Jan 11, 2019

Backtrace from a core dump with GDB: pitfalls

At work I mostly program in Ruby, but our system (YaST) has a C/C++ part
too. So I get to debug C crashes infrequently enough to forget some
tricks. Here I write them down for the next time.

  1. Contents and tl;dr
  • $ ulimit -c unlimited so that a core dump is saved
  • $ sudo coredumpctl dump -o core so that it is saved to a file
  • $ gdb -c core is wrong, gdb program core is right
  • (gdb) info sh mylib
  • (gdb) select a stack frame before querying variables or macros
  • $ CFLAGS="-g3 ..." for debugging macros
  1. (Un)helpful crash dump

When Ruby crashes, it produces a very verbose dump of information. It is not
much helpful in our case:

$ rake run[fail]
/sbin/yast2 src/clients/fail.rb
/usr/lib64/ruby/vendor_ruby/2.5.0/yast/yast.rb:204: [BUG] Segmentation fault at 0x0000000000000008
ruby 2.5.0p0 (2017-12-25 revision 61468) [x86_64-linux-gnu]

-- Control frame information -----------------------------------------------
c:0011 p:---- s:0066 e:000065 CFUNC  :call_yast_function
c:0010 p:0061 s:0058 e:000057 BLOCK  /usr/lib64/ruby/vendor_ruby/2.5.0/yast/yast.rb:204 [FINISH]
c:0009 p:0023 s:0054 e:000053 METHOD /local/home-mvidner/svn/yast/samba-server/src/clients/fail.rb:5
c:0002 p:0489 s:0011 E:000c18 EVAL   /usr/lib/YaST2/bin/y2start:58 [FINISH]
c:0001 p:0000 s:0003 E:001300 (none) [FINISH]

-- Ruby level backtrace information ----------------------------------------
/usr/lib/YaST2/bin/y2start:58:in `<main>'
/usr/lib64/ruby/vendor_ruby/2.5.0/yast/wfm.rb:195:in `CallFunction'
/usr/lib64/ruby/vendor_ruby/2.5.0/yast/yast.rb:204:in `call_yast_function'

-- Machine register context ------------------------------------------------
 RIP: 0x00007fa423bf9677 RBP: 0x00007fff30f5ff20 RSP: 0x00007fff30f5fe10
 R14: 0x00007fff30f5ff48 R15: 0x00007fff30f5fe10 EFL: 0x0000000000010202

-- C level backtrace information -------------------------------------------
/usr/lib64/libruby2.5.so.2.5(rb_print_backtrace+0x15) [0x7fa428543f15]
/usr/lib64/libruby2.5.so.2.5(0x1c814c) [0x7fa42854414c]
/usr/lib64/libruby2.5.so.2.5(0x93e44) [0x7fa42840fe44]
/usr/lib64/libruby2.5.so.2.5(0x158eb2) [0x7fa4284d4eb2]
/lib64/libc.so.6(0x7fa427ff8160) [0x7fa427ff8160]
/usr/lib64/YaST2/plugin/libpy2lang0_ruby.so(_ZN5YRuby9callInnerENSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEES5_7YCPList8constPtrI4TypeS8_E+0x4c7) [0x7fa423bf9677]
/usr/bin/ruby.ruby2.5(_start+0x2a) [0x40086a]

-- Other runtime information -----------------------------------------------

* Loaded script: /usr/lib/YaST2/bin/y2start

* Loaded features:

    0 enumerator.so
    1 thread.rb
    2 rational.so
    3 complex.so
    4 /usr/lib64/ruby/2.5.0/x86_64-linux-gnu/enc/encdb.so
   87 /usr/lib64/ruby/vendor_ruby/2.5.0/yast/y2start_helpers.rb
   88 /local/home-mvidner/svn/yast/samba-server/src/modules/Fail.rb

* Process memory map:

00400000-00401000 r-xp 00000000 08:01 7766                               /usr/bin/ruby.ruby2.5
7fa42363b000-7fa42365c000 r--s 00000000 08:01 6998                       /usr/lib64/YaST2/plugin/libpy2lang_ruby.so
7fa428a5f000-7fa428a60000 rw-p 00026000 08:01 1310795                    /lib64/ld-2.26.so
7fa428a60000-7fa428a61000 rw-p 00000000 00:00 0 
7fff30767000-7fff30f66000 rw-p 00000000 00:00 0                          [stack]
7fff30ff1000-7fff30ff4000 r--p 00000000 00:00 0                          [vvar]
7fff30ff4000-7fff30ff6000 r-xp 00000000 00:00 0                          [vdso]
ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0                  [vsyscall]

You may have encountered a bug in the Ruby interpreter or extension libraries.
Bug reports are welcome.
For details: http://www.ruby-lang.org/bugreport.html

/sbin/yast2: line 455: 25102 Aborted                 (core dumped) $ybindir/y2start $module "$@" "$SELECTED_GUI" $Y2_GEOMETRY $Y2UI_ARGS
  1. "(core dumped)" is lying

It means to say: Per /usr/lib/sysctl.d/50-coredump.conf the core has been sent
to /usr/lib/systemd/systemd-coredump which obeyed "ulimit -c 0" and did not
save it.
So let's

  • use the ulimit -c unlimited command (bash shell builtin, actually)
  • Let it crash again
  • sudo coredumpctl dump -o core

Also note that without the dump subcommand, the core dump will be deleted
after a day. (Why?)

(To avoid systemd-coredump, you can use
sudo /usr/sbin/sysctl kernel.core_pattern="core.%p"; thanks lslezak)

  1. gdb -c core is not useful without the executable

When we do that, the backtrace is very unhelpful:

(gdb) bt
#0  0x00007eff7d0140e0 in ?? ()
#1  0x0000000000000400 in ?? ()
#2  0xffffffffffffffff in ?? ()
#3  0xffffffffffffffff in ?? ()
#4  0xffffffffffffffff in ?? ()
#5  0xffffffffffffffff in ?? ()
#6  0xffffffffffffffff in ?? ()
#7  0xffffffffffffffff in ?? ()
#8  0xffffffffffffffff in ?? ()
#9  0xffffffffffffffff in ?? ()
#10 0xffffffffffffffff in ?? ()
#11 0xffffffffffffffff in ?? ()
#12 0xffffffffffffffff in ?? ()
#13 0xffffffffffffffff in ?? ()
#14 0x0000000000000000 in ?? ()

For some reason, gdb will not load the executable file even though it is named
in the core file. Do it by hand:

