UDISKS(8) System Administration UDISKS(8)
NAME
udisks - Disk Manager
DESCRIPTION
udisks provides interfaces to enumerate and perform operations on disks
and storage devices. Any application (including unprivileged ones) can
access the udisksd(8) daemon via the name org.freedesktop.UDisks2 on
the system message bus[1]. In addition to the D-Bus API, a library,
libudisks2 is also provided. This library can be used from C/C++ and
any high-level language with GObjectIntrospection[2] support such as
Javascript and Python. udisks is only indirectly involved in what
devices and objects are shown in the user interface.
ACCESS CONTROL
By default, logged-in users in active log-in sessions are permitted to
perform operations (for example, mounting, unlocking or modifying) on
devices attached to the seat their session is on. Access-control is
fine-grained and based on polkit(8), see the “Authorization Checks”
chapter in the udisks documentation for more information. Note that the
x-udisks-auth option can be used in the /etc/fstab and /etc/crypttab
files to specify that additional authorization is required to mount
resp. unlock the device (typically requiring the user to authenticate
as an administrator).
DRIVE CONFIGURATION
At start-up and when a drive is connected, udisksd(8) will apply
configuration stored in the file /etc/udisks2/IDENTIFIER.conf where
IDENTIFIER is the value of the Drive:Id property for the drive. If the
file changes on disk its new contents will also be applied to the
drive. Typically, users or administrators will never need to edit drive
configuration files as they are effectively managed through graphical
applications such as gnome-disks(1). Manually editing configuration
files is however supported — the file format is a simple .ini-like
format (see the Desktop Entry Specification[3] for the exact syntax).
New groups and keys may be added in the future.
ATA group
The ATA group is for settings that apply to drives using the ATA
command-set. The following keys are supported:
StandbyTimeout
The standby timeout. A value of zero means "timeouts are disabled":
the device will not automatically enter standby mode. Values from 1
to 240 specify multiples of 5 seconds, yielding timeouts from 5
seconds to 20 minutes. Values from 241 to 251 specify from 1 to 11
units of 30 minutes, yielding timeouts from 30 minutes to 5.5
hours. A value of 252 signifies a timeout of 21 minutes. A value of
253 sets a vendor-defined timeout period between 8 and 12 hours,
and the value 254 is reserved. 255 is interpreted as 21 minutes
plus 15 seconds. Note that some older drives may have very
different interpretations of these values. This is similar to the
-S option in hdparm(8).
APMLevel
The Advanced Power Management level. A low value means aggressive
power management and a high value means better performance.
Possible settings range from values 1 through 127 (which permit
spin-down), and values 128 through 254 (which do not permit
spin-down). The highest degree of power management is attained with
a setting of 1, and the highest I/O performance with a setting of
254. A value of 255 can be used to disable Advanced Power
Management altogether on the drive (not all drives support
disabling it, but most do). This is similar to the -B option in
hdparm(8).
AAMLevel
The Automatic Acoustic Management level. Most modern harddisk
drives have the ability to speed down the head movements to reduce
their noise output. The possible values are between 0 and 254. 128
is the most quiet (and therefore slowest) setting and 254 the
fastest (and loudest). Some drives have only two levels (quiet /
fast), while others may have different levels between 128 and 254.
At the moment, most drives only support 3 options, off, quiet, and
fast. These have been assigned the values 0, 128, and 254 at
present, respectively, but integer space has been incorporated for
future expansion, should this change. This is similar to the -M
option in hdparm(8).
WriteCacheEnabled
A boolean specifying whether to enable or disable the Write Cache.
Valid values for this key are “true” and “false”. This is similar
to the -W option in hdparm(8). This key was added in 2.1.
ReadLookaheadEnabled
A boolean specifying whether to enable or disable the Read
Look-ahead. Valid values for this key are “true” and “false”. This
is similar to the -A option in hdparm(8). This key was added in
2.6.0.
DEVICE INFORMATION
udisks relies on recent versions of udev(7) and the Linux kernel.
Influential device properties in the udev database include:
UDISKS_SYSTEM
If set, this overrides the value of the HintSystem property.
UDISKS_IGNORE
If set, this overrides the value of the HintIgnore property.
UDISKS_AUTO
If set, this overrides the value of the HintAuto property.
UDISKS_CAN_POWER_OFF
If set, this overrides the value of the CanPowerOff property.
UDISKS_NAME
The name to use for the device when presenting it in an user
interface. This corresponds to the HintName property.
