From: cym224@gmail.com (Nemo)
Subject: [TUHS] Device special files
Date: Wed, 7 Feb 2018 11:34:40 -0500 [thread overview]
Message-ID: <CAJfiPzwGuzuqMiUs36yuXaMDTUaUmm8AEDmXR+cjh+XNzK_kfw@mail.gmail.com> (raw)
In-Reply-To: <ec74c580-34f7-794b-815c-d3a5949a7f5a@kilonet.net>
[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 at 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 at 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.
next prev parent reply other threads:[~2018-02-07 16:34 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-06 15:56 ron minnich
2018-02-06 17:56 ` Larry McVoy
2018-02-06 18:03 ` ron minnich
2018-02-06 19:48 ` Random832
2018-02-07 1:25 ` Greg 'groggy' Lehey
2018-02-07 1:36 ` Ron Natalie
2018-02-07 1:40 ` Clem Cole
2018-02-07 1:47 ` Henry Bent
2018-02-07 1:48 ` Dave Horsfall
2018-02-07 2:06 ` Dan Cross
2018-02-07 16:24 ` Arthur Krewat
2018-02-07 16:34 ` Dan Cross
2018-02-07 16:34 ` Nemo [this message]
2018-02-07 16:59 ` ron minnich
2018-02-08 0:39 ` Dave Horsfall
2018-02-08 16:18 ` Arthur Krewat
2018-02-08 22:47 ` Dave Horsfall
2018-02-07 2:13 ` Bakul Shah
2018-02-07 5:39 ` Dave Horsfall
2018-02-07 18:36 ` Steffen Nurpmeso
2018-02-07 19:07 ` Ian Zimmerman
2018-02-07 22:05 ` Clem Cole
2018-02-07 22:38 ` ron minnich
2018-02-07 22:48 ` Ron Natalie
2018-02-08 18:59 ` Random832
2018-02-07 23:06 ` Bakul Shah
2018-02-08 19:06 ` Steffen Nurpmeso
2018-02-07 22:04 ` Dave Horsfall
2018-02-08 13:03 ` Rafael R Obelheiro
2018-02-08 19:25 ` Steffen Nurpmeso
2018-02-07 1:38 Noel Chiappa
2018-02-09 0:09 Doug McIlroy
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