  1. gdb program core
$ gdb /usr/bin/ruby.ruby2.5 core

[... lots of text that we'll get back to in the next section ...]
(gdb) bt
#0  0x00007eff7d0140e0 in __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:51
#1  0x00007eff7d01579f in __GI_abort () at abort.c:100
#2  0x00007eff7d42be51 in die () at error.c:552
#3  0x00007eff7d42be51 in rb_bug_context (ctx=ctx@entry=0xcebac0, fmt=fmt@entry=0x7eff7d5925c4 "Segmentation fault at %p") at error.c:582
#4  0x00007eff7d4f0eb2 in sigsegv (sig=11, info=0xcebbf0, ctx=0xcebac0) at signal.c:928
#5  0x00007eff7d014160 in <signal handler called> () at /lib64/libc.so.6
#6  0x00007eff78c15677 in YRuby::callInner(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, YCPList, constPtr<Type, Type>) () at /usr/lib64/YaST2/plugin/libpy2lang_ruby.so
#7  0x00007eff78c19d80 in Y2RubyFunction::evaluateCall() () at /usr/lib64/YaST2/plugin/libpy2lang_ruby.so

Note that the frames 0 to 4 show the source code locations (file name and line
number) as well as the argument names and values. It's because gdb has found
the debugging information for glibc and the Ruby library:

(gdb) info sh libc
From                To                  Syms Read   Shared Object Library
0x00007eff7cffe770  0x00007eff7d14365c  Yes         /lib64/libc.so.6
0x00007eff7c981cd0  0x00007eff7c9895e8  Yes         /lib64/libcrypt.so.1
0x00007eff73c256f0  0x00007eff73c27007  Yes (*)     /usr/lib64/libcap.so.2
0x00007eff6972ca10  0x00007eff69731b65  Yes         /usr/lib64/qt5/plugins/platforminputcontexts/libcomposeplatforminputcontextplugin.so
(*): Shared library is missing debugging information.
(gdb) info sh ruby
From                To                  Syms Read   Shared Object Library
0x00007eff7d3c73c0  0x00007eff7d566ea8  Yes         /usr/lib64/libruby2.5.so.2.5
0x00007eff7c433850  0x00007eff7c4344c0  Yes (*)     /usr/lib64/ruby/2.5.0/x86_64-linux-gnu/enc/encdb.so
0x00007eff7b9ec2c0  0x00007eff7b9f4cb0  Yes (*)     /usr/lib64/ruby/vendor_ruby/2.5.0/x86_64-linux-gnu/yastx.so
0x00007eff78c0fc00  0x00007eff78c1e740  Yes (*)     /usr/lib64/YaST2/plugin/libpy2lang_ruby.so
0x00007eff789f82a0  0x00007eff78a001a5  Yes (*)     /usr/lib64/ruby/vendor_ruby/2.5.0/x86_64-linux-gnu/yast/builtinx.so
(*): Shared library is missing debugging information.

info sh is short for info sharedlibrary. If you omit the library name filter, the
length of the list will easily obscure the "(*)" footnote.

  1. Add debuginfo

On openSUSE (and SUSE Linux Enterprise), the debugging symbols are in separate
RPM packages:

zypper in yast2-ruby-bindings-debug{info,source}

Or take the hint from the gdb message that we omitted in the previous section:

Missing separate debuginfo for /usr/lib64/YaST2/plugin/libpy2lang_ruby.so
Try: zypper install -C "debuginfo(build-id)=8c6a1d943255c6f935e029140e75b49b1b7c22fb"

After restarting gdb:

(gdb) bt
#5  0x00007eff7d014160 in <signal handler called> () at /lib64/libc.so.6
#6  0x00007eff78c15677 in rb_array_len (a=8) at /usr/include/ruby-2.5.0/ruby/ruby.h:2057
#7  0x00007eff78c15677 in YRuby::callInner(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, YCPList, constPtr<Type, Type>) (this=this@entry=0xfefcc0, module_name=..., function=..., argList=..., wanted_result_type=...) at /usr/src/debug/yast2-ruby-bindings-4.0.6-lp150.1.1.x86_64/src/binary/YRuby.cc:220

In frame #6, rb_array_len (a=8), is the a argument equal to nil?
Let's check:

(gdb) p Qnil
No symbol "Qnil" in current context.

That's misleading! Although Qnil is defined in a header, and you've been
taught to prefer static const int to macros because of macros being
"global", they are in fact not as much global as for gdb to see them now. We
have to select a frame to have a context of a compilation unit.

(gdb) f 6
#6  rb_array_len (a=8) at /usr/include/ruby-2.5.0/ruby/ruby.h:2057
2057        return (RBASIC(a)->flags & RARRAY_EMBED_FLAG) ?
(gdb) p Qnil
No symbol "Qnil" in current context.

WTF?! Well, having debugging information loaded is not enough, the debuginfo
must have an elevated level that includes the macros.

  1. Debuginfo with macros

Instead of the -g flag to gcc, I had to specify -g3 in CFLAGS and
rebuild and reinstall. After that, finally:

(gdb) f 6
#6  rb_array_len (a=8) at /usr/include/ruby-2.5.0/ruby/ruby.h:2057
2057        return (RBASIC(a)->flags & RARRAY_EMBED_FLAG) ?
(gdb) p Qnil
$1 = 8
(gdb) f 7
#7  YRuby::callInner (this=this@entry=0xfefcc0, module_name=..., function=..., argList=..., wanted_result_type=...) at /usr/src/debug/yast2-ruby-bindings-4.0.6-lp150.1.1.x86_64/src/binary/YRuby.cc:220
220         VALUE backtrace = RARRAY_LEN(trace)>0 ? rb_ary_entry(trace, 0) : rb_str_new2("Unknown");

So a = 8 and Qnil is 8, so we have confirmed that the trace array being
nil is causing the crash.

(For the record, this is bsc#1119690.)

Sep 18, 2017

Fibre Channel over Ethernet: Basics of FCoE in SUSE Linux

I had to apply a fix for a FCoE module in YaST, and I had no idea.

After learning a couple of things I still only have a vague idea, but I am writing it down to help my future self, my team mates, and perhaps you too.

FCoE stands for "Fibre channel over Ethernet". Apparently if you have some disk on a Fibre Channel SAN (storage area network), you can use FCoE to extend the reachability of that disk to the ethernet parts of your network. It still needs to be a kind of special ethernet (10Gb, with special network cards) but that seems less special than FC hardware.

For a better overview, including a diagram, see: SUSE Linux Enterprise Server Documentation / Storage Administration Guide / Fibre Channel Storage over Ethernet Networks: FCoE.

FCoE typically uses a virtual LAN, (VLAN, IEEE 802.1Q).

