Messages in this thread | | | Date | Sun, 18 Aug 2002 19:03:42 -0400 (EDT) | From | Alexander Viro <> | Subject | Re: devfs |
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On 18 Aug 2002, Ed Sweetman wrote:
> This has nothing to do with not mounting devfs and still using devfs to > work with devices. If devfs is not mounted but you're still using > devfs, you shouldn't need anything in /dev. The documentation says you > can use devfs without mounting and This is what i'm saying is > problematic and doesn't seem possible in normal usage. It's an > optional config so are we using devfs when we dont mount it or not? > and if not, then why make not mounting it an option ?
What? If program calls open("/dev/zero",...) and there's no such file, how the fuck would having devfs enabled help you?
Come on, use common sense - devfs provides a tree with some device nodes. You can mount it wherever you want (or not mount it anywhere). Just as with any other filesystem.
If you mount it on /dev - well, duh, you see that tree on /dev. If you do not - you see whatever is in /dev on underlying fs.
If program wants to access a device, it opens that device. Just as any other file. By name. There is nothing magical about names that begin with /dev/ - it's just a conventional place for device nodes.
devfs "mount" option is an idiotic kludge that makes _kernel_ mount it on /dev after the root fs had been mounted. Why it had been introduced is a great mistery, since the normal way is to have a corresponding line in /etc/fstab and have userland mount whatever it needs.
Said option is, indeed, not required for anything - in a sense that it does nothing that system wouldn't be perfectly capable of in regular ways.
But you _do_ need stuff in /dev, no matter what filesystem it comes from. Kernel doesn't need it, but userland programs expect to find it there. If you had deleted device nodes from underlying /dev and do not care to mount something on top of it - well, there won't be anything in that directory.
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