Provided by: u-boot-tools_2025.01-1~0ubuntu2_amd64 
NAME
mkimage - generate images for U-Boot
SYNOPSIS
mkimage [-T type] -l image-file-name
mkimage [option ...] [-T type] image-file-name
mkimage [option ...] -f image-tree-source-file|auto|auto-conf image-file-name
mkimage [option ...] -F image-file-name
DESCRIPTION
The mkimage command is used to create images for use with the U-Boot boot loader. These images can
contain the Linux kernel, device tree blob, root file system image, firmware images etc., either separate
or combined.
mkimage supports many image formats. Some of these formats may be used by embedded boot firmware to load
U-Boot. Others may be used by U-Boot to load Linux (or some other kernel):
The legacy image format concatenates the individual parts (for example, kernel image, device tree blob
and ramdisk image) and adds a 64 byte header containing information about the target architecture,
operating system, image type, compression method, entry points, time stamp, checksums, etc.
The new FIT (Flattened Image Tree) format allows for more flexibility in handling images of various types
and also enhances integrity protection of images with stronger checksums. It also supports verified boot.
OPTIONS
General options
-h
--help Print a help message and exit.
-l
--list mkimage lists the information contained in the header of an existing U-Boot image.
-s
--no-copy
Don't copy in the image data. Depending on the image type, this may create just the header,
everything but the image data, or nothing at all.
-T image-type
--type image-type
Parse image file as image-type. Pass list as image-type to see the list of supported image types.
If this option is absent, then it defaults to kernel (legacy image). If this option is absent when
-l is passed, then mkimage will attempt to automatically detect the image type. Not all image
types support automatic detection, so it may be necessary to pass -T explicitly.
When creating a FIT image with -f, the image type is always set to flat_dt. In this case, -T
specifies the image node's ‘type’ property. If -T is absent, then the ‘type’ property will default
to kernel.
-q
--quiet
Quiet. Don't print the image header.
-v
--verbose
Verbose. Print file names as they are added to the image.
-V
--version
Print version information and exit.
General image-creation options
-A architecture
--architecture architecture
Set the architecture. Pass -h as the architecture to see the list of supported architectures. If
-A is absent, it defaults to ppc.
-O os
--os os
Set the operating system. The U-Boot bootm command changes boot method based on the OS type. Pass
-h as the os to see the list of supported OSs. If -O is absent, it defaults to linux.
-C compression-type
--compression compression-type
Set the compression type. The image data should have already been compressed using this
compression type. mkimage will not automatically compress image data. Pass -h as the
compression-type to see the list of supported compression types. If -C is absent, it defaults to
gzip.
-a load-address
--load-address load-address
Set the absolute address to load the image data to. load-address will be interpreted as a
hexadecimal number.
-e entry-point
--entry-point entry-point
Set the absolute address of the image entry point. The U-Boot bootm command will jump to this
address after loading the image. entry-point will be interpreted as a hexadecimal number.
-n primary-configuration
--config primary-configuration
Images may require additional configuration not specified with other options, often in a image-
type-specific format. The image types which support this option and the format of their
configuration are listed in CONFIGURATION.
-R secondary-configuration
--secondary-config secondary-configuration
Some image types support a second set of configuration data. The image types which support
secondary configuration and the formap of their configuration are listed in CONFIGURATION.
-d image-data-file
--image image-data-file
Use image data from image-data-file. If the image-type is multi, then multiple images may be
specified, separated by colons:
image-data-file[:image-data-file...]
-x
--xip Set the XIP (execute in place) flag. The U-Boot bootm command will not load the image data, and
instead will assume it is already accessible at the load address (such as via memory-mapped
flash).
Options for creating FIT images
-b device-tree-file
--device-tree device-tree-file
Appends the device tree binary file (.dtb) to the FIT.
-c comment
--comment comment
Specifies a comment to be added when signing. This is typically a message which describes how the
image was signed or some other useful information.
-D dtc-options
--dtcopts dtc-options
Provide additional options to the device tree compiler when creating the image. See dtc(1) for
documentation of possible options. If -D is absent, it defaults to -I dts -O dtb -p 500.
