Planet Linux Australia

Syndicate content
Planet Linux Australia - http://planet.linux.org.au
Updated: 1 hour 26 sec ago

Gary Pendergast: Straight White Guy Discovers Diversity and Inclusion Problem in Open Source

Mon, 2018-09-24 23:04

This is a bit of strange post for me to write, it’s a topic I’m quite inexperienced in. I’ll warn you straight up: there’s going to be a lot of talking about my thought processes, going off on tangents, and a bit of over-explaining myself for good measure. Think of it something like high school math, where you had to “show your work”, demonstrating how you arrived at the answer. 20 years later, it turns out there really is a practical use for high school math.

Michael Still: Scared Weird Frozen Guy

Sat, 2018-09-22 11:00

The true life story of a kid from Bribie Island (I’ve been there!) running a marathon in Antartica, via being a touring musical comedian, doing things like this:

This book is an interesting and light read, and came kindly recommended by Michael Carden, who pretty much insisted I take the book off him at a cafe. I don’t regret reading it and would recommend it to people looking for a light autobiography for a rainy (and perhaps cold) evening or two.

Oh, and the Scared Weird Little Guys of course are responsible for this gem…

This book is highly recommended and now I really want to go for a run.

Title: Scared Weird Frozen Guy
Author: Rusty Berther
Genre: Comedians
Release Date: 2012
Pages: 325

After 20 incredible years as part of a musical comedy duo, Scared Weird Little Guy, Rusty Berther found himself running a marathon in Antarctica. What drove him to this? In this hilarious and honest account of his life as a Scared Weird Little Guy, and his long journey attempting an extreme physical and mental challenge at the bottom of the world, Rusty examines where he started from, and where he just might be going to.

Russell Coker: Words Have Meanings

Fri, 2018-09-21 01:03

As a follow-up to my post with Suggestions for Trump Supporters [1] I notice that many people seem to have private definitions of words that they like to use.

There are some situations where the use of a word is contentious and different groups of people have different meanings. One example that is known to most people involved with computers is “hacker”. That means “criminal” according to mainstream media and often “someone who experiments with computers” to those of us who like experimenting with computers. There is ongoing discussion about whether we should try and reclaim the word for it’s original use or whether we should just accept that’s a lost cause. But generally based on context it’s clear which meaning is intended. There is also some overlap between the definitions, some people who like to experiment with computers conduct experiments with computers they aren’t permitted to use. Some people who are career computer criminals started out experimenting with computers for fun.

But some times words are misused in ways that fail to convey any useful ideas and just obscure the real issues. One example is the people who claim to be left-wing Libertarians. Murray Rothbard (AKA “Mr Libertarian”) boasted about “stealing” the word Libertarian from the left [2]. Murray won that battle, they should get over it and move on. When anyone talks about “Libertarianism” nowadays they are talking about the extreme right. Claiming to be a left-wing Libertarian doesn’t add any value to any discussion apart from demonstrating the fact that the person who makes such a claim is one who gives hipsters a bad name. The first time penny-farthings were fashionable the word “libertarian” was associated with left-wing politics. Trying to have a sensible discussion about politics while using a word in the opposite way to almost everyone else is about as productive as trying to actually travel somewhere by penny-farthing.

Another example is the word “communist” which according to many Americans seems to mean “any person or country I don’t like”. It’s often invoked as a magical incantation that’s supposed to automatically win an argument. One recent example I saw was someone claiming that “Russia has always been communist” and rejecting any evidence to the contrary. If someone was to say “Russia has always been a shit country” then there’s plenty of evidence to support that claim (Tsarist, communist, and fascist Russia have all been shit in various ways). But no definition of “communism” seems to have any correlation with modern Russia. I never discovered what that person meant by claiming that Russia is communist, they refused to make any comment about Russian politics and just kept repeating that it’s communist. If they said “Russia has always been shit” then it would be a clear statement, people can agree or disagree with that but everyone knows what is meant.

The standard response to pointing out that someone is using a definition of a word that is either significantly different to most of the world (or simply inexplicable) is to say “that’s just semantics”. If someone’s “contribution” to a political discussion is restricted to criticising people who confuse “their” and “there” then it might be reasonable to say “that’s just semantics”. But pointing out that someone’s writing has no meaning because they choose not to use words in the way others will understand them is not just semantics. When someone claims that Russia is communist and Americans should reject the Republican party because of their Russian connection it’s not even wrong. The same applies when someone claims that Nazis are “leftist”.

