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SYSUPDATE.D(5) sysupdate.d SYSUPDATE.D(5)
sysupdate.d - Transfer Definition Files for Automatic Updates
/etc/sysupdate.d/*.conf
/run/sysupdate.d/*.conf
/usr/local/lib/sysupdate.d/*.conf
/usr/lib/sysupdate.d/*.conf
sysupdate.d/*.conf files describe how specific resources on the
local system shall be updated from a remote source. Each such
file defines one such transfer: typically a remote HTTP/HTTPS
resource as source; and a local file, directory or partition as
target. This may be used as a simple, automatic, atomic update
mechanism for the OS itself, for containers, portable services or
system extension images — but in fact may be used to update any
kind of file from a remote source.
The systemd-sysupdate(8) command reads these files and uses them
to determine which local resources should be updated, and then
executes the update.
Both the remote HTTP/HTTPS source and the local target typically
exist in multiple, concurrent versions, in order to implement
flexible update schemes, e.g. A/B updating (or a superset
thereof, e.g. A/B/C, A/B/C/D, ...).
Each *.conf file defines one transfer, i.e. describes one
resource to update. Typically, multiple of these files (i.e.
multiple of such transfers) are defined together, and are bound
together by a common version identifier in order to update
multiple resources at once on each update operation, for example
to update a kernel, a root file system and a Verity partition in
a single, combined, synchronized operation, so that only a
combined update of all three together constitutes a complete
update.
Each *.conf file contains three sections: [Transfer], [Source]
and [Target].
Disk-image based OS updates typically consist of multiple
different resources that need to be updated together, for example
a secure OS update might consist of a root file system image to
drop into a partition, a matching Verity integrity data partition
image, and a kernel image prepared to boot into the combination
of the two partitions. The first two resources are files that are
downloaded and placed in a disk partition, the latter is a file
that is downloaded and placed in a regular file in the boot file
system (e.g. EFI system partition). Hence, during an update of a
hypothetical operating system "foobarOS" to a hypothetical
version 47 the following operations should take place:
1. A file "https://download.example.com/foobarOS_47.root.xz"
should be downloaded, decompressed and written to a
previously unused partition with GPT partition type UUID
4f68bce3-e8cd-4db1-96e7-fbcaf984b709 for x86-64, as per
Discoverable Partitions Specification[1].
2. Similarly, a file
"https://download.example.com/foobarOS_47.verity.xz" should
be downloaded, decompressed and written to a previously empty
partition with GPT partition type UUID of
2c7357ed-ebd2-46d9-aec1-23d437ec2bf5 (i.e. the partition type
for Verity integrity information for x86-64 root file
systems).
3. Finally, a file
"https://download.example.com/foobarOS_47.efi.xz" (a unified
kernel, as per Boot Loader Specification[2] Type #2) should
be downloaded, decompressed and written to the $BOOT file
system, i.e. to EFI/Linux/foobarOS_47.efi in the ESP or
XBOOTLDR partition.
The version-independent generalization of this would be (using
the special marker "@v" as wildcard for the version identifier):
1. A transfer of a file
"https://download.example.com/[email protected]" → a local,
previously empty GPT partition of type
4f68bce3-e8cd-4db1-96e7-fbcaf984b709, with the label to be
set to "foobarOS_@v".
2. A transfer of a file
"https://download.example.com/[email protected]" → a
local, previously empty GPT partition of type
2c7357ed-ebd2-46d9-aec1-23d437ec2bf5, with the label to be
set to "foobarOS_@v_verity".
3. A transfer of a file
"https://download.example.com/[email protected]" → a local
file $BOOT/EFI/Linux/[email protected].
An update can only complete if the relevant URLs provide their
resources for the same version, i.e. for the same value of "@v".
The above may be translated into three *.conf files in
sysupdate.d/, one for each resource to transfer. The *.conf files
configure the type of download, and what place to write the
download to (i.e. whether to a partition or a file in the file
system). Most importantly these files contain the URL, partition
name and filename patterns shown above that describe how these
resources are called on the source and how they shall be called
on the target.
