How can I ensure certain kernel modules are included in the initrd or initramfs in RHEL?

Solution Verified - Updated

Environment

  • Red Hat Enterprise Linux

Issue

  • How can I configure the system to load a module early in the boot process?
  • How can I ensure mkinitrd includes certain modules in RHEL 4 and 5?
  • How can I ensure dracut includes certain modules in RHEL 6, 7, 8, 9 & 10?
  • When I manually run mkinitrd I can include my own modules using --with=<module>, but I need to configure the system so that modules will be included when mkinitrd is run automatically by a kernel rpm installation.

Resolution

The method for including kernel modules in the initrd / initramfs varies based on RHEL version.  In all examples replace <kernel module> with the module name, not including .ko.

RHEL 6, 7, 8, 9 and 10.


There are two methods to achieve this: 
IMPORTANT NOTE: Replace <kernelVersion> with the full version of the kernel you wish to rebuild in the below steps. 
EXAMPLE:  (for kernel version "5.14.0-70.22.1.el9_0.x86_64")
# cp /boot/initramfs-5.14.0-70.22.1.el9_0.x86_64.img /boot/5.14.0-70.22.1.el9_0.x86_64.bak.$(date +%m-%d-%H%M%S).img
# dracut -f /boot/initramfs-5.14.0-70.22.1.el9_0.x86_64.img 5.14.0-70.22.1.el9_0.x86_64

Method 1


Step 1. Make a backup copy of the initramfs: 
# cp /boot/initramfs-<kernelVersion>.img /boot/<kernelVersion>.bak

Step 2. Use the --add-drivers option and specify the module name[without.ko extension] when manually building the initramfs with dracut:

# dracut -fv --add-drivers <kernel module> /boot/initramfs-<kernelVersion>.img <kernelVersion>

Step 3. Verify the module has been loaded in initramfs image file created by dracut:

# lsinitrd /boot/initramfs-<kernelVersion>.img | grep <module_name>

Method 2


Step 1. Add a space-separated list of kernel modules(minus any file extensions such as `.ko`) to the `add_drivers` directive in `/etc/dracut.conf` or `/etc/dracut.conf.d/.conf` configuration file (see man page `dracut.conf(5)`): 
add_drivers+="<kernel module>"

Step 2. Make a backup copy of the initramfs:

# cp /boot/initramfs-<kernelVersion>.img /boot/<kernelVersion>.bak

Step 3. Rebuild the initramfs: 

# dracut -fv /boot/initramfs-<kernelVersion>.img <kernelVersion>

Step 4. Verify the module has been loaded in initramfs image file created by dracut:

# lsinitrd /boot/initramfs-<kernelVersion>.img | grep <module_name>

RHEL 4 and 5


Three methods can be used to include  a kernel module in the initial RAM disk:

  • Use the --with option when manually building the ram disk with mkinitrd:

      # mkinitrd --with=<kernel module> /boot/initrd-$(uname -r).img $(uname -r)

  • For storage-related modules put an alias in /etc/modprobe.conf. If more than one is needed increment the alias entry:

      alias scsi_hostadapter <kernel module>
  alias scsi_hostadapter1 <kernel module>
  alias scsi_hostadapter2 <kernel module>

The above will cause the kernel module (plus any dependencies) to be included in the initrd.

  • For non-storage kernel modules, add a line to /etc/modprobe.conf similar to the following:

      install <kernel module> /sbin/modprobe -q --ignore-install <kernel module>; /bin/true
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