systemd ukify 1 ukify Combine kernel and initrd into a signed Unified Kernel Image /usr/lib/systemd/ukify LINUX INITRD OPTIONS Note: this command is experimental for now. While it is intended to become a regular component of systemd, it might still change in behaviour and interface. ukify is a tool that combines a kernel and an initrd with a UEFI boot stub to create a Unified Kernel Image (UKI) — a PE binary that can be executed by the firmware to start the embedded linux kernel. See systemd-stub7 for details about the stub. Additional sections will be inserted into the UKI, either automatically or only if a specific option is provided. See the discussions of --cmdline=, --os-release=, --devicetree=, --splash=, --pcrpkey=, --uname=, and --section= below. If PCR signing keys are provided via the --pcr-public-key= and --pcr-private-key= options, PCR values that will be seen after booting with the given kernel, initrd, and other sections, will be calculated, signed, and embedded in the UKI. systemd-measure1 is used to perform this calculation and signing. The calculation of PCR values is done for specific boot phase paths. Those can be specified with --phases= option. If not specified, the default provided by systemd-measure is used. It is also possible to specify the --pcr-private-key=, --pcr-public-key=, and --phases= arguments more than once. Signatures will be then performed with each of the specified keys. When both --phases= and --pcr-private-key= are used, they must be specified the same number of times, and then the n-th boot phase path set will be signed by the n-th key. This can be used to build different trust policies for different phases of the boot. If a SecureBoot signing key is provided via the --secureboot-private-key= option, the resulting PE binary will be signed as a whole, allowing the resulting UKI to be trusted by SecureBoot. Also see the discussion of automatic enrollment in systemd-boot7. Note that the LINUX positional argument is mandatory. The INITRD positional arguments are optional. If more than one is specified, they will all be combined into a single PE section. This is useful to for example prepend microcode before the actual initrd. The following options are understood: --cmdline=TEXT|@PATH Specify the kernel command line (the .cmdline section). The argument may be a literal string, or @ followed by a path name. If not specified, no command line will be embedded. --os-release=TEXT|@PATH Specify the os-release description (the .osrel section). The argument may be a literal string, or @ followed by a path name. If not specified, the os-release5 file will be picked up from the host system. --devicetree=PATH Specify the devicetree description (the .dtb section). The argument is a path to a compiled binary DeviceTree file. If not specified, the section will not be present. --splash=PATH Specify a picture to display during boot (the .splash section). The argument is a path to a BMP file. If not specified, the section will not be present. --pcrpkey=PATH Specify a path to a public key to embed in the .pcrpkey section. If not specified, and there's exactly one --pcr-public-key= argument, that key will be used. Otherwise, the section will not be present. --uname=VERSION Specify the kernel version (as in uname -r, the .uname section). If not specified, an attempt will be made to extract the version string from the kernel image. It is recommended to pass this explicitly if known, because the extraction is based on heuristics and not very reliable. If not specified and extraction fails, the section will not be present. --section=NAME:TEXT|@PATH Specify an arbitrary additional section NAME. Note that the name is used as-is, and if the section name should start with a dot, it must be included in NAME. The argument may be a literal string, or @ followed by a path name. This option may be specified more than once. Any sections specified in this fashion will be inserted (in order) before the .linux section which is always last. --pcr-private-key=PATH Specify a private key to use for signing PCR policies. This option may be specified more than once, in which case multiple signatures will be made. --pcr-public-key=PATH Specify a public key to use for signing PCR policies. This option may be specified more than once, similarly to the --pcr-private-key= option. If not present, the public keys will be extracted from the private keys. If present, the this option must be specified the same number of times as the --pcr-private-key= option. --phases=LIST A comma or space-separated list of colon-separated phase paths to sign a policy for. If not present, the default of systemd-measure1 will be used. When this argument is present, it must appear the same number of times as the --pcr-private-key= option. Each set of boot phase paths will be signed with the corresponding private key. --pcr-banks=PATH A comma or space-separated list of PCR banks to sign a policy for. If not present, all known banks will be used (sha1, sha256, sha384, sha512), which will fail if not supported by the system. --secureboot-private-key=SB_KEY A path to a private key to use for signing of the resulting binary. If the --signing-engine= option is used, this may also be an engine-specific designation. --secureboot-certificate=SB_CERT A path to a certificate to use for signing of the resulting binary. If the --signing-engine= option is used, this may also be an engine-specific designation. --signing-engine=ENGINE An "engine" to for signing of the resulting binary. This option is currently passed verbatim to the --engine= option of sbsign1. --sign-kernel --no-sign-kernel Override the detection of whether to sign the Linux binary itself before it is embedded in the combined image. If not specified, it will be signed if a SecureBoot signing key is provided via the --secureboot-private-key= option and the binary has not already been signed. If --sign-kernel is specified, and the binary has already been signed, the signature will be appended anyway. --tools=DIRS Specify one or more directories with helper tools. ukify will look for helper tools in those directories first, and if not found, try to load them from $PATH in the usual fashion. --measure --no-measure Enable or disable a call to systemd-measure to print pre-calculated PCR values. Defaults to false. --output=FILENAME The output filename. If not specified, the name of the LINUX argument, with the suffix .unsigned.efi or .signed.efi will be used, depending on whether signing for SecureBoot was performed. ukify \ /lib/modules/6.0.9-300.fc37.x86_64/vmlinuz \ /some/path/initramfs-6.0.9-300.fc37.x86_64.img \ --cmdline='quiet rw' This creates an unsigned UKI ./vmlinuz.unsigned.efi. /usr/lib/systemd/ukify \ /lib/modules/6.0.9-300.fc37.x86_64/vmlinuz \ early_cpio \ /some/path/initramfs-6.0.9-300.fc37.x86_64.img \ --pcr-private-key=pcr-private-initrd-key.pem \ --pcr-public-key=pcr-public-initrd-key.pem \ --phases='enter-initrd' \ --pcr-private-key=pcr-private-system-key.pem \ --pcr-public-key=pcr-public-system-key.pem \ --phases='enter-initrd:leave-initrd enter-initrd:leave-initrd:sysinit \ enter-initrd:leave-initrd:sysinit:ready' \ --pcr-banks=sha384,sha512 \ --secureboot-private-key=sb.key \ --secureboot-certificate=sb.cert \ --sign-kernel \ --cmdline='quiet rw rhgb' This creates a signed UKI ./vmlinuz.signed.efi. The initrd section contains two concatenated parts, early_cpio and initramfs-6.0.9-300.fc37.x86_64.img. The policy embedded in the .pcrsig section will be signed for the initrd (the enter-initrd phase) with the key pcr-private-initrd-key.pem, and for the main system (phases leave-initrd, sysinit, ready) with the key pcr-private-system-key.pem. The Linux binary and the resulting combined image will be signed with the SecureBoot key sb.key. systemd1, systemd-stub7, systemd-boot7, objcopy1, systemd-pcrphase.service8