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Updated: 1 hour 11 min ago

Chris Lamb: Python quirk: Signatures are evaluated at import time

Thu, 21/07/2016 - 12:07

Every Python programmer knows to avoid mutable default arguments:

def fn(mutable=[]): mutable.append('elem') print mutable fn() fn() $ python ['elem'] ['elem', 'elem']

However, many are not clear that this is due to arguments being evaluated at import time, rather than the first time the function is evaluated.

This results in related quirks such as:

def never_called(error=1/0): pass $ python Traceback (most recent call last): File "", line 1, in <module> ZeroDivisionError: integer division or modulo by zero

... and an—implementation-specific—quirk caused by naive constant folding:

def never_called(): 99999999 ** 9999999 $ python [hangs]

I suspect that this can be used as denial-of-service vector.

Categories: LUG Community Blogs

Chris Lamb: Python quirk: os.stat's return type

Tue, 19/07/2016 - 11:20
import os import stat st = os.stat('/etc/fstab') # __getitem__ x = st[stat.ST_MTIME] print((x, type(x))) # __getattr__ x = st.st_mtime print((x, type(x))) (1441565864, <class 'int'>) (1441565864.3485234, <class 'float'>)
Categories: LUG Community Blogs

Mick Morgan: show me yours

Wed, 13/07/2016 - 17:30

As Theresa May moves from the Home Office to Number 10, it is perhaps timely to reflect on public attitudes to surveillance as evidenced in Liberty’s campaign film “Show me yours” in April of this year. In the film (shown below), comedian Olivia Lee pursues members of the public with the intention of taking details from their mobile phones of all their recent communications or browsing activity. The reactions of the people approached speak for themselves. Unfortunately, Liberty research suggests that 75% of adults in the UK had never heard of the impending legislation laid out in the Investigatory Powers Bill.

Categories: LUG Community Blogs

Jonathan McDowell: Confirming all use of an SSH agent

Sun, 03/07/2016 - 16:55

For a long time I’ve wanted an ssh-agent setup that would ask me before every use, so I could slightly more comfortably forward authentication over SSH without worrying that my session might get hijacked somewhere at the remote end (I often find myself wanting to pull authenticated git repos on remote hosts). I’m at DebConf this week, which is an ideal time to dig further into these things, so I did so today. As is often the case it turns out this is already possible, if you know how.

I began with a setup that was using GNOME Keyring to manage my SSH keys. This isn’t quite what I want (eventually I want to get to the point that I can sometimes forward a GPG agent to remote hosts for signing purposes as well), so I set about setting up gpg-agent. I used Chris’ excellent guide to GnuPG/SSH Agent setup as a starting point and ended up doing the following:

$ echo use-agent >> ~/.gnupg/options $ echo enable-ssh-support >> ~/.gnupg/gpg-agent.conf $ sudo sed -i.bak "s/^use-ssh-agent/# use-ssh-agent/" /etc/X11/Xsession.options $ sudo rm /etc/xdg/autostart/gnome-keyring-ssh.desktop

The first 2 commands setup my local agent, and told it to do SSH agent foo. The next stopped X from firing up ssh-agent, and the final one prevents GNOME Keyring from being configured to be the SSH agent, without having to remove libpam-gnome-keyring as Chris did. After the above I logged out of and into X again, and could see ~/.gnupg/S.gpg-agent.ssh getting created and env | grep SSH showing SSH_AUTH_SOCK pointing to it (if GNOME Keyring is still handling things it ends up pointing to something like /run/user/1000/keyring/ssh).

[Update: Luca Capello emailed to point out this was a bad approach; there’s thankfully no need to do the last 2 commands that require root. #767341 removed the need to edit Xsession.options and you can prevent GNOME Keyring starting on a per user basis with:

(cat /etc/xdg/autostart/gnome-keyring-ssh.desktop ; echo 'X-GNOME-Autostart-enabled=false') > \ ~/.config/autostart/gnome-keyring-ssh.desktop


After this it turned out all I need to do was ssh-add -c <ssh keyfile>. The -c says “confirm use” and results in the confirm flag being appended to the end of ~/.gnupg/sshcontrol (so if you’ve already done the ssh-add you can go and add the confirm if that’s the behaviour you’d like).

Simple when you know how, but I’ve had conversations with several people in the past who wanted the same thing and hadn’t figured out how, so hopefully this is helpful to others.

Categories: LUG Community Blogs

Chris Lamb: Free software activities in June 2016

Thu, 30/06/2016 - 21:32

Here is my monthly update covering a large part of what I have been doing in the free software world (previously):


My work in the Reproducible Builds project was covered in our weekly reports. (#58, #59 & #60)

Debian LTS

This month I have been paid to work 18 hours on Debian Long Term Support (LTS). In that time I did the following:

  • "Frontdesk" duties, triaging CVEs, etc.
  • Extended the script to ignore packages that are not subject to Long Term Support.

  • Issued DLA 512-1 for mantis fixing an XSS vulnerability.
  • Issued DLA 513-1 for nspr correcting a buffer overflow in a sprintf utility.
  • Issued DLA 515-1 for libav patching a memory corruption issue.
  • Issued DLA 524-1 for squidguard fixing a reflected cross-site scripting vulnerability.
  • Issued DLA 525-1 for gimp correcting a use-after-free vulnerability in the channel and layer properties parsing process.
  • redis (2:3.2.1-1) — New upstream bugfix release, plus subsequent upload to the backports repository.
  • python-django (1.10~beta1-1) — New upstream experimental release.
  • libfiu (0.94-5) — Misc packaging updates.
Patches contributed
RC bugs

