systemd-repart, systemd-repart.service — Automatically grow and add partitions, and generate disk images (DDIs)
systemd-repart [OPTIONS...] [[BLOCKDEVICE]...]
systemd-repart.service
systemd-repart creates partition tables, and adds or grows partitions, based on the configuration files described in repart.d(5).
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.
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.
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.
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.
The algorithm executed by systemd-repart is roughly as follows:
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.
The partition table on the block device is loaded and parsed, if present.
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.
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. New partitions are always appended to the end of the partition table, taking the first partition table slot whose index is greater than the indexes of all existing partitions. 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.
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.
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.
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.
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.
The new partition table is finally written to disk. The kernel is asked to reread the partition table.
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.
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.
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.
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.
The following options are understood:
--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.
--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.
--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.
--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.
--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.
--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.
--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=.
--image=¶Takes a path to a disk image file or device to mount and use in a similar fashion to
--root=, see above.
--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.
--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.
--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.
--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.
--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, 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.
--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.
--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.
--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.
--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.
--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.
--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.
--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.
--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.
--tpm2-pcrlock=PATH¶Configures a TPM2 pcrlock policy to bind encryption to. See systemd-cryptenroll(1) for details on this option.
--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.
--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)).
--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.
--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.
--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".
--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.
--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 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.
--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.
--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. 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.
-S, -C, -P¶Shortcuts for --make-ddi=sysext,
--make-ddi=confext, --make-ddi=portable,
respectively.
--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.
--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.
--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.
--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.
-h, --help¶--version¶--no-pager¶Do not pipe output into a pager.
--no-legend¶Do not print the legend, i.e. column headers and the footer with hints.
--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).
Example 1. Generate a configuration extension image
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
The DDI generated that way may be applied to the system with systemd-confext(1).
Example 2. Generate a system extension image and sign it via PKCS11
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
The DDI generated that way may be applied to the system with systemd-sysext(8).
Example 3. Generate a dm-verity signature offline and append it to a pre-built image
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