprobe -r <module>

/lib/modules/$(uname -r)

/sys/module: echo 1 | sudo tee /sys/module/usbcore/parameters/usbfs_memory_mb, volatile FS