I also filed 170 FTBFS bugs against a7xpg, acepack, android-platform-dalvik, android-platform-frameworks-base, android-platform-system-extras, android-platform-tools-base, apache-directory-api, aplpy, appstream-generator, arc-gui-clients, assertj-core, astroml, bamf, breathe, buildbot, cached-property, calf, celery-haystack, charmtimetracker, clapack, cmake, commons-javaflow, dataquay, dbi, django-celery, django-celery-transactions, django-classy-tags, django-compat, django-countries, django-floppyforms, django-hijack, django-localflavor, django-markupfield, django-model-utils, django-nose, django-pipeline, django-polymorphic, django-recurrence, django-sekizai, django-sitetree, django-stronghold, django-taggit, dune-functions, elementtidy, epic4-help, fcopulae, fextremes, fnonlinear, foreign, fort77, fregression, gap-alnuth, gcin, gdb-avr, ggcov, git-repair, glance, gnome-twitch, gnustep-gui, golang-github-audriusbutkevicius-go-nat-pmp, golang-github-gosimple-slug, gprbuild, grafana, grantlee5, graphite-api, guacamole-server, ido, jless, jodreports, jreen, kdeedu-data, kdewebdev, kwalify, libarray-refelem-perl, libdbusmenu, libdebian-package-html-perl, libdevice-modem-perl, libindicator, liblrdf, libmail-milter-perl, libopenraw, libvisca, linuxdcpp, lme4, marble, mgcv, mini-buildd, mu-cade, mvtnorm, nose, octave-epstk, onioncircuits, opencolorio, parsec47, phantomjs, php-guzzlehttp-ringphp, pjproject, pokerth, prayer, pyevolve, pyinfra, python-asdf, python-ceilometermiddleware, python-django-bootstrap-form, python-django-compressor, python-django-contact-form, python-django-debug-toolbar, python-django-extensions, python-django-feincms, python-django-formtools, python-django-jsonfield, python-django-mptt, python-django-openstack-auth, python-django-pyscss, python-django-registration, python-django-tagging, python-django-treebeard, python-geopandas, python-hdf5storage, python-hypothesis, python-jingo, python-libarchive-c, python-mhash, python-oauth2client, python-proliantutils, python-pytc, python-restless, python-tidylib, python-websockets, pyvows, qct, qgo, qmidinet, quodlibet, r-cran-gss, r-cran-runit, r-cran-sn, r-cran-stabledist, r-cran-xml, rgl, rglpk, rkt, rodbc, ruby-devise-two-factor, ruby-json-schema, ruby-puppet-syntax, ruby-rspec-puppet, ruby-state-machine, ruby-xmlparser, ryu, sbd, scanlogd, signond, slpvm, sogo, sphinx-argparse, squirrel3, sugar-jukebox-activity, sugar-log-activity, systemd, tiles, tkrplot, twill, ucommon, urca, v4l-utils, view3dscene, xqilla, youtube-dl & zope.interface.

FTP Team

As a Debian FTP assistant I ACCEPTed 186 packages: akonadi4, alljoyn-core-1509, alljoyn-core-1604, alljoyn-gateway-1504, alljoyn-services-1504, alljoyn-services-1509, alljoyn-thin-client-1504, alljoyn-thin-client-1509, alljoyn-thin-client-1604, apertium-arg, apertium-arg-cat, apertium-eo-fr, apertium-es-it, apertium-eu-en, apertium-hbs, apertium-hin, apertium-isl, apertium-kaz, apertium-spa, apertium-spa-arg, apertium-tat, apertium-urd, arc-theme, argus-clients, ariba, beast-mcmc, binwalk, bottleneck, colorfultabs, dh-runit, django-modeltranslation, dq, dublin-traceroute, duktape, edk2, emacs-pdf-tools, eris, erlang-p1-oauth2, erlang-p1-sqlite3, erlang-p1-xmlrpc, faba-icon-theme, firefox-branding-iceweasel, golang-1.6, golang-defaults, golang-github-aelsabbahy-gonetstat, golang-github-howeyc-gopass, golang-github-oleiade-reflections, golang-websocket, google-android-m2repository-installer, googler, goto-chg-el, gr-radar, growl-for-linux, guvcview, haskell-open-browser, ipe, labplot, libalt-alien-ffi-system-perl, libanyevent-fcgi-perl, libcds-savot-java, libclass-ehierarchy-perl, libconfig-properties-perl, libffi-checklib-perl, libffi-platypus-perl, libhtml-element-library-perl, liblwp-authen-oauth2-perl, libmediawiki-dumpfile-perl, libmessage-passing-zeromq-perl, libmoosex-types-portnumber-perl, libmpack, libnet-ip-xs-perl, libperl-osnames-perl, libpodofo, libprogress-any-perl, libqtpas, librdkafka, libreoffice, libretro-beetle-pce-fast, libretro-beetle-psx, libretro-beetle-vb, libretro-beetle-wswan, libretro-bsnes-mercury, libretro-mupen64plus, libservicelog, libtemplate-plugin-datetime-perl, libtext-metaphone-perl, libtins, libzmq-ffi-perl, licensecheck, link-grammar, linux, linux-signed, lua-busted, magics++, mkalias, moka-icon-theme, neutron-vpnaas, newlisp, node-absolute-path, node-ejs, node-errs, node-has-flag, node-lodash-compat, node-strip-ansi, numba, numix-icon-theme, nvidia-graphics-drivers, nvidia-graphics-drivers-legacy-304xx, nvidia-graphics-drivers-legacy-340xx, obs-studio, opencv, pacapt, pgbackrest, postgis, powermock, primer3, profile-sync-daemon, pyeapi, pypandoc, pyssim, python-cutadapt, python-cymruwhois, python-fisx, python-formencode, python-hkdf, python-model-mommy, python-nanomsg, python-offtrac, python-social-auth, python-twiggy, python-vagrant, python-watcherclient, python-xkcd, pywps, r-bioc-deseq2, r-bioc-dnacopy, r-bioc-ensembldb, r-bioc-geneplotter, r-cran-adegenet, r-cran-adephylo, r-cran-distory, r-cran-fields, r-cran-future, r-cran-globals, r-cran-htmlwidgets, r-cran-listenv, r-cran-mlbench, r-cran-mlmrev, r-cran-pheatmap, r-cran-pscbs, r-cran-r.cache, refind, relatorio, reprotest, ring, ros-ros-comm, ruby-acts-as-tree, ruby-chronic-duration, ruby-flot-rails, ruby-numerizer, ruby-u2f, selenium-firefoxdriver, simgrid, skiboot, smtpping, snap-confine, snapd, sniffles, sollya, spin, subuser, superlu, swauth, swift-plugin-s3, syncthing, systemd-bootchart, tdiary-theme, texttable, tidy-html5, toxiproxy, twinkle, vmtk, wait-for-it, watcher, wcslib & xapian-core.