Generally the aim of a political debate is to convince people that your cause is better than other causes. To achieve that aim you have to state your cause in language that can be understood by everyone in the discussion. Would the person who called Russia “communist” be more or less happy if Russia had common ownership of the means of production and an absence of social classes? I guess I’ll never know, and that’s their failure at debating politics.

Related posts:

  1. TED – Defining Words I recently joined the community based around the TED conference...
  2. political compass It appears that some people don’t understand what right-wing means...
  3. Terms of Abuse for Minority Groups Due to the comments on my blog post about Divisive...

Linux Users of Victoria (LUV) Announce: LUV October 2018 Workshop

Tue, 2018-09-18 01:03
Start: Oct 20 2018 12:30 End: Oct 20 2018 16:30 Start: Oct 20 2018 12:30 End: Oct 20 2018 16:30 Location:  Infoxchange, 33 Elizabeth St. Richmond Link:  http://luv.asn.au/meetings/map

Topic To Be Announced

There will also be the usual casual hands-on workshop, Linux installation, configuration and assistance and advice. Bring your laptop if you need help with a particular issue. This will now occur BEFORE the talks from 12:30 to 14:00. The talks will commence at 14:00 (2pm) so there is time for people to have lunch nearby.

The meeting will be held at Infoxchange, 33 Elizabeth St. Richmond 3121.  Late arrivals please call (0421) 775 358 for access to the venue.

LUV would like to acknowledge Infoxchange for the venue.

Linux Users of Victoria is a subcommittee of Linux Australia.

October 20, 2018 - 12:30

Linux Users of Victoria (LUV) Announce: LUV October 2018 Main Meeting

Tue, 2018-09-18 01:03
Start: Oct 2 2018 18:30 End: Oct 2 2018 20:30 Start: Oct 2 2018 18:30 End: Oct 2 2018 20:30 Location:  Kathleen Syme Library, 251 Faraday Street Carlton VIC 3053 Link:  http://www.melbourne.vic.gov.au/community/hubs-bookable-spaces/kathleen-syme-lib...

PLEASE NOTE RETURN TO ORIGINAL START TIME

6:30 PM to 8:30 PM Tuesday, October 2, 2018
Training Room, Kathleen Syme Library, 251 Faraday Street Carlton VIC 3053

Speakers:

  • To Be Announced

Many of us like to go for dinner nearby after the meeting, typically at Brunetti's or Trotters Bistro in Lygon St.  Please let us know if you'd like to join us!

Linux Users of Victoria is a subcommittee of Linux Australia.

October 2, 2018 - 18:30

Gary Pendergast: The Mission: Democratise Publishing

Sun, 2018-09-16 15:04

It’s exciting to see the Drupal Gutenberg project getting under way, it makes me proud of the work we’ve done ensuring the flexibility of the underlying Gutenberg architecture. One of the primary philosophies of Gutenberg’s technical architecture is platform agnosticism, and we can see the practical effects of this practice coming to fruition across a variety of projects.

Yoast are creating new features for the block editor, as well as porting existing features, which they’re able to reuse in the classic editor.

Outside of WordPress Core, the Automattic teams who work on Calypso have been busy adding Gutenberg support, in order to make the block editor interface available on WordPress.com. Gutenberg and Calypso are large JavaScript applications, built with strong opinions on design direction and technical architecture, and having significant component overlap. That these two projects can function together at all is something of an obscure engineering feat that’s both difficult and overwhelming to appreciate.

If we reached the limit of Gutenberg’s platform agnosticism here, it would still be a successful project.

But that’s not where the ultimate goals of the Gutenberg project stand. From early experiments in running the block editor as a standalone application, to being able to compile it into a native mobile component, and now seeing it running on Drupal, Gutenberg’s technical goals have always included a radical level of platform agnosticism.

Better Together

Inside the WordPress world, significant effort and focus has been on ensuring backwards compatibility with existing WordPress sites, plugins, and practices. Given that WordPress is such a hugely popular platform, it’s exceedingly important to ensure this is done right. With Gutenberg expanding outside of the WordPress world, however, we’re seeing different focuses and priorities arise.

