BigSmoke

Smokes your problems, coughs fresh air.

Author: Rowan Rodrik (Page 10 of 27)

Rowan is mainly a writer. This blog here is a dumping ground for miscellaneous stuff that he just needs to get out of his head. He is way more passionate about the subjects he writes about on Sapiens Habitat: the connections between humans, each other, and to nature, including their human nature.

If you are dreaming of a holiday in the forests of Drenthe (the Netherlands), look no further than “De Schuilplaats”: a beautiful vacation home, around which Rowan maintains a magnificent ecological garden and a private heather field, brimming with biological diversity.

FlashMQ is a business that offers managed MQTT hosting and other services that Rowan co-founded with Jeroen and Wiebe.

Ubuntu Desktop Linux and Acer TravelMate 7513WSMi

February 3, 2011 /

My youngest sister has retired her big-ass (17″) Acer TravelMate (model 7513WSMi 7510) with a more modern offering from Sony. That was last year. Now, she thought it’d be a good idea to donate it to our oldest sister. But since the thing has always “run” like a pig with Windows Vista, her girl-geek instincts thought it better if I’d equip the old monster with Ubuntu Linux instead.

AMD 64bit

I’m also considering upgrading my own laptop to 64 bit. (They’ve told me that, really, the 32 bit age is over.) So, the first thing I’m trying to find out (now that I’m getting on the 64 bit train) is if this thing supports 64 bit. I can’t really think of a quick way to find out, so I’m just going to create a 64bit installation CD and see how that works.

…

Or, I could have just popped open the hood to see the “AMD Turion64x2 Mobile Technology” sticker. 😯

Installation

After changing the boot order, the installation CD (burned from my T61 using “wodim -data ubuntu-10.10-desktop-amd64.iso”) seems to be booting despite the worrying sounds that seem to indicate that the laptop is trying to rip apart and eat the disc.

I’m surprised how good the current installation program looks and that it asks me if I want to “download updates while installing” and “install third-party software”. Nice.

Great idea to ask all the annoying questions (timezone, etc.) during installation instead of after! I’m amused with how much I’m behind the time if I see all the promotional screens for new and improved software which is meant to keep me inspired during the installation process. “OpenOffice.org is fully compatible with Microsoft Office[…]” Am I really that much behind with the times? Nah, I can’t imagine. I must still have some very, very nasty Excel sheet lying around somewhere, gathering dust. If I feed that monster of a thing to OpenOffice, then I’m pretty sure… Yeah, that’s going to be fun. 😈

Post-installation configuration

I had expected to spend at least an hour or two hunting around forums to find solutions for obscure driver-related issues and other nuisances. But no issues popped up. It just worked. Ubuntu is very compatible with the Acer TravelMate 7513WSMi! 😀

So, I spent some of the time saved on setting a user pic and a few other niceties, but I refrained from doing anything fancy, because I’ve figured out a new sister support strategy that I might blog about later. (It involves a four-hour work-week…)

[For my own reference, I started on the first draft of this post on Januari 14.]

Making a shell-script run with setuid root

February 3, 2011 /

If you want to run a process with root privileges that you can invoke as a less unprivileged user, you can make the program setuid root. This can be very useful, for example, when you want a PHP or CGI script to call a backup process, or to create a new site or irrevocably delete you whole system. The latter example points to a serious security problem: if anyone can figure out a way to make your program do something you don’t want, you’re screwed, because you just gave them root privileges to wreak maximum havoc. That’s why, normally, scripts (anything executed by an interpreter by the kernel because of a shebang) won’t get elevated privileges when you set their setuid bit.

To understand the setuid bit, let’s first see what happens when I try to cat a file that belongs to root:

su -
# I am now root; fear me
touch no-one-can-touch-me
chmod 600 no-one-can-touch-me
cat no-one-can-touch-me
# cat: Permission denied

Next, I’ll create a shell script that cats the file:

#!/bin/bash
 
cat no-one-can-touch-me

And make the script setuid root:

su -
chown root:root script.sh
chmod +xs script.sh

If I now execute the script, I still get the permission denied. What I need to make this work is a wrapper program. For that, I refer to Wiebe’s post about the same subject. (Yeah, I know: why bother publishing this if Wiebe already did an excellent job explaining? Well, I just hate to throw away an otherwise fine draft.)

