systemd-mountfsd8
Disk image file system mount service
Part of systemd-mountfsd.service(8).
Usage
systemd-mountfsd.service
Overview
systemd-mountfsd is a system service that dissects disk images, and returns mount file descriptors for the file systems contained therein to clients, via a Varlink IPC API.
The disk images provided must contain a raw file system image or must follow the Discoverable Partitions Specification[1]. Before mounting any file systems authenticity of the disk image is established in one or a combination of the following ways:
1. If the disk image is located in a regular file in one of the directories /var/lib/machines/, /var/lib/portables/, /var/lib/extensions/, /var/lib/confexts/ or their counterparts in the /etc/, /run/, /usr/lib/ it is assumed to be trusted.
2. If the disk image contains a Verity enabled disk image, along with a signature partition with a key in the kernel keyring or in /etc/verity.d/ (and related directories) the disk image is considered trusted.
This service provides one Varlink[2] service: io.systemd.MountFileSystem which accepts a file descriptor to a regular file or block device, and returns a number of file descriptors referring to an fsmount() file descriptor the client may then attach to a path of their choice.
The returned mounts are automatically allowlisted in the per-user-namespace allowlist maintained by systemd-nsresourced.service(8).
The file systems are automatically fsck(8)'ed before mounting.
Notes
- 1.
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Discoverable Partitions Specification
https://uapi-group.org/specifications/specs/discoverable_partitions_specification/
- 2.
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Varlink
https://varlink.org/