INITRAMFS.CONF

Section: File Formats Manual (5)
Updated: 2018/07/18
Page Index

NAME

initramfs.conf - configuration file for mkinitramfs

DESCRIPTION

The behaviour of mkinitramfs can be modified by its configuration file.

Each line in the file can be a configuration variable, a blank line, or a comment. The value of an variable is assigned by an statement of the form: name=[value]

Configuration options can be broken out into configuration snippets and placed in individual files in the /etc/initramfs-tools/conf.d directory. Files in this directory are always read after the main configuration file, so you can override the settings in the main config file without editing it directly.

GENERAL VARIABLES

MODULES

Specifies the modules for the initramfs image.

Modules listed in /etc/initramfs-tools/modules and /usr/share/initramfs-tools/modules.d/* are always included in the initramfs, and are loaded early in the boot process.

list doesn't load any additional modules at boot time, other than those listed in the above files.

most adds most file system, all ata, sata, scsi and usb drivers.

dep tries to guess which modules are necessary for the running box and only adds those modules.

netboot adds the base and network modules, but skips block devices.

The default setting is most.

BUSYBOX

Include busybox utilities for the boot scripts. If set to 'n' mkinitramfs will build an initramfs without busybox. Beware that many boot scripts need busybox utilities.

COMPCACHE_SIZE

Amount of RAM to use for RAM-based compressed swap space. The default is not to use compcache.
An empty value - compcache isn't used, or added to the initramfs at all.

An integer and K (e.g. 65536 K) - use a number of kilobytes.

An integer and M (e.g. 256 M) - use a number of megabytes.

An integer and G (e.g. 1 G) - use a number of gigabytes.

An integer and % (e.g. 50 %) - use a percentage of the amount of RAM.

You can optionally install the compcache package to configure this setting via debconf and have userspace scripts to load and unload compcache.

COMPRESS

Specifies the compression method used for the initramfs image. mkinitramfs will default to gzip if the kernel lacks support (CONFIG_RD) or the corresponding userspace utility is not present.

UMASK

Set the umask value of the generated initramfs file. Useful to not disclose eventual keys.

BOOT

Allows one to use an nfs drive as the root of the drive. The default is to boot from local media (hard drive, USB stick). Set to nfs for an NFS root share.

RUNSIZE

The size of the /run tmpfs mount point in bytes (suffixes are supported) or as percentage of your physical RAM. This parameter is used as the value of the size mount option to tmpfs. See https://www.kernel.org/doc/Documentation/filesystems/tmpfs.txt for details. Can be overridden by an optional initramfs.runsize= bootarg. The default is 10%.

VARIABLES FOR LOCAL BOOT

RESUME: Specifies the device used for suspend-to-disk (hibernation), which the initramfs code should attempt to resume from. If this is not defined or is set to auto, mkinitramfs will automatically select the largest available swap partition. Set it to none to disable resume from disk.

VARIABLES FOR NFS BOOT

DEVICE: Specifies the default network interface to use, like eth0. The ip or BOOTIF bootargs may override this.
ROOT: Allows optional root bootarg hardcoding, when no root bootarg can be passed. A root bootarg overrides that special setting.
NFSROOT: Defaults to auto in order to pick up value from DHCP server. Otherwise you need to specify HOST:MOUNT.

FILES

/etc/initramfs-tools/initramfs.conf

AUTHOR

The initramfs-tools are written by Maximilian Attems <maks@debian.org>, Jeff Bailey <jbailey@raspberryginger.com> and numerous others. Loosely based on mkinitrd.conf by Herbert Xu.