OS Manuals

systemd-repart(8)

SYSTEMD-REPART(8) systemd-repart SYSTEMD-REPART(8)


.SH "NAME" systemd-repart, systemd-repart.service - Automatically grow and add partitions, and generate disk images (DDIs)


.SH "SYNOPSIS"


.HP 360u


systemd-repart
[OPTIONS...]
[BLOCKDEVICE]


.PP systemd-repart.service


.SH "DESCRIPTION"


.PP systemd-repart creates partition tables, and adds or grows partitions, based on the configuration files described in repart.d(5). It operates on the block device or file image specified on the command line.


.PP systemd-repart is used when building OS images, and also when deploying images to automatically adjust them, during boot, to the system they are running on. This way the image can be minimal in size and may be augmented automatically at boot, taking possession of the disk space available.


.PP If invoked with no arguments, systemd-repart operates on the block device backing the root file system partition of the running OS, thus adding and growing partitions of the booted OS itself. When called in the initrd, it operates on the block device backing /sysroot/ instead, i.e. on the block device the system will soon transition into. If --image= is used, it will operate on the specified device or image file. The systemd-repart.service service is generally run at boot in the initrd, in order to augment the partition table of the OS before its partitions are mounted.


.PP If the block device is specified as - (or as an empty string), systemd-repart will not operate on any block device or image file, and instead determine and output the minimum disk/image size for the specified partition configuration, taking all configured size constraints into account.


.PP systemd-repart operations are mostly incremental: it grows existing partitions or adds new ones, but does not shrink, delete, or move existing partitions. The service is intended to be run on every boot, but when it detects that the partition table already matches the installed repart.d/*.conf configuration files, it executes no operation.


.PP The following use cases are among those covered:

•The root partition may be grown to cover the whole available disk space.

•A /home/, swap, or /srv/ partition can be added.

•A second (or third, ...) root partition may be added, to cover A/B style setups where a second version of the root file system is alternatingly used for implementing update schemes. The deployed image would carry only a single partition ("A") but on first boot a second partition ("B") for this purpose is automatically created.


.PP The algorithm executed by systemd-repart is roughly as follows:

1.The repart.d/*.conf configuration files are loaded and parsed, and ordered by filename (without the directory prefix). For each configuration file, drop-in files are loaded from directories with same name as the configuration file with the suffix ".d" added.

2.The partition table on the block device is loaded and parsed, if present.

3.The existing partitions in the partition table are matched with the repart.d/*.conf files by GPT partition type UUID. The first existing partition of a specific type is assigned the first configuration file declaring the same type. The second existing partition of a specific type is then assigned the second configuration file declaring the same type, and so on. After this iterative assigning is complete, any existing partitions that have no matching configuration file are considered "foreign" and left as they are. And any configuration files for which no partition was matched are treated as requests to create a partition.

4.Partitions that shall be created are now allocated on the disk, taking the size constraints and weights declared in the configuration files into account. Free space is used within the limits set by size and padding requests. In addition, existing partitions that should be grown are grown. When possible, newly created partitions are assigned partition table slots after existing partitions of the same type, as those are matched to configuration files in partition number order and a new partition inserted before an existing one would change that matching on the next invocation. If no such slot is available, the first unused slot is used. Partitions are never reordered and thus partition numbers remain stable. When partitions are created, they are placed in the smallest area of free space that is large enough to satisfy the size and padding limits. This means that partitions might have different order on disk than in the partition table. Note that this allocation happens in memory only, the partition table on disk is not updated yet.

5.All existing partitions for which configuration files exist and which currently have no GPT partition label set will be assigned a label, either explicitly configured in the configuration or — if that's missing — derived automatically from the partition type. The same is done for all partitions that are newly created. These assignments are done in memory only, too, the disk is not updated yet.

6.Similarly, all existing partitions for which configuration files exist and which currently have an all-zero identifying UUID will be assigned a new UUID. This UUID is cryptographically hashed from a common seed value together with the partition type UUID (and a counter in case multiple partitions of the same type are defined), see below. The same is done for all partitions that are created anew. These assignments are done in memory only, too, the disk is not updated yet.

