Month: February 2014

Link: Linux Terminal: sshfs, Remote directory over ssh

Often one wants a shared access to files across machines. Traditionally one uses the network file system (nfs). The network file server works as follows: There is an nfs server that exports some directories in its filesystem hiearchy to various nfs clients that mount these directory over the network into their file system hierarchy. As a result, each of the clients shares the directories exported by the nfs server.

However a lot of times you just have to mount a directory from a server to your local computer and in these cases NFS it’s not so useful, sshfs it’s much better

Sshfs is a filesystem client based on the SSH File Transfer Protocol. Since most SSH servers already support this protocol it is very easy to set up: i.e. on the server side there’s nothing to do.  On the client side mounting the filesystem is as easy as logging into the server with ssh.

Full article here:
Linux Terminal: sshfs, Remote directory over ssh (Linuxaria)

Link: Trying to choose between the Raspberry Pi or BeagleBone Black? This article will help you decide which one is best for the job

There are already many articles out there comparing Arduino, Raspberry Pi, and BeagleBone Black; this is not one of those articles. I believe it is clear that Arduino is in a different league than the Raspberry Pi or BeagleBone Black, and serves an entirely different purpose. What I was looking for and couldn’t find was a comprehensive article that would summarize all of the pros and cons of the Raspberry Pi and the BeagleBone Black, and what each platform is best suited for. When I couldn’t find that article, I decided to write it myself.

I begin by giving a short introduction to each platform and then we will take an in-depth look at the two platforms side-by-side to determine which one is best for each category.

Full article here:
Trying to choose between the Raspberry Pi or BeagleBone Black? This article will help you decide which one is best for the job. (Maker Corner)
This article was also reposted here, with more reader comments under the main article:
How to Choose the Right Platform: Raspberry Pi or BeagleBone Black (Make)

Link: How to run “unkillable” programs in Linux

Here is a neat trick. If you want to start a program that always respawns if it gets killed, just put it in /etc/inittab. The init process will respawn the program. That’s what it’s for.

Here’s an example. …

Full article here:
How to run unkillable* programs in Linux (catonmat.net)
* “unkillable” refers to a program that respawns when you kill it.

Link: Uninterruptible Power Supply (UPS) for BeagleBone Black – a DIY Project

The following DIY manual describes an easy-to-implement battery backup module for the BeagleBone Black. This can be useful in certain applications, such as out-door usage where constant power is not present and it is not desirable to just drop power on the BBB board. It was built for a RasPBX setup with the motivation to have a safely powered BBB in all situations. The BBB is unfortunately suceptible to slowly rising supply voltage when powered on. It sometimes does not boot at all, which can be a serious problem after a power glitch. On top, voltage irregularities can cause the device to crash as well.

The battery backup can be applied to any BBB installation, running RasPBX, the original Anstrom Linux or any other distribution. However, USB devices cannot be used while running on battery, as the UPS does not power the USB host port.

Full article here:
Uninterruptible Power Supply (UPS) for BeagleBone Black – a DIY Project

Link: Enabling Remote Desktop Access with xdrp on a Raspberry Pi

If you need to run your Raspberry Pi “headless” (without a monitor) you can connect to it via SSH. But if you need access to the desktop then one option is to use VNC, which is great if you aren’t already using Microsoft’s Remote Desktop Protocol (RDP) to connect with other servers. But if you are already using RDP then it is more convenient to enable RDP access to the Raspberry Pi and stick with just one type of client viewer.

RDP is a proprietary protocol developed by Microsoft. It is used primarily in Microsoft’s Windows Server products so that the servers can run without a monitor attached. All modern desktop versions of Windows (like Windows Vista, Windows 7 and Windows 8) all come with an RDP viewer (called Remote Desktop Connection) pre-installed. This means you won’t need to install any extra software to access the Pi’s full desktop from a Windows PC.

