QODS ec

Saturday, July 10, 2004

LINUX: Geeky secrets of a Linux road warrior

Edd Dumbill's Weblog: Behind the Times

Geeky secrets of a Linux road warrior

So, the first week for nearly five years without a Wednesday deadline for publishing XML.com. What's a guy to do? I already filed the copy for this week's XML-Deviant column on Monday. Tuesday was wiped out thanks to England's defeat in the cricket. The answer, naturally, is work displacement of the highest order.

Since I moved my office at the beginning of the year and retired my venerable gateway machine, replete with its ISA slots and serial ports, I've lost some of the services it provided me. These include two that were handy while I travelled: voicemail and old-fashioned dial-in PPP access to my network. As I was putting it all back together again I thought I may as well write about the setup.

Voicemail

Thanks to a cheap external 56k modem (these days, the only reliable way to ensure you're not getting a crazy software modem), I have an answering facility on my office phone line, and messages are emailed to me as WAV attachments. The software required to do this is mgetty and its voice-capable extension, vgetty. I installed it via the mgetty-voice package in Debian. There are also a bunch of tools in the mgetty-pvftools package that support mangling of the various modem voice file formats.

After recording a message using the GNOME sound recorder program, I resampled it down to 8khz with sox and converted it so I was able to use it for an outgoing message. That was by far the trickiest and most time consuming part of the process. A swift editing of the configuration files in /etc/mgetty was enough to get me up and running. I then just needed to write a small script to scan the incoming message spool, convert the message back to a WAV and email it to myself. The audio seemed quiet, so I used sox again (what a fantastic tool) to increase the volume of the messages.

Now my voicemail follows me around the world via my inbox.

Dial-in

However hard you try, there are still times when things go so badly wrong you can't use ssh to get back into your home network. Under these circumstances having old-fashioned dial-in access is a nice fallback. It turns out to be trivially easy to set this up with mgetty or vgetty, and it even auto-detects a PPP connect and runs pppd for you. The only wrinkle was that, despite what the Debian docs say, I had to manually set up a username and password for the connecting user, rather than just use the system passwords. Probably something deep to do with PAM that I don't understand.

VPN

As I've written about before, I use OpenVPN for my VPN needs. Although it wasn't part of the modem setup, I think it's worth mentioning again as a couple of people have recently asked me about it. For my setup, OpenVPN has some advantageous characteristics: it's easy to configure and doesn't require kernel adjustments; it tunnels over just one UDP port and so requires minimal changes to the firewall; and it is failure tolerant, so it can always be running and automatically works whenever the network is available.

What would be really nice is to have all this integrated into some kind of personal or workgroup remote access product. The work required to configure the software was by and large minimal, and completely scriptable. Maybe add in VNC for remote desktops, and you're there.

Some other tools that make life on the road workable, but I don't have time to write about: the Courier IMAP daemon, Evolution mail client, Exim mail server with TLS and authorization, and my Bluetooth-enabled cellphone.

My biggest wishlist item is a straightforward way of setting up GnomeMeeting so I can videoconference with my family at home when away. For some reason I have been repeatedly defeated by the complexity of setting this up behind a NATting Linux firewall.

0 Comments:

Post a Comment

<< Home


Get Firefox!