There needs to be a Fibre Channel Forwarder (FCF) between the FC and ethernet parts. It has a MAC address. Note a difference from iSCSI which works on the IP level, one layer up.

YaST helps you set things up. The rest of this article could be useful if you cannot use YaST for some reason.

SLES uses open-fcoe. On SLES-12 the package is called fcoe-utils.

fipvlan (stands for FCoE Initialization Protocol VLAN discovery) shows FCFs and which interface and VLAN they are reachable with:

# fipvlan --auto
Fibre Channel Forwarders Discovered
interface       | VLAN | FCF MAC
eth1            | 500  | 00:0d:ec:b3:ca:00

It can also --create the VLAN interface and --start up the FCoE connection, but it won't make that permanent for the next boot

To make it permanent you need to

  1. enable the FCoE service (SLE11:/etc/init.d/boot.fcoe, SLE12: fcoe.service). Under the hood it uses two programs: fcoemon is the daemon, fcoeadm is a front end (fcoeadm -p shows the pid of fcoemon).
  2. write a config file, /etc/fcoe/cfg-*IFACE*, where IFACE is
    • eth1.500 if AUTO_VLAN is no; in this case, you also need /etc/sysconfig/network/ifcfg-eth1.500, see man ifcfg-vlan.
    • eth1 if AUTO_VLAN is yes; in this case, the interface is named eth1.500-fcoe. Note the unusual -fcoe suffix!

With the config files in place, rcfcoe start (and ifup eth1.500, unless AUTO_VLAN). Then you should see the disk devices:

# fcoeadm --target
    Interface:        eth1.500
    Roles:            FCP Target
    Node Name:        0x50060160BB600160
    Port Name:        0x500601663B600160
    Target ID:        0
    MaxFrameSize:     2048
    OS Device Name:   rport-2:0-2
    FC-ID (Port ID):  0x710D00
    State:            Online

    LUN ID  Device Name   Capacity   Block Size  Description
    ------  -----------  ----------  ----------  ----------------------------
         0  /dev/sdb      16.00 GiB      512     DGC VRAID (rev 0430)

People who actually know their way around FCoE will note that I have omitted many important details. Let me know in the comments whether I should come back to this and expand on some topics.

Mar 1, 2017

Getting Started in Android Development: Part 3: Reducing Bloat

So far we have seen Part 1: Building the First App, and Part 2: Publishing the first App.

That Feeling When you build a brilliant piece of software and the users are ripping it from your fingers to the sound of raving reviews:

  • dad: I'm home! Have you seen my first app I've e-mailed you about?
  • kid: Hi. Yup.
  • dad: So?? Do you like it? Have you given it any stars?
  • kid: Just one. It can do almost nothing and it takes up too much space.

And the kid is right. App description: Press a button and get a random number between 1 and 6. App size: 6MB. Six. Megabytes.

In this post we will reduce that over a hundred times to 44KB.

Thanks to SUSE, my employer, for sponsoring a company-wide Hack Week which this project was a part of!

Debug or Release Build?

I did not manage to make a release build in the Android Studio IDE. So I tried from the command line. (J. Reidinger has pointed out that I should read Configure Build Variants.)

$ sudo zypper install java-1_8_0-openjdk-devel       # to provide javac
$ ./gradlew assemble
[downloads some deps at first... 280MB]
[lots of output for normal build too]
$ (cd app/build/outputs/apk; stat -c "%'9s %n" *.apk)
1,443,734 app-debug.apk
1,337,890 app-release-unsigned.apk

Apparently my hopes that a release build would be significantly smaller were unfounded. The APK has 1.5MB and takes up 6MB when installed.

Shrink Your Code and Resources

First I searched the web for "minify android app" and eventually arrived at Shrink Your Code and Resources in the IDE manual.

Using minifyEnabled true in build.gradle shrunk the signed release build from 1,347,038 bytes to 786,674, which results in 2.39MB installed size. (Did not find a way to install this build from the IDE, used adb install -r ./app/app-release.apk.)

Changing proguardFiles from proguard-android.txt to proguard-android-optimize.txt slightly shrinks the APK to 771,406 bytes.

Adding shrinkResources true: 745,490 bytes, 2.21MB installed.

Code Bloat: Activity Base Class

It seems that now the main reason for bloat is the sheer amount of included code: 5 methods of mine vs 4823(!) methods from the android.* classes.

Changed the base class of the main activity from android.support.v7.app.AppCompatActivity to android.app.Activity but then adb install says "Failure [INSTALL_FAILED_UPDATE_INCOMPATIBLE]". adb uninstall net.vidner.justrollonedie solved it. But I wonder what would happen if my users on the app store wanted to update. Fortunately I have none :D

The base class change improved the sizes to 661,870 APK, 1.62MB installed.

Code Bloat: API Version

I thought a 4x reduction in installed size was good enough, even if still bloated. I decided to fix one more thing before pushing an update to the store: the minimal required Android platform. (In the process of tinkering with a demo OpenGL app I discovered that android-8, supporting my old 2.2 Froyo phone, gets automatically downloaded if I declare it in the app manifest.)

So I did, and the side effect was perfect: all boilerplate code was gone and I ended up with a 17,282 byte APK, 44KB (kilobytes!) installed. Still too much for a microcontroller ;-) but good enough for Android.

Figuring out how to downgrade my code and layout and styles to still run on the older API seemed tricky at first, but then I simply generated a scratch project for android-9 and copied the differences. Then I changed one style name with the help of the API version filter (see screenshot).

Get the App, Get the Source

The source code for Just Roll One Die is on GitHub under a MIT license. You can try out Just Roll One Die on Google Play.

Feb 28, 2017

Getting Started in Android Development: Part 2: Publishing the First App

Here I simply describe what it takes to publish an Android application that I described in the previous part, Building the First App.

Thanks to SUSE, my employer, for sponsoring a company-wide Hack Week which this project was a part of!

I will only deal with free apps: no cost for the user and no advertisements. I guess it would be easy to slap an advertisement module on it or put a minimal price tag on the app. But then it would be morally wrong for me to keep the profits without giving SUSE a cut, and the organizational and accounting process would quickly turn this into a lawyer's Hack Week. Scratch that.

Registering a Publisher Account: $25

I started with the instructions at Get Started with Publishing.

I could have reused my existing Google account but decided to create a new one. The next step may put you off: a 25 USD registration fee is needed.

Then a fair amount of legalese, which I did skim through, and I was rewarded by the knowledge that Google apparently does not like developers to publish web browsers or search engines.

Publishing the App

When I thought my application was good enough to be published I went to the Developer Console to make a Store Listing.