Full article here:
Enabling Remote Desktop Access with xdrp on a Raspberry Pi (Make Tech Easier)

If you used the information from the article, “A possible way to thwart SIP hack attempts on your Asterisk (or other) PBX server”, please read this

If you took the advice in the article, A possible way to thwart SIP hack attempts on your Asterisk (or other) PBX server, please be aware that an important note has been added:

IMPORTANT: Be sure to have a separate iptables rule (higher on the list than those above) that allows connections to port 5060 from devices on your local network. Otherwise, you may find that new extensions that you are adding for the first time will not register with your Asterisk server, or that after a system reboot, none of your local extensions will register!

Please take heed of that note, or you may be one power failure or reboot away from discovering that none of your local extensions are able to register with your PBX server.

Link: Remotely Working Together on a Terminal Session in Linux

I often get a chance to work from home, and this has given me opportunities to look for ways to share sessions with my colleagues. Windows XP used to have the excellent NetMeeting tool, but I recently switched to Ubuntu and haven’t yet found an equivalent.

Yes, I’ve heard of VNC and used it a lot too, but I wasn’t happy with its remote desktop sharing performance. Ekiga is interoperable with NetMeeting calls, but doesn’t support screen sharing. Even Skype’s screen sharing does not seem to support remote screen controlling.

However, Linux’s power is at the command line, and this is true even in the case of remote sharing. So here comes screen to the rescue – this magical command allows you to flawlessly resume lost sessions and share them with multiple users at the same time.

Full article here:
Remotely Working Together on a Terminal Session in Linux (TechNonStop)

Link: How To Configure Port Knocking Using Only IPTables on an Ubuntu VPS

Servers that are connected to the internet are subjected to all manners of attacks and probes by malicious users, scripts, and automated bots. It is sometimes a balancing act to secure your server from attacks without affecting legitimate access to your services and resources.

Certain types of services are meant to be visible and consumable to the public internet. An example of this is a web server. Other types of services are typically used by only the system administrator or a select number of individuals and are not meant to be a public resource.

A concept known as port knocking is a way of shielding processes that fit into the latter description. Port knocking works by covering the ports associated with a process behind a firewall until a specific, predetermined sequence of network activity occurs. At this point, the port knocking service reconfigures the firewall to allow access to the protected application.

Full article here:
How To Configure Port Knocking Using Only IPTables on an Ubuntu VPS (DigitalOcean)
Related:
How To Use Port Knocking to Hide your SSH Daemon from Attackers on Ubuntu (DigitalOcean)

Links: A low-cost surveillance camera using the Raspberry Pi

We have recently come across two articles on the same topic:

Although people have been toying with USB webcams on the Raspberry Pi for some time now, the release of the official camera module has reinvigorated interest in video related projects.

The official Raspberry Pi camera module is a Full HD camera that plugs into the Raspberry Pi via the Camera Serial Interface (next to the Ethernet port) on the device. The sensor on the camera is a 5MP with fixed focus lens. It can shoot still images with a maximum resolution of 2592×1944 as well as Full HD 1080p video @ 30 FPS and 720p video @ 60 FPS.

And you get all this in a module that’s only 25x20x9mm in size and weighs just 9 grams! This makes it ideal for projects that require a small steady camera, like surveillance.

Full article here:
Use the Raspberry Pi as a DIY Surveillance camera (Make Tech Easier)

This article describes how to build a surveillance cam based on a Raspberry Pi micro-computer which records HD video when something moves in the monitored area. Live picture can be viewed from any web browser, even from your mobile while you’re on the road.

What you will get:

  • See live stream in any web browser from anywhere
  • Record any motion into video file

Usually, such a cam will cost you around US$1.000, but with the result from this article, you will get such a cam for only about US$120.

Full article here:
Raspberry Pi as low-cost HD surveillance camera (CodeProject)

The only suggestion we might make as a possible addition to either project is that if you are using this to monitor an entry area (such as a front or back porch), why not include a few bright white LED’s to provide illumination at night?  Those could be turned on and off via a cron job on the Pi, or by some type if logic that detects when there’s not enough ambient light to get a decent image, and then applies power to the LEDs (which could be powered via a GPIO pin on the Raspberry Pi if they don’t draw too much current).