GMT Versus UTC
by Lawrence D'Oliveiro
It still seems to be common among groups outside the computing and
scientific worlds to talk about “GMT” rather than “UTC”. The trouble
with “GMT” is that it doesn’t seem to be clearly defined; it might or
might not differ from UTC by up to 0.9 seconds.
The (unadjusted) time reference defined by an official collection of
atomic clocks worldwide is called “TAI”. This pays no heed to the
slowing rotation of the Earth. Astronomers prefer a time reference
called “UT1”, which is based on the actual rotation of the Earth
(subject to some time-averaging, I think). The definition of “UTC” comes
from TAI, adjusted by applying leap seconds. These accumulate as needed
so as to keep UTC within 0.9 seconds of UT1, and we are currently up to
36 of them. That is, at 0:00:00 UTC today, TAI was actually 0:00:36.
The trouble with GMT is that it is not officially clear whether it is
the same as UT1, or the same as UTC. Given that it was originally
defined at the Greenwich Observatory, which was (is?) run by
astronomers, one would think they would make it the same as UT1. But
the practical fact is, our usual everyday timekeeping is based on
standard time zones, which are all defined as whole-second
(indeed, whole multiples of a half-hour) offsets from UTC.
4 years, 11 months
How Long Can A Filename Be?
by Lawrence D'Oliveiro
Allowed length of an individual file/directory name:
ldo@theon:~> getconf NAME_MAX /
255
Allowed length of a full path name:
ldo@theon:~> getconf PATH_MAX /
4096
The answers can be filesystem-specific; here “/” is an ext3 filesystem.
But on my /home, which is ext4, I get the same numbers.
4 years, 11 months
So How Did Your Leap-Second Go?
by Lawrence D'Oliveiro
At noon today NZ time, an extra second was inserted into UTC, the time
kept by the world’s atomic clocks. The time that was one second before
midnight UTC (one second before noon NZST) became two seconds before
intead: after 23:59:59 UTC came 23:59:60 UTC, before ticking over to
0:00:00 UTC.
The previous time this happened, three years ago, several Linux-based
systems malfunctioned. No word yet on how this one went...
<http://lwn.net/Articles/648313/>
4 years, 11 months
Doing For Video What PulseAudio Did For Audio
by Lawrence D'Oliveiro
Pinos is a project to allow better handling of video input across
multiple applications.
Pinos will make it easier to switch cameras in applications
and for the same camera source to be used by multiple apps
simultaneously, there will be support for multiple types of
video inputs, GStreamer integration, and some audio support.
Pinos should allow better screencasting within GNOME 3, video
support for desktop sandboxes, and many other potential
use-cases.
In an email, Christian mentioned why it didn't end up being
called PulseVideo over name squatting.
<http://phoronix.com/scan.php?page=news_item&px=Fedora-Pinos-Announced>
4 years, 11 months
presentations/demos for next meeting
by Peter Reutemann
Hi everyone
At the moment, we're still looking for a theme (read presenters) for
this month's WLUG meeting on July 27. Any takers?
As a fallback option, I was thinking of giving the new Linux Mint 17.2
a spin (MATE and Cinnamon) and Ian has plenty of Debian 8
installations on his machine to show off briefly.
Thanks.
Cheers, Peter
--
Peter Reutemann
Dept. of Computer Science
University of Waikato, NZ
+64 (7) 858-5174
http://www.cms.waikato.ac.nz/~fracpete/
http://www.data-mining.co.nz/
4 years, 11 months
MAC Address Privacy Standard Coming
by Lawrence D'Oliveiro
Every network interface (wired or wireless) on every networked device in
the world is assigned a unique 48-bit identifier—the MAC address—burned
into its ROM at manufacturing time. While it’s often (usually?)
possible to change this via the software driver, nobody thought of it
as a big deal.
Until recently, when certain, ahem, spying revelations have woken
people to the privacy implications of being able to track a machine,
particularly on wi-fi networks, based on its unique MAC address.
And so some folks at the Internet Engineering Task Force have been
doing experiments to determine whether randomly changing these addresses
would cause hiccups for any network protocols. The good news is that
the answer so far seems to be “no”.
<http://www.theregister.co.uk/2015/06/26/mac_address_privacy_inches_toward...>
4 years, 11 months