The Gutenberg Cloud service is a fascinating extension being built as part of the Drupal Gutenberg project, for example. It provides a method for new blocks to be shared and discovered, the sample hero block sets a clear tone of providing practical components that can be rapidly put together into a full site. While we’ve certainly seen similar services appear for the various site builder plugins, this is the first one (that I’m aware of, at least) build specifically for Gutenberg.

By making the Gutenberg experience available for everyone, regardless of their technical proficiency, experience, or even preferred platform, we pave the way for a better future for all.

Democratising Publishing

You might be able to guess where this is going.

David Rowe: Porting a LDPC Decoder to a STM32 Microcontroller

Sat, 2018-09-15 09:04

A few months ago, FreeDV 700D was released. In that post, I asked for volunteers to help port 700D to the STM32 microcontroller used for the SM1000. Don Reid, W7DMR stepped up – and has been doing a fantastic job porting modules of C code from the x86 to the STM32.

Here is a guest post from Don, explaining how he has managed to get a powerful LDPC decoder running on the STM32.

LDPC for the STM32

The 700D mode and its LDPC function were developed and used on desktop (x86) platforms. The LDPC decoder is implemented in the mpdecode_core.c source file.

We’d like to run the decoder on the SM1000 platform which has an STM32F4 processor. This requires the following changes:

  • The code used doubles in several places, while the stm32 has only single precision floating point hardware.
  • It was thought that the memory used might be too much for a system with just 192k bytes of RAM.
  • There are 2 LDPC codes currently supported, HRA_112_112 used in 700D and, H2064_516_sparse used for Balloon Telemetry. While only the 700D configuration needed to work on the STM32 platform, any changes made to the mainstream code needed to work with the H2064_516_sparse code.

Testing

Before making changes it was important to have a well defined test process to validate new versions. This allowed each change to be validated as it was made. Without this the final debugging would likely have been very difficult.

The ldpc_enc utility can generate standard test frames and the ldpc_dec utility receive the frames and measure bit errors. So errors can be detected directly and BER computed. ldpc_enc can also output soft decision symbols to emulate what the modem would receive and pass into the LDPC decoder. A new utility ldpc_noise was written to add AWGN to the sample values between the above utilities. here is a sample run:

$ ./ldpc_enc /dev/zero - --sd --code HRA_112_112 --testframes 100 | ./ldpc_noise - - 1 | ./ldpc_dec - /dev/null --code HRA_112_112 --sd --testframes single sided NodB = 1.000000, No = 1.258925 code: HRA_112_112 code: HRA_112_112 Nframes: 100 CodeLength: 224 offset: 0 measured double sided (real) noise power: 0.640595 total iters 3934 Raw Tbits..: 22400 Terr: 2405 BER: 0.107 Coded Tbits: 11200 Terr: 134 BER: 0.012

ldpc_noise is passed a “No” (N-zero) level of 1dB, Eb=0, so Eb/No = -1, and we get a 10% raw BER, and 1% after LDPC decoding. This is a typical operating point for 700D.

A shell script (ldpc_check) combines several runs of these utilities, checks the results, and provides a final pass/fail indication.

All changes were made to new copies of the source files (named *_test*) so that current users of codec2-dev were not disrupted, and so that the behaviour could be compared to the “released” version.

Unused Functions

The code contained several functions which are not used anywhere in the FreeDV/Codec2 system. Removing these made it easier to see the code that was used and allowed the removal of some variables and record elements to reduce the memory used.

First Compiles

The first attempt at compiling for the stm32 platform showed that the the code required more memory than was available on the processor. The STM32F405 used in the SM1000 system has 128k bytes of main RAM.

The largest single item was the DecodedBits array which was used to saved the results for each iteration, using 32 bit integers, one per decoded bit.

int *DecodedBits = calloc( max_iter*CodeLength, sizeof( int ) );

This used almost 90k bytes!

The decode function used for FreeDV (SumProducts) used only the last decoded set. So the code was changed to save only one pass of values, using 8 bit integers. This reduced the ~90k bytes to just 224 bytes!

