Archive for July, 2013

How to fix slow DNS look-up’s in Firefox running under Linux

Sunday, July 21st, 2013

I’ve had this problem for some time now and chose today to do some research. Luckily, I found a workaround pretty quickly.

I use the Mozilla based browser GNU IceCat which is functionally equivalent to Mozilla Firefox. When a page is requested, the browser displays a small spinning icon in the left corner of the tab. Loading a page involves three basic steps: converting the URL into an IP address, contacting the web server at the IP address, receiving the web page (and other resources). During the first two steps, the icon will be grey and spinning counter-clockwise. The status bar will show messages like “Looking up google.com” and “Waiting for google.com”. Typically, DNS queries (the first step) take on the order of 100 ms to complete. Therefore if you see the first message, you may have the same problem.

The symptom was that IceCat (Firefox) was taking about 3 to 5 seconds to make DNS queries every time I tried to navigate to a new address. The cause of the problem seems to be that my system is making IPv6 DNS queries first by default but these types of requests are being ignored by the DNS resolver which doesn’t support IPv6. My system sends a query and then waits a certain amount of time before giving up and trying an IPv4 query. That time waiting was the delay I was experiencing.

The ideal fix would be to change the way the DNS resolver responds to IPv6 DNS queries. That’s obviously out of my control. A system-wide fix involves setting up your own DNS resolver – a bit more work than I’m interested in. The easy fix was to address the issue for IceCat (Firefox) only which is good enough for me as web-browsing is my primary internet activity.

The fix is to change the value for the key “network.dns.disableIPv6″ from “false” to “true” in IceCat’s (Firefox’s) “about:config” page.

For more information, the issue has been discussed extensively here:

https://bugs.launchpad.net/ubuntu/+source/eglibc/+bug/417757

The ‘Register’ page is now the ‘Log’ page

Wednesday, July 17th, 2013

I renamed the ‘Register’ page to the ‘Log’ page because the former was misleading. While I used the term as a noun (a list or record) it is more typically used online in its verb form (as in ‘to enroll’). Given the context, I decided that ‘log’ was less confusing. I refuse to use the term ‘blog’, since that term more often than not refers to useless narcissistic ramblings made specifically with a public audience in mind. In my case, my ‘log’ is as much for me as anyone else.

Edit 07/26/14:

Can someone tell me why this is the most popular page on this site? I’m very confused.

Binder clip alligator clip

Wednesday, July 17th, 2013

I needed alligator clips to connected some wires from a heater to the terminals of a power source but didn’t have any. The solution I came up with was to solder small metal binder clips on the ends of the wires instead.

To prepare the binder clip, I scrubbed the bottom, nearly flat side with steel wool and applied flux to the surface. I wetted the entire bottom of the cleaned surface with solder. I also pre-tinned the wired. Connecting the two went smoothly, simply heating both simultaneously with the iron until the solder melted on both and merged to a single junction. I’m really happy with this solution since I rarely have alligator clips handy whereas the opposite is true of binder clips.

binder alligator clip

How to make a hole in a light bulb without shattering it

Sunday, July 7th, 2013

In order to use a light bulb to illuminate the inside of a vacuum chamber, I needed to release the gas contained within the bulb else it would likely have exploded the bulb when the external pressure was reduced. However, I wanted to keep the glass intact in order to protect the fragile filament from my clumsy hands and to provide that soft white glow.

I first tried scoring and breaking only a small piece of the bulb, but that always resulted in an uncontrolled cracking/shattering of the entire bulb. The best suggestion I found on the internet involved using a CO2 laser to make the hole. That would probably work, but I’ll save building a CO2 laser from scratch for another day. Other suggestions typically involved drilling under running water at very low speeds with a very sharp drill bit. Since both patience and drills were in short supply, I tried another method.

I found that by using a metal file at a tangent to the glass, one can very slowly thin the glass in a relatively small area. In my experience, eventually the thinned glass breaks away leaving a small hole. The hole isn’t round and doesn’t form in an absolutely controllable way. Perhaps it may be possible to “punch” a smaller hole after thinning the glass but before it breaks.

light bulb