nullinitrd

NULL's Modular Initramfs Generator.

Building

make defconfig
make

Installation

sudo make install

Usage

nullinitrd

Options

Option	Description
-o, --output FILE	Output initramfs file (default: /boot/initrd.img)
-c, --config FILE	Configuration file (default: /etc/nullinitrd/config)
-k, --kernel VER	Kernel version (default: current)
-v, --verbose	Verbose output
-h, --help	Show help
--version	Show version

Configuration

Edit /etc/nullinitrd/config:

COMPRESSION=zstd
ROOTFS_TYPE=ext4
INIT_PATH=/sbin/init
AUTODETECT_MODULES=y
MODULES=
HOOKS=
FEATURE_LVM=n
FEATURE_LUKS=n
FEATURE_MDADM=n
FEATURE_BTRFS=n
FEATURE_ZFS=n

Compression

Supported: zstd, gzip, xz, lz4, bzip2, lzma, none

Kernel Parameters

Parameter	Description
root=	Root device (e.g., /dev/sda1, UUID=..., PARTUUID=..., LABEL=...)
rootfstype=	Root filesystem type
rootflags=	Mount flags for root
rootdelay=	Seconds to wait before mounting root
init=	Path to init on root filesystem
rw	Mount root read-write
ro	Mount root read-only
rd.debug	Enable verbose initramfs output
initrd.debug	Alias for rd.debug
rd.modules=	Additional modules to load (comma-separated)

Build Configuration

Run make menuconfig or edit .config:

Option	Description
CONFIG_STATIC=y	Static linking
CONFIG_DEBUG=y	Debug build
CONFIG_LTO=y	Link-time optimization

Default Modules

The following modules are loaded by default (if available):

• NVMe: nvme, nvme_core
• SATA/SCSI: ahci, sd_mod, sr_mod
• Filesystems: ext4, btrfs, xfs, vfat, fat
• USB: usb_storage, uas, ehci_hcd, ehci_pci, xhci_hcd, xhci_pci, ohci_hcd, ohci_pci
• Device Mapper: dm_mod, dm_crypt
• RAID: raid0, raid1, raid456, md_mod

Additional modules can be specified via the MODULES config option or the rd.modules= kernel parameter.

Features

Enable features in the config file to include additional tools:

Feature	Description
FEATURE_LVM=y	Include LVM tools (lvm)
FEATURE_LUKS=y	Include disk encryption (cryptsetup)
FEATURE_MDADM=y	Include software RAID (mdadm)

Hooks

Custom hooks can be placed in /usr/share/nullinitrd/hooks/ and enabled via the HOOKS config option.

Dependencies

nullinitrd currently only depends on kmod.