Categories: LUG Community Blogs

Jonathan McDowell: Hire me!

Mon, 27/06/2016 - 23:21

It’s rare to be in a position to be able to publicly announce you’re looking for a new job, but as the opportunity is currently available to me I feel I should take advantage of it. That’s especially true given the fact I’ll be at DebConf 16 next week and hope to be able to talk to various people who might be hiring (and will, of course, be attending the job fair).

I’m coming to the end of my Masters in Legal Science and although it’s been fascinating I’ve made the decision that I want to return to the world of tech. I like building things too much it seems. There are various people I’ve already reached out to, and more that are on my list to contact, but I figure making it more widely known that I’m in the market can’t hurt with finding the right fit.

  • Availability: August 2016 onwards. I can wait for the right opportunity, but I’ve got a dissertation to write up so can’t start any sooner.
  • Location: Preferably Belfast, Northern Ireland. I know that’s a tricky one, but I’ve done my share of moving around for the moment (note I’ve no problem with having to do travel as part of my job). While I prefer an office environment I’m perfectly able to work from home, as long as it’s as part of a team that is tooled up for disperse workers - in my experience being the only remote person rarely works well. There’s a chance I could be persuaded to move to Dublin for the right role.
  • Type of role: I sit somewhere on the software developer/technical lead/architect spectrum. I expect to get my hands dirty (it’s the only way to learn a system properly), but equally if I’m not able to be involved in making high level technical decisions then I’ll find myself frustrated.
  • Technology preferences: Flexible. My background is backend systems programming (primarily C in the storage and networking spaces), but like most developers these days I’ve had exposure to a bunch of different things and enjoy the opportunity to learn new things.

I’m on LinkedIn and OpenHUB, which should give a bit more info on my previous experience and skill set. I know I’m light on details here, so feel free to email me to talk about what I might be able to specifically bring to your organisation.

Categories: LUG Community Blogs

Steve Engledow (stilvoid): Brugger Off

Fri, 24/06/2016 - 13:32

I'm putting this here and then I'm going to try not to say anything else on the subject for a while.

I'm disappointed and upset by result of the referendum. Not because we're (probably) leaving the EU. Us leaving may be the beginning of the fall of the EU and I can't tell one way or another how that will affect anyone in the world.

I'm hurt and ashamed because it's a measure of the sentiments of the people who live in the UK. 52% of you are leaning in a direction that I want no part of and don't want my son to be surrounded by as he grows up. I grew up in the tail of end of Thatcher's Britain and the UK today has the same oppressive feeling that you can sense when you watch the Young Ones.

I have some very good friends who voted out and they are good people so I'm certainly not tarring everyone with the racist brush but I've seen much fear and hate generally and I'm just saddened that this country is following the international trend and moving to the far right.

It's not an exaggeration to say that I'm pretty damn scared of the future with the US possibly about to vote in a right wing leadership too.

Don't tell me "it'll be alright" because it's not the fact of the decision that has me upset; it's what it tells me about the country I love. Or used to love. I don't know.

Categories: LUG Community Blogs

Jonathan McDowell: Fixing missing text in Firefox

Thu, 23/06/2016 - 15:23

Every now and again I get this problem where Firefox won’t render text correctly (on a Debian/stretch system). Most websites are fine, but the odd site just shows up with blanks where the text should be. Initially I thought it was NoScript, but turning that off didn’t help. Daniel Silverstone gave me a pointer today that the pages in question were using webfonts, and that provided enough information to dig deeper. The sites in question were using Cantarell, via:

src: local('Cantarell Regular'), local('Cantarell-Regular'), url(cantarell.woff2) format('woff2'), url(cantarell.woff) format('woff');

The Firefox web dev inspector didn’t show it trying to fetch the font remotely, so I removed the local() elements from the CSS. That fixed the page, letting me pinpoint the problem as a local font issue. I have fonts-cantarell installed so at first I tried to remove it, but that breaks gnome-core. So instead I did an fc-list | grep -i cant to ask fontconfig what it thought was happening. That gave:

/usr/share/fonts/opentype/cantarell/Cantarell-Regular.otf.dpkg-tmp: Cantarell:style=Regular /usr/share/fonts/opentype/cantarell/Cantarell-Bold.otf.dpkg-tmp: Cantarell:style=Bold /usr/share/fonts/opentype/cantarell/Cantarell-Bold.otf: Cantarell:style=Bold /usr/share/fonts/opentype/cantarell/Cantarell-Oblique.otf: Cantarell:style=Oblique /usr/share/fonts/opentype/cantarell/Cantarell-Regular.otf: Cantarell:style=Regular /usr/share/fonts/opentype/cantarell/Cantarell-Bold-Oblique.otf: Cantarell:style=Bold-Oblique /usr/share/fonts/opentype/cantarell/Cantarell-Oblique.otf.dpkg-tmp: Cantarell:style=Oblique /usr/share/fonts/opentype/cantarell/Cantarell-BoldOblique.otf: Cantarell:style=BoldOblique

Hmmm. Those .dpkg-tmp files looked odd, and sure enough they didn’t actually exist. So I did a sudo fc-cache -f -v to force a rebuild of the font cache and restarted Firefox (it didn’t seem to work before doing so) and everything works fine now.

It seems that fc-cache must have been run at some point when dpkg had not yet completed installing an update to the fonts-cantarell package. That seems like a bug - fontconfig should probably ignore .dpkg* files, but equally I wouldn’t expect it to be run before dpkg had finished its unpacking stage fully.