Remove appending slash from a path using Sed

January 29, 2011 /

Here’s how you can remove the appending slash from a path using sed, the stream editor:

/just/a/path/ | sed -e 's#/$##'
# Output: /just/a/path
 
# And, if there isn't an appending slash, nothing happens:
 /just/another/path | sed -e 's#/$##'
# Output: /just/another/path

It works quite simple. Sed executes expression (-e) on its standard input. The expression is a substitution using regular expressions. The #-sign is the delimiter. The part (#/) between the first two hash signs is the matching expression and the (empty) part between the second and the third hash sign is the replacement expression. This expression (“s#/$##”) basically says: replace all occurrences of “/” at the end of the line (the dollar sign is the end-of-line anchor) with nothing.

To use this in a script is easy-peasy. Suppose $1 is a system path that may or may not include an appending slash:

#!/bin/bash
 
sanitized_path= "$1" | sed -e 's#/$##'`
 $sanitized_path

This script outputs its first parameter with the appending slash removed.

Ubuntu and SiS 671 VGA chipset driver

January 18, 2011 /

The video on my mom’s laptop, A Fujitsu Siemens Esprimo Mobile V5535, had recently gone awry. At the time, the laptop was running Ubuntu 9.04 (I think). Reconfiguring the driver didn’t do much good, so I upgraded the machine to 10.04, hoping that that would fix it. It didn’t.

lspci|grep -i vga
01:00.0 VGA compatible controller: Silicon Integrated Systems [SiS] 771/671 PCIE VGA Display Adapter (rev 10)

I solved the problem by manually installing a replacement driver that I found through a blog post that I found through another blog post that I found through a forum post.

Or something like that. Who cares? The point is that I’m uploading the files I found here so that I don’t have to jump through MegaUpload hoops again (and sit through MedaAnnoying ads):

Installing the binary driver wasn’t too difficult. (I just always cringe when something happens outside of package management.) 🙁

mkdir sis; sis
wget http://blog.bigsmoke.us/uploads/2011/01/xorg-driver-sis671-0.9.1-fixed-build.zip
unzip *zip
sudo cp sis671_drv.* /usr/lib/xorg/modules/drivers
 
#Edit /etc/X11/xorg.conf and set `Driver   "sis671"` on the "Device" Section
[ -z $EDITOR ] && EDITOR=/usr/bin/vim
$EDITOR /etc/x11/xorg.conf

Restarting the X server after that was a bit difficult, since the upgrade to 10.04 also fucked up the console (that damn framebuffer) and because Ctrl-Alt-Backspace is disabled by default. I had to reboot. (Ok, I hate to admit: it’s not that it’s difficult, it’s just wrong.)

Anyway, after the system restart, it worked just fine again. The X log agrees:

(II) SIS: driver for SiS chipsets: SIS5597/5598, SIS530/620,
        SIS6326/AGP/DVD, SIS300/305, SIS630/730, SIS540, SIS315, SIS315H,
        SIS315PRO/E, SIS550, SIS650/M650/651/740, SIS330(Xabre),
        SIS[M]661[F|M]X/[M]741[GX]/[M]760[GX]/[M]761[GX]/662, SIS340,
        [M]670/[M]770[GX], [M]671/[M]771[GX]
(II) SIS: driver for XGI chipsets: Volari Z7 (XG20),
        Volari V3XT/V5/V8/Duo (XG40/XG42)
(II) Primary Device is: PCI 01@00:00:0
(WW) Falling back to old probe method for sis671
(--) Assigning device section with no busID to primary device
(--) Chipset [M]671/[M]771[GX] found
(II) SIS(0): SiS driver (2006/10/17-1, compiled for X.org 1.7.4.0)
(II) SIS(0): Copyright (C) 2001-2005 Thomas Winischhofer  and others
(II) SIS(0): *** See http://www.winischhofer.at/linuxsisvga.shtml
(II) SIS(0): *** for documentation, updates and a Premium Version.
(II) SIS(0): RandR rotation support not available in this version.
(II) SIS(0): Dynamic modelist support not available in this version.
(II) SIS(0): Screen growing support not available in this version.
(II) SIS(0): Advanced Xv video blitter not available in this version.
(II) SIS(0): Advanced MergedFB support not available in this version.
(--) SIS(0): sisfb not found
(--) SIS(0): Relocated I/O registers at 0x9000