7.Similarly, if the disk's volume UUID is all zeroes it is also initialized, also cryptographically hashed from the same common seed value. This is done in memory only too.

8.The disk space assigned to new partitions (i.e. what was previously free space) is now erased. Specifically, all file system signatures are removed, and if the device supports it, the BLKDISCARD I/O control command is issued to inform the hardware that the space is now empty. In addition any "padding" between partitions and at the end of the device is similarly erased.

9.The new partition table is finally written to disk. The kernel is asked to reread the partition table.


.PP As an exception to the normal incremental operation, when called in a special "factory reset" mode, systemd-repart may be used to erase existing partitions to reset an installation back to vendor defaults. This mode of operation is used when either the --factory-reset=yes switch is passed on the tool's command line, or the systemd.factory_reset=yes option is specified on the kernel command line, or the FactoryResetRequest EFI variable (vendor UUID 8cf2644b-4b0b-428f-9387-6d876050dc67) is set to "yes". It alters the algorithm above slightly: between the 3rd and the 4th step above any partition marked explicitly via the FactoryReset= boolean is deleted, and the algorithm restarted, thus immediately re-creating these partitions anew empty.


.PP Note that systemd-repart by default only changes partition tables, it does not create or resize any file systems within these partitions, unless the Format= configuration option is specified. Also note that there are also separate mechanisms available for this purpose, for example systemd-growfs(8) and systemd-makefs.


.PP The UUIDs identifying the new partitions created (or assigned to existing partitions that have no UUID yet), as well as the disk as a whole are hashed cryptographically from a common seed value. This seed value is usually the machine-id(5) of the system, so that the machine ID reproducibly determines the UUIDs assigned to all partitions. If the machine ID cannot be read (or the user passes --seed=random, see below) the seed is generated randomly instead, so that the partition UUIDs are also effectively random. The seed value may also be set explicitly, formatted as UUID via the --seed= option. By hashing these UUIDs from a common seed images prepared with this tool become reproducible and the result of the algorithm above deterministic.


.PP The positional argument should specify the block device or a regular file to operate on. If --empty=create is specified, the specified path is created as regular file, which is useful for generating disk images from scratch.


.SH "OPTIONS"


.PP The following options are understood:


.PP -n, --dry-run=


Takes a boolean. If this switch is not specified, --dry-run=yes is the implied default. Controls whether systemd-repart executes the requested re-partition operations or whether it should only show what it would do. Unless --dry-run=no is specified systemd-repart will not actually touch the device's partition table. The short option -n is equivalent to --dry-run=yes and was added in version 262.


Added in version 245.


.RE


.PP --empty=


Takes one of refuse, allow, require, force or create. Controls how to operate on block devices that are entirely empty, i.e. carry no partition table/disk label yet. If this switch is not specified, the implied default is refuse.


If refuse systemd-repart requires that the block device it shall operate on already carries a partition table and refuses operation if none is found. If allow the command will extend an existing partition table or create a new one if none exists. If require the command will create a new partition table if none exists so far, and refuse operation if one already exists. If force it will create a fresh partition table unconditionally, erasing the disk fully in effect. If force no existing partitions will be taken into account or survive the operation. Hence: use with care, this is a great way to lose all your data. If create a new loopback file is create under the path passed via the device node parameter, of the size indicated with --size=, see below.


Added in version 245.


.RE


.PP --discard=


Takes a boolean. If this switch is not specified ,--discard=yes is the implied default. Controls whether to issue the BLKDISCARD I/O control command on the space taken up by any added partitions or on the space in between them. Usually, it is a good idea to issue this request since it tells the underlying hardware that the covered blocks shall be considered empty, improving performance. If operating on a regular file instead of a block device node, a sparse file is generated.


Added in version 245.


.RE


.PP --size=


Takes a size in bytes, using the usual K, M, G, T suffixes, or the special value auto. If used the specified device node path must refer to a regular file, which is then grown to the specified size if smaller, before any change is made to the partition table. If specified as auto the minimal size for the disk image is automatically determined (i.e. the minimal sizes of all partitions are summed up, taking space for additional metadata into account). This switch is not supported if the specified node is a block device. This switch has no effect if the file is already as large as the specified size or larger. The specified size is implicitly rounded up to multiples of 4096. When used with --empty=create this specifies the initial size of the loopback file to create.


