table of contents
REPART.D(5) | repart.d | REPART.D(5) |
NAME¶
repart.d - Partition Definition Files for Automatic Boot-Time Repartitioning
SYNOPSIS¶
DESCRIPTION¶
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 exist. The systemd-repart(8) 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 partition 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.
[PARTITION] SECTION OPTIONS¶
Type=
The supported identifiers are:
Table 1. GPT partition type identifiers
Identifier | Explanation |
esp | EFI System Partition |
xbootldr | Extended Boot Loader Partition |
swap | Swap partition |
home | Home (/home/) partition |
srv | Server data (/srv/) partition |
var | Variable data (/var/) partition |
tmp | Temporary data (/var/tmp/) partition |
linux-generic | Generic Linux file system partition |
root | Root file system partition type appropriate for the local architecture (an alias for an architecture root file system partition type listed below, e.g. root-x86-64) |
root-verity | Verity data for the root file system partition for the local architecture |
root-verity-sig | Verity signature data for the root file system partition for the local architecture |
root-secondary | Root file system partition of the secondary architecture of the local architecture (usually the matching 32-bit architecture for the local 64-bit architecture) |
root-secondary-verity | Verity data for the root file system partition of the secondary architecture |
root-secondary-verity-sig | Verity signature data for the root file system partition of the secondary architecture |
root-{arch} | Root file system partition of the given architecture (such as root-x86-64 or root-riscv64) |
root-{arch}-verity | Verity data for the root file system partition of the given architecture |
root-{arch}-verity-sig | Verity signature data for the root file system partition of the given architecture |
usr | /usr/ file system partition type appropriate for the local architecture (an alias for an architecture /usr/ file system partition type listed below, e.g. usr-x86-64) |
usr-verity | Verity data for the /usr/ file system partition for the local architecture |
usr-verity-sig | Verity signature data for the /usr/ file system partition for the local architecture |
usr-secondary | /usr/ file system partition of the secondary architecture of the local architecture (usually the matching 32-bit architecture for the local 64-bit architecture) |
usr-secondary-verity | Verity data for the /usr/ file system partition of the secondary architecture |
usr-secondary-verity-sig | Verity signature data for the /usr/ file system partition of the secondary architecture |
usr-{arch} | /usr/ file system partition of the given architecture |
usr-{arch}-verity | Verity data for the /usr/ file system partition of the given architecture |
usr-{arch}-verity-sig | Verity signature data for the /usr/ file system partition of the given architecture |
Architecture specific partition types can use one of these
architecture identifiers:
alpha, arc, arm (32-bit), arm64 (64-bit, aka
aarch64), ia64, loongarch64, mips-le, mips64-le,
parisc, ppc, ppc64, ppc64-le, riscv32,
riscv64, s390, s390x, tilegx, x86
(32-bit, aka i386) and x86-64 (64-bit, aka amd64).
Most of the partition type UUIDs listed above are defined in the Discoverable Partitions Specification[1].
Added in version 245.
Label=
Added in version 245.
UUID=
Added in version 246.
Priority=
Added in version 245.
Weight=
The 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 SizeMinBytes= and SizeMaxBytes= with the same value in order to fixate the size to one value, in which case the weight has no effect.
Added in version 245.
PaddingWeight=
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.
Added in version 245.
SizeMinBytes=, SizeMaxBytes=
Added in version 245.
PaddingMinBytes=, PaddingMaxBytes=
Added in version 245.
CopyBlocks=
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 declared with 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 volumes. "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 at 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 Format= or CopyFiles=.
Added in version 246.
Format=
This option has no effect if the partition already exists.
Similarly 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 file system.
This option cannot be combined with CopyBlocks=.
Added in version 247.
CopyFiles=
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.
Note that CopyFiles= will skip copying files that aren't supported by the target filesystem (e.g symlinks, fifos, sockets and devices on vfat). When an unsupported file type is encountered, systemd-repart will skip copying this file and write a log message about it.