Then, to also fix the console:

grep vga16fb /etc/modprobe.d/* || sudo sh -c "echo blacklist vga16fb >> /etc/modprobe.d/blacklist-framebuffer.conf"
 
sudo update-initramfs -u
 
sudo reboot
 
# pray

I had two other issues that popped up after the upgrade the 10.04. I was inclined to blame the first on the new video driver, but I solved it by disabling “Hardware Acceleration” in the Flash plugin preferences. [source]

Another problem that confused my mother was that the volume control icon had gone. [solution]

How to make a wiki work: PALDAP

January 14, 2011 /

The first ever wiki I started was www.paldap.org. PALDAP stands for “PALDAP: A Lazy Directory Administrator’s Pal”. Yes, that’s a recursive acronym. Cute, ainnit? I actually registered the domain because it was the name of a crappy abandonware PHP LDAP administration tool that I wrote in PHP, but decided instead to configure it as a wiki to host some of my assorted experiences with LDAP and OpenLDAP in particular.

I never much bother with LDAP anymore, but the wiki remains because cool URLs don’t change and it doesn’t cost me that much. AdSense income for the wiki is only marginal (€15 in over three years) because the wiki’s content is only marginally useful and the traffic (300 visitors/month) reflects that fact.

[…]

Six days passed since I wrote the last paragraph. It’s a funny thing how writing can mess with your head. I was going to use PALDAP as in introduction to my struggle to make money of my wikis in general. Because the most promising of these wikis are my Hardwood Wikis and not my LDAP wiki, I wasn’t going to linger too much on it. But it’s a week later and some unexpected things happened.

Often, since becoming more familiar with Semantic MediaWiki, I’ve been considering the idea of converting the DokuWiki installation that runs www.paldap.org to a Semantic MediaWiki installation. Yet, nothing ever happened. I no longer work with LDAP professionally and most of the time I just kind of forgot that the site even existed. Until a week ago, when I started writing this post.

So, what happened? How do decisions happen? I have no idea. I’m not a neurologist. (I’m not even a sceintist; Hell, I can’t even spell “scientist”.)

What I have now are rationalizations for my decision but my decision is quite clear: I can’t kill my darling, even though I never really properly cared for it. For the last four years or so I had simply abandoned it on the grounds that it wasn’t costing me much anyway (it’s hosted at NearlyFreeSpeech.Net). Yes, the costs have gone up, but that’s just a rationalization. I could have just gone on and ignore the site’s existence without it ever making much of an impact on my cash flow. (I did some years ago actually promise the site’s most active contributer to never take the site off-line.)

So, if I was being rational, I would have just left the site alone. But, I’m not a rational being. Increasingly less so, in fact. A happy fact, if you ask me.

PALDAP logo

The PALDAP logo designed by Jeroen Dekker

The looks

Anyway, I still haven’t told you what happened last week. I didn’t leave the site alone. I created a development version of the site based on Semantic MediaWiki. It’s fucking kick-ass. It looks awesome thanks to MediaWiki’s new vector skin. But it looks even more awesome thanks to Jeroen Dekker. As we often do, we were hanging out at his place in a lazy haze, being generally unproductive but with random bursts of intelligent conversation and productivity. This day I had been absent-mindedly hacking away on my new MediaWiki darling and I was about to leave and jump on my bicycle when I mentioned that I could use a logo for PALDAP.