In order to enumerate available versions and figuring out
candidates to update to, a mechanism is necessary to list
suitable files:
• For partitions: the surrounding GPT partition table contains
a list of defined partitions, including a partition type UUID
and a partition label (in this scheme the partition label
plays a role for the partition similar to the filename for a
regular file).
• For regular files: the directory listing of the directory the
files are contained in provides a list of existing files in a
straightforward way.
• For HTTP/HTTPS sources a simple scheme is used: a manifest
file SHA256SUMS, following the format defined by
sha256sum(1), lists file names and their SHA256 hashes.
Transfers are done in the alphabetical order of the .conf file
names they are defined in. First, the resource data is downloaded
directly into a target file/directory/partition. Once this is
completed for all defined transfers, in a second step the
files/directories/partitions are renamed to their final names as
defined by the target MatchPattern=, again in the order the .conf
transfer file names dictate. This step is not atomic, however it
is guaranteed to be executed strictly in order with suitable disk
synchronization in place. Typically, when updating an OS one of
the transfers defines the entry point when booting. Thus it is
generally a good idea to order the resources via the transfer
configuration file names so that the entry point is written last,
ensuring that any abnormal termination does not leave an entry
point around whose backing is not established yet. In the example
above it would hence make sense to establish the EFI kernel image
last and thus give its transfer configuration file the
alphabetically last name.
See below for an extended, more specific example based on the
above.
Each transfer file defines one source resource to transfer to one
target resource. The following resource types are supported:
1. Resources of type "url-file" encapsulate a file on a web
server, referenced via a HTTP or HTTPS URL. When an update
takes place, the file is downloaded and decompressed and then
written to the target file or partition. This resource type
is only available for sources, not for targets. The list of
available versions of resources of this type is encoded in
SHA256SUMS manifest files, accompanied by SHA256SUMS.gpg
detached signatures.
2. The "url-tar" resource type is similar, but the file must be
a .tar archive. When an update takes place, the file is
decompressed and unpacked into a directory or btrfs
subvolume. This resource type is only available for sources,
not for targets. Just like "url-file", "url-tar" version
enumeration makes use of SHA256SUMS files, authenticated via
SHA256SUMS.gpg.
3. The "regular-file" resource type encapsulates a local regular
file on disk. During updates the file is uncompressed and
written to the target file or partition. This resource type
is available both as source and as target. When updating no
integrity or authentication verification is done for
resources of this type.
4. The "partition" resource type is similar to "regular-file",
and encapsulates a GPT partition on disk. When updating, the
partition must exist already, and have the correct GPT
partition type. A partition whose GPT partition label is set
to "_empty" is considered empty, and a candidate to place a
newly downloaded resource in. The GPT partition label is used
to store version information, once a partition is updated.
This resource type is only available for target resources.
5. The "tar" resource type encapsulates local .tar archive
files. When an update takes place, the files are uncompressed
and unpacked into a target directory or btrfs subvolume.
Behaviour of "tar" and "url-tar" is generally similar, but
the latter downloads from remote sources, and does integrity
and authentication checks while the former does not. The
"tar" resource type is only available for source resources.
6. The "directory" resource type encapsulates local directory
trees. This type is available both for source and target
resources. If an update takes place on a source resource of
this type, a recursive copy of the directory is done.
7. The "subvolume" resource type is identical to "directory",
except when used as the target, in which case the file tree
is placed in a btrfs subvolume instead of a plain directory,
if the backing file system supports it (i.e. is btrfs).