Entered the app name, summary, long description; no surprise there, I had expected that from openSUSE RPM packaging. Then came the innovation: screenshots are required! In fact,

  • Two screenshots
  • a high-resolution icon (512x512 pixels)
  • a feature graphic (1024x500 px) which appears as the heading of the app listing page

Reportedly the new standard way to take a screenshot is Power + Volume Down. But that did not work for my Xperia phone. I had to enable the following setting, after which a Screenshot option appeared in the menu that appears after holding Power.

  • Settings, then
  • Device / Buttons, then
  • Power button / Power menu, there
  • enable Screenshot ☑.

For a moment I feared I would need to hire a designer for the icon, but then I told LibreOffice to write a 6 in a 360pt big font and used that. whew!

More form items to fill: App type: Applications (not Games); Category: Entertainment (I guess); Pricing and distribution: Free, All countries, No ads.

We do not process any user data so we check a box that we're Not submitting a privacy policy.

Now we are at a point in the form where it says that we need to submit a content rating, but it won't let us do it. I think it only allows to rate after the app has been uploaded.

Are we ready to upload the app code? Upload APK... bzzzt, wrong! must not upload a debug build. Did not find a way to make a production build in the GUI so used the CLI for a change: ./gradlew assemble... bzzzt, wrong! must not upload an unsigned build.

Signing software makes sense. Except the signing mechanism is unfamiliar to me, something involving a Java KeyStore. So I followed the manual: Sign Your App. Ended up with a file in my home directory and needing to enter two passwords each time I build a signed APK. At least no certification authority needed to be involved.

Content Rating: Category: Utility, No violence, No sexuality, No offensive language, No controlled substances (illegal drugs), No communication with other users, No sharing of personal information, No sharing of location, No digital goods purchasing, No Nazi symbolism, Not a browser or search engine.

Finally all information was there, I hit Publish, and I wondered how long the review process would take. It took about 3 hours on a European Tuesday noon.

You can try out Just Roll One Die on Google Play. The source code for Just Roll One Die is on GitHub under a MIT license.


In the next part we will deal with software bloat. Because an app that can roll a 6 is justified in taking up 6MB on your kid's tablet, right? Right??

Feb 27, 2017

Getting Started in Android Development: Part 1: Building the First App

Getting Started in Android Development: Part 1: Building the First App

Do you know programming and want to start with the Android platform? Just like me! Read on.

Thanks to SUSE, my employer, for sponsoring a company-wide Hack Week which this project was a part of!

In case you wonder why Android: it is a good balance of work and play. Android is not the coolest toy to play with at the moment, but it is the most versatile device that people are likely to have at hand, especially when traveling. And Android already outnumbers openSUSE and all other OSs in my household.

This is a three part series: 1) building an app, 2) publishing it on Google Play, 3) trimming it down. In this part, we'll set up the development environment, follow the official tutorial to build a trivial app, then build a trivial yet useful app of our own.

a screenshot of my first app

a screenshot of my first app

Installing the SDK

I am using openSUSE Leap 42.1 (x86_64). You will notice that I keep tallying the disk space taken. This is because I am a bit short of space on one of my machines, and need to have an idea how much cleanup is needed.

Went to https://developer.android.com/.

Downloaded Android Studio (2.2.3 for Linux, 438 MiB, unpacks to 785 MiB), followed the instructions, unpacking to /opt (getting /opt/android-studio).

Ran /opt/android-studio/bin/studio.sh. Was greeted by an "Android Studio Setup Wizard": chose a Standard setup. Additional download of 890MB (1412MB unpacked) to ~/Android/Sdk.

Got a slightly confusing notice about KVM emulator acceleration. It seems that if you have used KVM before on your machine, the SDK will use it out of the box. But even with acceleration, don't expect the emulator to be fast. If you have a real device, use that.

"Building Your First App"

For the most part I simply followed the tutorial for building, installing, and running a trivial app that asks for a message and then displays it. The documentation feels excellent!

The one non-obvious part was choosing which Android version, in other words, which API level, to target. in the Target Android Devices dialog, the preselected option is API 15: Android 4.0.3 (IceCreamSandwich). That is presumably based on the current active device statistics which result in the app being compatible with 97% of devices. The oldest one is API 9: Android 2.3 (Gingerbread), which was a bit disappointing since my older phone from 2010 runs API 8, 2.2 (Froyo). (Don't worry, I eventually solved that in part 3.) Fortunately my newer phone has API 22: Android 5.1.1. Installed the API 22 platform too, to match the phone, about 100MB.

Connected my phone with a USB cable, pressed Run, and there it was! Don't worry, a buggy app will just crash and not affect the rest of your phone.

Just Roll One Die

Now it looked like I knew enough to make a useful app, so I did: Once my family was on a train with a board game table but we had no dice. So my first actual app is Just Roll One Die. A totally simple application that can just roll one ordinary six-faced die. Six faces ought to be enough for anybody. No pictures, just digits.

The source code for Just Roll One Die is on GitHub under a MIT license. You can try out Just Roll One Die on Google Play. (The details of how to get an app there are described in Part 2: Publishing the First App.)

How about you?

I was amazed how easy it was and I can't believe that it took me so long to try this. Wy don't you too give it a try and let me know how you are doing.

Feb 16, 2017

Text to Speech with eSpeak and Epos

A humanoid robot should be able to talk. So I looked around for some open source speech synthesis software.

(The above video does feature a talking robot (and a multilingual dolphin) but that's where similarities with the following content end.)


Hello world:

espeak 'Hello, world!'

Standard input works too:

espeak <<EOS
A robot may not injure a human being or, through inaction,
allow a human being to come to harm.

I need the robot to speak Czech too:

espeak -v cs 'Dobrý den!'

Chinese also seems to work, at least to my beginner ear:

espeak -v zh '认识你很高兴'
# The same in pinyin
espeak -v zh 'ren4shi ni3 hen3 gao1xing4'

To put the words to the robot's mouth we first need to save the sound to a file:

espeak -w dobry-den.wav -v cs 'Dobrý den!'    # 16 bit, mono 22050 Hz

Now a thing that is not so useful for the robot, but a cool diversion. This tells eSpeak to be quiet, and transcribe the text in International Phonetic Alphabet.

espeak -q --ipa 'All human beings are born free and equal
  in dignity and rights. They are endowed with reason and conscience
  and should act towards one another in a spirit of brotherhood.'