It was probably way past one in the morning already, but Jeroen was still in a creative mood from play-practicing with his new lighting set. All I can say about his creativity is that it was late, I hadn’t slept very long the night before (and the night before that and the night before and…) Let’s just say that he besides his excellent gear he didn’t have some very good material to work with. I was feeling ugly and tired. Yet…

Rowan, Januari 7, 2010

Jeroen's creative genius is a compliment to my awesome facial features 🙂

He went into a kind of frenzy on his big-ass touch-screen and being coaxed by me he created the perfect offset for the boring technical subject that is LDAP.

The brains

In the meantime, since last weekend, I’ve been starting to assemble a logical structure of semantic properties (think of LDAP attributes or SQL fields) and templates (sort of like MediaWiki functions) that’ll allow me to capture all the semantics related to the LDAP and the ecology around it.

The booty

I still don’t believe that PALDAP has a huge revenue potential, but hosting costs have increased and if I can get the website to awaken from its winter sleep, maybe it’ll at least start paying for itself again. Not that I really care, honestly. Somehow it’s just masturbatorily satisfying to use the expressiveness of RDF to capture the semantics of LDAP. What I like about it is that the wiki concept (and especially the semantic wiki concept) is a very tight fit for technical documentation. Another thing that I like about working with a wiki about a technical subject is that the wiki has a technical audience. I mean, there’s a reason that the visitors of my Hardwood Investment Wikis click on all those expensive links and that reason is not the technical insight that’ll lead to users clicking the edit button and actually contributing content.

In fact, even with the old DokuWiki version of the site, much of the content was actually created by other users (most by the same user called brontolo). If the community of my Hardwood Wikis worked this well… Let’s just say that I could remain in retirement for a while then.

So, even if this’ll just be an exercise in effective community building/plumbing rather than a way to make advertising income easily, it’ll still be effective as an exercise. I’m going to follow my intuition on this one and see how successful it’ll become and how much time it’ll take.

Fuck, this post sucks, but it sure does help me. Don’t ask me how, but it does. Kinda.

Effective CLI habits

December 24, 2010 /

Just an example of some effective CLI magic that I copy/pasted into a draft aboutexactly a year ago. Can you see what’s happening? I’m moving some selected files into a subdirectory.

$ ls *png
boucoule-17jaar-met-steen.png         evening_cloud.png  small-map-molenweg.png  tile11.png
boucoule-2001-2002-face5-400x300.png  hardwood-logo.png  step-01.png             tile9a.png

$ ls *png|while read f; do echo $f; done
boucoule-17jaar-met-steen.png
boucoule-2001-2002-face5-400x300.png
evening_cloud.png
hardwood-logo.png
small-map-molenweg.png
step-01.png
tile11.png
tile9a.png

$ ls *png|while read f; do svn mv $f index; done
A         index/boucoule-17jaar-met-steen.png
D         boucoule-17jaar-met-steen.png
A         index/boucoule-2001-2002-face5-400x300.png
D         boucoule-2001-2002-face5-400x300.png
A         index/evening_cloud.png
D         evening_cloud.png
A         index/hardwood-logo.png
D         hardwood-logo.png
A         index/small-map-molenweg.png
D         small-map-molenweg.png
A         index/step-01.png
D         step-01.png
A         index/tile11.png
D         tile11.png
A         index/tile9a.png
D         tile9a.png

Bonus points if you notice that I could have moved the JPEGs and PNGs in one command instead of doing the same thing for the second time for the JPEGs as below. (I probably forgot that I also had some JPEGs lying around, or there must have been some other lame excuse.)

