cowloop technology

Matthew Dillon dillon at
Sat Jan 21 11:21:24 PST 2006

    A devfs is not going to impact performance.  That isn't the problem
    with it.  There are three problems with it.

    First, the dynamic nature of a devfs means that set permissions
    and ownership for devices are not 'sticky' across reboots unless you
    add hacks to adjust them on boot.

    Second, devfs does not solve the basic incorrectness of relying on the
    device namespace to list all available devices (e.g. all slices, all
    partitions, all ttys, all ptys, and so forth) when what you really want
    is simply a namespace interpretation that routes a device name to the
    proper device code.

    Third, one of the reasons a devfs is created is to get rid of the
    major/minor number paradigm.  I think this is a grand idea, and FreeBSD
    has done it, but I don't think you need a devfs to accomplish this 
    feat.  I think all you need is to have base names in a special 
    filesystem or filesystem overlay and a VFS layer which parses the name
    out and accesses the correct device with the correct parameters.


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