[TAG] pppd changing file permissions (Was Re: lpr works for user not root in Basiclinux 2.1)
Kapil Hari Paranjape
kapil at imsc.res.in
Tue Mar 27 19:54:41 MSD 2007
On Tue, 27 Mar 2007, Karolis Lyvens wrote:
> To clear up the matter about devfs/udev in BL:
> Baslinux runs on 2.2.26 kernel by default, which is pre-devfs/hotplug
> (which appeared in 2.4, if I'm not mistaken). There are several 2.4
> images available, but BL doesn't use devfs. 2.6.x kernel isn't used in
> BL at all (it could be compiled, but there's no need for that), so it
> can't possibly have udev.
> Instead of all this fancy automatic stuff, we use mknod to manually
> create and manage our devices :)
I think the "udev/devfs" stuff was a McGuffin.
The original problem was that "some" program was changing the permissions
of the "dialout" device.
Now, *if* devices are removed and created (a la devfs/udevd) by some
automated process then *that* could be the reason for the changing
Otherwise, it is some other program... :-(
Unfortunately, it seems as if too many aspects of BL are
"non-standard" for most of us to be able to help in debugging this.
This is especially so with regard to the "deconstruction" of the
permissions system of Posix.
On a Debian system (which I use) the solution used is that all
dialout devices have "group" ownership of "dialout". The users who
belong to that group can access these devices. No program accessing
these devices is "permitted" (by policy) to play around with its
mode/ownership and so on.
 The flaws of this system are well-known and many people have spent
hours designing "better" systems. However, any implementation of a
replacement of a "core" aspect like this is fraught with great
burdens: "legacy" software re-write/review and user education.
 This policy is currently one that governs the writers/packagers
of the programs rather than the programs themselves!
More information about the TAG