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    SubjectRe: devfs
    Alan Cox writes:
    > > 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

    If you have an embedded system with a ROM-FS or a CD-ROM then your
    root FS is read-only. From my updated README:

    You can get around this by creating a RAMDISC at boot time, making
    an ext2 filesystem in it, mounting it somewhere and copying the
    contents of /dev into it, then unmounting it and mounting it over
    /dev. A devfs is a cleaner way of solving this.


    > > 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.

    True, you can do it with a user-space daemon. But you then have to
    change applications to call it. Devfs doesn't need application
    changes.

    Regards,

    Richard....

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