Categories: LUG Community Blogs

Chris Lamb: Free software activities in May 2016

Tue, 31/05/2016 - 21:49

Here is my monthly update covering a large part of what I have been doing in the free software world (previously):

  • Modified LetsEncrypt's "certbot" tool (previously the Let's Encrypt Client) to ensure that the documentation is built reproducibly. The issue was that a Python default keyword argument was non-deterministic and was appearing in documentation with the function's definition. (#3005)
  • Sent a pull request to Mailvelope, a browser extension for GPG/OpenPGP encryption with webmail services, to ensure that passphrase field is cleared when entered incorrectly. (#385)
  • Proposed an optional addition to django-enumfield, a custom Django web development field for type-safe named constants, that automatically enumerations to the template context to save DRY violations in views, etc. (#33)
  • Fixed an issue in the cdist configuration management's build system to ensure that the documentation builds reproducibly. It was previously including various documentation sections non-deterministically depending on the filesystem ordering. (#437)
  • Various improvements to django-slack, my library to easily post messages to the Slack group-messaging utility from projects using the Django web development framework:
    • Raise more specific exception types (instead of the more generic ValueError) wherever possible so that clients can detect specific error conditions. (#45)
    • Pass through arbitrary Python keyword arguments to the backend, allowing custom behaviour for special case. (#46)
    • Ensure that the backend result is returned by the Celery distributed task queue wrapper. (#47)
  • Updated my Strava Enhancement Suite, a Chrome extension that improves and fixes annoyances in the web interface of the Strava cycling and running tracker, to hide more internal advertisements. (#49)
  • Sent a pull request to the build system for gtk-gnutella (a server/client for the Gnutella peer-to-peer network) to ensure the build is reproducible if the SOURCE_DATE_EPOCH environment variable is available. (#17)
  • Updated the SSL certificate for, a hosted version of the diffoscope in-depth and content-aware diff utility. Thanks to Bytemark for sponsoring the hardware.

My work in the Reproducible Builds project was covered in our weekly reports. (#53, #54, #55, #56 & #57)

Debian LTS

This month I have been paid to work 18 hours on Debian Long Term Support (LTS). In that time I did the following:

  • A week of "frontdesk" duties, triaging CVEs, assigning tasks, etc.
  • Issued DLA 464-1 for libav, a multimedia player, server, encoder and transcoder library that fixed a use-after free vulnerability.
  • Issued DLA 469-1 for libgwenhywfar (an OS abstraction layer that allows porting of software to different operating systems like Linux, *BSD, Windows, etc.) correcting the use of an outdated CA certificate bundle.
  • Issued DLA 470-1 for libksba, a X.509 and CMS certificate support library. patching a buffer vulnerability.
  • Issued DLA 474-1 for dosfstools, a collection of utilities for making and checking MS-DOS FAT filesystems, fixing an invalid memory and heap overflow vulnerability.
  • Issued DLA 482-1 for libgd2 graphics library, rectifying a stack consumption vulnerability.
  • python-django (1.9.6-1) — New upstream bugfix release.
  • redis (3.2.0-1, etc.) — New upstream release, correct build on more exotic architectures and minor packaging fixups.
  • gunicorn (19.5.0-1 & 19.6.0-1) — New upstream releases and minor packaging fixups.
Bugs filed Patches contributed RC bugs

I also filed 74 FTBFS bugs against abtransfers, asedriveiiie, assword, astroquery, audit, bibtool, cargo, ccdproc, clearsilver, discover, emoslib, etsf-io, gfs2-utils, globus-io, gnunet, graxxia, groovycsv, gtkspell3, hg-git, hgsubversion, ices2, jekyll, jhighlight, libdist-zilla-plugin-ourpkgversion-perl, libetonyek, libgd-perl, libgnomekbd, libimager-perl, libint2, libnet-dns-zonefile-fast-perl, libnl3, libspring-java, libtkx-perl, ltt-control, lua-discount, lua-lgi, metview, montage-wrapper, networkmanager-qt, nevow, ngrok, obex-data-server, octave-interval, omnievents, pcl, php-arc, php-codecoverage, proguard, pyexcelerator, python-autobahn, python-babel, python-biopython, python-mne, python-pgmagick, python-shotgun, python-snuggs, python-urllib3, python-xdo, qemu, radicale, raptor2, rjava, ruby-albino, scamper, simpleparse, spectral-cube, specutils, sugar-browse-activity, sugar-memorize-activity, swift, telepathy-haze, telepathy-ring, unicap & vorbis-tools.

Categories: LUG Community Blogs

Wayne Stallwood (DrJeep): UPS for Octopi or Octoprint

Mon, 30/05/2016 - 21:13
So it only took one mid print power cut to realise I need a UPS for my 3D printer.

it's even worse for a machine like mine with a E3D all metal head as it requires active cooling to stop damage to the head mount or prevent a right mess of molten filament inside the heatbreak.

See below for instructions on setting up an APC UPS so that it can send a command to octopi to abort the print and start cooling the head before the batteries in the UPS are exhausted.

I used a APC BackUPS Pro 550, which seems to be about the minimum spec I can get away with, on my printer this gives me approximately 5 minutes of print time without power, or 40 minutes of the printer powered but idle, other UPS's would work but APC is the only type tested with these instructions

Test this throughly and make sure you have enough runtime to cool the head before the batteries are exhausted, the only way to do this properly is to set up a test print and pull the power.

Once you have installed the power leads to and from the UPS and got the printer powered through it (not forgetting the Rpi or whatever you have running octoprint also needs power...mine is powered via the printer PSU ) You need to install acpupsd, it's in the default repo for raspian so just install it with apt.

sudo apt-get install apcupsd

Now we need to tweak apcupsd's configuration a bit

Edit the apcupsd configuration as follows, you can find it at /etc/apcupsd/apcupsd.conf, just use your favourite editor.

