SYSTEMD-MOUNTFSD.SERVICE(8)

NAME
systemd-mountfsd.service, systemd-mountfsd - Disk Image File System Mount Service

SYNOPSIS

systemd-mountfsd.service

/usr/lib/systemd/systemd-mountfsd

DESCRIPTION

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 UAPI.2 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.

SEE ALSO

systemd(1), systemd-nsresourced.service(8)

NOTES

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

2.  Varlink
    https://varlink.org/