$ Linux Command

Administration

mkinitrd

Create an initial RAM disk image for booting.

initrdinitramfsbootkernelmodules

Additional Notes

mkinitrd creates an initial RAM disk (initrd) image for the Linux kernel. The initrd is a temporary root filesystem loaded into memory during boot that contains essential kernel modules and tools needed to mount the real root filesystem.

On modern systems, mkinitrd is often a wrapper around mkinitcpio (Arch), dracut (Fedora/RHEL), or initramfs-tools (Debian/Ubuntu). The initramfs handles loading storage drivers, filesystem modules, LVM, encryption, and other requirements before the real root filesystem is mounted.

Syntax

mkinitrd [options] [image-name] [kernel-version]

Parameters

  • image-name: The output path for the initrd image (e.g., /boot/initramfs-linux.img).
  • kernel-version: The kernel version string (e.g., 6.8.0-arch1-1). Defaults to the currently running kernel.

Common Options

  • -f: Overwrite an existing initrd image without prompting.
  • -v: Verbose output.
  • -k kernel-version: Specify the kernel version.
  • -m module-list: Comma-separated list of kernel modules to include.
  • -P: Only print the configuration and exit (dry-run).
  • -b basedir: Use an alternative base directory for boot files.
  • -preload module: Preload a module before others.
  • -s: Skip any initial setup commands.

Examples

mkinitrd

Create an initrd for the current kernel with default settings.

mkinitrd /boot/initramfs-linux-fallback.img 6.8.0-arch1-1

Create an initrd with a specific name and kernel version.

mkinitrd -f /boot/initramfs-linux.img

Overwrite an existing initrd image.

mkinitrd -v -m "ext4,ata_piix,ehci_hcd"

Create an initrd with specific modules and verbose output.

Practical Notes

  • Each distribution has its own preferred tool: dracut (RHEL/Fedora), mkinitcpio (Arch), update-initramfs (Debian/Ubuntu).
  • Always rebuild the initrd after adding new hardware controllers, changing filesystem types, or modifying kernel module configuration.
  • A fallback or backup initrd image is recommended in case the primary image fails to boot.
  • The kernel version corresponds to a directory under /lib/modules/.