How to Manage Kernel Modules with modprobe

Kernel modules are pieces of code that can be loaded into the Linux kernel on demand, adding support for hardware, filesystems, network protocols, and more — without rebooting. The modprobe command is the primary tool for managing these modules.

Understanding Kernel Modules

# List all currently loaded modules
lsmod

# The output shows:
# Module     Size  Used by
# nf_tables  32768  2 nf_tables_inet
# ip_tables  28672  0
# ext4      98304   1

# Size: Memory used by the module
# Used by: Count and list of dependent modules

Loading Modules

# Load a module (and its dependencies automatically)
sudo modprobe vhost_net       # Virtio networking
sudo modprobe br_netfilter    # Bridge netfilter (needed for Docker)
sudo modprobe ip_vs           # IPVS load balancing

# Load with parameters
sudo modprobe bonding mode=4 miimon=100

# Verify module is loaded
lsmod | grep vhost_net

Removing Modules

# Unload a module
sudo modprobe -r vhost_net

# Force removal (use with caution)
sudo modprobe -r -f module_name

# Cannot remove a module that is in use
# Check what is using it first:
lsmod | grep module_name

Getting Module Information

# Show module details
modinfo ext4

# Key fields:
# filename:    Path to the module file
# description: What the module does
# author:      Who wrote it
# license:     GPL, proprietary, etc.
# depends:     Other modules this one requires
# parm:        Configurable parameters

# Show only parameters
modinfo -p ext4

# Find a module by alias
modprobe -c | grep "alias.*usb"

Making Module Loading Persistent

# Load a module at boot
echo "br_netfilter" | sudo tee /etc/modules-load.d/bridge.conf

# Load multiple modules at boot
cat << EOF | sudo tee /etc/modules-load.d/k8s.conf
br_netfilter
overlay
ip_vs
ip_vs_rr
ip_vs_wrr
ip_vs_sh
nf_conntrack
EOF

Blacklisting Modules

# Prevent a module from loading (e.g., disable IPv6, disable Nouveau)
echo "blacklist nouveau" | sudo tee /etc/modprobe.d/blacklist-nouveau.conf
echo "options nouveau modeset=0" | sudo tee -a /etc/modprobe.d/blacklist-nouveau.conf

# Rebuild initramfs after blacklisting
sudo update-initramfs -u    # Ubuntu/Debian
sudo dracut --force         # RHEL/Rocky

# Verify module is not loaded after reboot
lsmod | grep nouveau

Setting Module Parameters

# Set parameters at load time
sudo modprobe tcp_bbr

# Set parameters permanently
echo "options bonding mode=4 miimon=100" | sudo tee /etc/modprobe.d/bonding.conf

# View current parameter values
cat /sys/module/tcp_bbr/parameters/*
# Or for a specific parameter:
cat /sys/module/nf_conntrack/parameters/hashsize

Common Server Modules

# Docker/Kubernetes requirements
sudo modprobe overlay          # OverlayFS for container storage
sudo modprobe br_netfilter     # Bridge netfilter for container networking

# Performance modules
sudo modprobe tcp_bbr          # Google BBR congestion control
echo "net.core.default_qdisc=fq" | sudo tee -a /etc/sysctl.d/99-bbr.conf
echo "net.ipv4.tcp_congestion_control=bbr" | sudo tee -a /etc/sysctl.d/99-bbr.conf

# WireGuard VPN
sudo modprobe wireguard

Troubleshooting

# Module fails to load
# Check dmesg for error messages
dmesg | tail -20

# Verify module exists
find /lib/modules/$(uname -r) -name "*.ko*" | grep module_name

# Rebuild module dependencies
sudo depmod -a

# If module is missing, you may need to install kernel extras
sudo apt install linux-modules-extra-$(uname -r)