The --size=auto option takes the sizes of pre-existing partitions into account. However, it does not accommodate for partition tables that are not tightly packed: the configured partitions might still not fit into the backing device if empty space exists between pre-existing partitions (or before the first partition) that cannot be fully filled by partitions to grow or create.


Also note that the automatic size determination does not take files or directories specified with CopyFiles= into account: operation might fail if the specified files or directories require more disk space then the configured per-partition minimal size limit.


Added in version 246.


.RE


.PP --cow=BOOL


Controls copy-on-write for newly created image files on filesystems that support it. If true, copy-on-write is enabled; if false, it is disabled. If set to auto, the filesystem or parent directory default is left unchanged. Copy-on-write allows files to be reflinked into the image, reducing both build time and disk usage, but may result in fragmentation for images subject to frequent random writes. Defaults to auto.


Added in version 262.


.RE


.PP --factory-reset=


Takes boolean. If this switch is not specified, --factory-reset=no is the implied default. Controls whether to operate in "factory reset" mode, see above. If set to true this will remove all existing partitions marked with FactoryReset= set to yes early while executing the re-partitioning algorithm. Use with care, this is a great way to lose all your data. Note that partition files need to explicitly turn FactoryReset= on, as the option defaults to off. If no partitions are marked for factory reset this switch has no effect. Note that there are two other methods to request factory reset operation: via the kernel command line and via an EFI variable, see above.


Added in version 245.


.RE


.PP --can-factory-reset


If this switch is specified the disk is not re-partitioned. Instead it is determined if any existing partitions are marked with FactoryReset=. If there are the tool will exit with exit status zero, otherwise non-zero. This switch may be used to quickly determine whether the running system supports a factory reset mechanism built on systemd-repart.


Added in version 245.


.RE


.PP --root=


Takes a path to a directory to use as root file system when searching for repart.d/*.conf files, for the machine ID file to use as seed and for the CopyFiles= and CopyBlocks= source files and directories. By default when invoked on the regular system this defaults to the host's root file system /. If invoked from the initrd this defaults to /sysroot/, so that the tool operates on the configuration and machine ID stored in the root file system later transitioned into itself.


See --copy-source= for a more restricted option that only affects CopyFiles=.


Added in version 245.


.RE


.PP --image=


Takes a path to a disk image file or device to mount and use in a similar fashion to --root=, see above.


Added in version 249.


.RE


.PP --image-policy=policy


Takes an image policy string as argument, as per systemd.image-policy(7). The policy is enforced when operating on the disk image specified via --image=, see above. If not specified, defaults to the * policy, i.e. all recognized file systems in the image are used.


.RE


.PP --seed=


Takes a UUID as argument or the special value random. If a UUID is specified the UUIDs to assign to partitions and the partition table itself are derived via cryptographic hashing from it. If not specified, it is attempted to read the machine ID from the host (or more precisely, the root directory configured via --root=) and use it as seed instead, falling back to a randomized seed otherwise. Use --seed=random to force a randomized seed. Explicitly specifying the seed may be used to generated strictly reproducible partition tables.


Added in version 245.


.RE


.PP --pretty=


Takes a boolean argument. If this switch is not specified, it defaults to on when called from an interactive terminal and off otherwise. Controls whether to show a user friendly table and graphic illustrating the changes applied.


Added in version 245.


.RE


.PP --definitions=


Takes a file system path. If specified the *.conf files are read from the specified directory instead of searching in /usr/lib/repart.d/*.conf, /etc/repart.d/*.conf, /run/repart.d/*.conf.


This parameter can be specified multiple times.


Added in version 245.


.RE


.PP --key-file=


Takes a file system path. Configures the encryption key to use when setting up LUKS2 volumes configured with the Encrypt=key-file setting in partition files. Should refer to a regular file containing the key, or an AF_UNIX stream socket in the file system. In the latter case, a connection is made to it and the key read from it. If this switch is not specified, and no KeyFile= is specified in the partition file, the empty key (i.e. zero length key) is used. This behaviour is useful for setting up encrypted partitions during early first boot that receive their user-supplied password only in a later setup step.


