Linux Kernel Modules

Kernel Module Management

Distro support

One-family-tool skill. The module commands (lsmod, modinfo, modprobe, modprobe -r/rmmod) and the config directories (/etc/modules-load.d/, /etc/modprobe.d/) are part of kmod and are identical on both families. The only thing that differs is the command used to rebuild the initramfs after you blacklist or change options for a module that loads at boot. Body uses the common tooling; substitute the initramfs command per this matrix.

The split matters because blacklist/options lines in /etc/modprobe.d/ are only consulted at boot if they are also baked into the initramfs — the early-userspace image that loads storage and root-filesystem drivers before /etc is available. Editing /etc/modprobe.d/ alone does not change a module that the initramfs already loads. Full detail, including the per-family initramfs mechanics, is in references/module-management.md.

Use When

• Inspecting which drivers/modules are loaded and with what parameters.
• Loading or unloading a kernel module by hand or persisting it across reboots.
• Setting a module option/parameter (e.g. a NIC or sound driver tweak).
• Blacklisting a problematic or conflicting driver.

Do Not Use When

• The task is sysctl / runtime kernel parameter tuning; use linux-sysctl-tuning.
• The task is profiling CPU/IO/perf hot paths; use linux-perf-profiling.
• GRUB or initramfs is already broken and the box won't boot; use linux-disaster-recovery.

Required Inputs

• The module name(s) involved and what you intend to do (inspect, load, unload, set an option, blacklist).
• Whether the change must survive a reboot.
• Whether the module is needed at boot time (storage/root-fs, network on a headless/remote host) — this decides whether an initramfs rebuild is required and raises the safety stakes.

Capability Contract

Module inspection is read-only. Load/unload, persistent config, blacklist, initramfs rebuild, and reboot require explicit authority. A remote boot-time storage or network change additionally requires working console/out-of-band recovery.

Degraded Mode

Without host/kernel access, provide inspection commands only. Without dependency, boot-role, or console evidence, refuse unload/blacklist and mark reboot safety unassessed.

Decision Rules

Workflow

1. Inspect first: lsmod to see what is loaded, modinfo <mod> for params, dependencies, and the file path.

2. Make the change — load/unload at runtime, or write a /etc/modules-load.d/ or /etc/modprobe.d/ file for persistence.

3. If you blacklisted or changed options for a boot-time module, rebuild the initramfs (update-initramfs -u / dracut -f).

4. Verify: re-run lsmod, confirm the parameter under /sys/module/<mod>/parameters/, and (for boot-time changes) confirm a clean reboot — ideally with console/out-of-band access available.

5. Stop if the module owns root storage/networking or console recovery is unavailable; recover through the known-good initramfs/kernel entry, remove the drop-in, and re-verify the device.

Quality Standards

• Always modinfo and lsmod before unloading or blacklisting.
• Persist intent in /etc/modprobe.d/ or /etc/modules-load.d/ rather than relying on one-off runtime modprobe commands.
• Treat any boot-time module change as a change that requires an initramfs rebuild and a tested reboot.

Anti-Patterns

• Blacklisting a guessed driver. Fix: map the actual device-bound module first.

• Unloading without dependency/use checks. Fix: inspect modinfo, holders, devices, and prefer modprobe -r.

• Changing boot modules without console. Fix: require out-of-band access and a known-good image.

• Skipping initramfs rebuild. Fix: rebuild the family-specific image when early boot is affected.

• Calling runtime success boot-safe. Fix: perform a controlled reboot and verify root/network devices.

• Blacklisting a storage or network driver on a remote/headless box with no console fallback — a classic way to make a machine unbootable or unreachable.

• Editing /etc/modprobe.d/ for a boot-time module and forgetting to rebuild the initramfs (the change silently does nothing).

• Using rmmod (no dependency handling) where modprobe -r is safer.

• Persisting an option unsupported by the running module. Correction: verify with modinfo and /sys/module/.../parameters.

• Rebooting without a known-good initramfs. Correction: retain the prior image and boot entry and verify console recovery.

• Blacklisting by guessed module name. Correction: map the actual bound driver from the target device first.