Find and change the following lines



DEVICE (this should be blank)



You might need to tweak BATTERYLEVEL and MINUTES for your printer and UPS. this is the percentage of power left before the shutdown will trigger or the minutes of runtime, whichever one happens first

Remember this is minutes as calculated whilst the printer is still running. Once the print is stopped the runtime will be longer as the heaters will be off, so setting 5 minutes here would in my case give me 20 minutes of runtime once the print has aborted for the hot-end to cool

Plug the USB cable from the UPS into a spare port on the Rpi

Now activate the service by editing /etc/default/apcupsd and changing the following line


Now start the service, it will start by itself on the next boot

sudo service apcupsd start

If all is well typing acpaccess at the prompt should get you some stats from the UPS, battery level etc

If that's all good then apcupsd is configured, now for the script that aborts your print

First go into the octoprint settings from the web interface, make sure API access is turned on and record the API key carefully

Back on the rpi go to the home directory

cd ~

Now download my custom shutdown script with wget

wget sudo cp doshutdown /etc/apcupsd cd /etc/apcupsd

Set the permissions so the script can run

chmod 755 doshutdown

Don't be tempted to rename the file, leave it as this name

Now edit the script and change the variable at the top API_KEY to the API key you got from your copy of octoprint earlier

That should be it, the script does 3 things when the power fails and the battery goes below one of the trigger points

Prints a warning on the printer's LCD screen

Records the current printer status and print file position to a file in /home/pi, so that maybe you can work out how to slice the reminder of the model and save the print

Aborts the print

This hasn't had a massive amount of testing and there are a few bugs, if you have a really big layer going on when the power goes you might not have enough power to make it to the end, octoprint only aborts at specific points in the print, same if you are at the first stages and are heating the bed, octoprint will wait until the bed is up to temp before running the next command (abort).

The sleep at the end of the script stops the rpi from shutting down, we need to wait here and make sure the printer has taken the abort command before killing the pi so that's an unknown amount of time so I leave it running by sleeping indefinitely here

If I get time I will make a proper octoprint plugin for all this

Categories: LUG Community Blogs

Steve Engledow (stilvoid): Eurodivision

Sat, 21/05/2016 - 15:14

I'm going to a Eurovision party tonight because I'm not the only person of impeccable taste who was away last week :)

I really don't know what it is about Eurovision that makes for such a fun evening but I've had a fantastic Eurovision party every year since I was at uni.

For the next 5 weeks, I'm at home alone as my wife and child are staying with family in Turkey. In order to make sure I won't be bored, I appear to have overfilled my calendar and now I find myself worrying I won't have a moment to myself. Ah well, busy is better than leaving myself open to the temptation of sitting in front of the telly for evenings on end.

I've ordered a Raspberry Pi 3 with the intention of setting it up as a retro gaming machine. I want something that can live permanently attached to my telly so that I can just pick up a controller and have a 10 minute blast on Sonic or Mario at the drop of a hat. I tried doing this before with my original Pi but it was just too slow.

In other news, I posted this on Facebook a while ago and decided it might as well live here too:

I'll be voting that we stay in thanks very much. I know the EU is far from perfect but I hate the idea of slumping backward into a world of tribes. Hating the other guy because he’s on the other side of a fence or believes in a particular magical sky man is ridiculous and childish and exactly the kind of thing we in the west deride and see as the cause of conflicts in the east.

I’m proud of my country. And like any prized possession, I want to show it off to everyone. I want free movement so that I can visit (and maybe one day live and work in) some of the wonderful places that other people are proud of.

I'm married to a foreigner; I frequently meet, work with, and have many friends who are foreign; I love travelling and being the foreigner. I’d love to be in a world where this post doesn’t make any sense because “foreign” and “country” don’t mean anything any more. It’s one planet, guys.

Try this one weird trick to help you realise why I think your ideas about borders are daft: You want tighter border control in the UK... Why the UK? Why not Great Britain? Make the Irish need visas to get in. Why not individual countries? Who wouldn’t enjoy a nice driving break while you queue for passport control at the Welsh border? In fact, why stop there; we could do this regionally! The great wall of East Anglia? County? District? City? Neighbourhood? Street? Why do you draw the line where you draw it?

If you must have a border, draw it around the planet for now. I wouldn’t mind working as a passport officer aboard the ISS.

Be excellent to each other and party on dudes.

Categories: LUG Community Blogs

Jonathan McDowell: First steps with the ATtiny45

Wed, 18/05/2016 - 22:25

These days the phrase “embedded” usually means no console (except, if you’re lucky, console on a UART for debugging) and probably busybox for as much of userspace as you can get away with. You possibly have package management from OpenEmbedded or similar, though it might just be a horrible kludged together rootfs if someone hates you. Either way it’s rare for it not to involve some sort of hardware and OS much more advanced than the 8 bit machines I started out programming on.

That is, unless you’re playing with Arduinos or other similar hardware. I’m currently waiting on some ESP8266 dev boards to arrive, but even they’re quite advanced, with wifi and a basic OS framework provided. A long time ago I meant to get around to playing with PICs but never managed to do so. What I realised recently was that I have a ready made USB relay board that is powered by an ATtiny45. First step was to figure out if there were suitable programming pins available, which turned out to be all brought out conveniently to the edge of the board. Next I got out my trusty Bus Pirate, installed avrdude and lo and behold:

$ avrdude -p attiny45 -c buspirate -P /dev/ttyUSB0 Attempting to initiate BusPirate binary mode... avrdude: Paged flash write enabled. avrdude: AVR device initialized and ready to accept instructions Reading | ################################################## | 100% 0.01s avrdude: Device signature = 0x1e9206 (probably t45) avrdude: safemode: Fuses OK (E:FF, H:DD, L:E1) avrdude done. Thank you.

Perfect. I then read the existing flash image off the device, disassembled it, worked out it was based on V-USB and then proceeded to work out that the only interesting extra bit was that the relay was hanging off pin 3 on IO port B. Which led to me knocking up what I thought should be a functionally equivalent version of the firmware, available locally or on GitHub. It’s worked with my basic testing so far and has confirmed to me I understand how the board is set up, meaning I can start to think about what else I could do with it…

Categories: LUG Community Blogs

Steve Engledow (stilvoid): Today's discoveries

Sun, 15/05/2016 - 23:47
  1. Dorock have opened a new bar in Kadıköy and it's good :)

  2. A home win for Beṣiktaṣ means a crazy street party with fireworks, marching, and a lot of shouting.

    Uber thankfully provided us a taxi so we didn't have to walk through it all with our sleeping 4 year old.

  3. When all of your podcasts are on a server somewhere and you want to copy them to your mp3 player but all you have to hand is a Chromebook, you're in for some fun.

    Really. There's not enough internal storage to download it all and then copy over. There's no scp client. No command line from which to cd to the mp3 player and wget everything.

  4. rclone is badical!

    Really! rclone config holds your hand through setting it up and then it was a simple rclone sync ./podcasts google:/podcasts to get my podcasts folder copied into Google Drive. Once that was done, I could use the file manager to copy from Drive over to the mp3 player. Simples. Ish.

  5. Autocorrect helpfully invented my new catchphrase: Weird up!

Categories: LUG Community Blogs

Steve Engledow (stilvoid): s3cmd ls

Fri, 13/05/2016 - 22:22

I'm currently having a very enjoyable holiday with my family in Bodrum. We're staying in an all-inclusive hotel by the beach. This is the first time either of us have ever had such a holiday; we usually like to go rushing around seeing as many sights as we can cram in to a few days before moving on to another place. It's the final night of our time here and I feel like I'm just settling in to it. Next time, we'll do two weeks. (By way of compromise, we had decided to do a week in Bodrum followed by a week in Istanbul/Adapazarı.)

The good

In what feels like a very short week of doing very little, here are some of my highlights:

Bodrum Castle

The castle doesn't look much from the outside and it advertises itself as "Museum of Underwater Archaeology" but once you get through the doors you realise it's a magnificent ruined castle with beautiful gardens and a smattering of museum about the place. We barely stopped to look at the museum pieces (mostly shipwrecks and amphora dredged up from the Aegean) and it took us a good couple of hours to walk around the castle. Do not make the mistake we made in a parallel universe by deciding we didn't fancy a museum that day!

Boat tour

There are a lot of places offering boat tours and I can only vouch for the one we took: Gencel Water Sports. The boat tour takes a full day (ours was 10:30 to 16:30) and stops off at a number of interesting locations around Bodrum. The highlights for me were Aquarium Bay: snorkeling with thousands of fish around; and the place that I can't recall the name of where I ticked off an ambition (I don't know why): to swim to shore. OK it was only 50 metres or so but it was in proper sea and I'm hardly an olympic swimmer ;)

In all, I did a lot of swimming that day.

Tent bar, Gümbet

This bar is hardly a tourist hot spot but it was a short walk from the hotel and we had a really good evening sitting and chatting with the barman (whose name is either Ricardo or Bora depending on which language you ask him in).

Spending a day doing not very much

This really was a revelation! One such day went like this: wake, breakfast, steam room, swim, turkish bath, beer by the pool, lunch, swimming, lazing around by the pool with a beer, swimming, lazing, beer, swimming, lazing, beer, beer and lazing, dinner, rakı, sleep.

As I said, neither of us had ever had a holiday that didn't involve loads of walking and sightseeing. I'm amazed at how much I enjoyed just relaxing.

The bad

On the somewhat less positive side I lost a filling and the hole is really annoying.

The unrealised

Next week: Istanbul, second only to Bruges in my favourite places list :)

Categories: LUG Community Blogs

Mick Morgan: raid performance

Mon, 02/05/2016 - 16:46

I have recently been building a new NAS box (of which, possibly, more later). In fact the build is really a rebuild because I initially built the server about three years ago in order to consolidate a bunch of services I was running on assorted separate servers into one place. That first build was a RAID 1 array of two 2 TB disks (to give me a mirrored setup with a total of 2 TB store). At the time that was sufficient to hold all my important data (backed up both to other networked devices and to standalone USB disks for safety). But I have just upgraded my main desktop machine to a nice shiny new core i7 Skylake box with 16 GB of DDR4 and a 3 TB disk. That disk is already two thirds full (my old machine had a rather full 2 TB disk). This meant that my NAS backup storage requirements exceeded the capacity of my RAID 1 setup. Adding disks wouldn’t help of course because all that would do is add mirror capability rather than capacity. So I decided to upgrade the NAS and bought a bunch of new 2 TB disks with the intention of setting up a RAID 5 array of 4 disks, thus giving a total storage capacity of 6 TB (8 TB minus 2 TB for parity). Furthermore I initially looked at using FreeNAS rather than my usual debian or ubuntu server with software RAID simply because it looked interesting and, with plugins, could probably meet most of my requirements. But I could not get the software to install properly and after three abortive attempts I gave up and decided that I didn’t really like freeBSD anyway….

So I opted to go back to mdadm on linux – at least I know that works. Better still I would be able to retain all my old setup from the old RAID 1 system without having to worry about finding plugins to handle my media streaming requirements, or owncloud installation, for example.

My previous build was on debian (which is by far my preferred server OS) but ubuntu server has recently been released in a LTS version at 16.04 and I thought it might be fun to try that instead. So I did. (For any readers who have not tried installing linux on a RAID system there are plenty of sites offering advice, but the official ubuntu pages are pretty good). During the build I hit what I initially thought was a snag because the installation seemed to get stuck at around the 83% level when it was apparently installing the linux kernel image and headers. Indeed I confess that on the first such installation I pulled the plug after about three hours of no apparent activity because I was beginning to think that there might be something wrong with my hardware (the earlier FreeNAS failures worried me). My on-line searches for assistance were initially not particularly helpful since none of the huge number of sites advising on software RAID installation bothered to mention that initial RAID 5 build (or rebuild) using large capacity disks takes a very long time because of the need to calculate the parity data. Incidentally, it is this parity data and its layout that gives RAID 5 its write performance penalty.

One useful outcome of my research about RAID 5 build times (which in my case eventually took just over 6 hours) was my discovery of the wintelguy’s site providing an on-line calculator (and much more besides) for RAID performance and capacity. There is even a very useful page allowing you to compare two separate configurations side by side – thoroughly recommended. More worrying, and thought provoking, is the calculator for RAID failure. That site suggests that the probability of successfully rebuilding a RAID 5 array of 4 * 2 TB disks after a failure is only 52.8%.