As already indicated, only a subset of source and target resource
type combinations are supported:
Table 1. Resource Types
┌──────────────┬─────────────┬────────┬───────────────┬────────────────┬───────────────┬────────┬──────────────┐
│ Identifier │ Description │ Usable │ When │ When │ When │ Usable │ When │
│ │ │ as │ Used as │ Used as │ Used as │ as │ Used as │
│ │ │ Source │ Source: │ Source: │ Source: │ Target │ Target: │
│ │ │ │ Compatible │ Integrity │ Decompression │ │ Compatible │
│ │ │ │ Targets │ + │ │ │ Sources │
│ │ │ │ │ Authentication │ │ │ │
├──────────────┼─────────────┼────────┼───────────────┼────────────────┼───────────────┼────────┼──────────────┤
│ url-file │ HTTP/HTTPS │ yes │ regular-file, │ yes │ yes │ no │ - │
│ │ files │ │ partition │ │ │ │ │
├──────────────┼─────────────┼────────┼───────────────┼────────────────┼───────────────┼────────┼──────────────┤
│ url-tar │ HTTP/HTTPS │ yes │ directory, │ yes │ yes │ no │ - │
│ │ .tar │ │ subvolume │ │ │ │ │
│ │ archives │ │ │ │ │ │ │
├──────────────┼─────────────┼────────┼───────────────┼────────────────┼───────────────┼────────┼──────────────┤
│ regular-file │ Local files │ yes │ regular-file, │ no │ yes │ yes │ url-file, │
│ │ │ │ partition │ │ │ │ regular-file │
├──────────────┼─────────────┼────────┼───────────────┼────────────────┼───────────────┼────────┼──────────────┤
│ partition │ Local GPT │ no │ - │ - │ - │ yes │ url-file, │
│ │ partitions │ │ │ │ │ │ regular-file │
├──────────────┼─────────────┼────────┼───────────────┼────────────────┼───────────────┼────────┼──────────────┤
│ tar │ Local .tar │ yes │ directory, │ no │ yes │ no │ - │
│ │ archives │ │ subvolume │ │ │ │ │
├──────────────┼─────────────┼────────┼───────────────┼────────────────┼───────────────┼────────┼──────────────┤
│ directory │ Local │ yes │ directory, │ no │ no │ yes │ url-tar, │
│ │ directories │ │ subvolume │ │ │ │ tar, │
│ │ │ │ │ │ │ │ directory, │
│ │ │ │ │ │ │ │ subvolume │
├──────────────┼─────────────┼────────┼───────────────┼────────────────┼───────────────┼────────┼──────────────┤
│ subvolume │ Local btrfs │ yes │ directory, │ no │ no │ yes │ url-tar, │
│ │ subvolumes │ │ subvolume │ │ │ │ tar, │
│ │ │ │ │ │ │ │ directory, │
│ │ │ │ │ │ │ │ subvolume │
└──────────────┴─────────────┴────────┴───────────────┴────────────────┴───────────────┴────────┴──────────────┘
Both the source and target resources typically exist in multiple
versions concurrently. An update operation is done whenever the
newest of the source versions is newer than the newest of the
target versions. To determine the newest version of the resources
a directory listing, partition listing or manifest listing is
used, a subset of qualifying entries selected from that, and the
version identifier extracted from the file names or partition
labels of these selected entries. Subset selection and extraction
of the version identifier (plus potentially other metadata) is
done via match patterns, configured in MatchPattern= in the
[Source] and [Target] sections. These patterns are strings that
describe how files or partitions are named, with named wildcards
for specific fields such as the version identifier. The following
wildcards are defined:
Table 2. Match Pattern Wildcards
┌──────────┬────────────────┬────────────────┬───────────────────┐
│ Wildcard │ Description │ Format │ Notes │
├──────────┼────────────────┼────────────────┼───────────────────┤
│ "@v" │ Version │ Valid version │ Mandatory │
│ │ identifier │ string │ │
├──────────┼────────────────┼────────────────┼───────────────────┤