Added in version 247.


.RE


.PP --private-key=


Takes a file system path or an engine or provider specific designation. Configures the signing key to use when creating verity signature partitions with the Verity=signature setting in partition files.


Added in version 252.


.RE


.PP --private-key-source=


Takes one of file, engine or provider. In the latter two cases, it is followed by the name of a provider or engine, separated by colon, that will be passed to OpenSSL's "engine" or "provider" logic. Configures how to load the private key to use when creating verity signature partitions with the Verity=signature setting in partition files.


Added in version 256.


.RE


.PP --certificate=


Takes a file system path or a provider specific designation. Configures the PEM encoded X.509 certificate to use when creating verity signature partitions with the Verity=signature setting in partition files.


Added in version 252.


.RE


.PP --certificate-source=


Takes one of file, or provider. In the latter case, it is followed by the name of a provider, separated by colon, that will be passed to OpenSSL's "provider" logic. Configures how to load the X.509 certificate to use when creating verity signature partitions with the Verity=signature setting in partition files.


Added in version 257.


.RE


.PP --join-signature=


Specifies a colon-separated tuple with a hex-encoded top-level Verity hash of a Verity=hash partition as first element, and a PKCS7 signature of the roothash as a path to a DER-encoded signature file, or as an ASCII base64 string encoding of a DER-encoded signature prefixed by base64:. To be used on a pre-existing image that was created with a parameter such as --defer-partitions=root-verity-sig, in order to allow implementing offline signing of the verity signature partition.


This is an alternative to online signing using parameters such as --private-key=, for build systems where the private key for production signing is not available in the same context where content is created.


Added in version 258.


.RE


.PP --tpm2-device=, --tpm2-pcrs=


Configures the TPM2 device and list of PCRs to use for LUKS2 volumes configured with the Encrypt=tpm2 option. These options take the same parameters as the identically named options to systemd-cryptenroll(1) and have the same effect on partitions where TPM2 enrollment is requested.


Added in version 248.


.RE


.PP --tpm2-device-key=PATH, --tpm2-seal-key-handle=HANDLE


Configures a TPM2 SRK key to bind encryption to. See systemd-cryptenroll(1) for details on this option.


Added in version 255.


.RE


.PP --tpm2-public-key=PATH, --tpm2-public-key-pcrs=PCR[+PCR...]


Configures a TPM2 signed PCR policy to bind encryption to. See systemd-cryptenroll(1) for details on these two options.


Added in version 252.


.RE


.PP --tpm2-public-key-policyref=STRING


Configures the policy reference to use together with the signed PCR policy configured via --tpm2-public-key=. See systemd-cryptenroll(1) for details on this option.


Added in version 262.


.RE


.PP --tpm2-pcrlock=PATH


Configures a TPM2 pcrlock policy to bind encryption to. See systemd-cryptenroll(1) for details on this option.


Added in version 255.


.RE


.PP --split=BOOL


Enables generation of split artifacts from partitions configured with SplitName=. If enabled, for each partition with SplitName= set, a separate output file containing just the contents of that partition is generated. The output filename consists of the loopback filename suffixed with the name configured with SplitName=. If the loopback filename ends with .raw, the suffix is inserted before the .raw extension instead.


Note that --split is independent from --dry-run. Even if --dry-run is enabled, split artifacts will still be generated from an existing image if --split is enabled.


Added in version 252.


.RE


.PP --include-partitions=PARTITIONS, --exclude-partitions=PARTITIONS


These options specify which partition types systemd-repart should operate on. If --include-partitions= is used, all partitions that are not specified are excluded. If --exclude-partitions= is used, all partitions that are specified are excluded. Both options take a comma separated list of GPT partition type UUIDs or identifiers (see Type= in repart.d(5)).


Added in version 253.


