Mailinglist Archive: opensuse (4054 mails)

["Carlos E. R." <robin1.listas@xxxxxxxxxx>]

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The Sunday 2006-01-22 at 11:43 +0100, Roger Oberholtzer wrote:

> > In file /etc/logindevperm:
> > 
> > :0 0600 /dev/cdrom:/dev/cdrom1:/dev/cdrom2:/dev/cdrom3
> 
> How does logindevperms relate to udev and HAL? 

It doesn't, or not directly.

HAL:

|  1.1. About
|        
| This document concerns the specification of HAL which is a piece of 
| software that provides a view of the various hardware attached to a 
| system. In addition to this, HAL keeps detailed metadata for each piece of 
| hardware and provide hooks such that system- and desktop-level software 
| can react to changes in the hardware configuration in order to maintain 
| system policy.

So, any piece of hardware is listed by it (try "lshal"). With udev I'm not 
familiar, but it serves to create the devices files (the /dev tree) on the 
fly. I suppose it gets info from hal (hardware abstraction layer?) about 
which node to create. What permissions does it use? Dunno.

Looking at it, it is configured in /etc/udev/udev.conf. I see two 
interesting entries:

 udev_log - set to "yes" if you want logging, else "no"
udev_log="yes"

# udev_perms - The name and location of the permissions device
udev_devperms="/dev/devperms"

You should have a look at file "/dev/devperms" to see what it has, mine is 
empty. Udev is active in my 9.3, but the device nodes are static, I think 
(judging by the creation date). Not sure how to know.

Grepping with "mc" in "/etc/udev/" for references to "cdrom" I don't find 
permissions references. Looking for "hda" I find two, but I don't think 
those are the ones we are looking for:

KERNEL="dos_hda*", NAME="%k", GROUP="disk", MODE="660"

KERNEL="i2o/hda*", NAME="%k", GROUP="disk", MODE="660"



Finally, we have "logindevperm" (man logindevperm):

| NAME
|        /etc/logindevperm - configuration file for pam_devperm.so

So it is used by PAM.


> I would guess that if a
> device is already present when you log in, logindevperms will replace
> any udev/HAL settings. If the device gets inserted while logged in, the
> udev/HAL settings are used and not logindevperms.

Not sure of that.

> 
> Joy. Another piece of the puzzle.
> 
> And, what happens if someone logs in after you while you are logged in?
> login runs as root, so there is nothing stopping it from claiming the
> device for the new login. Meaning that any changes made by the first
> person would be set to logindevperms when the second person logs in.

No, the permissions do not change, the first user keeps control.


> I guess the first item on each logindevperms line allows a bit of
> control over this. But I would happy to fully understand the interaction
> with udev/HAL. The default logindevperms explains why you only get the
> device settings when you log in as the first GUI login on the console,
> as only that is defined in the default SUSE logindevperms.

It doesn't matter if you log in X or in the console, as long as it is a 
local one. Or it did not when I looked at this time ago, I might be 
mistaken.

> 
> Anyway, thanks for the pointer to logindevperms. It is now on the radar.
> Too bad it still does not explain why /dev/ttyS0 is set to rw access
> only for the current login. I have not traced who does that.

The /dev/ttyS0 is symlinked to /dev/modem: look for this one in those 
configuration files and you will find it.

I will shove more clutter on your radar: have a look at /etc/resmgr.conf 
as well :-P


Anyway, just try to modify the cdrom line in logindevperm, and find out if 
it solves your issue. Or, comment it out, and find if it sticks put.

- -- 
Cheers,
       Carlos Robinson

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