│ "@u" │ GPT partition │ Valid 128-Bit │ Only relevant │
│ │ UUID │ UUID string │ if target │
│ │ │ │ resource type │
│ │ │ │ chosen as │
│ │ │ │ partition │
├──────────┼────────────────┼────────────────┼───────────────────┤
│ "@f" │ GPT partition │ Formatted │ Only relevant │
│ │ flags │ hexadecimal │ if target │
│ │ │ integer │ resource type │
│ │ │ │ chosen as │
│ │ │ │ partition │
├──────────┼────────────────┼────────────────┼───────────────────┤
│ "@a" │ GPT partition │ Either "0" or │ Controls │
│ │ flag NoAuto │ "1" │ NoAuto bit of │
│ │ │ │ the GPT │
│ │ │ │ partition │
│ │ │ │ flags, as per │
│ │ │ │ Discoverable │
│ │ │ │ Partitions │
│ │ │ │ Specification[1]; │
│ │ │ │ only relevant │
│ │ │ │ if target │
│ │ │ │ resource type │
│ │ │ │ chosen as │
│ │ │ │ partition │
├──────────┼────────────────┼────────────────┼───────────────────┤
│ "@g" │ GPT partition │ Either "0" or │ Controls │
│ │ flag │ "1" │ GrowFileSystem │
│ │ GrowFileSystem │ │ bit of the GPT │
│ │ │ │ partition flags, │
│ │ │ │ as per │
│ │ │ │ Discoverable │
│ │ │ │ Partitions │
│ │ │ │ Specification[1]; │
│ │ │ │ only relevant if │
│ │ │ │ target resource │
│ │ │ │ type chosen as │
│ │ │ │ partition │
├──────────┼────────────────┼────────────────┼───────────────────┤
│ "@r" │ Read-only flag │ Either "0" or │ Controls ReadOnly │
│ │ │ "1" │ bit of the GPT │
│ │ │ │ partition flags, │
│ │ │ │ as per │
│ │ │ │ Discoverable │
│ │ │ │ Partitions │
│ │ │ │ Specification[1] │
│ │ │ │ and other output │
│ │ │ │ read-only flags, │
│ │ │ │ see ReadOnly= │
│ │ │ │ below │
├──────────┼────────────────┼────────────────┼───────────────────┤
│ "@t" │ File │ Formatted │ Only relevant if │
│ │ modification │ decimal │ target resource │
│ │ time │ integer, μs │ type chosen as │
│ │ │ since UNIX │ regular-file │
│ │ │ epoch Jan 1st │ │
│ │ │ 1970 │ │
├──────────┼────────────────┼────────────────┼───────────────────┤
│ "@m" │ File access │ Formatted │ Only relevant if │
│ │ mode │ octal integer, │ target resource │
│ │ │ in UNIX │ type chosen as │
│ │ │ fashion │ regular-file │
├──────────┼────────────────┼────────────────┼───────────────────┤
│ "@s" │ File size │ Formatted │ Useful for │
│ │ after │ decimal │ measuring │
│ │ decompression │ integer │ progress and to │
│ │ │ │ improve partition │
│ │ │ │ allocation logic │
├──────────┼────────────────┼────────────────┼───────────────────┤
│ "@d" │ Tries done │ Formatted │ Useful when │
│ │ │ decimal │ operating with │
│ │ │ integer │ kernel image │
│ │ │ │ files, as per │
│ │ │ │ Automatic Boot │
│ │ │ │ Assessment[3] │
├──────────┼────────────────┼────────────────┼───────────────────┤
│ "@l" │ Tries left │ Formatted │ Useful when │
│ │ │ decimal │ operating with │
│ │ │ integer │ kernel image │
│ │ │ │ files, as per │
│ │ │ │ Automatic Boot │
│ │ │ │ Assessment[3] │
├──────────┼────────────────┼────────────────┼───────────────────┤
│ "@h" │ SHA256 hash of │ 64 hexadecimal │ The SHA256 hash │
│ │ compressed │ characters │ of the compressed │
│ │ file │ │ file; not useful │
│ │ │ │ for url-file or │
│ │ │ │ url-tar where the │
│ │ │ │ SHA256 hash is │
│ │ │ │ already included │
│ │ │ │ in the manifest │
│ │ │ │ file anyway │
└──────────┴────────────────┴────────────────┴───────────────────┘
Of these wildcards only "@v" must be present in a valid pattern,
all other wildcards are optional. Each wildcard may be used at
most once in each pattern. A typical wildcard matching a file
system source image could be "[email protected]",
i.e. any file whose name begins with "foobar_", followed by a
version ID and suffixed by ".raw.xz".
