Re: Soundcard packet and permissions
On Sun, 01/08/2006, 05:09PM, vk4akm wrote:
> G'day
> I am new to Linux and this might be the wrong forum for this query, if
> it is please tell me.
>
> I have been fighting with Linux (now Debian 3.1) and soundcardmodem
> packet applications for some time and have eventually managed to decode
> some packets using the "listen" command.
> However the only way I can do this is as a superuser.
> Any attempt to link a terminal program like LinPac or TNOS will not work.
> I have found that all the "/usr/" directories and files are either owned
> by or in the group owned by "root" so I assume as a user I am not
> allowed access.
> As soundmodem resides in /usr/sbin/ any script I write as a user will
> not start it.
> To my limited understanding of Linux for me to link "root" to start
> "soundmodem" would defeat the whole purpose of the superuser level.
> I can only think that I must have installed Debian incorrectly (although
> I mostly followed the automatic installation procedure).
Hi Ken
You've installed it properly. The AX25 apps need root permissions
because they open network sockets. To run them as a 'regular' user you
can do one of two things.
1. Install 'sudo' and give your regular user account super user access
via the 'visudo' applicaton which runs 'vim' on the file /etc/sudoers.
This makes sense on a multiuser system; see the man pages for sudo once
you install it but once it's setup, simply prepend 'sudo' to the app
name when you run it, e.g. 'sudo soundmodem'.
2. Set the SETUID bit on 'soundmodem', 'listen', and any other AX25 app
you want to run, e.g. 'chmod +s /usr/sbin/soundmodem'. The security
minded will tell you to be careful of this but on a single user system,
like your desktop PC, it's no big deal. See the man page for 'chmod'.
>
> Generally packages like gmfsk etc have worked with little effort after
> downloading and installing with the Synaptic Package manager, so
> something must be right.
'gmfsk' only needs access to the soundcard (/dev/dsp) and debian probably
added your user account to the 'audio' group which has write permissions
to /dev/dsp. The permissions on this file on my system is
'crw-rw---- 1 root audio 14, 3 2004-09-18 07:52 /dev/dsp'
and if I type 'groups' to see the groups I'm in I get
'jmarkw dialout cdrom floppy audio src video'
As you can see I'm in the 'audio' group so I have write permisson to
/dev/dsp. Again, check out the man page for 'chmod' and that will give
you an idea about file permissions.
73 de KE4QKT
Mark
Reply to: