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.Dd March 10, 2023
.Dt DEV 4FS
.Os
.Sh NAME
.Nm dev
.Nd Device name file system
.Sh DESCRIPTION
The
.Nm
filesystem manages the name spaces of devices in the operating system.
The global zone's instance of the
.Nm
filesystem is mounted during boot on
.Pa /dev .
This filesystem is colloquially called
.Sq sdev
as a way to distinguish it from the
.Xr devfs 4FS
filesystem mounted at
.Pa /devices .
.Pp
A subdirectory under
.Pa /dev
may have unique operational semantics.
Most of the common device names under
.Pa /dev
are created automatically by
.Xr devfsadm 8
Others, such as
.Pa /dev/pts ,
.Pa /dev/net ,
and
.Pa /dev/zvol
are dynamic and reflect the operational state of the system.
You can manually generate device names for newly attached hardware by invoking
.Xr devfsadm 8
or implicitly, by indirectly causing a lookup or readdir operation in the
filesystem to occur.
For example, you can discover a disk that was attached when the system was
powered down (and generate a name for that device) by invoking
.Xr format 8 .
.Pp
In a non-global zone, the
.Nm
filesystem is also mounted at
.Pa /dev ;
however, it is generally speaking read-only.
Unlike in the global zone, a privileged user in a non-global zone cannot create
directories or files, directories, or other objects within the filesystem.
.Sh FILES
.Bl -tag -width Pa
.It Pa /dev
Mount point for the
.Nm
filesystem in the global zone and non-global zones.
.El
.Sh SEE ALSO
.Xr devfs 4FS ,
.Xr devfsadm 8 ,
.Xr format 8
.Sh NOTES
The global
.Pa /dev
instance cannot be unmounted.