The FreeDV 700D mode requires on LDPC decode every 160ms. At this point the code compiled and ran but was too slow – using around 25ms per iteration, or 300 – 2500ms per frame!

C/V Nodes

The two main data structures of the LDPC decoder are c_nodes and v_nodes. Each is an array where each node contains additional arrays. In the original code these structures used over 17k bytes for the HRA_112_112 code.

Some of the elements of the c and v nodes (index, socket) are indexes into these arrays. Changing these from 32 bit to 16 bit integers and changing the sign element into a 8 bit char saved about 6k bytes.

The next problem was the run time. Each 700D frame must be fully processed in 160 ms and the decoder was taking several times this long. The CPU load was traced to the phi0() function, which was calling two maths library functions. After optimising the phi0 function (see below) the largest use of time was the index computations of the nested loops which accessed these c and v node structures.

With each node having separate arrays for index, socket, sign, and message these indexes had to be computed separately. By changing the node structures to hold an array of sub-nodes instead this index computation time was significantly reduced. An additional benefit was about a 4x reduction in the number of memory blocks allocated. Each allocation block includes additional memory used by malloc() and free() so reducing the number of blocks reduces memory use and possible heap fragmentation.

Additional time was saved by only calculating the degree elements of the c and v nodes at start-up rather than for every frame. That data is kept in memory that is statically allocated when the decoder is initialized. This costs some memory but saves time.

This still left the code calling malloc several hundred times for each frame and then freeing that memory later. This sort of memory allocation activity has been known to cause troubles in some embedded systems and is usually avoided. However the LDPC decoder needed too much memory to allow it to be statically allocated at startup and not shared with other parts of the code.

Instead of allocating an array of sub-nodes for each c or v node, a single array of bytes is passed in from the parent. The initialization function which calculates the degree elements of the nodes also counts up the memory space needed and reports this to its caller. When the decoder is called for a frame, the node’s pointers are set to use the space of this array.

Other arrays that the decoder needs were added to this to further reduce the number of separate allocation blocks.

This leaves the decisions of how to allocate and share this memory up to a higher level of the code. The plan is to continue to use malloc() and free() at a higher level initially. Further testing can be done to look for memory leakage and optimise overall memory usage on the STM32.

PHI0

There is a non linear function named “phi0” which is called inside several levels of nested loops within the decoder. The basic operation is:

phi0(x) = ln( (e^x + 1) / (e^x - 1) )

The original code used double precision exp() and log(), even though the input, output, and intermediate values are all floats. This was probably an oversight. Changing to the single single precision versions expf() and logf() provided some improvements, but not enough to meet our CPU load goal.

The original code used piecewise approximation for some input values. This was extended to cover the full range of inputs. The code was also structured differently to make it faster. The original code had a sequence of if () else if () else if () … This can take a long time when there are many steps in the approximation. Instead two ranges of input values are covered with linear steps that is implemented with table lookups.

The third range of inputs in non linear and is handled by a binary tree of comparisons to reduce the number of levels. All of this code is implemented in a separate file to allow the original or optimised version of phi0 to be used.

The ranges of inputs are:

x >= 10 result always 0 10 > x >= 5 steps of 1/2 5 > x >= 1/16 steps of 1/16 1/16 > x >= 1/4096 use 1/32, 1/64, 1/128, .., 1/4096 1/4096 > x result always 10

The range of values that will appear as inputs to phi0() can be represented with as fixed point value stored in a 32 bit integer. By converting to this format at the beginning of the function the code for all of the comparisons and lookups is reduced and uses shifts and integer operations. The step levels use powers of 2 which let the table index computations use shifts and make the fraction constants of the comparisons simple ones that the ARM instruction set can create efficiently.

Misc

Two of the configuration values are scale factors that get multiplied inside the nested loops. These values are 1.0 in both of the current configurations so that floating point multiply was removed.

Results

The optimised LDPC decoder produces the same output BER as the original.

The optimised decoder uses 12k of heap at init time and needs another 12k of heap at run time. The original decoder just used heap at run time, that was returned after each call. We have traded off the use of static heap to clean up the many small heap allocations and reduce execution time. It is probably possible to reduce the static space further perhaps at the cost of longer run times.

The maximum time to decode a frame using 100 iterations is 60.3 ms and the median time is 8.8 ms, far below our budget of 160ms!

