TR Forums

... how do I make you perform a remote call?

Short version: How do I get a Raspberry Pi to update a Git project and multiple modules inside that project on a recurring basis? I don't think I'll be able to remote into the Pi, due to it being on another person's network that may or may not allow SSH.

Long version: This coming weekend, I'm going to a wedding for a friend of my wife's. I built a magic mirror as a wedding gift:

It's a Raspberry Pi running a monitor behind one-way glass. The software is stored in GitHub and the module system also uses GitHub to store individual modules (Instagram, Twitter, etc.). I'm not sure I can VNC into the Pi due to it being on someone else's wireless network and who knows how I would find its IP address after this weekend. So my thought was to use GitHub to maintain a fork of the mirror code, plus a fork of each module I want to keep updated. Or possibly use Git subprojects, but I don't understand how that works well enough to set it up. I can set up a cron to pull from my fork every night and if I want to change configuration, I can just update the repository.

Is there a simpler solution I'm missing? Is there an easy way to find your Pi after you give it away?

Cool project! Hand-made gifts are the best gifts. Hope the recipients are geeky enough to really appreciate it (I mean, anybody can appreciate the utility; but I mean appreciating the craftsmanship). Is the frame easily replaced in case it doesn't fit into somebody's decor?

I'd be interested in seeing a build log if you have photos and care to post one.

That is pretty awesome right there.

Darkmage wrote:

Is there a simpler solution I'm missing? Is there an easy way to find your Pi after you give it away?

You can build some phone-home functionality. E.g., you could have it pull a certain URL to parse instructions, or you could have it post data (ideally with a unique identifier in case you ever make another one).

At a minimum, if it checks in you'll have its IP address. Anything beyond that is up to you. If the home router supports UPnP, a daemon on the Pi could automatically open ports for VNC or SSH. I believe most routers ship with this enabled out of the box.

You could have it setup a secure tunnel as a fallback in the event that UPnP is not available. As long as you have a domain registered on the public internet (or a subdomain on a dynamic DNS service), you should have no problems when the setup is outbound from their network.

Anything you do is probably a security risk unless you seed it with some keys for SSH/SSL/TLS in advance. I would generate new key pairs for this particular case---that keeps your personal keys isolated, and it's not like there is much effort involved.

If you use ssh regularly you might know about reverse ssh proxys, meaning you could have the pi connect to a vm or other server, and from there, back to the pi whenever you need to. Check the following gists I use on a regular basis:

ssh-tunnel.sh
https://gist.github.com/niofis/a1407f7755b76d13d360
Uses autossh to keep the ssh connection alive, and connects to a remote server using ssh key-based authentication. It creates a reverse tunnel.

ssh-tunnel.service
https://gist.github.com/niofis/bc24f1b33414fd77d77f
Is a systemd service to start the tunnel after reboots.


Regards

UberGerbil wrote:

I'd be interested in seeing a build log if you have photos and care to post one.

Sure, I can do that. I'll throw it in the Back Porch after I get back from the wedding. In the meantime, you can click on the picture to see the pics I took while building it. It's brief, but it should give you an idea of the process.

UberGerbil wrote:

Is the frame easily replaced in case it doesn't fit into somebody's decor?

"Easily" is a relative term. The frame is a "backless frame" from Hobby Lobby. While it's easy to get a frame that matches your decor, you'd have to flip the mirror over and undo the dozen screws that are holding the box onto the frame. Best case scenario: A dozen wood screws and it will come right out and you can replace it. You'll have to drill new holes in the frame, but that's about it.

TheRazorsEdge wrote:

At a minimum, if it checks in you'll have its IP address. Anything beyond that is up to you. If the home router supports UPnP, a daemon on the Pi could automatically open ports for VNC or SSH. I believe most routers ship with this enabled out of the box.

You could have it setup a secure tunnel as a fallback in the event that UPnP is not available. As long as you have a domain registered on the public internet (or a subdomain on a dynamic DNS service), you should have no problems when the setup is outbound from their network.

Hmm. The dynamic DNS I already have. And I like the idea of the Pi us UPnP to open up a port and connect to my house, for no other reason than to let me know it's there and I can get into it if I need to. Let me do some research and see if I can figure this part out myself. I may beg for more assistance later.

I have zero advice for you. Just posting to say that is the coolest wedding gift idea I've ever seen. 

First question - if you're giving it as a gift and setting it up (which is the coolest wedding present I've ever seen, btw), couldn't you ask them for some help in accessing it once it's setup for upgrades/whatever? It's possible they don't want you messing with it once it's "installed", and the point might be moot.

So the most recent news on the mirror is that the wedding has been postponed upon account of Hurricane Matthew rolling across their back lawn sometime tomorrow. The silver lining is that I now have three months to finish the coding & configuration.

Waco wrote:

First question - if you're giving it as a gift and setting it up (which is the coolest wedding present I've ever seen, btw), couldn't you ask them for some help in accessing it once it's setup for upgrades/whatever? It's possible they don't want you messing with it once it's "installed", and the point might be moot.

I don't know. In my planning, I was kind of vague on how I was going to get it connected to their wireless network in the first place. I don't know how much time I'll have to explain it to them, hands-on time with the mirror while we're down there and whatnot. Additionally, these people have stupid amounts of money and a full time staff. I don't know who installed their wireless and what level of paranoia a professional installation entails. I'm barely competent to edit a file in Linux, I don't think I can walk their assistant through the process over the phone.

Ideally, I can get the Pi to run a VNC server and I can just jump on the box if I ever need to. But there are a lot of unknowns.

And thanks for the compliments, guys. It started as a combination of "What do you get for the people who have everything?" and "I just saw this neat thing on the Internet and I wanna make one but I don't have a good reason."

Cool project!

Darkmage wrote:

Hmm. The dynamic DNS I already have. And I like the idea of the Pi us UPnP to open up a port and connect to my house, for no other reason than to let me know it's there and I can get into it if I need to. Let me do some research and see if I can figure this part out myself. I may beg for more assistance later.

You only really need UPnP if you want it to open a port so it can listen passively from their network. If you have the device create a secure tunnel to your network (using dynamic DNS), you can ignore UPnP entirely.

As background, UPnP is primarily useful for P2P applications, where an unknown client may need to communicate into your network. It allows the internal hosts to dynamically configure port forwarding on the router.

If you implement a secure tunnel, you may want to go out on port 443. This is the same port that web sites use for SSL, so it is generally unrestricted. If this happens to be restricted, then there is probably no simple option available. Proxying/monitoring SSL traffic is one of the most annoying defense measures to implement, so if their "staff" is doing it then you probably need explicit permission for anything to work.

Wow, awesome idea, beautiful mirror!

Thank you. I forgot to mention, the build log is up in the Back Porch.

Talk about a weird coincidence... the day you created this thread I saw it, read about it and was impressed... then the next day went to a local museum that just opened (in the woods, half an hour from civilization) and they actually had an exhibit that presented information in a display much like the one in this thread. The mirror glass and display looked similar to this, but it didn't have the IR interaction and was a little smaller. Still, very strange to hear about this then see one in person within 24 hours.

Awesome idea BTW.

Awesome project and gift!

This makes me want to retrofit the mirror above my bathroom sink. If only my wife wasn't a luddite.

gerbilspy wrote:

Awesome project and gift!

This makes me want to retrofit the mirror above my bathroom sink.  If only my wife wasn't a luddite.

How much of a Luddite?  Once she hears that she can preen AND browse Pinterest at the same time, you might have a sale.