That is why you need to keep backups…….

Categories: LUG Community Blogs

Chris Lamb: Free software activities in April 2016

Sat, 30/04/2016 - 23:20

Here is my monthly update covering a large part of what I have been doing in the free software world (previously):

  • Added Python 3 support to django-template-tests, a tool to perform simple static analysis on Django templates. (#1)
  • Corrected my Chrome extension for the FastMail web interface to not disable the CTRL+Enter keyboard shortcut when authoring emails. (#3)
  • Corrected a subtle bug in my django-staticfiles-dotd "staticfiles" library where the Content-Length HTTP header was calculated incorrectly in the presence of Unicode characters resulting in truncated output. (#2)
  • Various fixes to django-slack, a library to easily post messages to the Slack group-messaging utility from projects using the Django web development framework:
    • Don't require an explicit backend import when using the Celery task queue backend. (#41)
    • Actually generate and send messages asynchronously when using the Celery backend. (#44)
  • Fixed an issue with my local-debian-mirror tool where the option to disable DEP-11 mirroring wasn't working. (#1)
  • Fixed an issue in django-hipchat, a library to easily post messages to the Hipchat group-messaging utility from projects using the Django web development framework where the templates were not includes when installing via PyPI. (#1)
  • Created a quick-and-dirty tool to scrape a Squarespace blog and convert it to a PDF so I can read them on my Kindle e-reader. (tree)
  • Updated django-keyerror — a library to post exceptions to the error tracking service — to silence an AttributeError exception in some error-reporting edge-cases. (commit)
  • Suggested an improvement to the documentation for the upcoming Twitter Bootstrap version for the deprecated .hidden and .show CSS classes. (#19789)
  • Submitted a documentation update to the Ansible server configuration tool's ufw firewall module. (commit)
  • I also blogged about parsing Jenkins CI output to determine job success or failure.

My work in the Reproducible Builds project was covered in our weekly reports. (#48, #49, #50, #51 & #52)

  • redis (2:3.0.7-3) — Adding, amongst some other changes, systemd LimitNOFILE support to allow a higher number of open file descriptors.
RC bugs

I filed 58 FTBFS bugs against agg, basex, c++-annotations,, cl-babel, cl-lparallel, collab-qa-tools, diagnostics, enjarify, enscript, felix-main, girara, gnome-shell-pomodoro, golang-github-spf13-viper, gst-plugins-base0.10, gstreamer0.10, guessnet, htslib, ifrit, indicator-session, jackson-module-afterburner, kamera, lgogdownloader, libbde, libmlx4, libsqlite3-0:, libykneomgr, nifti2dicom, node-starttls, nuitka, oath-toolkit, pdf-presenter-console, perlbal, poker-engine, pycountry, pysycache, python-oslo.privsep, python-shade, r-cran-tgp, raincat, rapache, resteasy, ruby-crb-blast, ruby-email-reply-parser, ruby-gollum-lib, samtools, sipwitch, sooperlooper, tomcat-maven-plugin, transmission, trivial-features, tuskar-ui, twinkle, twisted-web2, uclmmbase, workrave, xlog & yafc.

FTP Team

As a Debian FTP assistant I ACCEPTed 135 packages: aptitude, asm, beagle, blends, btrfs-progs, camitk, cegui-mk2, cmor-tables, containerd, debian-science, debops, debops-playbooks, designate-dashboard, efitools, facedetect, flask-testing, fstl, ganeti-os-noop, gnupg, golang-fsnotify, golang-github-appc-goaci, golang-github-benbjohnson-tmpl, golang-github-dchest-safefile, golang-github-docker-go, golang-github-dylanmei-winrmtest, golang-github-hawkular-hawkular-client-go, golang-github-hlandau-degoutils, golang-github-hpcloud-tail, golang-github-klauspost-pgzip, golang-github-kyokomi-emoji, golang-github-masterminds-semver-dev, golang-github-masterminds-vcs-dev, golang-github-masterzen-xmlpath, golang-github-mitchellh-ioprogress, golang-github-smartystreets-assertions, golang-gopkg-hlandau-configurable.v1, golang-gopkg-hlandau-easyconfig.v1, golang-gopkg-hlandau-service.v2, golang-objx, golang-pty, golang-text, gpaste, gradle-plugin-protobuf, grip, haskell-brick, haskell-hledger-ui, haskell-lambdabot-haskell-plugins, haskell-text-zipper, haskell-werewolf, hkgerman, howdoi, jupyter-client, jupyter-core,, libbpp-phyl, libbpp-raa, libbpp-seq, libbpp-seq-omics, libcbor-xs-perl, libdancer-plugin-email-perl, libdata-page-pageset-perl, libevt, libevtx, libgit-version-compare-perl, libgovirt, libmsiecf, libnet-ldap-server-test-perl, libpgobject-type-datetime-perl, libpgobject-type-json-perl, libpng1.6, librest-client-perl, libsecp256k1, libsmali-java, libtemplates-parser, libtest-requires-git-perl, libtext-xslate-perl, linux, linux-signed, mandelbulber2, netlib-java, nginx, node-rc, node-utml, nvidia-cuda-toolkit, openfst, openjdk-9, openssl, php-cache-integration-tests, pulseaudio, pyfr, pygccxml, pytest-runner, python-adventure, python-arrayfire, python-django-feincms, python-fastimport, python-fitsio, python-imagesize, python-lib389, python-libtrace, python-neovim-gui, python3-proselint, pythonpy, pyzo, r-cran-ca, r-cran-fitbitscraper, r-cran-goftest, r-cran-rnexml, r-cran-rprotobuf, rrdtool, ruby-proxifier, ruby-seamless-database-pool, ruby-syslog-logger, rustc, s5, sahara-dashboard, salt-formula-ceilometer, salt-formula-cinder, salt-formula-glance, salt-formula-heat, salt-formula-horizon, salt-formula-keystone, salt-formula-neutron, salt-formula-nova, seer, simplejson, smrtanalysis, tiles-autotag, tqdm, tran, trove-dashboard, vim, vulkan, xapian-bindings & xapian-core.