ˈɔːl hjˈuːmən bˈiːɪŋz ɑː bˈɔːn fɹˈiː and ˈiːkwəl ɪn dˈɪɡnɪti and ɹˈaɪts

ðeɪ ɑːɹ ɛndˈaʊd wɪð ɹˈiːzən and kˈɒnʃəns and ʃˌʊd ˈakt tʊwˈɔːdz wˈɒn ɐnˈʌðəɹ ɪn ɐ spˈɪɹɪt ɒv bɹˈʌðəhˌʊd

And it also works for Czech:

espeak -q -v cs --ipa 'Všichni lidé rodí se svobodní a sobě rovní
  co do důstojnosti a práv. Jsou nadáni rozumem a svědomím
  a mají spolu jednat v duchu bratrství.'

fʃˈixɲi lˈideː rˈoɟiː se svˈobodɲiː a sˈobje rˈovɲiː tsˈo do dˈuːstojnˌosci a prˈaːv

jsoʊ nˈadaːɲi rˈozumem a svjˈedomiːm a mˌajiː spˈolu jˈednat v dˈuxu brˈatr̩stviː


The problem with eSpeak is that it sounds quite robotic. I remembered that for Czech, the epos system was much better, also for its availability of better quality downloadable voices.

I installed epos (here as an openSUSE RPM) and downloaded the high quality voices epos-tdp.tgz, then unpacked them to the right place:

cd /usr/share/epos/inv
sudo tar xvf .../epos-tdp.tgz

At first I got no sound but strace showed me a problem with /dev/dsp and a bit of searching turned out that I must run eposd with a dsp wrapper:

padsp eposd $OPTIONS
# eg.
padsp eposd --voice machac
padsp eposd --voice violka

Another quirk is that epos wants the input in ISO Latin 2, so I used iconv:

while read S; do say-epos $(echo "$S" | iconv -f utf8 -t l2); done

For saving the sound to a file, use -w to use a fixed file name ./said.wav, or -o to use stdout:

say-epos -w Ahoj
say-epos -o Ahoj > ahoj.wav

Other systems?

The thing that reminded me of epos was this summary written by a small Czech phone operator.

Have you tried text-to-speech software? Which one sounds the best?

Feb 7, 2017

Jenkins as Code

I saw a couple of talks last week, and learned about several ways of automating Jenkins CI.

The problem being solved is: if you automate your builds and tests, why still click the Jenkins web UI by hand? Script it instead.

Jenkins Job DSL, which is based on Groovy (a JVM language). Another topic was Jenkins Pipeline which helps managing many jobs that depend on each other.

In Test Driven Infrastructure, Yury Tsarev presents, among many other things, Jenkins Job Builder. JJB takes descriptions written in YAML or JSON and translates them to Jenkins API with Python.

Jan 30, 2017

Capturing and Decoding Lego Mindstorms EV3 Bluetooth Communication

The Lego Mindstorms EV3 robots can be controlled with an Android app (Lego Mindstorms Commander) communicating with the brick via Bluetooth. The command protocol is documented by Lego in the EV3 Communication Developer Kit and the commands themselves in the EV3 Firmware Developer Kit (get them from Mindstorms Downloads).

I wondered what exactly goes on and I decided to capture the communication and decode it, to learn both about Bluetooth and about the details of the EV3 protocol.

Good Robot. Good Robot!!

I succeeded and made a couple of useful tools along the way:

See also the previous post about sending data (EV3 commands) over USB.


  1. Enable Android Bluetooth logging
  2. Run the Commander app and exercise the robot a bit
  3. Transfer the log to a PC
  4. Extract the serial data (RFCOMM) from the Bluetooth dump
  5. Decode the EV3 protocol
  6. Disassemble the EV3 instructions

1. Enable Android Bluetooth Logging

  • Open Settings
  • In the System section, choose Developers (this needs to be enabled first by tapping Build number 7 times)
  • Enable Bluetooth HCI Log

2. Run the Commander app and exercise the robot a bit

3. Transfer the log to a PC

On the phone/tablet:

  • Open Settings
  • System > Developers
  • Disable Bluetooth HCI Log

Connect to the PC with a USB cable.

My older Android phone offered to mount its storage as a USB disk drive, but the newer one no longer has that option, offering MTP instead. I transfered the log file with a KDE tool:

$ kioclient cp 'mtp:/Xperia Z3/Interní úložiště/btsnoop_hci.log' .

4. Extract the serial data (RFCOMM) from the Bluetooth dump

The tool I made for this is btsnoop-decode.rb.

I learned the bare minimum needed about Bluetooth so it is very likely the tool only works for this specific use case.

Originally I opened the btsnoop log with Wireshark and guessed my way through the BT protocol layers. In the end the RFCOMM length field was harder than usual to guess and half of my packets were wrong. So I resorted to finding the appropriate part of the Linux kernel source to find out the format.

5+6. Decode the EV3 protocol and dissassemble the EV3 instructions

The people of the ev3dev project have already produced a disassembler which we will use in the next step. But that one assumes you start with a program file (RBF).

Here we have a log containing not only the usual RBF instructions but also System Commands.

I made an ugly hack of the lmsdisasm tool and arrived at a version that disassembles the log produced by the RFCOMM extractor.

Play time

The above experiments enabled me to put together a little script that can control the robot from a Linux terminal, having it ride around and even speak a custom sound file: lethargic-ministers/lms.py.

Jan 2, 2017

USB Communication with Python and PyUSB

Say we have a robot with a USB connection and command documentation. The only thing missing is knowing how to send a command over USB. Let's learn the basic concepts needed for that.

General Bunny catching Pokemon

Installing the Library

We'll use the pyusb Python library. On openSUSE we install it from the main RPM repository:

sudo zypper install python-usb

On other systems we can use the pip tool:

pip install --user pyusb

Navigating USB Concepts

To send a command, we need an Endpoint. To get to the endpoint we need to descend down the hierarchy of

  1. Device
  2. Configuration
  3. Interface
  4. Alternate setting
  5. Endpoint

First we import the library.

#!/usr/bin/env python2

import usb.core

The device is identified with a vendor:product pair included in lsusb output.

Bus 002 Device 043: ID 0694:0005 Lego Group

VENDOR_LEGO = 0x0694
device = usb.core.find(idVendor=VENDOR_LEGO, idProduct=PRODUCT_EV3)

A Device may have multiple Configurations, and only one can be active at a time. Most devices have only one. Supporting multiple Configurations is reportedly useful for offering more/less features when more/less power is available. EV3 has only one configuration.

configuration = device.get_active_configuration()

A physical Device may have multiple Interfaces active at a time. A typical example is a scanner-printer combo. An Interface may have multiple Alternate Settings. They are kind of like Configurations, but easier to switch. I don't quite understand this, but they say that if you need Isochronous Endpoints (read: audio or video), you must go to a non-primary Alternate Setting. Anyway, EV3 has only one Interface with one Setting.

interface = configuration[(INTERFACE_EV3, SETTING_EV3)]

An Interface will typically have multiple Endpoints. The Endpoint 0 is reserved for control functions by the USB standard so we need to use Endpoint 1 here.