Do not confuse the "@" pattern matching wildcard prefix with the
"%" specifier expansion prefix. The former encapsulate a variable
part of a match pattern string, the latter are simple shortcuts
that are expanded while the drop-in files are parsed. For details
about specifiers, see below.
This section defines general properties of this transfer.
MinVersion=
Specifies the minimum version to require for this transfer to
take place. If the source or target patterns in this transfer
definition match files older than this version they will be
considered obsolete, and never be considered for the update
operation.
Added in version 251.
ProtectVersion=
Takes one or more version strings to mark as "protected".
Protected versions are never removed while making room for
new, updated versions. This is useful to ensure that the
currently booted OS version (or auxiliary resources
associated with it) is not replaced/overwritten during
updates, in order to avoid runtime file system corruptions.
Like many of the settings in these configuration files this
setting supports specifier expansion. It's particularly
useful to set this setting to one of the "%A", "%B" or "%w"
specifiers to automatically refer to the current OS version
of the running system. See below for details on supported
specifiers.
Added in version 251.
Verify=
Takes a boolean, defaults to yes. Controls whether to
cryptographically verify downloaded resources (specifically:
validate the GPG signatures for downloaded SHA256SUMS
manifest files, via their detached signature files
SHA256SUMS.gpg in combination with the system keyring
/usr/lib/systemd/import-pubring.gpg or
/etc/systemd/import-pubring.gpg).
This option is essential to provide integrity guarantees for
downloaded resources and thus should be left enabled, outside
of test environments.
Note that the downloaded payload files are unconditionally
checked against the SHA256 hashes listed in the manifest.
This option only controls whether the signatures of these
manifests are verified.
This option only has an effect if the source resource type is
selected as url-file or url-tar, as integrity and
authentication checking is only available for transfers from
remote sources.
Added in version 251.
This section defines properties of the transfer source.
Type=
Specifies the resource type of the source for the transfer.
Takes one of url-file, url-tar, tar, regular-file, directory
or subvolume. For details about the resource types, see
above. This option is mandatory.
Note that only certain combinations of source and target
resource types are supported, see above.
Added in version 251.
Path=
Specifies where to find source versions of this resource.
If the source type is selected as url-file or url-tar this
must be a HTTP/HTTPS URL. The URL is suffixed with
/SHA256SUMS to acquire the manifest file, with
/SHA256SUMS.gpg to acquire the detached signature file for
it, and with the file names listed in the manifest file in
case an update is executed and a resource shall be
downloaded.
For all other source resource types this must be a local path
in the file system, referring to a local directory to find
the versions of this resource in.
Added in version 251.
MatchPattern=
Specifies one or more file name match patterns that select
the subset of files that are update candidates as source for
this transfer. See above for details on match patterns.
This option is mandatory. Any pattern listed must contain at
least the "@v" wildcard, so that a version identifier may be
extracted from the filename. All other wildcards are
optional.
If the source type is regular-file or directory, the pattern
may contain slash characters. In this case it will match the
file or directory in corresponding subdirectory. For example
"MatchPattern=foo_@v/bar.efi" will match "bar.efi" in
directory "foo_1".
Added in version 251.
This section defines properties of the transfer target.
Type=
Specifies the resource type of the target for the transfer.
Takes one of partition, regular-file, directory or subvolume.
For details about the resource types, see above. This option
is mandatory.
Note that only certain combinations of source and target
resource types are supported, see above.
Added in version 251.
Path=
Specifies a file system path where to look for already
installed versions or place newly downloaded versions of this
configured resource. If Type= is set to partition, expects a
path to a (whole) block device node, or the special string
"auto" in which case the block device which contains the root
file system of the currently booted system is automatically
determined and used. If Type= is set to regular-file,
directory or subvolume, must refer to a path in the local
file system referencing the directory to find or place the
version files or directories under.
Note that this mechanism cannot be used to create or remove
partitions, in case Type= is set to partition. Partitions
must exist already, and a special partition label "_empty" is
used to indicate empty partitions. To automatically generate
suitable partitions on first boot, use a tool such as
systemd-repart(8).
Added in version 251.
