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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:
o Low-level APIs and commands such as e.g. sysfs[7], libudev[8],
/proc/self/mountinfo[9] and util-linux[10].
o 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 AT 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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