.RE


.PP --defer-partitions=PARTITIONS


This option specifies for which partition types systemd-repart should defer. All partitions that are deferred using this option are still taken into account when calculating the sizes and offsets of other partitions, but are not actually written to the disk image. The net effect of this option is that if you run systemd-repart again without this option, the missing partitions will be added as if they had not been deferred the first time systemd-repart was executed.


Added in version 253.


.RE


.PP --defer-partitions-empty=yes


This is very similar to --defer-partitions= but automatically selects all partitions for deferral that have Format=empty set and do not configure a custom label, or which set Label=_empty. It may be used in conjunction with --defer-partitions= or --defer-partitions-factory-reset=yes, in which case all matching partitions are deferred.


Added in version 259.


.RE


.PP --defer-partitions-factory-reset=yes


This is very similar to --defer-partitions= but automatically selects all partitions for deferral that have FactoryReset=yes set. It may be used in conjunction with --defer-partitions= or --defer-partitions-empty=yes, in which case all matching partitions are deferred.


Added in version 259.


.RE


.PP --sector-size=BYTES


This option allows configuring the sector size of the image produced by systemd-repart. It takes a value that is a power of 2 between 512 and 4096. This option is useful when building images for disks that use a different sector size as the disk on which the image is produced.


Added in version 253.


.RE


.PP --grain-size=BYTES


This option controls the partition alignment granularity used when placing partitions. It takes a power-of-2 value that is at least the sector size. All partition start offsets will be rounded up to a multiple of this value. Defaults to MAX(4096, sector_size), matching the conventional 4 KiB alignment. Setting this to 1M ensures proper alignment for modern storage devices even after small fixed-size partitions such as a verity signature partition.


Added in version 261.


.RE


.PP --architecture=ARCH


This option allows overriding the architecture used for architecture specific partition types. For example, if set to arm64 a partition type of root-x86-64 referenced in repart.d/ drop-ins will be patched dynamically to refer to root-arm64 instead. Takes one of alpha, arc, arm, arm64, ia64, loongarch64, mips-le, mips64-le, parisc, ppc, ppc64, ppc64-le, riscv32, riscv64, s390, s390x, tilegx, x86 or x86-64.


Added in version 254.


.RE


.PP --offline=BOOL


Instructs systemd-repart to build the image offline. Takes a boolean or auto. Defaults to auto. If enabled, the image is built without using loop devices. This is useful to build images unprivileged or when loop devices are not available. If disabled, the image is always built using loop devices. If auto, systemd-repart will build the image online if possible and fall back to building the image offline if loop devices are not available or cannot be accessed due to missing permissions.


Added in version 254.


.RE


.PP --copy-from=PATH


Instructs systemd-repart to synthesize partition definitions from the partition table in the given image or device. This option can be specified multiple times to synthesize definitions from each of the given images or devices. The generated definitions will copy the partitions into the destination partition table. The copied partitions will have the same or a slightly larger size (partitions may be enlarged to align to the new grain or sector size), metadata and contents but might have a different partition number and might be located at a different offset in the destination partition table. These definitions can be combined with partition definitions read from regular partition definition files. The synthesized definitions take precedence over the definitions read from partition definition files.


Added in version 255.


.RE


.PP --copy-source=PATH, -s PATH


Specifies a source directory all CopyFiles= source paths shall be considered relative to. This is similar to --root=, but exclusively applies to the CopyFiles= setting. If --root= and --copy-source= are used in combination the former applies as usual, except for CopyFiles= where the latter takes precedence.


Added in version 255.


.RE


.PP --make-ddi=TYPE


Takes one of sysext, confext or portable. Generates a Discoverable Disk Image (DDI) for a system extension (sysext, see systemd-sysext(8) for details), configuration extension (confext) or Portable Services[1]. The generated image will consist of a signed Verity erofs file system as root partition. In this mode of operation the partition definitions in /usr/lib/repart.d/*.conf and related directories are not read, and --definitions= is not supported, as appropriate definitions for the selected DDI class will be chosen automatically.


Must be used in conjunction with --copy-source= to specify the file hierarchy to populate the DDI with. The specified directory should contain an etc/ subdirectory if confext is selected. If sysext is selected it should contain either a usr/ or opt/ directory, or both. If portable is used a full OS file hierarchy can be provided.