PathRelativeTo=
Specifies what partition Path= should be relative to. Takes
one of root, esp, xbootldr, or boot. If unspecified, defaults
to root.
If set to boot, the specified Path= will be resolved relative
to the mount point of the $BOOT partition (i.e. the ESP or
XBOOTLDR), as defined by the Boot Loader Specification[2].
The values esp, xbootldr, and boot are only supported when
Type= is set to regular-file or directory.
Added in version 254.
MatchPattern=
Specifies one or more file name or partition label match
patterns that select the subset of files or partitions that
are update candidates as targets for this transfer. See above
for details on match patterns.
This option is mandatory. Any pattern listed must contain at
least the "@v" wildcard, so that a version identifier may be
extracted from the filename. All other wildcards are
optional.
This pattern is both used for matching existing installed
versions and for determining the name of new versions to
install. If multiple patterns are specified, the first
specified is used for naming newly installed versions.
If the target type is regular-file or directory, the pattern
may contain slash characters. In this case it will match the
file or directory in corresponding subdirectory. For example
"MatchPattern=foo_@v/bar.efi" will match "bar.efi" in
directory "foo_1". Directories in the path will be created
when file is installed. Empty directories will be removed
when file is removed.
Added in version 251.
MatchPartitionType=
When the target Type= is chosen as partition, specifies the
GPT partition type to look for. Only partitions of this type
are considered, all other partitions are ignored. If not
specified, the GPT partition type linux-generic is used.
Accepts either a literal type UUID or a symbolic type
identifier. For a list of supported type identifiers, see the
Type= setting in repart.d(5).
Added in version 251.
PartitionUUID=, PartitionFlags=, PartitionNoAuto=,
PartitionGrowFileSystem=
When the target Type= is picked as partition, selects the GPT
partition UUID and partition flags to use for the updated
partition. Expects a valid UUID string, a hexadecimal
integer, or booleans, respectively. If not set, but the
source match pattern includes wildcards for these fields
(i.e. "@u", "@f", "@a", or "@g"), the values from the
patterns are used. If neither configured with wildcards or
these explicit settings, the values are left untouched. If
both the overall PartitionFlags= flags setting and the
individual flag settings PartitionNoAuto= and
PartitionGrowFileSystem= are used (or the wildcards for
them), then the latter override the former, i.e. the
individual flag bit overrides the overall flags value. See
Discoverable Partitions Specification[1] for details about
these flags.
Note that these settings are not used for matching, they only
have effect on newly written partitions in case a transfer
takes place.
Added in version 251.
ReadOnly=
Controls whether to mark the resulting file, subvolume or
partition read-only. If the target type is partition this
controls the ReadOnly partition flag, as per Discoverable
Partitions Specification[1], similar to the PartitionNoAuto=
and PartitionGrowFileSystem= flags described above. If the
target type is regular-file, the writable bit is removed from
the access mode. If the target type is subvolume, the
subvolume will be marked read-only as a whole. Finally, if
the target Type= is selected as directory, the "immutable"
file attribute is set, see chattr(1) for details.
Added in version 251.
Mode=
The UNIX file access mode to use for newly created files in
case the target resource type is picked as regular-file.
Expects an octal integer, in typical UNIX fashion. If not
set, but the source match pattern includes a wildcard for
this field (i.e. "@t"), the value from the pattern is used.
Note that this setting is not used for matching, it only has
an effect on newly written files when a transfer takes place.
Added in version 251.
TriesDone=, TriesLeft=
These options take positive, decimal integers, and control
the number of attempts done and left for this file. These
settings are useful for managing kernel images, following the
scheme defined in Automatic Boot Assessment[3], and only have
an effect if the target pattern includes the "@d" or "@l"
wildcards.
Added in version 251.
InstancesMax=
Takes a decimal integer equal to or greater than 2. This
configures how many concurrent versions of the resource to
keep. Whenever a new update is initiated it is made sure that
no more than the number of versions specified here minus one
exist in the target. Any excess versions are deleted (in case
the target Type= of regular-file, directory, subvolume is
used) or emptied (in case the target Type= of partition is
used; emptying in this case simply means to set the partition
label to the special string "_empty"; note that no partitions
are actually removed). After an update is completed the
number of concurrent versions of the target resources is
equal to or below the number specified here.