-E
--external
After processing, move the image data outside the FIT and store a data offset in the FIT. Images
will be placed one after the other immediately after the FIT, with each one aligned to a 4-byte
boundary. The existing ‘data’ property in each image will be replaced with ‘data-offset’ and
‘data-size’ properties. A ‘data-offset’ of 0 indicates that it starts in the first (4-byte-
aligned) byte after the FIT.
-B alignment
--alignment alignment
The alignment, in hexadecimal, that external data will be aligned to. This option only has an
effect when -E is specified.
-p external-position
--position external-position
Place external data at a static external position. Instead of writing a ‘data-offset’ property
defining the offset from the end of the FIT, -p will use ‘data-position’ as the absolute position
from the base of the FIT. See -E for details on using external data.
-f image-tree-source-file | auto | auto-conf
--fit image-tree-source-file | auto | auto-conf
Image tree source file that describes the structure and contents of the FIT image.
In some simple cases, the image tree source can be generated automatically. To use this feature,
pass -f auto. The -d, -A, -O, -T, -C, -a, and -e options may be used to specify the image to
include in the FIT and its attributes. No image-tree-source-file is required. The -g, -o, and -k
or -G options may be used to get ‘images’ signed subnodes in the generated auto FIT. Instead, to
get ‘configurations’ signed subnodes and ‘images’ hashed subnodes, pass -f auto-conf. In this
case -g, -o, and -k or -G are mandatory options.
-F
--update
Indicates that an existing FIT image should be modified. No dtc compilation will be performed and
-f should not be passed. This can be used to sign images with additional keys after initial image
creation.
-i ramdisk-file
--initramfs ramdisk-file
Append a ramdisk or initramfs file to the image.
-k key-directory
--key-dir key-directory
Specifies the directory containing keys to use for signing. This directory should contain a
private key file name.key for use with signing, and a certificate name.crt (containing the public
key) for use with verification. The public key is only necessary when embedding it into another
device tree using -K. name is the value of the signature node's ‘key-name-hint’ property.
-G key-file
--key-file key-file
Specifies the private key file to use when signing. This option may be used instead of -k. Useful
when the private key file basename does not match ‘key-name-hint’ value. But note that it may lead
to unexpected results when used together with -K and/or -k options.
-K key-destination
--key-dest key-destination
Specifies a compiled device tree binary file (typically .dtb) to write public key information
into. When a private key is used to sign an image, the corresponding public key is written into
this file for for run-time verification. Typically the file here is the device tree binary used by
CONFIG_OF_CONTROL in U-Boot.
-g key-name-hint
--key-name-hint key-name-hint
Specifies the value of signature node ‘key-name-hint’ property for an automatically generated FIT
image. It makes sense only when used with -f auto or -f auto-conf. This option also indicates
that the images or configurations included in the FIT should be signed. If this option is
specified, then -o must be specified as well.
-o checksum,crypto
--algo checksum,crypto
Specifies the algorithm to be used for signing a FIT image, overriding value taken from the
signature node ‘algo’ property in the image-tree-source-file. It is mandatory for automatically
generated FIT.
The valid values for checksum are:
sha1
sha256
sha384
sha512
The valid values for crypto are:
rsa2048
rsa3072
rsa4096
ecdsa256
-r
--key-required
Specifies that keys used to sign the FIT are required. This means that images or configurations
signatures must be verified before using them (i.e. to boot). Without this option, the
verification will be optional (useful for testing but not for release). It makes sense only when
used with -K. When both, images and configurations, are signed, ‘required’ property value will be
"conf".
-N engine
--engine engine
The openssl engine to use when signing and verifying the image. For a complete list of available
engines, refer to engine(1).
-t
--touch
Update the timestamp in the FIT.
Normally the FIT timestamp is created the first time mkimage runs, when converting the source .its
to the binary .fit file. This corresponds to using -f. But if the original input to mkimage is a
binary file (already compiled), then the timestamp is assumed to have been set previously.
CONFIGURATION
This section documents the formats of the primary and secondary configuration options for each image type
which supports them.
aisimage
The primary configuration is a file containing a series of AIS (Application Image Script) commands, one
per line. Each command has the form
command argument ...
See TI application report SPRAAG0E for details.
atmelimage
The primary configuration is a comma-separated list of NAND Flash parameters of the form
parameter=value[,parameter=value...]
