---
name: "systemd-mountfsd.service"
section: "8"
platform: "linux"
package: "systemd"
version: "262.1-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/systemd-mountfsd.service"
---

# systemd-mountfsd.service(8)

Disk Image File System Mount Service

## 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/\*.crt (and related directories) the disk image is considered trusted. Note that the GPT partition table of the disk image is parsed by the kernel to discover its contents and **systemd-mountfsd** assumes that the GPT parser is robust against malformed input and applies no security policies or checks around it.

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)](/systemd-nsresourced.service/8.md).

The file systems are automatically [**fsck**(8)](/fsck/8.md)'ed before mounting.

## SEE ALSO

[**systemd**(1)](/systemd/1.md), [**systemd-nsresourced.service**(8)](/systemd-nsresourced.service/8.md)

## NOTES

- 1\.

  UAPI.2 Discoverable Partitions Specification

  https://uapi-group.org/specifications/specs/discoverable\_partitions\_specification/

- 2\.

  Varlink

  https://varlink.org/