SYSTEMD.IMAGE-FILTER(7)

NAME
systemd.image-filter - Disk Image Dissection Filter

DESCRIPTION

In systemd, whenever a disk image (DDI) implementing the UAPI.2 Discoverable Partitions Specification[1] is activated, a filter may be specified controlling which partitions to consider for mounting. Such a disk image dissection filter is a string that contains per-partition-type patterns, separated by colons (":"). The individual rules consist of a partition identifier, an equal sign ("="), and a shell globbing pattern applied to the GPT label string of the partition. See glob(7) for details on shell globbing.

The partition identifiers currently defined are: root, usr, home, srv, esp, xbootldr, swap, root-verity, root-verity-sig, usr-verity, usr-verity-sig, tmp, var. These identifiers match the relevant partition types in the Discoverable Partitions Specification, but are agnostic to CPU architectures.

USE

Various systemd components that support operating with disk images support a --image-filter= command line option to specify the image filter to use. If no filter is specified all partitions in partition table are considered and no per-label filtering is applied (except that partitions with the "_empty" label are always ignored).

For the host root file system image itself systemd-gpt-auto-generator(8) is responsible for processing the GPT partition table and making use of the included discoverable partitions. It accepts an image filter via the kernel command line option systemd.image_filter=.

EXAMPLES

The following image filter string dictates that for the root file system partition only partitions shall be considered whose label begins with "ParticleOS-". For the /usr/ partition the precise label "ParticleOS_47110815" is required.

    root=ParticleOS-*:usr=ParticleOS_47110815

SEE ALSO

systemd(1), systemd-dissect(1), systemd-gpt-auto-generator(8), systemd.image-policy(7)

NOTES

1.  UAPI.2 Discoverable Partitions Specification
    https://uapi-group.org/specifications/specs/discoverable_partitions_specification