/proc/modules: Explanation & Insights

Lists the kernel modules that are currently loaded on the system

The file /proc/modules is a representation of the state of the kernel's module loader at a particular point in time. It provides a snapshot of all modules that are currently loaded into the Kernel.

What does /proc/modules contain?

The /proc/modules file contains several pieces of information about each loaded module, including:

  • The module name
  • The size of the module (in bytes)
  • The number of instances of the module currently loaded
  • The state of the module (Live, Loading, Unloading)
  • The list of modules that this module depends on
  • The memory addresses where the module is loaded

Here is an example of what you might see in a /proc/modules file:

nf_conntrack 139264 9 nf_conntrack_ipv6,iptable_nat,nf_nat,nf_nat_ipv4,nf_nat_ipv6,xt_conntrack,nf_conntrack_ipv4,nf_conntrack_ipv6,Live 0xffffffffc0a6a000
ip_tables 24576 1 iptable_nat,Live 0xffffffffc0a62000
x_tables 40960 10 xt_conntrack,iptable_nat,ip_tables,Live 0xffffffffc0a58000

Why is /proc/modules important?

Understanding the /proc/modules file can prove crucial in several situations. For example, if your system is experiencing a high load or other performance issues, you might be able to trace the problem to a specific module by looking at this file. Additionally, if you're trying to load a module and it's failing, the /proc/modules file might provide insight into why.

How to use /proc/modules?

The /proc/modules file can be simply read using the cat command. For example:

cat /proc/modules

You can also use the grep command to search for a specific module:

grep 'module_name' /proc/modules

Common problems related to /proc/modules

One common problem is having a module that is stuck in the 'Loading' or 'Unloading' state. If a module is in this state for a long time, it could be causing a performance issue.

Another typical problem is a module failing to load due to a dependency on another module that isn't loaded. In this case, /proc/modules can help you identify the missing dependency.

Conclusion

In this post, we've explored the /proc/modules file - an important file in Linux that contains valuable information about the currently loaded modules in the kernel. Understanding this file can greatly assist system administrators in diagnosing and solving performance issues.

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