Future Possibilities

The remaining floating point computations in the decoder are addition and subtraction so the values could be represented with fix point values to eliminate the floating point operations.

Some values which are computed from the configuration (degree, index, socket) are constants and could be generated at compile time using a utility called by cmake. However this might actually slow down the operation as the index computations might become slower.

The index and socket elements of C and V nodes could be pointers instead of indexes into arrays.

Experiments would be required to ensure these changes actually speed up the decoder.

Bio

Don got his first amateur license in high school but was soon distracted with getting an engineering degree (BSEE, Univ. of Washington), then family and life. He started his IC design career with the CPU for the HP-41C calculator. Then came ICs for printers and cameras, work on IC design tools, and some firmware for embedded systems. Exposure to ARES public service lead to a new amateur license – W7DMR and active involvement with ARES. He recently retired after 42 years and wanted to find an open project that combined radio, embedded systems and DSP.

Don lives in Corvallis, Oregon, USA a small city with the state technical university and several high tech companies.

Open Source Projects and Volunteers

Hi it’s David back again ….

Open source projects like FreeDV and Codec 2 rely on volunteers to make them happen. The typical pattern is people get excited, start some work, then drift away after a few weeks. Gold is the volunteer that consistently works week in, week out until their particular project is done. The number of hours/week doesn’t matter – it’s the consistency that is really helpful to the projects. I have a few contributors/testers/users of FreeDV in this category and I appreciate you all deeply – thank you.

If you would like to help out, please contact me. You’ll learn a lot and get to work towards an open source future for HF radio.

If you can’t help out technically, but would like to support this work, please consider Patreon or PayPal.

Reading Further

LDPC using Octave and the CML library. Our LDPC decoder comes from Coded Modulation Library (CML), which was originally used to support Matlab/Octave simulations.

Horus 37 – High Speed SSTV Images. The CML LDPC decoder was converted to a regular C library, and used for sending images from High Altitude Balloons.

Steve Ports an OFDM modem from Octave to C. Steve is another volunteer who put in a fine effort on the C coding of the OFDM modem. He recently modified the modem to handle high bit rates for voice and HF data applications.

Rick Barnich KA8BMA did a fantastic job of designing the SM1000 hardware. Leading edge, HF digital voice hardware, designed by volunteers.

David Rowe: Tony K2MO Tests FreeDV

Thu, 2018-09-13 09:04

Tony, K2MO, has recently published some fine videos of FreeDV 1600, 700C, and 700D passing through simulated HF channels. The results are quite interesting.

This video shows the 700C mode having the ability to decode with 50% of it’s carriers removed:

This 700C modem sends two copies of the tx signal at high and low frequencies, a form of diversity to help overcome selective fading. These are the combined at the receiver.

Tony’s next video shows three FreeDV modes passing through a selective fading HF channel simulation:

This particular channel has slow fading, a notch gradually creeps across the spectrum.

Tony originally started testing to determine which FreeDV mode worked best on NVIS paths. He used path parameters based on VOACAP prediction models which show the relative time delay and signal power for the each propagation mode i.e., F1, F2:

Note the long delay paths (5ms). The CCIR NVIS path model also suggests a path delay of 7ms. That much delay puts the F-layer at 1000 km (well out into space), which is a bit of a puzzle.

This video shows the results of the VOCAP NVIS path:

In this case 700C does better than 700D. The 700C modem (COHPSK) is a parallel tone design, which is more robust to long multipath delays. The OFDM modem used for 700D is configured for multipath delays of up to 2ms, but tends to fall over after that as the “O” for Orthogonal assumption breaks down. It can be configured for longer delays, at a small cost in low SNR performance.

The OFDM modem gives much tighter packing for carriers, which allows us to include enough bits for powerful FEC, and have a very narrow RF bandwidth compared to 700C. FreeDV 700D has the ability to perform interleaving (Tools-Options “FreeDV 700 Options”), which is a form of time diversity. This feature is not widely used at present, but simulations suggest it is worth up to 4dB.

It would be interesting to combine frequency diversity, LDPC, and OFDM in a wider bandwidth signal. If anyone is interested in doing a little C coding to try this let me know.