UDISKS_ICON_NAME
The icon to use for the device when presenting it in an user
interface. If set, the name must adhere to the freedesktop.org icon
theme specification[4]. This corresponds to the HintIconName
property.
UDISKS_SYMBOLIC_ICON_NAME
The icon to use for the device when presenting it in an user
interface using a symbolic icon. If set, the name must adhere to
the freedesktop.org icon theme specification[4]. This corresponds
to the HintSymbolicIconName property.
UDISKS_FILESYSTEM_SHARED
If set to 1, the filesystem on the device will be mounted in a
shared directory (e.g. /media/VolumeName) instead of a private
directory (e.g. /run/media/$USER/VolumeName) when the
Filesystem.Mount() method is handled.
ID_SEAT
The physical seat the device is attached to. If unset or set to the
empty string, “seat0” (the first seat) is assumed.
API STABILITY
udisks guarantees a stable D-Bus API within the same major version and
this guarantee also extends to the client-side library libudisks2.
Additionally, several major versions of udisks can be installed and
operate at the same time although interoperability may be limited - for
example, a device mounted using the udisks N.x API may require
additional authorization if attempting to unmount it through the the
(N-1).x API.
The udisks developers do not anticipate breaking API but does reserve
the right to do so and if it happens, promises to bump the major
version and ensure the new major version of udisks is
parallel-installable with any older major version. However, note that
programs, man pages and other artifacts may change name (for example,
adopt a “2” suffix) to make room for the next major version. Therefore,
applications can not rely on tools like e.g. udisksctl(1) to be
available. Additionally, there is no guarantee that the options,
command-line switches etc. of command-line tools or similar will remain
stable.
Instead, applications should only use the D-Bus API, the libudisks2
library or tools such as dbus-send(1) or gdbus(1) to interact with
udisksd(8).
AUDIENCE
The intended audience of udisks include operating system developers
working on the higher-level parts of the operating system, for example
the desktop shell (such as GNOME[5]) and disk management applications
(e.g. GNOME's Disks[6] application). Software on this level typically
depend on a specific (major) version of udisks and may even have
support for previous versions of udisks or alternative interfaces
performing the same role as udisks.
While udisks indeed provides a stable API and a clear upgrade path, it
may not be an appropriate dependency for third party applications. For
example, if the operating system switches to udisks version N.x and an
application is still using the udisks (N-1).x API, the application will
not work unless udisks (N-1).x is installed. While this situation is
still workable (since both udisks N.x and udisks (N-1).x can be
installed) it may not be desirable to ask the user to install the old
version - in fact, the operating system vendor may not even provide a
packaged version of the old version. Hence, if an application does not
want to tie itself to a specific version of the operating system, it
should not use udisks.
Viable alternatives to udisks are APIs that are guaranteed to be around
for longer time-frames, including:
• Low-level APIs and commands such as e.g. sysfs[7], libudev[8],
/proc/self/mountinfo[9] and util-linux[10].
• High-level APIs such as GVolumeMonitor[11].
In particular, for desktop applications it is a much better idea to use
something like GVolumeMonitor since it will make the application show
the same devices as the desktop shell (e.g. file manager, file chooser
and so on) is showing.
AUTHOR
This man page was originally written for UDisks2 by David Zeuthen
<zeuthen@gmail.com> with a lot of help from many others.
BUGS
Please send bug reports to either the distribution bug tracker or the
upstream bug tracker at
https://github.com/storaged-project/udisks/issues.
SEE ALSO
udev(7), polkit(8), udisksd(8), udisksctl(1), umount.udisks2(8), gnome-
disks(1)
NOTES
1. system message bus
http://www.freedesktop.org/wiki/Software/dbus
2. GObjectIntrospection
https://live.gnome.org/GObjectIntrospection
3. Desktop Entry Specification
http://freedesktop.org/wiki/Specifications/desktop-entry-spec
4. freedesktop.org icon theme specification
http://www.freedesktop.org/wiki/Specifications/icon-theme-spec
5. GNOME
http://www.gnome.org
6. Disks
https://live.gnome.org/Design/Apps/Disks
7. sysfs
http://en.wikipedia.org/wiki/Sysfs
8. libudev
https://www.freedesktop.org/software/systemd/man/libudev.html
9. /proc/self/mountinfo
http://www.kernel.org/doc/Documentation/filesystems/proc.txt
10. util-linux
http://en.wikipedia.org/wiki/Util-linux
11. GVolumeMonitor
http://developer.gnome.org/gio/stable/volume_mon.html
udisks 2.9.4 August 2018 UDISKS(8)
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