The standard distinguishes between input and output endpoints, as well as four transfer types, differing in latency and reliability. The nice thing is that the Python library nicely allows to abstract all that away (unlike cough Ruby cough) and we simply say to write to a non-control Endpoint.

endpoint = interface[ENDPOINT_EV3]

# make the robot beep
command = '\x0F\x00\x01\x00\x80\x00\x00\x94\x01\x81\x02\x82\xE8\x03\x82\xE8\x03'

Other than Robots?

Robots are great fun but unfortunately they do not come bundled with every computer. Do you know of a device that we could use for demonstration purposes? Everyone has a USB keyboard and mouse but I guess the OS will claim them for input and not let you play.

What Next

The Full Script

Dec 12, 2016

Web Application Hosting with Heroku

I know Ruby but have little experience with web apps. If you're like me then this article could be useful.

I needed a way to browse API documentation of multiple related code repositories. (Yes, it's YaST).

I made a tool for that in the form of a web application. This was really easy with the Sinatra framework.

First I ran it locally on my machine for myself. Then I ran it on a machine in the company network for team mates to use. It was a VM that I repurposed from a previous experiment. Then Pepa said it would be nice to have it publicly accessible. How hard could that be?

I had heard that Heroku makes that sort of thing easy, and it turned to be true!

  1. It's free. A low profile app, that only needs to run occasionally, fits into their Free service plan. It sleeps after 30 minutes and takes 10 seconds to wake up.

  2. Easy to sign up. Enter your e-mail, pick a password. No other details required.

  3. Easy app creation: pick the region (US or EU). Optionally pick a name (I got salty-waters-71436 for my demo app).

  4. Easy to set up the tooling. Well, they install the curl | bash way. Over https. And then the downloaded code downloads some more.

    If you want to start small, the setup by hand is easy too, now download required:

    touch ~/.netrc
    chmod 600 ~/.netrc
    echo "machine git.heroku.com login YOUR_EMAIL password ffffffff-ffff-ffff-ffff-ffffffffffff" >> ~/.netrc

    Where the hex string is your API Key (Top-right Person icon > Account Setings > scroll down)

Now let's write a trivial web app.

  1. Make a git repo.
  2. Make a two-line Sinatra app.

    require "sinatra"
    get "/" { "Hello, world!" }
  3. Add a two-line Gemfile declaration; add also Gemfile.lock to Git.

    source "https://rubygems.org"
    gem "sinatra", "~> 1.4.0"
  4. Add a oneliner Procfile.

    web: bundle exec ./timeserver

    (This was new to me. It's not needed locally but needed for Heroku, and anyway useful once you outgrow oneliners. Use foreman start to use it)

  5. Use your app name as the remote repo name. Push to deploy (or set up automatic deployment):

    git remote add heroku https://git.heroku.com/salty-waters-71436.git
    git push heroku

That's it! See the app in action: https://salty-waters-71436.herokuapp.com/?q=1_500_000_000.

To see my actual app, instead of the trivial demo built for this blog post, go to http://apitalism.herokuapp.com/.

Aug 1, 2016

Virtual Machine from a Hard Disk Image with virt-install --import

This is one of many ways to create a virtual machine. This way starts with a hard disk image.

wget -O /var/lib/libvirt/images/$NAME $IMG
virt-install --name $NAME \
       --ram 2048 --graphics type=vnc \
       --network bridge=br0 \
       --import \
       --disk bus=virtio,path=/var/lib/libvirt/images/$NAME

For IMG I used a SUSE-internal server with SLEnkins images.
The tricky part is knowing the right value for the --disk bus setting. At first I used the default but the machine wouldn't boot because it would see /dev/sda instead of /dev/vda it was expecting.

May 27, 2016

Ruby Call Graph

Call-graph makes a call graph among methods of a single Ruby file.
I made it to help me orient myself in unfamiliar legacy code and to help identify cohesive parts that could be split out.
Yes, it is quick and dirty.


One file in YaST has around 2700 lines and 73 methods. The call graph below was made with
$ ./call-graph ../yast/packager/src/modules/Packages.rb
$ dot -Tpng -oPackages.png ../yast/packager/src/modules/Packages.dot
If the resulting size is too big, use ImageMagick:
$ convert Packages.png -resize 1200 Packages-small.png
Packages.png, an example output
Packages.png, an example output




Nov 12, 2015

Git: Single Line History

You get a bug report from a user:
/usr/lib/foo/bar.rb:432:in `doit': undefined method `[]' for nil:NilClass (NoMethodError)
but in bar.rb at the line 432 there are no square brackets. The user must be using an older version of the script. Can we find out which one without asking them?

Git can help. This code will go back in history and show the line how it appeared during the past. It's a history of a single line, kind of like "git blame" but in a different dimension.

git log --format=format:%H $FILE \
| while read COMMIT_ID; do
    echo -n $COMMIT_ID:$FILE:$LINE:
    git show $COMMIT_ID:$FILE | sed -n "$LINE{p;q}"
  done \
| less 

Have I reinvented the wheel? What is its name?

Nov 10, 2015

Arabic Text Bugfix

Can you spot the difference?

If this rings a bell but you can't quite remember why, here's an English version of the screen, and the spoiler for the puzzle is below it:
Spoiler: The line containing "passwd" is clipped at the (left) end, showing only "المحا" instead of "المحلي۔". This bug got popular in the YaST team because the localization testers dutifully reported every instance of a truncated label so the bug accumulated 22 duplicates. It only happened for the Arabic script which made it a bit more challenging to work with, but luckily I know the script and a few words.

Thanks to Max Lin who pointed me to a problem between the Qt UI library and the HarfBuzz text shaping engine, the problem is now fixed.

Aug 2, 2013

YaST in Ruby

As already announced on Factory, yast-devel, and by Lukáš: YaST, the SUSE installation and configuration tool, has been automatically translated from YCP, an in-house custom language, to Ruby. In the past 6 months, we have built a tool to translate 600.000 lines of code developed over the course of 12 years.

My role in the project was mainly shedding light on ancient details of the YCP language and its interpreter. Stop pulling my beard, kids! Also, knowing Bison (the tool used to implement the YCP parser in C++) I designed a part that transfers the comments. Mind you, not only at the function or statement level, but from inside of expressions too. Fun!

Thanks to the team, it was great working on the project with you!