Valid parameters are
usePmecc
nbSectorPerPage
spareSize
eccBitReq
sectorSize
eccOffset
and valid values are decimal numbers. See section 11.4.4.1 of the SAMA5D3 Series Data Sheet for valid
values for each parameter.
imximage
The primary configuration is a file containing configuration commands, as documented in doc/imx/mkimage/
imximage.txt of the U-Boot source.
imx8image and imx8mimage
The primary configuration is a file containing configuration commands, as documented in doc/imx/mkimage/
imx8image.txt of the U-Boot source.
kwbimage
The primary configuration is a file containing configuration commands, as documented in doc/imx/mkimage/
kwbimage.txt of the U-Boot source.
mtk_image
The primary configuration is a semicolon-separated list of header options of the form
key=value[;key=value...]
where the valid keys are:
Key Description
───────────────────────────────────────────────────────────────────────────────────────────────────
lk If 1, then an LK (legacy) image header is used. Otherwise, a BootROM image header is
used.
lkname The name of the LK image header. The maximum length is 32 ASCII characters. If not
specified, the default value is U-Boot.
media The boot device. See below for valid values.
nandinfo The desired NAND device type. See below for valid values.
arm64 If 1, then this denotes an AArch64 image.
hdroffset Increase the reported size of the BRLYT header by this amount.
Valid values for media are:
Value Description
─────────────────────────────────────────
nand Parallel NAND flash
snand Serial NAND flash
nor Serial NOR flash
emmc eMMC (Embedded Multi-Media Card)
sdmmc SD (Secure Digital) card
Valid values for nandinfo are:
Value NAND type Page size OOB size Total size
──────────────────────────────────────────────────────────
2k+64 Serial 2KiB 64B
2k+120 Serial 2KiB 120B
2k+128 Serial 2KiB 128B
4k+256 Serial 4KiB 256B
1g:2k+64 Parallel 2KiB 64B 1Gbit
2g:2k+64 Parallel 2KiB 64B 2Gbit
4g:2k+64 Parallel 2KiB 64B 4Gbit
2g:2k+128 Parallel 2KiB 128B 2Gbit
4g:2k+128 Parallel 2KiB 128B 4Gbit
mxsimage
The primary configuration is a file containing configuration commands, as documented in doc/imx/mkimage/
mxsimage.txt of the U-Boot source.
omapimage
The primary configuration is the optional value byteswap. If present, each 32-bit word of the image will
have its bytes swapped (converting from little-endian to big-endian, or vice versa).
pblimage
The primary configuration is a file containing the PBI (Pre-Boot Image) header. Each line of the
configuration has the format
value[ value...]
Where value is a 32-bit hexadecimal integer. Each value will, after being converted to raw bytes, be
literally prepended to the PBI.
The secondary configuration is a file with the same format as the primary configuration file. It will be
inserted into the image after the primary configuration data and before the image data.
It is traditional to use the primary configuration file for the RCW (Reset Configuration Word), and the
secondary configuration file for any additional PBI commands. However, it is also possible to convert an
existing PBI to the above format and “chain” additional data onto the end of the image. This may be
especially useful for creating secure boot images.
rkimage
The primary configuration is the name of the processor to generate the image for. Valid values are:
px30
rk3036
rk3066
rk3128
rk3188
rk322x
rk3288
rk3308
rk3328
rk3368
rk3399
rv1108
rk3568
spkgimage
The primary configuration file consists of lines containing key/value pairs delimited by whitespace. An
example follows.
# Comments and blank lines may be used
key1 value1
key2 value2
The supported key types are as follows.
VERSION
NAND_ECC_BLOCK_SIZE
NAND_ECC_ENABLE
NAND_ECC_SCHEME
NAND_BYTES_PER_ECC_BLOCK
These all take a positive integer value as their argument. The value will be copied directly into
the respective field of the SPKG header structure. For details on these values, refer to Section
7.4 of the Renesas RZ/N1 User's Manual.
ADD_DUMMY_BLP
Takes a numeric argument, which is treated as a boolean. Any nonzero value will cause a fake BLp
security header to be included in the SPKG output.
PADDING
Takes a positive integer value, with an optional K or M suffix, indicating KiB / MiB respectively.