Safety note

Blacklisting or unloading the wrong module is one of the easiest ways to brick a server. A blacklisted storage driver (e.g. the disk controller) can leave the kernel unable to mount the root filesystem — the box panics at boot. A blacklisted or unloaded network driver on a headless/remote host cuts you off with no way back in over SSH. Before blacklisting a boot-time driver: confirm you have console or out-of-band (IPMI/iLO/cloud-console) access, keep a known-good kernel/initramfs to fall back to, and test the reboot when you can recover from a failure.

Outputs

Evidence Produced

Capture uname, modinfo, lsmod, device-driver mapping, dependency/use state, persistent config, initramfs command/result, kernel log checks, and reboot outcome.

Worked Example

Before blacklisting a conflicting NIC driver, map the interface to its bound module, confirm an alternate driver and console access, test the change at runtime when safe, rebuild the correct initramfs, and verify networking after a controlled reboot.

• What was inspected, loaded, unloaded, or blacklisted, and where it was persisted.
• Whether an initramfs rebuild was required and which command was run.
• The verification performed (re-lsmod, /sys/module/.../parameters/, reboot test) and any remaining boot/connectivity risk.

References

• references/module-management.md — deep reference: inspect/load/unload, load-on-boot, options/parameters, blacklisting (blacklist vs install <mod> /bin/true), and the per-family initramfs rebuild detail with examples.

This skill is self-contained. Every command below is a standard kmod tool present on both families; only the initramfs rebuild command differs per the Distro support matrix. The sk-module-info script in the Optional fast path section is a read-only convenience wrapper — never required.

Inspect modules

lsmod                                 # all loaded modules, size, usage count, users
lsmod | grep -i <name>                # is a specific module loaded?
modinfo <mod>                         # description, params, deps, file path, signature
modinfo -p <mod>                      # just the supported parameters
cat /sys/module/<mod>/parameters/<p>  # current live value of a parameter

Load / unload at runtime

sudo modprobe <mod>                   # load module AND its dependencies
sudo modprobe <mod> <param>=<value>   # load with a one-shot parameter
sudo modprobe -r <mod>                # unload, honoring dependency order (preferred)
sudo rmmod <mod>                      # unload a single module, no dep handling

Runtime changes do not survive a reboot — persist them below.

Load a module on boot

Create a file in /etc/modules-load.d/ with one module name per line:

echo 'br_netfilter' | sudo tee /etc/modules-load.d/br_netfilter.conf
# Applied by systemd-modules-load.service at next boot (or load now with modprobe).

Set module options / parameters (persistent)

Use options in a /etc/modprobe.d/*.conf file — applied whenever the module is loaded (boot or manual):

# /etc/modprobe.d/i915.conf
options i915 enable_guc=2

If the module loads from the initramfs (boot-time driver), rebuild it so the option is baked in — see below.

Blacklist a driver

# /etc/modprobe.d/blacklist-nouveau.conf
blacklist nouveau                 # stops modprobe from auto-loading 'nouveau'
install nouveau /bin/true         # STRONGER: runs /bin/true instead of loading it,
                                  # also defeating loads pulled in as a dependency

blacklist only blocks the module from being auto-loaded by name; another module that lists it as a dependency can still pull it in. install <mod> /bin/true overrides the load action entirely, so even dependency-triggered loads become a no-op — use it when blacklist alone is not enough.

Rebuild the initramfs after a boot-time change

Blacklisting or re-parameterizing a module that the initramfs loads only takes effect once you regenerate that image:

sudo update-initramfs -u            # Debian/Ubuntu (rebuilds current kernel's image)
sudo dracut -f                      # RHEL family (force-rebuild current kernel's image)

Boot-time module changes can make a host unbootable or unreachable. See the Safety note above — confirm console/out-of-band access and a fallback kernel before rebooting.

Optional fast path (when sk-* scripts are installed)

Running sudo install-skills-bin linux-kernel-modules installs:

This is an optional read-only wrapper. The lsmod / modinfo / modprobe commands above are the source of truth.

Scripts

This skill installs the following scripts to /usr/local/bin/. To install:

sudo install-skills-bin linux-kernel-modules