This option implies --empty=create, --size=auto and --seed=random (the latter two can be overridden).


The private key and certificate for signing the DDI must be specified via the --private-key= and --certificate= switches.


Added in version 255.


.RE


.PP -S, -C, -P


Shortcuts for --make-ddi=sysext, --make-ddi=confext, --make-ddi=portable, respectively.


Added in version 255.


.RE


.PP --append-fstab=


Takes one of no, auto or replace. Controls how the generated fstab(5) file by --generate-fstab= will behave in case that there is a previously existing file.


If no systemd-repart will complain and abort in case that there is a file. This is the default behaviour. If replace the file will be silently replaced with the new generated one.


If auto systemd-repart will search in the pre-existing file the section that belong to the automatically generated content and will replace it with the newer generated content, and keep the user provided section if there is one. The generated section is identified looking for the automatic content surrounded by # Start section ↓ of automatically generated fstab by systemd-repart and # End section ↑ of automatically generated fstab by systemd-repart. The content that is before and after those comments are considered user provided, and kept in the new file.


Added in version 258.


.RE


.PP --generate-fstab=PATH


Specifies a path where to write fstab(5) entries for the mountpoints configured with MountPoint= in the root directory specified with --copy-source= or --root= or in the host's root directory if neither is specified. Disabled by default.


Added in version 256.


.RE


.PP --generate-crypttab=PATH


Specifies a path where to write crypttab entries for the encrypted volumes configured with EncryptedVolume= in the root directory specified with --copy-source= or --root= or in the host's root directory if neither is specified. Disabled by default.


Added in version 256.


.RE


.PP --list-devices


Show a list of candidate block devices this command may operate on. Specifically, this enumerates block devices currently present that support partition tables, and shows their device node paths along with any of their symlinks.


Added in version 257.


.RE


.PP --el-torito=BOOL


Write a minimal ISO9660 header with El Torito boot catalog. That will boot the ESP on EFI firmware.


The ISO9660 filesystem created by it will be empty. The initramfs is expected to create a partitionable loop device on top of the device to change the block size and enable GPT partitions.


The disk requires at least one partition with Type=esp. The first one will be the one referenced in the boot catalog.


Added in version 261.


.RE


.PP --el-torito-system=STRING


When creating an ISO9660 header, this value will be used as the system identifier. This is useful for the media to be matched against osinfo db.


The value is limited to 32 characters.


Added in version 261.


.RE


.PP --el-torito-volume=STRING


When creating an ISO9660 header, this value will be used as volume identifier. This is useful for the media to be matched against osinfo db.


The value is limited to 32 characters.


Added in version 261.


.RE


.PP --el-torito-publisher=STRING


When creating an ISO9660 header, this value will be used as publisher identifier. This is useful for the media to be matched against osinfo db.


The value is limited to 128 characters.


Added in version 261.


.RE


.PP -h, --help


Print a short help text and exit.


.RE
.PP --version


Print a short version string and exit.


.RE
.PP --no-pager


Do not pipe output into a pager.


.RE
.PP --no-legend


Do not print the legend, i.e. column headers and the footer with hints.


.RE
.PP --json=MODE


Shows output formatted as JSON. Expects one of short (for the shortest possible output without any redundant whitespace or line breaks), pretty (for a pretty version of the same, with indentation and line breaks) or off (to turn off JSON output, the default).


.RE


.SH "ENVIRONMENT"


.PP $SOURCE_DATE_EPOCH


Takes a UNIX timestamp in seconds. Clamps access and modification times written into the image. See the reproducible builds specification[2].


Added in version 262.


.RE


.PP Byte-for-byte reproducible images require --offline=yes mode. Populating a file system through the kernel writes metadata that cannot be corrected from userspace afterwards.


.PP Format=vfat images have additional noise: the directory entry of the volume label is written with a wallclock timestamp by mkfs.fat(8) with dosfstools versions up to and including 4.2. A later release or a backport of the upstream fix[3] sets it to $SOURCE_DATE_EPOCH.


.PP Offline and online mode also write vfat short names differently, so images built in both ways never match each other.