Note that systemd-repart does not change the UIDs/GIDs of any copied files and directories. When running systemd-repart as an unprivileged user to build an image of files and directories owned by the same user, you can run systemd-repart in a user namespace with the current user mapped to the root user to make sure the files and directories in the image are owned by the root user.
Note that when populating XFS filesystems with systemd-repart and loop devices are not available, populating XFS filesystems with files containing spaces, tabs or newlines might fail on old versions of mkfs.xfs(8) due to limitations of its protofile format.
Note that when populating XFS filesystems with systemd-repart and loop devices are not available, extended attributes will not be copied into generated XFS filesystems due to limitations mkfs.xfs(8)'s protofile format.
This option cannot be combined with CopyBlocks=.
When systemd-repart(8) is invoked with the --copy-source= command line switch the file paths are taken relative to the specified directory. If --copy-source= is not used, but the --image= or --root= switches are used, the source paths are taken relative to the specified root directory or disk image root.
Added in version 247.
ExcludeFiles=, ExcludeFilesTarget=
If the path is a directory and ends with "/", only the directory's contents are excluded but not the directory itself. If the path is a directory and does not end with "/", both the directory and its contents are excluded.
ExcludeFilesTarget= is like ExcludeFiles= except that instead of excluding the path on the host from being copied into the partition, it exclude any files and directories from being copied into the given path in the partition.
When systemd-repart(8) is invoked with the --image= or --root= command line switches the paths specified are taken relative to the specified root directory or disk image root.
Added in version 254.
MakeDirectories=
The primary use case 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 over-mount it.
Consider using systemd-tmpfiles(8) with its --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 attributes.
Added in version 249.
MakeSymlinks=
The primary use case for this option is to create symlinks that need to exist before systemd-tmpfiles(8) is executed. For example, when using systemd-confext(8), this setting can be used to create symlinks in /var/lib/extensions.mutable to redirect writes to mutable confexts to a custom location.
Consider using systemd-tmpfiles(8) with its --image= option to pre-create other symlinks (as well as other inodes) with fine-grained control of ownership, access modes and other file attributes.
Added in version 257.
Subvolumes=
Table 2. Subvolume Flags
Flag | Purpose |
"ro" | Make this subvolume read-only. |
Note that this option does not create the directories themselves,
that can be configured with
MakeDirectories= and CopyFiles=.
Note that this option only takes effect if the target filesystem supports subvolumes, such as "btrfs".
Note that this option is only supported in combination with --offline=yes since btrfs-progs 6.11 or newer.
Added in version 255.
DefaultSubvolume=
Note that this option only takes effect if the target filesystem supports subvolumes, such as btrfs(8).
Note that this option is only supported in combination with --offline=yes since btrfs-progs 6.11 or newer.
Added in version 256.
Encrypt=
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 "key-file+tpm2" is used, a key is added to the LUKS2 superblock that is enrolled to the local TPM2 chip, as configured with the --tpm2-device= and --tpm2-pcrs= options to systemd-repart.
When used this slightly alters the size allocation logic as the implicit, minimal size limits of Format= and CopyBlocks= are increased by the space necessary for the LUKS2 superblock (see above).
This option has no effect if the partition already exists.
Added in version 247.
Verity=
A matching verity partition is a partition with the same verity match key (as configured with VerityMatchKey=).
If not explicitly configured, the data partition's UUID will be set to the first 128 bits of the verity root hash. Similarly, if not configured, the hash partition's UUID will be set to the final 128 bits of the verity root hash. The verity root hash itself will be included in the output of systemd-repart.
This option has no effect if the partition already exists.
Usage of this option in combination with Encrypt= is not supported.
For each unique VerityMatchKey= value, a single verity data partition ("Verity=data") and a single verity hash partition ("Verity=hash") must be defined.
Added in version 252.
VerityMatchKey=
Added in version 252.
VerityDataBlockSizeBytes=
Added in version 255.
VerityHashBlockSizeBytes=
Added in version 255.
FactoryReset=
Added in version 245.
Flags=
Added in version 249.