$ ls *jpg
bruggetje-225x300.jpg  favicon.jpg  purple-rowan.jpg        rowan-2007.jpg                rowan-wilderness.jpg
bruggetje.jpg          hekje.jpg    rowan-2007-448x300.jpg  rowan-wilderness-400x300.jpg

$ ls *jpg|grep -v favi
bruggetje-225x300.jpg
bruggetje.jpg
hekje.jpg
purple-rowan.jpg
rowan-2007-448x300.jpg
rowan-2007.jpg
rowan-wilderness-400x300.jpg
rowan-wilderness.jpg

$ ls *jpg|grep -v favi|while read f; do svn mv $f index; done
A         index/bruggetje-225x300.jpg
D         bruggetje-225x300.jpg
A         index/bruggetje.jpg
D         bruggetje.jpg
A         index/hekje.jpg
D         hekje.jpg
A         index/purple-rowan.jpg
D         purple-rowan.jpg
A         index/rowan-2007-448x300.jpg
D         rowan-2007-448x300.jpg
A         index/rowan-2007.jpg
D         rowan-2007.jpg
A         index/rowan-wilderness-400x300.jpg
D         rowan-wilderness-400x300.jpg
A         index/rowan-wilderness.jpg
D         rowan-wilderness.jpg

Posting to WordPress via the command-line

December 24, 2010 /

In February I was interested in posting to WordPress from the command-line, a possibility that I enjoyed when I wanted to apply some CLI-magic to some of my MediaWiki installations in the past.

I came across a great Perl module (WordPress::CLI) by Leo Charre. It depends on WordPress::XMLRPC

Another approach is to use the appfs FUSE filesystem, which uses WordPress’ support for the Atom Publishing Protocol. There’s another FUSE filesystem, BlogFS. This one depends on WordPress’ XML-RPC instead of its Atom interface.

Taking control of the wpautop filter

December 9, 2010 /

WordPress does automatic paragraph formatting using the wpautop filter, some PHP code originally developed by Matt Mullenweg. For most of the time that this blog has existed, I’ve disabled the wpautop filter using the following two lines in my theme’s functions.php file:

remove_filter('the_content', 'wpautop');
remove_filter('the_excerpt', 'wpautop');

I’m not the only one to do this. But, I’m tired of having to manually type <p>s for every paragraph in every post that I write.

I’d like to be able have it back on, but preferably a bit smarter so that you don’t get all that crap (also common on bulletin boards with empty paragraphs around undetected block-level elements, especially if these are non-standard, related to plugins.

At the very least I want to be able to turn it off for when it does annoy me, on these moments that I don’t want auto-anything. Also, I need this if I don’t want to break the nearly 300 posts that I formatted manually. So, I want to use a custom field to turn the filter on or off.

I found an unpublished plugin (unpublished in the sense that the source isn’t hosted somewhere proper such as wordpress.org/extend/plugins/) which does some of what I want in a somewhat messy unmaintained manner. After years of just entering those damn <p>s (and over a year since this draft was in the making), I decided to do my own plugin for post-by-post (and global) control of the wpautop filter. It’s called wpautop-control:

<?php
/*
Plugin Name: wpautop-control
Plugin URI: http://blog.bigsmoke.us/tag/wpautop-control/
Description: This plugin allows you fine control of when and when not to enable the wpautop filter on posts.
Author: Rowan Rodrik van der Molen
Author URI: http://blog.bigsmoke.us/
Version: 1.0
*/
 
if ( is_admin() ) {
  add_action('admin_menu', 'wpautop_control_menu');
  add_action('admin_init', 'wpautop_control_settings');
 
  function wpautop_control_menu() {
    add_submenu_page('options-general.php', 'wpautop-control', 'wpautop control', 'manage_options', 'wpautop-control-menu', 'wpautop_control_options');
  }
 
  function wpautop_control_options() {
    if (!current_user_can('manage_options'))  {
      wp_die( __('You do not have sufficient permissions to access this page.') );
    }
 
  ?>
  <div class="wrap">
    <h2>wpautop control options</h2>
 
    <form method="post" action="options.php">
      <?php settings_fields('wpautop-control') ?>
      <table class="form-table">
        <tr valign="top">
          <th scope="row">wpautop filter on by default?</th>
          <td>
            <label><input type="radio" name="wpautop_on_by_default" value="1" <?php if ( get_option('wpautop_on_by_default') == '1' ) echo 'checked="1"' ?>> yes</label>
            <label><input type="radio" name="wpautop_on_by_default" value="0" <?php if ( get_option('wpautop_on_by_default') == '0' ) echo 'checked="1"' ?>> no</label>
          </td>
      </table>
 
