06-23-2013
Basically, for all *NIX systems, filesystems are created and used via block devices, not character devices.
By definition, character devices have a window of 1 char - a driver might buffer that a little bit (so you can unchar(), or back up one byte.
Block devices are, by definition - finite in size (while char devices may be infinite) - and block devices are "seekable". Because they are seekable, an information system, such as a file system can be stored on them.
Note: some device drivers use ioctl() to perform actions similar to seek - hence the confusion. However, the original definition (at least as far back as UNIX v6) was that character devices did not seek.
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devfs(7FS) File Systems devfs(7FS)
NAME
devfs - Devices file system
DESCRIPTION
The devfs filesystem manages a name space of all devices under the Solaris operating environment and is mounted during boot on the /devices
name space.
The /devices name space is dynamic and reflects the current state of accessible devices under the Solaris operating environment. The names
of all attached device instances are present under /devices.
The content under /devices is under the exclusive control of the devfs filesystem and cannot be changed.
The system may be configured to include a device in one of two ways:
By means of dynamic reconfiguration (DR), using, for example, cfgadm(1M).
For devices driven by driver.conf(4) enumeration, edit the driver.conf file to add a new entry, then use update_drv(1M) to cause
the system to re-read the driver.conf file and thereby enumerate the instance.
The device may be attached through a number of system calls and programs, including open(2), stat(2) and ls(1). During device attach, the
device driver typically creates minor nodes corresponding to the device via ddi_create_minor_node(9F). If the attach is successful, one or
more minor nodes referring to the device are created under /devices.
Operations like mknod(2), mkdir(2) and creat(2) are not supported in /devices.
FILES
/devices Mount point for devfs file system
SEE ALSO
devfsadm(1M), vfstab(4), attach(9E)
NOTES
The /devices name space cannot be unmounted.
All content at or below the /devices name space is an implementation artifact and subject to incompatible change or removal without notifi-
cation.
SunOS 5.10 26 Oct 2004 devfs(7FS)