.SH "EXIT STATUS"


.PP On success, 0 is returned, and a non-zero failure code otherwise.


.SH "EXAMPLE"


.PP Example 1. Generate a configuration extension image


.PP The following creates a configuration extension DDI (confext) for an /etc/motd update:

mkdir -p tree/etc/extension-release.d
echo "Hello World" >tree/etc/motd
cat >tree/etc/extension-release.d/extension-release.my-motd <<EOF
ID=fedora
VERSION_ID=38
IMAGE_ID=my-motd
IMAGE_VERSION=7
EOF
systemd-repart -C \


  --private-key=verity-private-key.pem \


  --certificate=verity-certificate.pem \


  -s tree/ \


  /var/lib/confexts/my-motd.confext.raw
systemd-confext refresh


.PP The DDI generated that way may be applied to the system with systemd-confext(8).


.PP Example 2. Generate a system extension image and sign it via PKCS11


.PP The following creates a system extension DDI (sysext) for an /usr/foo update and signs it with a hardware token via PKCS11:

mkdir -p tree/usr/lib/extension-release.d
echo "Hello World" >tree/usr/foo
cat >tree/usr/lib/extension-release.d/extension-release.my-foo <<EOF
ID=fedora
VERSION_ID=38
IMAGE_ID=my-foo
IMAGE_VERSION=7
EOF
systemd-repart --make-ddi=sysext \


  --private-key-source=engine:pkcs11 \


  --private-key="pkcs11:model=PKCS%2315%20emulated;manufacturer=piv_II;serial=0123456789abcdef;token=Some%20Cert" \


  --certificate=verity-certificate.pem \


  -s tree/ \


  /var/lib/extensions/my-foo.sysext.raw
systemd-sysext refresh


.PP The DDI generated that way may be applied to the system with systemd-sysext(8).


.PP Example 3. Generate a dm-verity signature offline and append it to a pre-built image


.PP The following creates an image with dm-verity metadata, signs it separately to simulate an offline signing system, and then appends the signature to the image:

mkdir -p repart.d/ /tmp/tree/usr/lib/
cat >/tmp/tree/usr/lib/os-release <<EOF
ID=debian
VERSION_ID=13
EOF
cat >repart.d/10-root.conf <<EOF
[Partition]
Type=root
Format=erofs
SizeMinBytes=100M
SizeMaxBytes=100M
Verity=data
VerityMatchKey=root
EOF
cat >repart.d/11-root-verity.conf <<EOF
[Partition]
Type=root-verity
Label=%o_%w_verity
Verity=hash
VerityMatchKey=root
SizeMinBytes=400M
SizeMaxBytes=400M
EOF
cat >repart.d/12-root-verity-sig.conf <<EOF
[Partition]
Type=root-verity-sig
Label=%o_%w_verity_sig
Verity=signature
VerityMatchKey=root
EOF
systemd-repart --definitions repart.d \


  --defer-partitions=root-verity-sig \


  --copy-source=/tmp/tree/ \


  --empty=create --size=600M \


  --json=short \


  /tmp/img.raw | jq --raw-output0 ".[-1].roothash" > /tmp/img.roothash
openssl smime -sign -in /tmp/img.roothash \


  -inkey verity-private-key.pem \


  -signer verity-certificate.pem \


  -noattr -binary -outform der \


  -out /tmp/img.roothash.p7s
systemd-repart --definitions repart.d \


  --dry-run=no --root=/tmp/tree/ \


  --join-signature="$(cat /tmp/img.roothash):/tmp/img.roothash.p7s" \


  --certificate=verity-certificate.pem \


  /tmp/img.raw


.SH "SEE ALSO"


.PP systemd(1), repart.d(5), machine-id(5), systemd-cryptenroll(1), portablectl(1), systemd-sysext(8)

1.
Portable Services
https://systemd.io/PORTABLE_SERVICES
2.
reproducible builds specification
https://reproducible-builds.org/specs/source-date-epoch/
3.
upstream fix
https://github.com/dosfstools/dosfstools/commit/8da7bc93315c
systemd 262.2

systemd 262.2-r1 · os · ingested 2026-11-06