Categories: LUG Community Blogs

Jonathan McDowell: Notes on Kodi + IR remotes

Tue, 26/04/2016 - 21:32

This post is largely to remind myself of the details next time I hit something similar; I found bits of relevant information all over the place, but not in one single location.

I love Kodi. These days the Debian packages give me a nice out of the box experience that is easy to use. The problem comes in dealing with remote controls and making best use of the available buttons. In particular I want to upgrade the VDR setup my parents have to a more modern machine that’s capable of running Kodi. In this instance an AMD E350 nettop, which isn’t recent but does have sufficient hardware acceleration of video decoding to do the job. Plus it has a built in fintek CIR setup.

First step was finding a decent remote. The fintek is a proper IR receiver supported by the in-kernel decoding options, so I had a lot of flexibility. As it happened I ended up with a surplus to requirements Virgin V Box HD remote (URC174000-04R01). This has the advantage of looking exactly like a STB remote, because it is one.

Pointed it at the box, saw that the fintek_cir module was already installed and fired up irrecord. Failed to get it to actually record properly. Googled lots. Found ir-keytable. Fired up ir-keytable -t and managed to get sensible output with the RC-5 decoder. Used irrecord -l to get a list of valid button names and proceed to construct a vboxhd file which I dropped in /etc/rc_keymaps/. I then added a

fintek-cir * vboxhd

line to /etc/rc_maps.cfg to force my new keymap to be loaded on boot.

That got my remote working, but then came the issue of dealing with the fact that some keys worked fine in Kodi and others didn’t. This seems to be an issue with scancodes above 0xff. I could have remapped the remote not to use any of these, but instead I went down the inputlirc approach (which is already in use on the existing VDR box).

For this I needed a stable device file to point it at; the /dev/input/eventN file wasn’t stable and as a platform device it didn’t end up with a useful entry in /dev/input/by-id. A ‘quick’

udevadm info -a -p $(udevadm info -q path -n /dev/input/eventN)

provided me with the PNP id (FIT0002) allowing me to create /etc/udev/rules.d/70-remote-control.rules containing


Bingo, a /dev/input/remote symlink. /etc/defaults/inputlirc ended up containing:

EVENTS="/dev/input/remote" OPTIONS="-g -m 0"

The options tell it to grab the device for its own exclusive use, and to take all scancodes rather than letting the keyboard ones through to the normal keyboard layer. I didn’t want anything other than things specifically configured to use the remote to get the key presses.

At this point Kodi refused to actually do anything with the key presses. Looking at ~kodi/.kodi/temp/kodi.log I could see them getting seen, but not understood. Further searching led me to construct an Lircmap.xml - in particular the piece I needed was the <remote device="/dev/input/remote"> bit. The existing /usr/share/kodi/system/Lircmap.xml provided a good starting point for what I wanted and I dropped my generated file in ~kodi/.kodi/userdata/.

(Sadly it turns out I got lucky with the remote; it seems to be using the RC-5x variant which was broken in 3.17; works fine with the 3.16 kernel in Debian 8 (jessie) but nothing later. I’ve narrowed down the offending commit and raised #117221.)

Helpful pages included:

Categories: LUG Community Blogs

Jonathan McDowell: Going to DebConf 16

Mon, 18/04/2016 - 14:12

Whoop! Looking forward to it already (though will probably spend it feeling I should be finishing my dissertation).


2016-07-01 15:20 DUB -> 16:45 LHR BA0837 2016-07-01 21:35 LHR -> 10:00 CPT BA0059


2016-07-10 19:20 CPT -> 06:15 LHR BA0058 2016-07-11 09:20 LHR -> 10:45 DUB BA0828

(image stolen from Gunnar)

Categories: LUG Community Blogs

Jonathan McDowell: Going to DebConf 16

Mon, 18/04/2016 - 14:12

Whoop! Looking forward to it already (though will probably spend it feeling I should be finishing my dissertation).


2016-07-01 15:20 DUB -> 16:45 LHR BA0837 2016-07-01 21:35 LHR -> 10:00 CPT BA0059


2016-07-10 19:20 CPT -> 06:15 LHR BA0058 2016-07-11 09:20 LHR -> 10:45 DUB BA0828

(image stolen from Gunnar)

Categories: LUG Community Blogs

Jonathan McDowell: Software in the Public Interest contributing members: Check your activity status!

Wed, 13/04/2016 - 13:04

That’s a longer title than I’d like, but I want to try and catch the attention of anyone who might have missed more directed notifications about this. If you’re not an SPI contributing member there’s probably nothing to see here…

Although I decided not to stand for re-election at the Software in the Public Interest (SPI) board elections last July, I haven’t stopped my involvement with the organisation. In particular I’ve spent some time working on an overhaul of the members website and rolling it out. One of the things this has enabled is implementation of 2009-11-04.jmd.1: Contributing membership expiry, by tracking activity in elections and providing an easy way for a member to indicate they consider themselves active even if they haven’t voted.

The plan is that this will run at some point after the completion of every board election. A first pass of cleanups was completed nearly a month ago, contacting all contributing members who’d never been seen to vote and asking them to update their status if they were still active. A second round, of people who didn’t vote in the last board election (in 2014), is currently under way. Affected members will have been emailed directly and there was a mail to spi-announce, but I’m aware people often overlook these things or filter mail off somewhere that doesn’t get read often.

If you are an SPI Contributing member who considers themselves an active member I strongly recommend you login to the SPI Members Website and check the “Last active” date displayed is after 2014-07-14 (i.e. post the start of the last board election). If it’s not, click on the “Update” link beside the date. The updated date will be shown once you’ve done so.

Why does pruning inactive members matter? The 2015 X.Org election results provide at least one indication of why ensuring you have an engaged membership is important - they failed to make a by-laws change that a vast majority of votes were in favour of, due to failing to make quorum. (If you’re an member, go vote!)

Categories: LUG Community Blogs