/lib/modules Directory: Explanation & Insights
Contains the Linux kernel modules
The /lib/modules directory houses all the Linux Kernel modules, which are essential components
for the functioning of your Linux server. Understanding this directory and its contents is fundamental for managing and
troubleshooting your Linux system.
What it Contains
The /lib/modules directory contains subdirectories for each version of the Kernel installed in your system. Each of
these subdirectories houses the respective Kernel modules for that specific version.
For example, if you have Kernel version 4.15.0-29-generic installed, you would see a corresponding directory
in /lib/modules like this:
/lib/modules/4.15.0-29-generic
Inside these subdirectories, you will find various files and directories that represent the different Kernel modules.
For instance, you might see files like nf_conntrack_ipv4.ko, which is a Kernel module related to networking.
What it is Used For
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. This is especially useful for adding support for new hardware or filesystems, or for adding system calls.
When the Kernel needs a module, it looks in the /lib/modules directory. The directory structure and files within
provide the Kernel with an index of where each module resides.
Why it is Important
The /lib/modules directory is vital because it provides modularity and flexibility to your Linux system. By storing
Kernel modules in this directory, you can add, remove, or update functionalities without needing to modify the Kernel or
reboot the system.
For servers and VMs, this ability to dynamically manage system resources is invaluable. It allows for system administrators to fine-tune their systems to the specific needs of their workload.
Relation to Other Directories/Commands/Files
The /lib/modules directory is closely related to the modprobe
and lsmod commands.
modprobe is a command used to add or remove modules from the Kernel. For instance, to add a module, you would use:
modprobe module-name
lsmod is a command used to display the status of modules in the Linux Kernel.
Another related file is /etc/modules, which is a simple text file that contains the names
of Kernel modules that should be loaded at boot time.
Potential Problems and Pitfalls
One common problem is having leftover module directories from old Kernels filling up your /lib/modules directory. This
can consume a significant amount of disk space. You can remove these old modules with the apt-get autoremove command.
Another potential issue is a Kernel panic due to a missing or failed module. This can
happen if a module fails to load correctly or if the module file is missing from the /lib/modules directory.
Examples
Here's an example of how you might interact with the /lib/modules directory. Let's suppose you want to see what
modules are available for your current Kernel. First, use the uname -r command to find out your current Kernel
version. Then, list the contents of the corresponding directory in /lib/modules:
uname -r
4.15.0-29-generic
ls /lib/modules/4.15.0-29-generic
kernel modules.alias modules.builtin modules.dep modules.devname modules.order modules.softdep modules.symbols