Jul 26, 2011

ruby-dbus 0.7.0 works with 1.9.2 again

I have made a new release of ruby-dbus, a Ruby language binding for the D-Bus IPC system.
  • Added ASystemBus and ASessionBus, non-singletons useful in tests and threads.
  • Fixed handling of multibyte strings (Issue#8, by Takayuki YAMAGUCHI).
  • Allow reopening of a dbus_interface declaration (Issue#9, by T. YAMAGUCHI).
  • Fixed ruby-1.9.2 compatibility again (Issue#12).
  • Fixed authentication on BSD (Issue#11, by Jonathan Walker).
  • Fixed exiting a nested event loop for synchronous calls (reported by Timo Warns).
  • Fixed introspection calls leaking reply handlers.
  • "rake test" now works, doing what was called "rake env:test"
Get a gem from RubyGems.org or an rpm from the openSUSE Build Service.

    May 16, 2011

    LinuxTag 2011 Pictures

    After a problem with the organizers' equipment, kobliha's openSUSE laptop was used to watch the live stream from Skynet I/O Chrome keynote.
    LinuxTag: openSUSE saves the day
    "Rule 1: Stay calm." Ralph Angenendt talks about problem solving.
    LinuxTag: Breathe!
    LinuxTag: Party in Umspannwerk Kreuzberg

    Dec 22, 2010

    network-autoconfig: Find a connected eth interface and create an ifcfg for it

    Use case: I want to create an appliance image for a build farm worker machine. I don't know its hardware configuration beforehand; in particular, it may have multiple network interfaces and I don't want to bother figuring out which is which. I will simply include network-autoconfig.rpm and plug the cable into any socket before booting.

    network-autoconfig helps setting up machines with multiple network interfaces. At the first boot, all available Ethernet interfaces are cycled until one is successfully configured with DHCP.

    I have submitted it to openSUSE:Factory now. Enjoy it in the upcoming openSUSE 11.4!

    It is referenced as Feature#311012. You are welcome to improve it on Gitorious.

    Nov 16, 2010


    dbus-dump is a tool to capture D-Bus messages in a libpcap capture file.

    It takes an idea from dbus-scrape, which processes a strace output of dbus-monitor, and takes it further by stracing dbus-daemon, thus not relying on any eavesdropping (mis)configuration.

    The intended purpose is to establish the libpcap capture format as a base for debugging tools like

    Thanks to Will Thompson for mentioning the pcap idea.


    $ sudo strace -p `pgrep -f 'dbus-daemon --system'` \
        -s 3000 -ttt -xx -o foo.strace
    $ ./dbus-dump foo.strace foo.pcap
    $ ./dbus-pcap-parse foo.pcap
    Tue Nov 16 12:56:47 +0100 2010 #<DBus::Message:0xb741f340
    Tue Nov 16 12:56:47 +0100 2010 #<DBus::Message:0xb741b060


    It is written in Ruby. The pcap format is handled by a small bundled module. dbus-dump has no other dependencies. dbus-pcap-parse uses ruby-dbus.


    This is an early proof-of-concept release, serving to introduce the libpcap format.

    The main problem of dbus-dump is duplicating the messages, seeing them both when the daemon receives them and when it sends them (multiple times, for the signals).

    The other tools haven't caught up yet:

    $ /usr/sbin/tcpdump -r foo.pcap
    reading from file foo.pcap, link-type 231
    tcpdump: unknown data link type 231

    Nov 9, 2010

    ruby-dbus 0.5.0 is a Gem with Errors

    I have made a new release of ruby-dbus, a Ruby language binding for the D-Bus IPC system.
    The main feature is a better binding of Ruby Exceptions to D-Bus Errors. See below for an excerpt of the documentation.
    Perhaps more importantly, the library is now primarily packaged as a RubyGem (Issue#6). Also I converted the tutorial from Webgen to Markdown.
    Bug fixes:
    • Don't pass file descriptors to subprocesses, they would not let go of the service name.
    • Fixed InterfaceElement::validate_name (Ticket#38, by Herwin Weststrate).
    • Fixed a typo in InvalidDestinationName description (Ticket#40).
    RPMs can be found via openSUSE Build Service Search.


    D-Bus calls can reply with an error instead of a return value. An error is translated to a Ruby exception.
    rescue DBus::Error => e
        puts e unless e.name == "org.freedesktop.NetworkManager.AlreadyAsleepOrAwake"

    Replying with an error

    To reply to a dbus_method with a D-Bus error, raise a DBus::Error, as constructed by the error convenience function:
    raise DBus.error("org.example.Error.SeatOccupied"), "Seat #{seat} is occupied"
    If the error name is not specified, the generic org.freedesktop.DBus.Error.Failed is used.
    raise DBus.error, "Seat #{seat} is occupied"
    raise DBus.error

    Aug 29, 2010

    n2n package improved

    Root.cz recently ran an article (in Czech) about the n2n virtual private network sofware, an open alternative to Hamachi. I intend to use it to cross the NAT in my mom's DSL modem so that I can connect to her computer with ssh and VNC.
    Thanks to happyman_eric and Grief, openSUSE Build Service already contained a package. I have made an improved version, adding an init script and a sysconfig file. Get the sources in my home project, or the binaries.

    Aug 20, 2010

    ruby-dbus 0.4.0 with TCP Transport

    I have made a feature release of ruby-dbus, a Ruby language binding for the D-Bus IPC system.
    • TCP transport which pangdudu coded a year ago. At that time I did not feel familiar enough with the library, and the test suite was much smaller too, so that's why it took me so long.
    • Enabled test code coverage report (rcov)
    • Classes should not share all interfaces (Ticket#36/Issue#5)
    • Ruby 1.9 compatibility (Ticket#37, by Myra Nelson)
    RPMs can be found via openSUSE Build Service Search

    Aug 10, 2010

    Who does not want such a gift

    This post is showing naked women packaged as a present (for openSUSE's 5th birthday) and asks Ah... who does not want such a gift, eh.

    I believe that the female users and contributors of openSUSE don't. It reduces them to pretty things, judged on their looks instead of their contribution.

    Raul, please stop such sexist postings. Your blog is your own, but keep it out from Planet openSUSE.

    Just in case common sense is not enough, let me quote for reference the relevant section of the openSUSE Guiding Principles:

    We value... respect for other persons and their contributions, for other opinions and beliefs. We listen to arguments and address problems in a constructive and open way. We believe that a diverse community based on mutual respect is the base for a creative and productive environment enabling the project to be truly successful. We don't tolerate social discrimination and aim at creating an environment where people feel accepted and safe from offense.
    and the activities in order to excel in our goals: Emphasize the value of communication and recognize cultural diversity within our community.