I’ve actually seen long delay on NVIS paths in the “real world”. Here is a 40M 700D contact between myself and Mark, VK5QI, who is about 40km away from me. Note at times there are notches on the waterfall 200Hz apart, indicating a round trip path delay of 1500km:

Reading Further

Modems for HF Digital Voice Part 1
, explaining the frequency diversity used in 700C
Testing FreeDV 700C, shows how to use some built in test features like noise insertion and interfering carriers.
FreeDV 700D
FreeDV User Guide, including new 700D features like interleaving

Russell Coker: Thinkpad X1 Carbon Gen 6

Tue, 2018-09-11 21:03

In February I reviewed a Thinkpad X1 Carbon Gen 1 [1] that I bought on Ebay.

I have just been supplied the 6th Generation of the Thinkpad X1 Carbon for work, which would have cost about $1500 more than I want to pay for my own gear. ;)

The first thing to note is that it has USB-C for charging. The charger continues the trend towards smaller and lighter chargers and also allows me to charge my phone from the same charger so it’s one less charger to carry. The X1 Carbon comes with a 65W charger, but when I got a second charger it was only 45W but was also smaller and lighter.

The laptop itself is also slightly smaller in every dimension than my Gen 1 version as well as being noticeably lighter.

One thing I noticed is that the KDE power applet disappears when battery is full – maybe due to my history of buying refurbished laptops I haven’t had a battery report itself as full before.

Disabling the touch pad in the BIOS doesn’t work. This is annoying, there are 2 devices for mouse type input so I need to configure Xorg to only read from the Trackpoint.

The labels on the lid are upside down from the perspective of the person using it (but right way up for people sitting opposite them). This looks nice for observers, but means that you tend to put your laptop the wrong way around on your desk a lot before you get used to it. It is also fancier than the older model, the red LED on the cover for the dot in the I in Thinkpad is one of the minor fancy features.

As the new case is thinner than the old one (which was thin compared to most other laptops) it’s difficult to open. You can’t easily get your fingers under the lid to lift it up.

One really annoying design choice was to have a proprietary Ethernet socket with a special dongle. If the dongle is lost or damaged it will probably be expensive to replace. An extra USB socket and a USB Ethernet device would be much more useful.

The next deficiency is that it has one USB-C/DisplayPort/Thunderbolt port and 2 USB 3.1 ports. USB-C is going to be used for everything in the near future and a laptop with only a single USB-C port will be as annoying then as one with a single USB 2/3 port would be right now. Making a small laptop requires some engineering trade-offs and I can understand them limiting the number of USB 3.1 ports to save space. But having two or more USB-C ports wouldn’t have taken much space – it would take no extra space to have a USB-C port in place of the proprietary Ethernet port. It also has only a HDMI port for display, the USB-C/Thunderbolt/DisplayPort port is likely to be used for some USB-C device when you want an external display. The Lenovo advertising says “So you get Thunderbolt, USB-C, and DisplayPort all rolled into one”, but really you get “a choice of one of Thunderbolt, USB-C, or DisplayPort at any time”. How annoying would it be to disconnect your monitor because you want to read a USB-C storage device?

As an aside this might work out OK if you can have a DisplayPort monitor that also acts as a USB-C hub on the same cable. But if so requiring a monitor that isn’t even on sale now to make my laptop work properly isn’t a good strategy.

One problem I have is that resume from suspend requires holding down power button. I’m not sure if it’s hardware or software issue. But suspend on lid close works correctly and also suspend on inactivity when running on battery power. The X1 Carbon Gen 1 that I own doesn’t suspend on lid close or inactivity (due to a Linux configuration issue). So I have one laptop that won’t suspend correctly and one that won’t resume correctly.

The CPU is an i5-8250U which rates 7,678 according to cpubenchmark.net [2]. That’s 92% faster than the i7 in my personal Thinkpad and more importantly I’m likely to actually get that performance without having the CPU overheat and slow down, that said I got a thermal warning during the Debian install process which is a bad sign. It’s also only 114% faster than the CPU in the Thinkpad T420 I bought in 2013. The model I got doesn’t have the fastest possible CPU, but I think that the T420 didn’t either. A 114% increase in CPU speed over 5 years is a long way from the factor of 4 or more that Moore’s law would have predicted.