Note that this setting may be set differently for each
transfer. However, it generally is advisable to keep this
setting the same for all transfers, since otherwise
incomplete combinations of files or partitions will be left
installed.
If the target Type= is selected as partition, the number of
concurrent versions to keep is additionally restricted by the
number of partition slots of the right type in the partition
table. I.e. if there are only 2 partition slots for the
selected partition type, setting this value larger than 2 is
without effect, since no more than 2 concurrent versions
could be stored in the image anyway.
Added in version 251.
RemoveTemporary=
Takes a boolean argument. If this option is enabled (which is
the default) before initiating an update, all left-over,
incomplete updates from a previous attempt are removed from
the target directory. This only has an effect if the target
resource Type= is selected as regular-file, directory or
subvolume.
Added in version 251.
CurrentSymlink=
Takes a symlink name as argument. If this option is used, as
the last step of the update a symlink under the specified
name is created/updated pointing to the completed update.
This is useful in to provide a stable name always pointing to
the newest version of the resource. This is only supported if
the target resource Type= is selected as regular-file,
directory or subvolume.
Added in version 251.
Specifiers may be used in the MinVersion=, ProtectVersion=,
Path=, MatchPattern= and CurrentSymlink= settings. The following
expansions are understood:
Table 3. 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 │ The operating system │
│ │ image version │ 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 │ The operating system │
│ │ build ID │ 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 │ The operating system │
│ │ image identifier │ 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 │ The operating system │
│ │ ID │ identifier of the │
│ │ │ running system, as │
│ │ │ read from the ID= │
│ │ │ field of │
│ │ │ /etc/os-release. See │
│ │ │ os-release(5) for more │
│ │ │ information. │
├───────────┼──────────────────┼────────────────────────┤
│ "%v" │ Kernel release │ Identical to uname -r │
│ │ │ output. │
├───────────┼──────────────────┼────────────────────────┤
│ "%w" │ Operating system │ The operating system │
│ │ version ID │ 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 │ The operating system │
│ │ variant ID │ 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 │ This is either /tmp or │
│ │ temporary files │ the path "$TMPDIR", │
│ │ │ "$TEMP" or "$TMP" are │
│ │ │ set to. (Note that the │
│ │ │ directory may be │
│ │ │ specified without a │
│ │ │ trailing slash.) │
├───────────┼──────────────────┼────────────────────────┤
│ "%V" │ Directory for │ This is either │
│ │ larger and │ /var/tmp or the path │
│ │ persistent │ "$TMPDIR", "$TEMP" or │
│ │ temporary files │ "$TMP" are set to. │
│ │ │ (Note that the │
│ │ │ directory may be │
│ │ │ specified without a │
│ │ │ trailing slash.) │
├───────────┼──────────────────┼────────────────────────┤
│ "%%" │ Single percent │ Use "%%" in place of │
│ │ sign │ "%" to specify a │
│ │ │ single percent sign. │
└───────────┴──────────────────┴────────────────────────┘
Do not confuse the "%" specifier expansion prefix with the "@"
pattern matching wildcard prefix. The former are simple shortcuts
that are expanded while the drop-in files are parsed, the latter
encapsulate a variable part of a match pattern string. For
details about pattern matching wildcards, see above.
Example 1. Updates for a Verity Enabled Secure OS
With the following three files we define a root file system
partition, a matching Verity partition, and a unified kernel
image to update as one. This example is an extension of the
example discussed earlier in this man page.
# /usr/lib/sysupdate.d/50-verity.conf
[Transfer]
ProtectVersion=%A
[Source]
Type=url-file
Path=https://download.example.com/
MatchPattern=foobarOS_@[email protected]
[Target]
Type=partition
Path=auto
MatchPattern=foobarOS_@v_verity
MatchPartitionType=root-verity
PartitionFlags=0
ReadOnly=1
The above defines the update mechanism for the Verity partition
of the root file system. Verity partition images are downloaded
from "https://download.example.com/foobarOS_@[email protected]" and
written to a suitable local partition, which is marked read-only.
