Re: devfs

Alan Cox (alan@lxorguk.ukuu.org.uk)
Thu, 8 Jan 1998 11:44:42 +0000 (GMT)


> The FSSTND (Linux filesystem standard document) suggests the possibility
> of a read-only root filesystem. Read-only filesystems help reduce the
> chance that mistakes, crashes, and crackers (evil hackers) might damage
> something. The Linux root filesystem can not be read-only because the
> normal /dev must be read-write to allow tty ownership changes. 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

> 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.

Alan