      <p class="submit">
      <input type="submit" class="button-primary" value="Save Changes" />
      </p>
    </form>
  </div>
  <?php
  }
 
  function wpautop_control_settings() {
    register_setting('wpautop-control', 'wpautop_on_by_default', 'intval');
  }
}
else { // ! is_admin()
  add_filter('the_content', 'wpautop_control_filter', 9);
 
  function wpautop_control_filter($content) {
    global $post;
 
    // Get the keys and values of the custom fields:
    $post_wpautop_value = get_post_meta($post->ID, 'wpautop', true);
 
    $default_wpautop_value = get_option('wpautop_on_by_default');
 
    $remove_filter = false;
    if ( empty($post_wpautop_value) )
      $remove_filter = ! $default_wpautop_value;
    elseif ($post_wpautop_value == 'true')
      $remove_filter = false;
    elseif ($post_wpautop_value == 'false')
      $remove_filter = true;
 
    if ( $remove_filter ) {
      remove_filter('the_content', 'wpautop');
      remove_filter('the_excerpt', 'wpautop');
    }
 
    return $content;
  }
}
 
?>

(I’ve requested the plugin to be added to the WordPress plugin repository, so that it won’t have to be reinvented another 20 times in the next year or so.) 😉

After installing the plugin, you can choose whether to enable or disable wpautop by default. Then, for every post where you want to deviate from the default, you can set the wpautop custom field to ‘true’ or ‘false’.

I want the new default to be to enable the filter, but since all my old posts have been manually formatted, I want all these to have the wpautop field added and set to ‘false’.

Adding the appropriate custom field values to all existing posts is easy thanks to MySQL’s INSERT … SELECT syntax:

INSERT INTO wp_postmeta (post_id, meta_key, meta_value)
     SELECT wp_posts.ID, 'wpautop', 'false'
       FROM wp_posts
      WHERE post_type = 'post';

grml

December 8, 2010 /

grml seems like an interesting Debian-based Linux Live CD. It seems interesting because “[it] includes a collection of GNU/Linux software especially for system administrators and users of texttools.”

C++ base 10 to base 26

December 8, 2010 /

Last februari/march, I’ve been working again on an old obsession from ten years ago (when I was eighteen): to write a Minesweeper program that could solve very big maps as well or better than the best human player. At the time I did this because I thought that this was actually a million dollar challenge from the Clay Mathematics Institute. Now, I understand that the problem I solved at the time was not actually what was required, but still, once upon a time (such as early this year), I like to revisit the old problem and try to redo my old segfault generator as something that benefits from the fact that I’m now working with 10 years of programming experience instead of 1.

Minesweeper is grid-based, and I wanted to be able to express a coordinate in something more natural than two numbers. My Coords class has a toString() method which I wanted to output a Spreadsheet-like coordinate comprised of a letter (for the column index) and a number (for the row index). It took me some time to find a nice method to convert an integer to hexavigesimal. (Hexavigesimal is base 26 and 26 happens to be the number of letters in the English alphabet.)

This is what I ended up with:

std::string
Coords::toString()
{
    Coord x = getCol()+1, y = getRow()+1;
    int dividend = x;
    int modulo;
    std::string base26column = "";
 
    while (dividend > 0)
    {  
        modulo = (dividend - 1) % 26;
        base26column = (char)(65 + modulo) + base26column;
        dividend = (int)((dividend - modulo) / 26);
    }
 
    char row[(y / 10) + 1];
    sprintf(row, "%d", (int)y);
 
    return base26column + row;
}

I used the following sources:

Maybe I’ll soon start fooling with this again. Finishing this draft of eleven months old actually makes my fingers ache to play with a real close-to-the-metal programming language again. An over-engineered minesweeper clone in C++ might be fun to play with some more.

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