Under the assumption this update is run from the image itself the
current image version (i.e. the "%A" specifier) is marked as
protected, to ensure it is not corrupted while booted. Note that
the partition UUID for the target partition is encoded in the
source file name. Fixating the partition UUID can be useful to
ensure that "roothash=" on the kernel command line is sufficient
to pinpoint both the Verity and root file system partition, and
also encode the Verity root level hash (under the assumption the
UUID in the file names match their top-level hash, the way
systemd-gpt-auto-generator(8) suggests).
# /usr/lib/sysupdate.d/60-root.conf
[Transfer]
ProtectVersion=%A
[Source]
Type=url-file
Path=https://download.example.com/
MatchPattern=foobarOS_@[email protected]
[Target]
Type=partition
Path=auto
MatchPattern=foobarOS_@v
MatchPartitionType=root
PartitionFlags=0
ReadOnly=1
The above defines a matching transfer definition for the root
file system.
# /usr/lib/sysupdate.d/70-kernel.conf
[Transfer]
ProtectVersion=%A
[Source]
Type=url-file
Path=https://download.example.com/
[email protected]
[Target]
Type=regular-file
Path=/EFI/Linux
PathRelativeTo=boot
MatchPattern=foobarOS_@v+@[email protected] \
foobarOS_@[email protected] \
[email protected]
Mode=0444
TriesLeft=3
TriesDone=0
InstancesMax=2
The above installs a unified kernel image into the $BOOT
partition, as per Boot Loader Specification[2] Type #2. This
defines three possible patterns for the names of the kernel
images, as per Automatic Boot Assessment[3], and ensures when
installing new kernels, they are set up with 3 tries left. No
more than two parallel kernels are kept.
With this setup the web server would serve the following files,
for a hypothetical version 7 of the OS:
• SHA256SUMS – The manifest file, containing available files
and their SHA256 hashes
• SHA256SUMS.gpg – The detached cryptographic signature for the
manifest file
• foobarOS_7_8b8186b1-2b4e-4eb6-ad39-8d4d18d2a8fb.verity.xz –
The Verity image for version 7
• foobarOS_7_f4d1234f-3ebf-47c4-b31d-4052982f9a2f.root.xz – The
root file system image for version 7
• foobarOS_7_efi.xz – The unified kernel image for version 7
For each new OS release a new set of the latter three files would
be added, each time with an updated version. The SHA256SUMS
manifest should then be updated accordingly, listing all files
for all versions that shall be offered for download.
Example 2. Updates for Plain Directory Container Image
[Source]
Type=url-tar
Path=https://download.example.com/
[email protected]
[Target]
Type=subvolume
Path=/var/lib/machines
MatchPattern=myContainer_@v
CurrentSymlink=myContainer
On updates this downloads
"https://download.example.com/[email protected]" and
decompresses/unpacks it to /var/lib/machines/myContainer_@v.
After each update a symlink /var/lib/machines/myContainer is
created/updated always pointing to the most recent update.
systemd(1), systemd-sysupdate(8), systemd-repart(8)
1. Discoverable Partitions Specification
https://uapi-group.org/specifications/specs/discoverable_partitions_specification
2. Boot Loader Specification
https://uapi-group.org/specifications/specs/boot_loader_specification
3. Automatic Boot Assessment
https://systemd.io/AUTOMATIC_BOOT_ASSESSMENT
This page is part of the systemd (systemd system and service
manager) project. Information about the project can be found at
⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have
a bug report for this manual page, see
⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
This page was obtained from the project's upstream Git repository
⟨https://github.com/systemd/systemd.git⟩ on 2024-06-14. (At that
time, the date of the most recent commit that was found in the
repository was 2024-06-13.) If you discover any rendering
problems in this HTML version of the page, or you believe there
is a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
[email protected]
systemd 257~devel SYSUPDATE.D(5)
Pages that refer to this page: systemd.directives(7), systemd.index(7), systemd-sysupdate(8)
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