repart.d — Partition Definition Files for Automatic Boot-Time Repartitioning
repart.d/*.conf files describe basic properties of partitions of block
devices of the local system. They may be used to declare types, names and sizes of partitions that shall
service reads these files and attempts to add new partitions currently missing and enlarge existing
partitions according to these definitions. Operation is generally incremental, i.e. when applied, what
exists already is left intact, and partitions are never shrunk, moved or deleted.
These definition files are useful for implementing operating system images that are prepared and delivered with minimally sized images (for example lacking any state or swap partitions), and which on first boot automatically take possession of any remaining disk space following a few basic rules.
Currently, support for partition definition files is only implemented for GPT partitition tables.
Partition files are generally matched against any partitions already existing on disk in a simple algorithm: the partition files are sorted by their filename (ignoring the directory prefix), and then compared in order against existing partitions matching the same partition type UUID. Specifically, the first existing partition with a specific partition type UUID is assigned the first definition file with the same partition type UUID, and the second existing partition with a specific type UUID the second partition file with the same type UUID, and so on. Any left-over partition files that have no matching existing partition are assumed to define new partition that shall be created. Such partitions are appended to the end of the partition table, in the order defined by their names utilizing the first partition slot greater than the highest slot number currently in use. Any existing partitions that have no matching partition file are left as they are.
Note that these definitions may only be used to create and initialize new partitions or to grow
existing ones. In the latter case it will not grow the contained files systems however; separate
mechanisms, such as
systemd-growfs(8) may be
used to grow the file systems inside of these partitions. Partitions may also be marked for automatic
growing via the
GrowFileSystem= setting, in which case the file system is grown on
first mount by tools that respect this flag. See below for details.
The GPT partition type UUID to match. This may be a GPT partition type UUID such as
4f68bce3-e8cd-4db1-96e7-fbcaf984b709, or one of the following special
Table 1. GPT partition type identifiers
|EFI System Partition|
|Extended Boot Loader Partition|
|Server data (|
|Variable data (|
|Temporary data (|
|Generic Linux file system partition|
|Root file system partition type appropriate for the local architecture (an alias for an architecture root file system partition type listed below, e.g. |
|Verity data for the root file system partition for the local architecture|
|Root file system partition of the secondary architecture of the local architecture (usually the matching 32bit architecture for the local 64bit architecture)|
|Verity data for the root file system partition of the secondary architecture|
|Root file system partition for the x86 (32bit, aka i386) architecture|
|Verity data for the x86 (32bit) root file system partition|
|Root file system partition for the x86_64 (64bit, aka amd64) architecture|
|Verity data for the x86_64 (64bit) root file system partition|
|Root file system partition for the ARM (32bit) architecture|
|Verity data for the ARM (32bit) root file system partition|
|Root file system partition for the ARM (64bit, aka aarch64) architecture|
|Verity data for the ARM (64bit, aka aarch64) root file system partition|
|Root file system partition for the ia64 architecture|
|Verity data for the ia64 root file system partition|
|Root file system partition for the LoongArch 64-bit architecture|
|Verity data for the LoongArch 64-bit root file system partition|
|Root file system partition for the RISC-V 32-bit architecture|
|Verity data for the RISC-V 32-bit root file system partition|
|Root file system partition for the RISC-V 64-bit architecture|
|Verity data for the RISC-V 64-bit root file system partition|
|Verity data for the |
|Verity data for the |
|Verity data for the x86 (32bit) |
|Verity data for the x86_64 (64bit) |
|Verity data for the ARM (32bit) |
|Verity data for the ARM (64bit, aka aarch64) |
|Verity data for the ia64 |
|Verity data for the LoongArch 64-bit |
|Verity data for the RISC-V 32-bit |
|Verity data for the RISC-V 64-bit |
This setting defaults to
Most of the partition type UUIDs listed above are defined in the Discoverable Partitions Specification.
The textual label to assign to the partition if none is assigned yet. Note that this setting is not used for matching. It is also not used when a label is already set for an existing partition. It is thus only used when a partition is newly created or when an existing one had a no label set (that is: an empty label). If not specified a label derived from the partition type is automatically used. Simple specifier expansion is supported, see below.