    Aug 5, 2010

    Upgraded to openSUSE 11.3

    I have upgraded my office workstation to openSUSE 11.3 today. Here I document the migration so that you don't have to repeat my mistakes.

    I went via the command line and ventured to keep all additional repos enabled. So switching the repos was done simply by sed -i "s/11\.2/11.3/g" /etc/zypp/repos.d/*

    The KDE session crashed after kdelibs4-core had been updated. No big deal, so I ran zypper dup again.
    The /home directory is mounted via NFS, so filesystem.rpm failed when it wanted to reset the permissions of /home. Updating it explicitly after unmounting /home was easy, only unmounting it was harder because the crashed session left processes still accessing the home. fuser -v /home found them.

    The NFS mount is also authenticated by Kerberos and there is a bug so I got
    mount.nfs: access denied by server while mounting nfs.example.com:/home
    I had to rebuild and update a package and tweak a config file. See bnc#614293 for the details (thanks to mcaj for the reference).

    Jul 22, 2010

    ruby-dbus 0.3.1

    I have made a bug-fix release of ruby-dbus, a Ruby language binding for the D-Bus IPC system.
    • Many on_signal could cause DBus.Error.LimitsExceeded (bnc#617350).
      Don't add a match rule that already exists, enable removing match rules. Now only one handler for a rule is called (but it is possible for one signal to match more rules). This reverts the half-fix done to fix Issue#3.
    • Re-added InterfaceElement#add_param for compatibility.
    • Handle more ways which tell us that a bus connection has died.
    RPMs can be found via Webpin.

    Jul 2, 2010

    Helping Newcomers

    Since the discussion (do check out the linked paper, BTW) and the opensuse-women announcement, I've been thinking about how to make the openSUSE community more friendly to women.

    I think one good way is to make sure that new people feel welcome when they join a conversation, be it on the forums, on IRC or on the mailing lists. Now this would be easier if we all had infinite time to read and answer all questions, but as we don't, I decided to focus somehow.

    The forums provide a handy shortcut for the focus, labeling a user who made few posts as a "Puzzled Penguin". So I've made a simple service, a feed of http://forums.opensuse.org showing only the posts by newcomer users: http://vidner.net/martin/software/rss-creator-blacklist

    (Actually right now it does not show Puzzled Penguins only but instead excludes the 100 most-posting users until I learn how to optimize the PHP code.)

    Jun 30, 2010


    I have started working on kiwi2puppet, a tool to convert KIWI image descriptions to Puppet manifests.

    The goal is to recycle the data that went into the building of an image and use it for managing a deployed appliance.

    So far it is a prototype that can write these resources
    • package
    • yumrepo
    • user
    • group
    It is written in Ruby, like Puppet.

    Source at GitHub: http://github.com/mvidner/kiwi2puppet
    RPMs: http://software.opensuse.org/search?q=kiwi2puppet&baseproject=ALL (currently it is a single Ruby script, so at the moment RPMs are not worth any trouble)
    Novell Reference: FATE#309497

    Get in touch if you're interested.

    In case you didn't know:
    "The openSUSE KIWI Image System provides a complete operating system image solution for Linux supported hardware platforms as well as for virtualisation systems like Xen Qemu or VMware."
    "Puppet is an open source data center automation and configuration management framework. Puppet provides system administrators with a simplified platform that allows for consistent, transparent, and flexible systems management."

    Mar 28, 2010

    ruby-dbus 0.3.0 Works on Ubuntu

    ruby-dbus has for a long time not worked on the default Ubuntu desktop. I thought I had fixed it in 0.2.12 but that was only for the server side. In fact, clients had another bug and I have released version 0.3.0 today to fix it.

    Bug fixes:
    • Fixed "undefined method `get_node' for nil:NilClass" on Ubuntu Karmic (Ticket#34).
    • Get the session bus address even if unset in ENV (Issue#4).
    • Improved exceptions a bit: UndefinedInterface, InvalidMethodName, NoMethodError, no RuntimeException
    These are by Klaus Kaempf:
    • Make the signal dispatcher call all handlers (Issue#3).
    • Run on Ruby < 1.8.7 (Issue#2).
    • Avoid needless DBus::IncompleteBufferException (Ticket#33).
    • Don't ignore DBus Errors in request_service, raise them (Ticket#32).
    • Automatic signature inference for variants.
    • Introduced FormalParameter where a plain pair had been used.
    RPMs can be found via Webpin.

    Feb 18, 2010


    [S]ometimes, when you are designing systems it is hard to realize that the circular friction reduction device with a central axis that you have just built is, in fact, a wheel.

    -- Russ Olsen, Design Patterns in Ruby, p.4

    Jan 24, 2010

    Service Activation Fixed in ruby-dbus 0.2.12

    Today I fixed a long-standing bug in ruby-dbus where a service activated by the bus would fail with "undefined method `get_node' for nil:NilClass" (tickets #25 and #29).
    RPMs can be found via Webpin.

    Nov 9, 2009

    Live upgrade from openSUSE 11.0 to 11.2

    Article update: it turns out many people come here hoping to find a solution and are disappointed to find only problems that I encountered.. Sorry, that's too bad. Until someone figures out a way to do it online, your best option is to boot off the Network installation CD (100MB).

    On Saturday I upgraded my wife's laptop from openSUSE 11.0 to 11.2 RC. I did it using zypper dup, and there were some problems so here I describe them for the benefit of others who might try the same.
    1. Edited /etc/zypp/repos.d/* to replace all 11.0 occurences with 11.2. It worked also for Packman and Videolan.
    2. zypper in zypper offered a suspiciously large update. It turned out it wanted to switch from x86_64 to i586, boo! The fix was zypper in zypper.x86_64\>1
    3. That did not go well. It installed the new rpm.rpm and then repo2solv failed, terminating the transaction. After that, I had the old libzypp and the new zypper, not working. So I manually downloaded the libraries and installed them using rpm, ignoring the broken dependencies for the yast2-* packages.
    4. Changed commit.downloadMode to DownloadInHeaps in /etc/zypp/zypp.conf, which exists primarily to avoid the previous problem. But Murphy does know when to strike.
    5. zypper dup
    Note that from 11.1 to 11.2, I used the live upgrade method without such problems. But for 11.0, you may be better off booting from an installation disc.

    Nov 2, 2009

    The suse-ncc User

    Got a question about the purpose of suse-ncc:x:106:110:Novell Customer Center User:/var/lib/YaST2/suse-ncc-fakehome:/bin/bash, and Google did not know, so I asked the usual suspects.

    Answer: It comes from yast2-registration.rpm and is used to switch away from root when we spawn the web browser and let you register your SUSE Linux Enterprise product.

    Thanks, mc.