Monthly Archives: May 2016

Beat 500 points gpx track limit using Qmapshack as gpx file editor

Many Garmin devices have a limit of how many points a gpx track might have. You can bypass the limit by splitting a GPS track to segments of 500 points or less. Here is how to do it with a free Qmapshack program:

As an example, I took a 100km ride track from Strawberry Fields Forever ride. (Click on the link, click on 100km, export tab, download as GPX)

Let’s see the complete track on map: In Qmapshack, File-> Load GIS Data, select the gpx file. “Open SFF 100K” folder in Data window and double-click on the track.


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Server Wake-on-LAN on access

Most ethernet NICs support Wake on LAN feature – when a so-called magic packet wakes up the computer. This can save money, as running a Mac Pro 1,1 server fully awake could cost you at least $24.5 per month of electricity in California prices (that’s at the lowest tier of consumption).

To put my server to sleep, I use powernap (easy install via apt in Ubuntu). As I use ssh to access files, tracking TCP port 22 connection to keep server awake is a no brainer config setting.

There is a number of software utilities that could be used to send a magic packet to wake a remote machine, but if all you want is to access a file, firing up the utility each time seems too much hassle.

Running the command below on a unix-based router (OpenWRT, DD-WRT) connected to the same LAN as server will send a magic packet to your server on any access attempt. It works by sniffing for broadcast ARP packets looking for server’s IP address (e.g. and issues a magic packet to its MAC address (e.g 00:17:f2:0a:a6:3f).

Just edit the address values below, substituting LAN bridge interface, server’s IP address and MAC address, and put this line into the startup script of your router:

tcpdump -i eth1 -l arp and ether[0x26:1]=192 and ether[0x27:1]=168 and ether[0x28:1]=1 and ether[0x29:1]=191|while read -r line; do etherwake -i eth1 00:17:f2:0a:a6:3f; done&

good  luck!