Well, those are surprising responses for me anyway I guess.
Here's the thing about special files. They have an integer 'x' attached to
them which basically means "this file represents an index into an internal
kernel struct'.
Now if you are comfortable with the idea that a file, with a number
attached to its metadata, said number representing an index into an array
of structs, which has to work for all time and all kernels: then we're just
comfortable with different things. 'nuf said.
moving right along, when did /dev first appear?
On Wed, Feb 7, 2018 at 8:40 AM Nemo <cym224(a)gmail.com> wrote:
[top-post righted]
On 2/6/2018 9:06 PM, Dan Cross wrote:
On Tue, Feb 6, 2018 at 8:48 PM, Dave Horsfall <dave(a)horsfall.org> wrote:
>
> On Wed, 7 Feb 2018, Greg 'groggy' Lehey wrote:
>>>
>>> V3 and earlier still *called* them special files, but it seems they
were
>>> essentially just magic inode numbers
(there was no physical file on
disk,
>>> just any directory entry with the
given inode would be the special
file).
Isn't that still the case?
Wasn't that "devfs" (which Penguin/OS calls "udev")? I've
never grokked
that concept.
No. devfs was (is?) a pseudo-filesystem where only special files
corresponding to the devices enumerated by the kernel during
autoconfiguration are present. The contents are synthesized at boot time
and
the filesystem is mounted at some canonical
location (like /dev), but is
otherwise ephemeral. This is in contrast to the older /dev, which is
usually
just a directory on the root filesystem, wherein
one created a number of
device files that may (or may not) correspond to an actual hardware
device
in the system (remember the old dance of,
"cd /dev && ./MAKEDEV foo" when
you added a "foo" onto your system?). The inodes and directory entries
for
those files actually exist in the disk-resident
filesystem structures
(though of course data blocks aren't allocated to those files and the
inode
doesn't refer to any data blocks).
[...]
- Dan C.
On 7 February 2018 at 11:24, Arthur Krewat <krewat(a)kilonet.net> wrote:
medusa# mount | egrep '^/dev'
/devices on /devices read/write/setuid/devices/rstchown/dev=9640000 on
Fri
Jan 19 16:33:07 2018
[...]
SunOS medusa 5.11 11.3 i86pc i386 i86pc
Further more (5.10 sun4u):
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 dur-
ing 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.
N.