The UUID to assign to the partition if none is assigned yet. Note that this setting is not used for matching. It is also not used when a UUID is already set for an existing partition. It is thus only used when a partition is newly created or when an existing one had a all-zero UUID set. If not specified a UUID derived from the partition type is automatically used.
A numeric priority to assign to this partition, in the range -2147483648…2147483647, with smaller values indicating higher priority, and higher values indicating smaller priority. This priority is used in case the configured size constraints on the defined partitions do not permit fitting all partitions onto the available disk space. If the partitions do not fit, the highest numeric partition priority of all defined partitions is determined, and all defined partitions with this priority are removed from the list of new partitions to create (which may be multiple, if the same priority is used for multiple partitions). The fitting algorithm is then tried again. If the partitions still do not fit, the now highest numeric partition priority is determined, and the matching partitions removed too, and so on. Partitions of a priority of 0 or lower are never removed. If all partitions with a priority above 0 are removed and the partitions still do not fit on the device the operation fails. Note that this priority has no effect on ordering partitions, for that use the alphabetical order of the filenames of the partition definition files. Defaults to 0.
A numeric weight to assign to this partition in the range 0…1000000. Available disk
space is assigned the defined partitions according to their relative weights (subject to the size
constraints configured with
that a partition with weight 2000 gets double the space as one with weight 1000, and a partition with
weight 333 a third of that. Defaults to 1000.
Weight= setting is used to distribute available disk space in an
"elastic" fashion, based on the disk size and existing partitions. If a partition shall have a fixed
size use both
SizeMaxBytes= with the same
value in order to fixate the size to one value, in which case the weight has no
Weight= but sets a weight for the free space after the
partition (the "padding"). When distributing available space the weights of all partitions and all
defined padding is summed, and then each partition and padding gets the fraction defined by its
weight. Defaults to 0, i.e. by default no padding is applied.
Padding is useful if empty space shall be left for later additions or a safety margin at the end of the device or between partitions.
Specifies minimum and maximum size constraints in bytes. Takes the usual K, M, G, T,
… suffixes (to the base of 1024). If
SizeMinBytes= is specified the partition is
created at or grown to at least the specified size. If
SizeMaxBytes= is specified
the partition is created at or grown to at most the specified size. The precise size is determined
through the weight value configured with
Weight=, see above. When
SizeMinBytes= is set equal to
SizeMaxBytes= the configured
weight has no effect as the partition is explicitly sized to the specified fixed value. Note that
partitions are never created smaller than 4096 bytes, and since partitions are never shrunk the
previous size of the partition (in case the partition already exists) is also enforced as lower bound
for the new size. The values should be specified as multiples of 4096 bytes, and are rounded upwards
(in case of
SizeMinBytes=) or downwards (in case of
SizeMaxBytes=) otherwise. If the backing device does not provide enough space to
fulfill the constraints placing the partition will fail. For partitions that shall be created,
depending on the setting of
Priority= (see above) the partition might be dropped
and the placing algorithm restarted. By default a minimum size constraint of 10M and no maximum size
constraint is set.
Specifies minimum and maximum size constraints in bytes for the free space after the
partition (the "padding"). Semantics are similar to
SizeMaxBytes=, except that unlike partition sizes free space can be shrunk and can
be as small as zero. By default no size constraints on padding are set, so that only
PaddingWeight= determines the size of the padding applied.
Takes a path to a regular file, block device node or directory, or the special value
auto". If specified and the partition is newly created, the data from the specified
path is written to the newly created partition, on the block level. If a directory is specified, the
backing block device of the file system the directory is on is determined, and the data read directly
from that. This option is useful to efficiently replicate existing file systems onto new partitions
on the block level — for example to build a simple OS installer or an OS image builder.
If the special value "
auto" is specified, the source to copy from is
automatically picked up from the running system (or the image specified with
--image= — if used). A partition that matches both the configured partition type (as
Type= described above), and the currently mounted directory
appropriate for that partition type is determined. For example, if the partition type is set to
root" the partition backing the root directory (
/) is used as
source to copy from — if its partition type is set to "
root" as well. If the
declared type is "
usr" the partition backing
/usr/ is used as
source to copy blocks from — if its partition type is set to "
usr" too. The logic is
capable of automatically tracking down the backing partitions for encrypted and Verity-enabled
CopyBlocks=auto" is useful for implementing "self-replicating" systems,
i.e. systems that are their own installer.
