My wild guess is that most people get a small Linux computer, like the Raspberry Pi, BeagleBone, Banana Pi or Orange Pi for a specific task. Unfortunately, most distributions are chock-full of software, with everything installed per default. But if you want to set up a lean single board computer for a specific task, you’re out of luck. Thankfully there is a Linux distribution, DietPi, that aims to fix that problem. ...
When you make your own NTP server, you probably spend a lot of time trying to get it as accurate and stable as possible. To get good results, you need to connect your server to a good time reference, like an atomic clock, GPS or a GPSDO to get the PPS (Pulse Per Second) to sync your server with the reference clock. In both Linux and BSD, there is kernel support to slave the very inaccurate CPU clock crystal to the PPS signal, continually adjusting the frequency, because the crystals of computers continuously drift due to temperature and barometric pressure differences. So most of the work is to get a crappy crystal to behave. What if you just jumped over that step, so the CPU clock gets synchronized with the same lab reference that the PPS signal uses, using a SI5351C Clock Generator? Read on to see a simple way of doing it and get an extremely accurate NTP server for under $200. ...
After becoming a full-fledged time-nut (I’m compiling a new Linux kernel on my second NTP server as we speak), I have started to use the statistics that I usually install on a server just to keep a check on it. Sure, when installing something like MRTG, it’s great to see if something is clogging the system, but mostly, it’s unused. But when working with an NTP server a lot of factors start to make a difference. The temperature of the processor (the whole computer actually, mostly due to crystal drift), the load of the CPU’s, etc. ...
Warning: as of yet, there is no official support for overclocking the Raspberry Pi 3, so you could damage your small computer. Just a reminder. Update: I’ve managed to make a DIY heatsink for the Raspberry Pi 3 for $4, and it’s running stable at 1.5GHz. Click here to read. The new version of Raspberry Pi 3 was released yesterday, so I naturally had to get two. I’m using two as Stratum-1 NTP servers, and with the old Raspberry Pi 2, I had hit the roof when it came down to getting better time resolution. So when I read that a new 50% faster version had been released, I raced to the nearest store and got a couple. I have one experimental NTP server that isn’t handing out time on the internet and another one that is the primary server, connected to the NTP Pool Project. I installed the experimental Raspberry Pi 3 first, so I could test performance and try to overclock it. And it went very well. ...
Update: You can download the Eagle PCB files for the PPS Pulse Width Extender here. The PCB is made to fit the Hammond 1455C802BK enclosure. I have two Stratum-1 NTP servers using Raspberry Pi 2’s as servers. But the two setups are entirely different. My primary NTP Stratum-1 server is available at ntp.jacken.se, but it is also in the .se pool of ntp.org. It’s a Raspberry Pi 2 I use a Raspberry Pi 3 that I have connected a U-Blox Neo-7 GPS receiver. But I’m not using the 1 PPS signal coming out of the U-Blox. I have a Trimble GPSDO that I bought from eBay. The unit has two 10 MHz lab reference outputs and one 1 PPS output. But after measuring the signal coming out from the GPSDO, I realized that the timing speed for the seconds “Tick” was only 10 µsec which is way to fast for the Raspberry Pi to pick up as an interrupt on one of the GPIO pins. So I built a pulse extender, making the pulse around 250 milliseconds instead. And now the Raspberry Pi picks up the pulse without problems. Some GPSDO units can set the pulse width by programming the unit via a serial port, but I can’t find that feature on this unit (which is poorly documented and was OEM made for some other manufacturer), so I had to do it with hardware. So how does it look when crunching the numbers on it? ...
The last couple of weeks I’ve been busy building a Raspberry Pi 2 Raspberry Pi 3 connected to my Trimble GPSDO using the 1 PPS output. The Trimble unit synchronizes with the atomic clocks onboard the GPS satellites, and the precision is fantastic! I bought the GPSDO to get a 10 MHz lab reference for my measure equipment, but after reading an article about Time-Nuts, people obsessed with measuring time as accurately as possible, and one of my friends showed me pictures of their new Stratum-1 NTP server rack he helped design, I was hooked. ...
Official Blog: A second spring of cleaning: We launched Google Reader in 2005 in an effort to make it easy for people to discover and keep tabs on their favorite websites. While the product has a loyal following, over the years usage has declined. So, on July 1, 2013, we will retire Google Reader. Users and developers interested in RSS alternatives can export their data, including their subscriptions, with Google Takeout over the course of the next four months. I don’t get it. So they count heads, and see that not as many people use Google Reader as they’d like. But the only people I know that use RSS on a daily basis are the one that counts. Bloggers, journalists and tech leaders. You know, the people that write and influence the rest of the heard. How can you not make money on the data Google gets by their reading habits? You want me to have to spend all day reading assorted ramblings on Google+ or Twitter to find some nuggets? I don’t have the time for that. ...
I love my music playback setup that consists of a couple of Squeezebox V3 players in different rooms so I can listen to music in lossless format wherever I am in the apartment. With the iPeng HD app on my iPad, I have a nice interface for controlling the players with album art and other nice features. But the best part is that I can playback high resolution audio directly on my iPad using the Camera Kit USB adapter and an HRT HeadStreamer DAC portable USB headphone amplifier. But I wanted a small, cheap and eco-friendly server for hosting my music files and wondered if I could use the Raspberry Pi. And here’s my findings. ...
Initial installation Ubuntu Server Last time I configured my web server with Ubuntu Server, I had problems finding all the instructions on what and how to install everything needed to get a WordPress blog with W3 Total Cache, CDN, Apache2 MPM Worker and fcgi working. So this is my attempt to write down the steps needed to get the server going. You might find it of interest if your needs are similar to mine. Here’s the requirements for my WordPress blog. Apache MPM Worker threaded version APC PHP Opcode optimizer All the required modules for W3 Total Cache Graphics libraries for Mint statistics ...
When setting up my new web server I had a problem when installing vsftpd on Ubuntu Server 12.04 LTS. After doing the sudo apt-get install vsftpd and enabling login for local users, I got a “Server 530 login incorrect error” when trying to connect with a local user. The settings for disabling anonymous login and allowing local users where set in /etc/vsftpd.conf. [cc lang=“bash”]anonymous_enable=NO local_enable=YES write_enable=YES[/cc] But the ftp server still refused to let me login with any of the users on the system. I tried remove and reinstall, but the problem persisted. Finally I found a thread where others had the same problem. And here’s how to fix the problem. [cc lang=“bash”] sudo apt-get remove vsftpd sudo rm /etc/pam.d/vsftpd sudo apt-get install vsftpd [/cc] ...