Re: PUBLIC CHALLENGE: (was RE: devfs again, (was RE: USB device alloc ation) )

Horst von Brand (vonbrand@inf.utfsm.cl)
Thu, 07 Oct 1999 17:50:14 -0400


Matthew Dharm <mdharm@one-eyed-alien.net> said:
> On Thu, 7 Oct 1999, Stephen Frost wrote:
> > /dev can be cleaned up using rm(1). devfs at one point used
> > tarballs to handle permissions, now it doesn't, it uses a configuration
> > file, which makes it even more strange and un-filesystem like. I don't
> > use a config file to specify my permissions on my / partition.

> I hate to point this out... but if the objection is to configuration
> files, then what about /etc/fstab and the mount options that allow me to
> mount CD-ROM drives and MS-DOS/FAT32 partitions as various users with
> various permissions?

In Unix, permissions on files are part of the files, not in some
configuration file. /etc/fstab is a configuration file for mount(8), the
information there can't be sensibly mapped on Unix owner/permissions. BTW,
the entries there allow you to mount _iff_ you have permissions on the
devices themselves. The permission bits are the systems' last (only?) line
of defense against miscreants; permissions of devices are extremely
critical, much more so than even the most critical normal files. Fooling
around with this if there is no *extremely* good reason is out. Needless to
say, I've seen only rather weak reasons for some scheme like devfs.

> The use of a config file to determine permissions/ownership is not foreign
> to the kernel or filesystems.

Name one use of configuration files for local permissions/ownership on
Unix/Linux.

-- 
Dr. Horst H. von Brand                       mailto:vonbrand@inf.utfsm.cl
Departamento de Informatica                     Fono: +56 32 654431
Universidad Tecnica Federico Santa Maria              +56 32 654239
Casilla 110-V, Valparaiso, Chile                Fax:  +56 32 797513

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