The file specified here must have a size that is a multiple of the basic block size 512 and not
be empty. If this option is used, the size allocation algorithm is slightly altered: the partition is
created as least as big as required to fit the data in, i.e. the data size is an additional minimum
size value taken into consideration for the allocation algorithm, similar to and in addition to the
SizeMin= value configured above.
This option has no effect if the partition it is declared for already exists, i.e. existing data is never overwritten. Note that the data is copied in before the partition table is updated, i.e. before the partition actually is persistently created. This provides robustness: it is guaranteed that the partition either doesn't exist or exists fully populated; it is not possible that the partition exists but is not or only partially populated.
This option cannot be combined with
Takes a file system name, such as "
xfs" or "
vfat", or the special value "
specified and the partition is newly created it is formatted with the specified file system (or as
swap device). The file system UUID and label are automatically derived from the partition UUID and
label. If this option is used, the size allocation algorithm is slightly altered: the partition is
created as least as big as required for the minimal file system of the specified type (or 4KiB if the
minimal size is not known).
This option has no effect if the partition already exists.
Similar to the behaviour of
CopyBlocks= the file system is formatted before
the partition is created, ensuring that the partition only ever exists with a fully initialized
This option cannot be combined with
Takes a pair of colon separated absolute file system paths. The first path refers to
a source file or directory on the host, the second path refers to a target in the file system of the
newly created partition and formatted file system. This setting may be used to copy files or
directories from the host into the file system that is created due to the
CopyFiles= is used without
Format=" with a suitable default is implied (currently
ext4", but this may change in the future). This option may be used multiple times
to copy multiple files or directories from host into the newly formatted file system. The colon and
second path may be omitted in which case the source path is also used as the target path (relative to
the root of the newly created file system). If the source path refers to a directory it is copied
This option has no effect if the partition already exists: it cannot be used to copy additional files into an existing partition, it may only be used to populate a file system created anew.
The copy operation is executed before the file system is registered in the partition table, thus ensuring that a file system populated this way only ever exists fully initialized.
This option cannot be combined with
When systemd-repart is invoked with the
--root= command line switches the source paths specified are taken relative to the
specified root directory or disk image root.
Takes one or more absolute paths, separated by whitespace, each declaring a directory
to create within the new file system. Behaviour is similar to
instead of copying in a set of files this just creates the specified directories with the default
mode of 0755 owned by the root user and group, plus all their parent directories (with the same
ownership and access mode). To configure directories with different ownership or access mode, use
CopyFiles= and specify a source tree to copy containing appropriately
owned/configured directories. This option may be used more than once to create multiple
MakeDirectories= are used
together the former is applied first. If a directory listed already exists no operation is executed
(in particular, the ownership/access mode of the directories is left as is).
The primary usecase for this option is to create a minimal set of directories that may be
mounted over by other partitions contained in the same disk image. For example, a disk image where
the root file system is formatted at first boot might want to automatically pre-create
/usr/ in it this way, so that the "
usr" partition may
--image= option to pre-create other, more complex directory hierarchies (as
well as other inodes) with fine-grained control of ownership, access modes and other file
Takes one of "
tpm2" and "
key-file+tpm2" (alternatively, also accepts a boolean
value, which is mapped to "
off" when false, and "
true). Defaults to "
off". If not "
off" the partition will be
formatted with a LUKS2 superblock, before the blocks configured with
are copied in or the file system configured with
Format= is created.
The LUKS2 UUID is automatically derived from the partition UUID in a stable fashion. If
key-file" or "
key-file+tpm2" is used, a key is added to the LUKS2
superblock, configurable with the
--key-file= option to
systemd-repart. If "
tpm2" or "
used, a key is added to the LUKS2 superblock that is enrolled to the local TPM2 chip, as configured
--tpm2-pcrs= options to
When used this slightly alters the size allocation logic as the implicit, minimal size limits
CopyBlocks= are increased by the space necessary
for the LUKS2 superblock (see above).
This option has no effect if the partition already exists.
Takes a boolean argument. If specified the partition is marked for removal during a factory reset operation. This functionality is useful to implement schemes where images can be reset into their original state by removing partitions and creating them anew. Defaults to off.
