Re: devfs

James Mastros (root@jennifer-unix.dyn.ml.org)
Thu, 8 Jan 1998 18:48:14 -0500 (EST)

On Thu, 8 Jan 1998, Alan Cox wrote:
> > The FSSTND (Linux filesystem standard document) suggests the possibility
> > of a read-only root filesystem. [...] With the
> > devfs, the root filesystem can be read-only. The current /dev could be
> > trouble for Linux embedded in ROM.
>
> Firstly. The fsstnd does not say /dev has to reamin on the root fs. Its also
> not really an issue for a ROM based Linux - you tend to unpack a compressed
> image from expensive slow flash into cheap ramdisk
But if it isn't you can't mount /dev; for device mounts, mount needs to
access a node. (Devfs, proc, smb, nfs, etc can be -- there is no file (or
node) in the fs that is being mounted.)

> > With devfs, the kernel can chown ptys back to root when a process
> > does not need them anymore. The kernel might be able to let normal
> > users chown their own pty or it might perform the chown automatically.
>
> This solvable in user space by having a single pty allocation daemon. The
> tty/pty issue is irrelevant the wisdom or otherwise of a devfs.

Umm... but which is the cleaner interface? I think that devfs is; you may
think that a ptyd is. I think that there are already to many daemons.
Also, the daemon wouldn't know when the pty should revert back to root
ownership without kernel modifications anyway.

> Alan

-=- James Mastros

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