Archive for the Linux Category

Glibc GHOST vulnerability

Posted in Linux with tags , , , , , on January 28, 2015 by xi'an

screen shot with ubuntu 10.10Just heard about a security vulnerability on Linux machines running Red Hat version 5 to 7, Ubuntu 10.04 and 12.04, Debian version 7, Fedora versions 19 and older, and SUSE versions 11 and older. The vulnerability occurs through a buffer overflow from some functions in the C library Glibc, which allows for a remote code to execute, and the fix to the problem is indicated on that NixCRaft webpage. (It is also possible to run the GHOST C code if you want to live dangerously!)



BibTool on the air

Posted in Books, Linux, Travel, University life with tags , , , , , , , , , , on October 23, 2014 by xi'an

Yesterday night, just before leaving for Coventry, I realised I had about 30 versions of my “mother of all .bib” bib file, spread over directories and with broken links with the original mother file… (I mean, I always create bib files in new directories by a hard link,

    ln ~/mother.bib

but they eventually and inexplicably end up with a life of their own!) So I decided a Spring clean-up was in order and installed BibTool on my Linux machine to gather all those versions into a new encompassing all-inclusive bib reference. I did not take advantage of the many possibilities of the program, written by Gerd Neugebauer, but it certainly solved my problem: once I realised I had to set the variates

check.double = on
check.double.delete = on
pass.comments = off

all I had to do was to call

bibtool -s -i ../*/*.bib -o mother.bib
bibtool -d -i mother.bib -o mother.bib
bibtool -s -i mother.bib -o mother.bib

to merge all bib file and then to get rid of the duplicated entries in mother.bib (the -d option commented out the duplicates and the second call with -s removed them). And to remove the duplicated definitions in the preamble of the file. This took me very little time in the RER train from Paris-Dauphine (where I taught this morning, having a hard time to make the students envision the empirical cdf as an average of Dirac masses!) to Roissy airport, in contrast with my pedestrian replacement of all stray siblings of the mother bib into new proper hard links, one by one. I am sure there is a bash command that could have done it in one line, but I spent instead my flight to Birmingham switching all existing bib files, one by one…

how far can we go with Minard’s map?!

Posted in Books, Linux, pictures, Statistics, Travel with tags , , , , , , , , , , on October 13, 2014 by xi'an

Like many others, I discovered Minard’s map of the catastrophic 1812 Russian campaign of Napoleon in Tufte’s book. And I consider it a masterpiece for its elegant way of summarising some many levels of information about this doomed invasion of Russia. So when I spotted Menno-Jan Kraak’s Mapping Time, analysing the challenges of multidimensional cartography through this map and this Naepoleonic campaign, I decided to get a look at it.

Apart from the trivia about Kraak‘s familial connection with the Russian campaign and the Berezina crossing which killed one of his direct ancestors, his great-great-grandfather, along with a few dozen thousand others (even though this was not the most lethal part of the campaign), he brings different perspectives on the meaning of a map and the quantity of information one could or should display. This is not unlike other attempts at competiting with Minard, including those listed on Michael Friendly’s page. Incl. the cleaner printing above. And the dumb pie-chart… A lot more can be done in 2013 than in 1869, indeed, including the use of animated videos, but I remain somewhat sceptical as to the whole purpose of the book. It is a beautiful object, with wide margins and nice colour reproductions, for sure, alas… I just do not see the added value in Kraak‘s work. I would even go as far as thinking this is an a-statistical approach, namely that by trying to produce as much data as possible into the picture, he forgets the whole point of the drawing which is I think to show the awful death rate of the Grande Armée along this absurd trip to and from Moscow and the impact of temperature (although the rise that led to the thaw of the Berezina and the ensuing disaster does not seem correlated with the big gap at the crossing of the river). If more covariates were available, two further dimensions could be added: the proportions of deaths due to battle, guerilla, exhaustion, desertion, and the counterpart map of the Russian losses. In the end, when reading Mapping Time, I learned more about the history surrounding this ill-planned military campaign than about the proper display of data towards informative and unbiased graphs.

unicode in LaTeX

Posted in Books, Linux, Statistics, University life with tags , , , , , , on October 9, 2014 by xi'an

As I was hurriedly trying to cram several ‘Og posts into a conference paper (!), I looked around for a way of including Unicode characters straight away. And found this solution on StackExchange:


which just suited me fine!

echo vulnerable

Posted in Linux with tags , , , on October 3, 2014 by xi'an

screen shot with ubuntu 10.10Even though most people are now aware of the Shellshock security problem on the bash shell, here is a test to check whether your Unix system is at risk:

env x='() { :;}; echo vulnerable' bash -c 'echo hello'

if the prompt returns vulnerable, it means the system is vulnerable and needs to be upgraded with the proper security patch… For instance running

sudo apt-get update && sudo apt-get install --only-upgrade bash

for Debian/Ubuntu versions. Check Apple support page for Apple OS.

a weird beamer feature…

Posted in Books, Kids, Linux, R, Statistics, University life with tags , , , , , , , , , , , , on September 24, 2014 by xi'an

As I was preparing my slides for my third year undergraduate stat course, I got a weird error that got a search on the Web to unravel:

! Extra }, or forgotten \endgroup.
\endframe ->\egroup
  \begingroup \def \@currenvir {frame}
l.23 \end{frame}

which was related with a fragile environment

\frametitle{simulation in practice}
\item For a given distribution $F$, call the corresponding 
pseudo-random generator in an arbitrary computer language
> x=rnorm(10)
> x
 [1] -0.021573 -1.134735  1.359812 -0.887579
 [7] -0.749418  0.506298  0.835791  0.472144
\item use the sample as a statistician would
> mean(x)
[1] 0.004892123
> var(x)
[1] 0.8034657
to approximate quantities related with $F$

but not directly the verbatim part: the reason for the bug was that the \end{frame} command did not have a line by itself! Which is one rare occurrence where the carriage return has an impact in LaTeX, as far as I know… (The same bug appears when there is an indentation at the beginning of the line. Weird!) [Another annoying feature is wordpress turning > into > in the sourcecode environment…]

new laptop with ubuntu 14.04

Posted in Linux, R, Statistics, University life with tags , , , , on August 14, 2014 by xi'an

Screenshot 2014-05-31 21:55:55As I was getting worried about the chances of survival of my current laptop (bought in emergency upon my return from Kyoto!), I decided to use some available grant money to buy a new laptop without stepping through the emergency square. Thanks to my local computer engineer, Thomas, I found a local dealer selling light laptops with an already installed Ubuntu 14.04… And qwerty (UK) keyboards. Even though the previous move to Kubuntu 12.04 had been seamless, a failed attempt to switch a Mac to Ubuntu a few months later left me wary about buying a computer first and testing later whether or not it was truly Linux compatible. I am therefore quite happy with the switch and grateful to Thomas for the suggestion. I managed to re-compile my current papers and to run my current R codes, plus connect by wireless and read photos from my camera, hence validating the basic operations I primarily require from a computer! And reinstalled KDE. (I am still having difficulties with the size of the fonts in Firefox though. Which do not seem coherent from a tab to the next.) Enough to sacrifice a new sticker to cover the brand on its cover….


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