The keyboard has the stupid positions for the PgUp and PgDn keys I noted on my last review. It’s still annoying and slows me down, but I am starting to get used to it.

The display is FullHD, it’s nice to have a laptop with the same resolution as my phone. It also has a slider to cover the built in camera which MIGHT also cause the microphone to be disconnected. It’s nice that hardware manufacturers are noticing that some customers care about privacy.

The storage is NVMe. That’s a nice feature, although being only 240G may be a problem for some uses.

Conclusion

Definitely a nice laptop if someone else is paying.

The fact that it had cooling issues from the first install is a concern. Laptops have always had problems with cooling and when a laptop has cooling problems before getting any dust inside it’s probably going to perform poorly in a few years.

Lenovo has gone too far trying to make it thin and light. I’d rather have the same laptop but slightly thicker, with a built-in Ethernet port, more USB ports, and a larger battery.

Related posts:

  1. More About the Thinkpad X301 Last month I blogged about the Thinkpad X301 I got...
  2. Thinkpad T420 I’ve owned a Thinkpad T61 since February 2010 [1]. In...
  3. Thinkpad X1 Carbon I just bought a Thinkpad X1 Carbon to replace my...

Jeremy Visser: ABC iview and the ‘Australia tax’

Tue, 2018-09-11 19:04
Unless you have been living in a cave, it is probable that you heard about a federal parliamentary inquiry into IT pricing (somewhat aptly entitled “At what cost? — IT pricing and the Australia tax”) which reported that, amongst other things, online geo-blocking can as much as double pricing for IT products in what is blatant price discrimination. Not only do Australians pay, on average, 42% more than US’ians for Adobe products, and 66% more for Microsoft products, but music (such as the iTunes Store), video games, and e-books (e.

Jeremy Visser: iPads as in-flight entertainment

Tue, 2018-09-11 19:04
I’m writing this whilst sitting on a Qantas flight from Perth to Sydney, heading home after attending the fantastic linux.conf.au 2014. The plane is a Boeing 767, and unlike most flights I have been on in the last decade, this one has no in-flight entertainment system built into the backs of seats. Instead, every passenger is issued with an Apple iPad (located in the back seat pocket), fitted with what appears to be a fairly robust leather jacket emblazoned with the words “SECURITY DEVICE ATTACHED” (presumably to discourage theft).

Jeremy Visser: You reap what you sow

Tue, 2018-09-11 19:04
So the ABC has broken iview for all non–Chrome Linux users. How so? Because the ABC moved iview to use a streaming format supported only by the latest versions of Adobe Flash (e.g. version 11.7, which is available on Windows and OS X), but Adobe have ceased Linux support for Flash as of version 11.2 (for reasons I don’t yet understand, some users report that the older Flash 10.3 continues to work with iview).

Jeremy Visser: Turning out the lights

Tue, 2018-09-11 19:04
We put an unbelievable amount of data in the hands of third parties. In plain text. Traceable right back to you with mimimal effort to do so. For me, giving my data to the likes of Google, Apple, Microsoft, and the rest of the crowd, has always been a tradeoff: convenience vs. privacy. Sometimes, privacy wins. Most of the time, convenience wins. My iPhone reports in to Apple. My Android phone reports in to Google.

Jeremy Visser: We do not tolerate bugs; they are of the devil

Tue, 2018-09-11 19:04
I was just reading an article entitled “Nine traits of the veteran network admin”, and this point really struck a chord with me: Veteran network admin trait No. 7: We do not tolerate bugs; they are of the devil On occasion, conventional troubleshooting or building new networks run into an unexplainable blocking issue. After poring over configurations, sketching out connections, routes, and forwarding tables, and running debugs, one is brought no closer to solving the problem.

Jeremy Visser: SPA525G with ASA 9.1.x

Tue, 2018-09-11 19:04
At work, we have a staff member who has a Cisco SPA525G phone at his home that has built-in AnyConnect VPN support. Over the weekend, I updated our Cisco ASA firewall (which sits in front of our UC500 phone system) from version 8.4.7 to 9.1.3 and the phone broke with the odd error “Failed to obtain WebVPN cookie”. Turns out the fix was very simple. Just update the firmware on the SPA525G to the latest version.