The output SPKG file will be padded to a multiple of this value.
sunxi_egon
The primary configuration is the name to use for the device tree.
ublimage
The primary configuration is a file containing configuration commands, as documented in doc/
README.ublimage of the U-Boot source.
zynqimage and zynqmpimage
For zynqmpimage, the primary configuration is a file containing the PMUFW (Power Management Unit
Firmware). zynqimage does not use the primary configuration.
For both image types, the secondary configuration is a file containinig initialization parameters, one
per line. Each parameter has the form
address data
where address and data are hexadecimal integers. The boot ROM will write each data to address when
loading the image. At most 256 parameters may be specified in this manner.
BUGS
Please report bugs to the U-Boot bug tracker.
EXAMPLES
List image information:
mkimage -l uImage
Create legacy image with compressed PowerPC Linux kernel:
mkimage -A powerpc -O linux -T kernel -C gzip \
-a 0 -e 0 -n Linux -d vmlinux.gz uImage
Create FIT image with compressed PowerPC Linux kernel:
mkimage -f kernel.its kernel.itb
Create FIT image with compressed kernel and sign it with keys in the /public/signing-keys directory. Add
corresponding public keys into u-boot.dtb, skipping those for which keys cannot be found. Also add a
comment.
mkimage -f kernel.its -k /public/signing-keys -K u-boot.dtb \
-c "Kernel 3.8 image for production devices" kernel.itb
Add public key to u-boot.dtb without needing a FIT to sign. This will also create a FIT containing an
images node with no data named unused.itb.
mkimage -f auto -d /dev/null -k /public/signing-keys -g dev \
-o sha256,rsa2048 -K u-boot.dtb unused.itb
Add public key with required = "conf" property to u-boot.dtb without needing a FIT to sign. This will
also create a useless FIT named unused.itb.
mkimage -f auto-conf -d /dev/null -k /public/signing-keys -g dev \
-o sha256,rsa2048 -K u-boot.dtb -r unused.itb
Update an existing FIT image, signing it with additional keys. Add corresponding public keys into
u-boot.dtb. This will resign all images with keys that are available in the new directory. Images that
request signing with unavailable keys are skipped.
mkimage -F -k /secret/signing-keys -K u-boot.dtb \
-c "Kernel 3.8 image for production devices" kernel.itb
Create a FIT image containing a kernel, using automatic mode. No .its file is required.
mkimage -f auto -A arm -O linux -T kernel -C none -a 43e00000 -e 0 \
-c "Kernel 4.4 image for production devices" -d vmlinuz kernel.itb
Create a FIT image containing a kernel and some device tree files, using automatic mode. No .its file is
required.
mkimage -f auto -A arm -O linux -T kernel -C none -a 43e00000 -e 0 \
-c "Kernel 4.4 image for production devices" -d vmlinuz \
-b /path/to/rk3288-firefly.dtb -b /path/to/rk3288-jerry.dtb kernel.itb
Create a FIT image containing a signed kernel, using automatic mode. No .its file is required.
mkimage -f auto -A arm -O linux -T kernel -C none -a 43e00000 -e 0 \
-d vmlinuz -k /secret/signing-keys -g dev -o sha256,rsa2048 kernel.itb
Create a FIT image containing a kernel and some device tree files, signing each configuration, using
automatic mode. Moreover, the public key needed to verify signatures is added to u-boot.dtb with required
= "conf" property.
mkimage -f auto-conf -A arm -O linux -T kernel -C none -a 43e00000 \
-e 0 -d vmlinuz -b /path/to/file-1.dtb -b /path/to/file-2.dtb \
-k /folder/with/signing-keys -g dev -o sha256,rsa2048 \
-K u-boot.dtb -r kernel.itb
Convert an existing FIT image from any of the three types of data storage (internal, external data-offset
or external data-position) to another type of data storage.
// convert FIT from internal data to data-position
mkimage -p 0x20000 -F internal_data.itb
// convert FIT from data-position to data-offset
mkimage -E -F external_data-position.itb
// convert FIT from data-offset to internal data
mkimage -F external_data-offset.itb
SEE ALSO
dtc(1), dumpimage(1), openssl(1), the U-Boot documentation
U-Boot 2022-06-11 MKIMAGE(1)