NoAuto=, ReadOnly=, GrowFileSystem=
If Flags= is used in conjunction with one or more of NoAuto=/ReadOnly=/GrowFileSystem= the latter control the value of the relevant flags, i.e. the high-level settings NoAuto=/ReadOnly=/GrowFileSystem= override the relevant bits of the low-level setting Flags=.
Note that the three flags affect only automatic partition mounting, as implemented by systemd-gpt-auto-generator(8) or the --image= option of various commands (such as systemd-nspawn(1)). It has no effect on explicit mounts, such as those done via mount(8) or fstab(5).
If both bit 60 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).
Added in version 249.
SplitName=
Added in version 252.
Minimize=
Added in version 253.
MountPoint=
Note that this setting is only taken into account when --generate-fstab= is specified on the systemd-repart command line.
Added in version 256.
EncryptedVolume=
Note that this setting is only taken into account when --generate-crypttab= is specified on the systemd-repart command line.
Added in version 256.
Compression=
Note that this setting is only taken into account when the filesystem configured with Format= supports compression ( btrfs(8), squashfs, erofs). Here's an incomplete list of compression algorithms supported by the filesystems known to systemd-repart:
Table 3. File System Compression Algorithms
File System | Compression Algorithms | Documentation |
squashfs | gzip, lzo, lz4, xz, zstd, lzma | mksquashfs(1) |
erofs | lz4, lz4hc, lzma, deflate, libdeflate, zstd | mkfs.erofs(1) |
Added in version 257.
CompressionLevel=
Note that this setting is only taken into account when the filesystem configured with Format= supports compression and the Compression= setting is configured explicitly.
Added in version 257.
SupplementFor=
The following fields are merged into the target definition in the specified ways: Weight= and PaddingWeight= are simply overwritten; SizeMinBytes= and PaddingMinBytes= use the larger of the two values; SizeMaxBytes= and PaddingMaxBytes= use the smaller value; and CopyFiles=, ExcludeFiles=, ExcludeFilesTarget=, MakeDirectories=, and Subvolumes= are concatenated.
Usage of this option in combination with CopyBlocks=, Encrypt=, or Verity= is not supported. The target definition cannot set these settings either. A definition cannot simultaneously be a supplement and act as a target for some other supplement definition. A target cannot have more than one supplement partition associated with it.
For example, distributions can use this to implement $BOOT as defined in the Boot Loader Specification[2]. Distributions may prefer to use the ESP as $BOOT whenever possible, but to adhere to the spec XBOOTLDR must sometimes be used instead. So, they should create two definitions: the first defining an ESP big enough to hold just the bootloader, and a second for the XBOOTLDR that's sufficiently large to hold kernels and configured as a supplement for the ESP. Whenever possible, systemd-repart will try to merge the two definitions to create one large ESP, but if that's not allowable due to the existing conditions on disk a small ESP and a large XBOOTLDR will be created instead.
As another example, distributions can also use this to seamlessly share a single /home partition in a multi-boot scenario, while preferring to keep /home on the root partition by default. Having a /home partition separated from the root partition entails some extra complexity: someone has to decide how to split the space between the two partitions. On the other hand, it allows a user to share their home area between multiple installed OSs (i.e. via systemd-homed.service (8)). Distributions should create two definitions: the first for a root partition that takes up some relatively small percentage of the disk, and the second as a supplement for the first to create a /home partition that takes up all the remaining free space. On first boot, if systemd-repart finds an existing /home partition on disk, it'll un-merge the definitions and create just a small root partition. Otherwise, the definitions will be merged and a single large root partition will be created.
Added in version 257.