Jeremy Visser: Floppy drive music

Tue, 2018-09-11 19:04
Some time in 2013 I set up a rig to play music with a set of floppy drives. At linux.conf.au 2015 in Auckland I gave a brief lightning talk about this, and here is a set of photos and some demo music to accompany. The hardware consists of six 3.5″ floppy drives connected to a LeoStick (Arduino) via custom vero board that connects the direction and step pins (18 and 20, respectively) as well as permanently grounding the select pin A (14).

Jeremy Visser: Configuring Windows for stable IPv6 addressing

Tue, 2018-09-11 19:04
By default, Windows will use randomised IPv6 addresses, rather than using stable EUI-64 addresses derived from the MAC address. This is great for privacy, but not so great for servers that need a stable address. If you run an Exchange mail server, or need to be able to access the server remotely, you will want a stable IPv6 address assigned. You may think this is possible simply by editing the NIC and setting a manual IPv6 address.

Jeremy Visser: One week with the Nexus 5

Tue, 2018-09-11 19:04
My ageing Motorola Milestone finally received a kick to the bucket last week when my shiny new Nexus 5 phone arrived. Though fantastic by 2009 standards, the Milestone could only officially run Android 2.2, and 2.3 with the help of an unofficial CyanogenMod port. Having been end-of-lifed for some time now, and barely being able to render a complex web page without running out of memory, it was time for me to move on.

Jeremy Visser: Restore ASA 5500 configuration from blank slate

Tue, 2018-09-11 19:04
The Cisco ASA 5500 series (e.g. 5505, 5510) firewalls have a fairly nice GUI interface called ASDM. It can sometimes be a pain, but it could be a lot worse than it is. One of the nice things ASDM does it let you save a .zip file backup of your entire ASA configuration. It includes your startup-configuration, VPN secrets, AnyConnect image bundles, and all those other little niceties. But when you set up an ASA from scratch to restore from said .

Russell Coker: Fail2ban

Sun, 2018-09-09 17:03

I’ve recently setup fail2ban [1] on a bunch of my servers. It’s purpose is to ban IP addresses associated with password guessing – or whatever other criteria for badness you configure. It supports Linux, OpenBSD [2] and probably most Unix type OSs too. I run Debian so I’ve been using the Debian packages of fail2ban.

The first thing to note is that it is very easy to install and configure (for the common cases at least). For a long time installing it had been on my todo list but I didn’t make the time to do it, after installing it I realised that I should have done it years ago, it was so easy.

Generally to configure it you just create a file under /etc/fail2ban/jail.d with the settings you want, any settings that are different from the defaults will override them. For example if you have a system running dovecot on the default ports and sshd on port 999 then you could put the following in /etc/fail2ban/jail.d/local.conf:

[dovecot] enabled = true [sshd] port = 999

By default the Debian package of fail2ban only protects sshd.

When fail2ban is running on Linux the command “iptables -L -n -v|grep f2b” will show the rules that match inbound traffic and the names of the chains they direct traffic to. To see if fail2ban has acted to protect a service you can run a command like “iptables -L f2b-sshd -n” to see the iptables rules.

The fail2ban entries in the INPUT table go before other rules, so it should work with any custom iptables rules you have configured as long as either fail2ban is the last thing to be started or your custom rules don’t flush old entries.

There are hooks for sending email notifications etc, that seems excessive to me but it’s always good to have options to extend a program.

In the past I’ve tried using kernel rate limiting to minimise hostile activity. That didn’t work well as there are legitimate end users who do strange things (like a user who setup their web-cam to email them every time it took a photo).

Conclusion

Fail2ban has some good features. I don’t think it will do much good at stopping account compromise as anything that is easily guessed could be guessed using many IP addresses and anything that has a good password can’t be guessed without taking many years of brute-force attacks while also causing enough noise in the logs to be noticed. What it does do is get rid of some of the noise in log files which makes it easier to find and fix problems. To me the main benefit is to improve the signal to noise ratio of my log files.

Related posts:

  1. Ethernet Interface Naming With Systemd Systemd has a new way of specifying names for Ethernet...
  2. Using LetsEncrypt Lets Encrypt is a new service to provide free SSL...
  3. Debian SSH Problems It has recently been announced that Debian had a serious...