From Linux Man Pages
mkinitrd, mk_initrd - create initrd disk image
mkinitrd [options] [root_dir]
DESCRIPTION
mkinitrd creates initial ramdisk images for booting Linux. The "/init" script in the compressed cpio archive
loads all driver modules, creates all device nodes currently know by the kernel, does a filesystem check on the
root filesystem and finally passes control to /sbin/init. udev is used to create the device nodes in a tmpfs
mounted /dev directory. This directory is moved over to the final root filesystem, essentially hiding the on-
disk content below /dev on the root filesystem.
A few options can be specified via the kernel command line to modify some hardcoded values in the "/init" script.
They are read from /proc/cmdline.
While in the old days the Linux kernel was responsible for mounting the rootfilesystem and running /sbin/init,
all the work is now done by the "/init" script.
OPTIONS
-h This Text.
-k "kernel list"
list of kernel images for which initrd files are created (relative to boot_dir), defaults to "vmlinux" on
powerpc, "image" on s390 and "vmlinuz" for everything else.
-i "initrd list"
list of file names (relativ to boot_dir) for the initrd; positions have to match the "kernel list",
defaults to "initrd"
-m "module list"
modules to include in initrd, defaults to INITRD_MODULES variable in /etc/sysconfig/kernel
-f "feature list"
features to be enabled for the initrd. In general mkinitrd configures the initrd for the root device it is
started from. With this option additional feature can be enabled.
-b boot_dir
boot dir, defaults to "/boot", where the initrd is created.
-d root_device
root device, defaults to the device from which the root_dir is mounted; overwrites the rootdev enviroment
variable if set
-s size
Add splash animation and bootscreen to initrd.
-D interface
Run dhcp on the specified interface.
-I interface
Configure the specified interface statically.
-a acpi_dsdt
Attach compiled ACPI DSDT (Differentiated System Description Table) to initrd. This replaces the DSDT of
the BIOS. Defaults to the ACPI_DSDT variable in /etc/sysconfig/kernel.
-t tmp_dir
tmp dir, defaults to "/tmp".
-e Use static binaries where possible. (currently unavailable)
-P Include modules for all IDE devices on the PCI bus.
-V script
Vendor specific script to run in linuxrc.
-M map System.map file to use.
-j device
External journal device to use for the root filesystem.
root_dir
the directory the root partition is mounted to defaults to "/"
KERNEL COMMAND-LINE PARAMETER
mkinitrd implements a set of additional kernel command-line parameters which are interpreted by the generated
init script. In addition to the standard kernel parameters the following parameter are supported:
linuxrc=trace
Enabling command tracing of the init script
noresume
Do not check for a resume device
sysrq=yes
sysrq=1 Enable sysrq
resume=<device>
Resume from device <device>
journal=<device>
Use device <device> as external journal device. This is only valid for reiser and xfs filesystems.
mduuid=<UUID>
Mount md RAID with uuid <UUID as the root filesystem.
TargetAddress=<IP Address>
[iSCSI] IP Address of the iSCSI Target
InitiatorName=<iqn>
[iSCSI] Use <iqn> as the iSCIS initiatorname.
ip=<ipspec>
Use <ipspec> to configure the network interface. Format of the <ipspec> is <client>:<server>:<gate-
way>:<netmask>:<hostname>:<device>:<proto>. <client>, <server>, <gateway>, <netmask> are in the standard
dotted-decimal IP notation. <proto> is currently ignored.
udev_timeout=<secs>
Set the timeout for root device detection to <secs> seconds. Default is 10.
FEATURES
Normally mkinitrd detects all required features automatically, based upon the current root filesystem. If addi-
tional features should be enabled, the -f option can be specified.
Currently, the following features can be selected:
iscsi Include iSCSI support
mpath Add support for multipathing
md Add support for Software RAID (md)
lvm2 Add support for LVM2
evms Add support for EVMS
lvm Add support for LVM1
Using NFS as root filesystem
To configure an initrd for an NFS client, specify these options to add nfs and network driver support into the
initrd:
mkinitrd -m "nfs e1000" -D eth0
This will add the required kernel modules and a dhcp client to the initrd, which will try to get an IP
address via eth0. Boot the NFS client with these additional command line options to mount the server:
nfsroot=1.2.3.4:/exported/directory
mkinitrd -m "nfs e1000" -I eth0
This will add the required kernel modules to the initrd, a static IP address must be specified on the ker-
nel cmdline. Boot the NFS client with these additional command line options to mount the server: nfs-
root=1.2.3.4:/exported/directory ip=1.2.3.42:1.2.3.4:1.2.3.1:255.255.255.0:clienthostname:eth0:none . See
the ip= description above for details about the ip= option.
NOTE
mk_initrd is now a symbolic link to mkinitrd.
ENVIRONMENT VARIABLES
You can specify the root device via the environment variable rootdev (e.g. "rootdev=/dev/hda mk_initrd").
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