Re: Advice Needed

[John McKendry <jmckendry@attbi.com>]

Tom Droege wrote:
> <snip>
> 
> 2) Telnet.  It does not work on my home network.  One "expert" said he did
> not know how to make it work.   That is enough for me.  If someone with
> more ability than me does not know how to make it work, then I give up real
> fast.
> 
 Telnet is pretty basic stuff. You should be able to get it to work. On
the target machine, as root, type
netstat -t -l
 This will list the TCP ports that can receive connect requests. If telnet
is enabled you should see an entry with "*:telnet" under "Local Address".

 If the entry is there, type "telnet localhost" or "telnet 127.0.0.1". This
should get you a login prompt, and you should be able to login as a plain
user (not as root; telnet access to root is usually disabled for security
reasons).

 If the netstat entry isn't there, you probably chose one of the paranoid settings
for network security when you installed Mandrake. You have to enable telnet.
The easy way is to use the netconf tool. If Mandrake 9 is like 8.1, this is
off the main menu under Configuration->Networking. In netconf, select the
"Server Tasks" tab and click the "Internet services" button. This will pop
up a new window called "Basic services". In this window, select "Internet
servers database". This will open yet *another* window. In this window,
scroll down to the "telnet" service, and check its "Enabled" box.

 In the window that pops up here, click "Enabled" on the State line.
(If it pops up a message about not being able to find /sbin/tcpd at this
point, tell it not to change anything.) Then click "Accept" at the bottom,
and click "Dismiss" in all the open windows, and finally click "Quit" in
the main netconf window.

 At this point you'll get a warning about "The state of the system is not
in sync with the current/updated configurations". Click the "Do it" button.
This will restart the xinetd daemon, which is the program in charge of
listening for network connect requests, and it will reread its configuration
file, and now when you type "netstat -t -l" you should see an entry for telnet.

 If none of that works, give us a specific problem description - what you
did and what error messages you got back.

> 3) Remote Linux pc on the ethernet in the dome.  Looking at the Mandrake
> hardware pages, there is not a single web cam listed.  Plenty of expensive
> cameras.  So unless one of you knows how to attach a simple cheap web cam
> to linux, I give up on linux.  I sure would like to do this with
> linux.  This will help me learn the system.  Surely someone had been
> running little cheap cameras under linux.  But Mandrake did not list any
> unless I don't know where to look.
> 
 Web cams are listed kind of higgledy-piggledy under "input device" on the
Mandrake hardware pages. 
 I got curious about this, and after a little Web research I went out to
the local Best Buy and bought a Creative WebCam Pro PD1030 for $50.00.
It works right out of the box on Mandrake 8.1, on a cheapo AMD Duron 700 
with on-board video; it works better, in terms of picture quality, when
I run the xawtv application on the Mandrake 8.1 system and use X to
direct the display to a Pentium 450 running Red Hat 7.2 across the room. 
It does seem to timeout a lot; it will run for, say, 10 minutes, and then
die with "interrupted system call" errors. I think there's a very good chance
that Mandrake 9 on a faster processor would not have this problem.
I might even be able to fix it by reading the manual and twiddling with
the configuration files

 What makes it easy is that Mandrake includes the drivers for the camera,
called ov511 and videodev, in its base distribution, so you don't have
to go through the process of building drivers, and your Mandrake distribution
CDs contain RPM packages for the application programs. Here's what I did (run
as root):

- make sure you have the ov511 driver/module:
modprobe ov511
should complete without error. This loads the ov511 module and the videodev
driver, which ov511 uses.

- connect the camera. Plug its USB cable into one of your computer's USB ports.
Now if you type "tail /var/log/messages" you should see some messages indicating
that the camera has been detected and identified. Mine says
hub.c: USB new device connect on bus 2/2, assigned device number 3
ov511.c: USB OV511+ camera found
ov511.c: camera: Creative Labs WebCam 3
ov511.c: Sensor is an OV7620

- now your hardware is working. You need an application to use it. I chose
the xawtv package; you can see some other choices at the ov511 Apps Web page
at http://alpha.dyndns.org/ov511/apps.html . Assuming you didn't choose to
install xawtv when you installed Mandrake,

- put the second Mandrake installation CD in your CD drive, wait for the file
manager window to come up, and go to the Mandrake/RPMS2 directory. Scroll down
to the x's and locate the xawtv-<somenumber>-<n>mdk.i586.rpm package file.
Right-click on this file and select "Open With"->"Software Installer", and
follow the instructions.
 You may have to insert the first Mandrake installation CD, if the rpminstall
program determines that the xawtv package requires other packages. This
happened to me, and I had to umount and eject a mounted CD from my second drive
to do it, and I think the umount caused rpminstall to get confused and fail,
so I ended up installing a couple of other packages by hand (libaa and libalsa)
and then trying xawtv again. Minor aggravation.

 At this point you should be able to type "xawtv -n" (the -n says "don't read the
config file". I got better results with this than with "xawtv" alone. YMMV.) and
see a picture, assuming that you're doing this with X running (but I've been assuming
that for a while).

 If that works, and if you've got two Linux computers on a local network, you can
now direct the xawtv display to the second computer. On my network, I'm running
xawtv on 172.16.1.35, and I have Red Hat and X running on 172.16.1.36.
 On 1.36, as root, I type
xhost 172.16.1.35
 and it says "172.16.1.35 being added to access control list".
 On 1.35 I type
export DISPLAY=172.16.1.36:0
xawtv -n
 and a second or two later my webcam picture (and some help text) pops up 
on the monitor of the computer across the room. "xawtv -n -remote" may
improve reliability at the cost of some speed; I'm trying it now. Nope.

 OK, controlling xawtv with telnet: I can telnet from 1.36 to 1.35 as
a plain user, type "export DISPLAY=172.16.1.36", and when I type
"xawtv -n" it gives me some errors, 
"v4l2: open /dev/v4l/video0: Permission denied
v4l: open /dev/v4l/video0: Permission denied

 I can get it to work if I su to root after I log in. chmod +rw on
/dev/v4l/video0 doesn't take, for some reason. I saw something about
this in one of the README files, but I can't find it right now.

 So it needs a little more work, but I hope it's enough for proof of
concept. The xawtv documentation says you shouldn't expect it to work
without reading the documentation. Seems to be right.

<snip talk about using Windows>

 Friends don't let friends run Windows.

John