Configures the 64bit GPT partition flags field to set for the partition when creating
it. This option has no effect if the partition already exists. If not specified the flags values is
set to all zeroes, except for the three bits that can also be configured via
below for details on the defaults for these three flags. Specify the flags value in hexadecimal (by
prefixing it with "
0x"), binary (prefix "
0b") or decimal (no
Configures the No-Auto, Read-Only and Grow-File-System partition flags (bit 63, 60
and 59) of the partition table entry, as defined by the Discoverable Partitions Specification. Only
available for partition types supported by the specification. This option is a friendly way to set
bits 63, 60 and 59 of the partition flags value without setting any of the other bits, and may be set
Flags= too, see above.
Flags= is used in conjunction with one or more of
GrowFileSystem= the latter
control the value of the relevant flags, i.e. the high-level settings
the relevant bits of the low-level setting
Note that the three flags affect only automatic partition mounting, as implemented by
--image= option of various commands (such as
has no effect on explicit mounts, such as those done via mount(8) or
If both bit 50 and 59 are set for a partition (i.e. the partition is marked both read-only and marked for file system growing) the latter is typically without effect: the read-only flag takes precedence in most tools reading these flags, and since growing the file system involves writing to the partition it is consequently ignored.
NoAuto= defaults to off.
ReadOnly= defaults to on for
Verity partition types, and off for all others.
GrowFileSystem= defaults to on for
all partition types that support it, except if the partition is marked read-only (and thus
effectively, defaults to off for Verity partitions).
Specifiers may be used in the
MakeDirectories= settings. The following expansions are
Table 2. Specifiers available
|"||Architecture||A short string identifying the architecture of the local system. A string such as |
|"||Operating system image version||The operating system image version identifier of the running system, as read from the |
|"||Boot ID||The boot ID of the running system, formatted as string. See random(4) for more information.|
|"||Operating system build ID||The operating system build identifier of the running system, as read from the |
|"||Host name||The hostname of the running system.|
|"||Short host name||The hostname of the running system, truncated at the first dot to remove any domain component.|
|"||Machine ID||The machine ID of the running system, formatted as string. See machine-id(5) for more information.|
|"||Operating system image identifier||The operating system image identifier of the running system, as read from the |
|"||Operating system ID||The operating system identifier of the running system, as read from the |
|"||Kernel release||Identical to uname -r output.|
|"||Operating system version ID||The operating system version identifier of the running system, as read from the |
|"||Operating system variant ID||The operating system variant identifier of the running system, as read from the |
|"||Directory for temporary files||This is either |
|"||Directory for larger and persistent temporary files||This is either |
|"||Single percent sign||Use "|
Example 1. Grow the root partition to the full disk size at first boot
With the following file the root partition is automatically grown to the full disk if possible during boot.
# /usr/lib/repart.d/50-root.conf [Partition] Type=root
Example 2. Create a swap and home partition automatically on boot, if missing
The home partition gets all available disk space while the swap partition gets 1G at most and 64M at least. We set a priority > 0 on the swap partition to ensure the swap partition is not used if not enough space is available. For every three bytes assigned to the home partition the swap partition gets assigned one.
# /usr/lib/repart.d/60-home.conf [Partition] Type=home
# /usr/lib/repart.d/70-swap.conf [Partition] Type=swap SizeMinBytes=64M SizeMaxBytes=1G Priority=1 Weight=333
Example 3. Create B partitions in an A/B Verity setup, if missing
Let's say the vendor intends to update OS images in an A/B setup, i.e. with two root partitions (and two matching Verity partitions) that shall be used alternatingly during upgrades. To minimize image sizes the original image is shipped only with one root and one Verity partition (the "A" set), and the second root and Verity partitions (the "B" set) shall be created on first boot on the free space on the medium.
# /usr/lib/repart.d/50-root.conf [Partition] Type=root SizeMinBytes=512M SizeMaxBytes=512M
# /usr/lib/repart.d/60-root-verity.conf [Partition] Type=root-verity SizeMinBytes=64M SizeMaxBytes=64M
The definitions above cover the "A" set of root partition (of a fixed 512M size) and Verity partition for the root partition (of a fixed 64M size). Let's use symlinks to create the "B" set of partitions, since after all they shall have the same properties and sizes as the "A" set.
# ln -s 50-root.conf /usr/lib/repart.d/70-root-b.conf # ln -s 60-root-verity.conf /usr/lib/repart.d/80-root-verity-b.conf