SPECIFIERS¶
Specifiers may be used in the Label=, CopyBlocks=, CopyFiles=, MakeDirectories=, SplitName= settings. The following expansions are understood:
Table 4. Specifiers available
Specifier | Meaning | Details |
"%a" | Architecture | A short string identifying the architecture of the local system. A string such as x86, x86-64 or arm64. See the architectures defined for ConditionArchitecture= in systemd.unit(5) for a full list. |
"%A" | Operating system image version | The operating system image version identifier of the running system, as read from the IMAGE_VERSION= field of /etc/os-release. If not set, resolves to an empty string. See os-release(5) for more information. |
"%b" | Boot ID | The boot ID of the running system, formatted as string. See random(4) for more information. |
"%B" | Operating system build ID | The operating system build identifier of the running system, as read from the BUILD_ID= field of /etc/os-release. If not set, resolves to an empty string. See os-release(5) for more information. |
"%H" | Host name | The hostname of the running system. |
"%l" | Short host name | The hostname of the running system, truncated at the first dot to remove any domain component. |
"%m" | Machine ID | The machine ID of the running system, formatted as string. See machine-id(5) for more information. |
"%M" | Operating system image identifier | The operating system image identifier of the running system, as read from the IMAGE_ID= field of /etc/os-release. If not set, resolves to an empty string. See os-release(5) for more information. |
"%o" | Operating system ID | The operating system identifier of the running system, as read from the ID= field of /etc/os-release. See os-release(5) for more information. |
"%q" | Pretty host name | The pretty hostname of the running system, as read from the PRETTY_HOSTNAME= field of /etc/machine-info. If not set, resolves to the short hostname. See machine-info(5) for more information. |
"%v" | Kernel release | Identical to uname -r output. |
"%w" | Operating system version ID | The operating system version identifier of the running system, as read from the VERSION_ID= field of /etc/os-release. If not set, resolves to an empty string. See os-release(5) for more information. |
"%W" | Operating system variant ID | The operating system variant identifier of the running system, as read from the VARIANT_ID= field of /etc/os-release. If not set, resolves to an empty string. See os-release(5) for more information. |
"%T" | Directory for temporary files | This is either /tmp or the path "$TMPDIR", "$TEMP" or "$TMP" are set to. (Note that the directory may be specified without a trailing slash.) |
"%V" | Directory for larger and persistent temporary files | This is either /var/tmp or the path "$TMPDIR", "$TEMP" or "$TMP" are set to. (Note that the directory may be specified without a trailing slash.) |
"%%" | Single percent sign | Use "%%" in place of "%" to specify a single percent sign. |
Additionally, for the
SplitName= setting, the following specifiers are also understood:
Table 5. Specifiers available
Specifier | Meaning | Details |
"%T" | Partition Type UUID | The partition type UUID, as configured with Type= |
"%t" | Partition Type Identifier | The partition type identifier corresponding to the partition type UUID |
"%U" | Partition UUID | The partition UUID, as configured with UUID= |
"%n" | Partition Number | The partition number assigned to the partition |
ENVIRONMENT¶
Extra filesystem formatting options can be provided using
filesystem-specific environment variables:
$SYSTEMD_REPART_MKFS_OPTIONS_BTRFS,
$SYSTEMD_REPART_MKFS_OPTIONS_XFS,
$SYSTEMD_REPART_MKFS_OPTIONS_VFAT,
$SYSTEMD_REPART_MKFS_OPTIONS_EROFS, and
$SYSTEMD_REPART_MKFS_OPTIONS_SQUASHFS. Each variable accepts valid
mkfs.filesystem command-line arguments. The content of
those variables is passed as-is to the command, without any
verification.
EXAMPLES¶
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
Example 4. Create a data partition and corresponding verity partitions from a OS tree
Assuming we have an OS tree at /var/tmp/os-tree that we want to package in a root partition together with matching verity partitions, we can do so as follows:
# 50-root.conf [Partition] Type=root CopyFiles=/var/tmp/os-tree Verity=data VerityMatchKey=root Minimize=guess
# 60-root-verity.conf [Partition] Type=root-verity Verity=hash VerityMatchKey=root # Explicitly set the hash and data block size to 4K VerityDataBlockSizeBytes=4096 VerityHashBlockSizeBytes=4096 Minimize=best
# 70-root-verity-sig.conf [Partition] Type=root-verity-sig Verity=signature VerityMatchKey=root
SEE ALSO¶
systemd(1), systemd-repart(8), sfdisk(8), systemd-cryptenroll(1)
NOTES¶
- 1.
- Discoverable Partitions Specification
- 2.
- Boot Loader Specification
systemd 257 |