|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|
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.
Print a help message and exit.
mkimage lists the information contained in the header of an existing U-Boot image.
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.
Quiet. Don't print the image header.
Verbose. Print file names as they are added to the image.
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:
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.
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.
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
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).
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.
This section documents the formats of the primary and secondary configuration options for each image type which supports them.
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.
The primary configuration is a comma-separated list of NAND Flash parameters of the form
Valid parameters are
and valid values are decimal numbers. See section 22.214.171.124 of the SAMA5D3 Series Data Sheet for valid values for each parameter.
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.
The primary configuration is a file containing configuration commands, as documented in doc/imx/mkimage/kwbimage.txt of the U-Boot source.
The primary configuration is a semicolon-separated list of header options of the form
where the valid keys are:
|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:
|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|
The primary configuration is a file containing configuration commands, as documented in doc/imx/mkimage/mxsimage.txt of the U-Boot source.
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).
The primary configuration is a file containing the PBI (Pre-Boot Image) header. Each line of the configuration has the format
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.
The primary configuration is the name of the processor to generate the image for. Valid values are:
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.
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.
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.
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.
The primary configuration is the name to use for the device tree.
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
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.
Please report bugs to the U-Boot bug tracker.
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
dtc(1), dumpimage(1), openssl(1), the U-Boot documentation