ShadowCat’s “Enlightened Perl Iron Man Competition”

Bingo!

ShadowCat Systems, an open-source development company from the UK posted an entry on their blog today which hits the nail on the head. Perl needs marketing and it needs it within the realms that the rest of the world moves.

We, the collective Perl consciousness, do not really like all this modern internet stuff. We don’t appear to like blogging, we don’t appear to like forums and pretty web 2.0 stuff? That’s right out. As Matt so correctly described it

Perl people hang out on mailing lists. We bottom post, carefully interleaved, with 76 character lines. We have signatures that meet the McQ standard for acceptable size. We hang out on IRC servers and bitch, moan, interact and collaborate with the aid of an 80×25 xterm with irssi, BitchX or IrcII in it[3]. Sometimes we sit at home with a beer and do one or more of the above. Forums? Meh. Those are the things the PHPtards like because they can’t figure out how to work a mailing list, right? Blogs? That’s not even a fucking word!

I hate to quote so much at once, but this paragraph captures the issue completely. The reason for all of the “Perl is fading” nonsense is almost entirely because we don’t seem to like to talk about Perl in any format which is post-1997.

But it seems that we have finally started to realize that this is a problem and have, to paraphrase, “become the change that we want to see” because we’re actually seeing blogs about Perl which if not exactly web 2.0 are at least not from 1997.

The most popular “new” site of course is Perl Buzz, but it isn’t the only site. There are many small blogs where people post infrequent articles about Perl, but finding them can be tricky. To help address this issue Shadowcat’s Matt Trought has decided to start handing out awards to people for frequent postings on Perl through his Enlightened Perl Iron Man Competition.

If you haven’t already read the article then you should do. Really. Matt expresses his frustrations with what can only be described as proper English enthusiasm – yeah, that does mean with lots of swearing. And frankly he’s right. Every word of it is true.

Indeed I can remember posting a similar rant on starting to post at perladmin.oreally.co.uk blog. Sadly the server behind it was a freebie server hosted by a friend and it needed to be ditched and, as yet, I’ve not seen the data since to resurrect the blog else where. My irritations were something similar – although I also went on to criticize the fact that for years we’ve been told that Perl 6 will be better and “is coming”. For my efforts I got a couple of snarky comments telling me that I shouldn’t criticize Perl 6 , that I was only adding to the problems by doing so, and one note saying that “I did go on..”.

Well that was my rant, and Matt has posted his. But Matt has also gone on to proposed a solution, his “Perl Iron Man Competition“. To paraphrase a commonly used term about the current economy, perhaps we are seeing Perl’s green shoots of recovery?

I hope so. Rock on Matt!

Fix for SVN::Web and ’subversion/libsvn_ra/deprecated.c’ line 289: assertion failed (*path != ‘/’)

Updated: April 22nd 2009:
This issue is actually SVN::Web Bug 37388. I didn’t see that because I that bug was filed using the error messages for SVN v1.5.0 and the function svn_ra_get_log() that is called is in a totally different library in v1.6.0 so searches for the v1.6.0 error do not find that bug report or the patches. Thanks to commenter Alexandr for drawing this to my attention.

The use base.pm and SIGDIE problem, still not fixed in Perl 5.8.8

This weekend I’ve been playing around with a “from scratch” idea for an app/framework thingy. I’ve been assembling the pieces in my head, in notes and in reading around. While I doubt its going to become the next “IT” framework, even if it gets released to the public, I’m hoping it will give me a clearer understanding of how to make a modern web app in Perl.

On of the things I’ve been trying to do is make the core of the app fairly sensible in terms of setting up lots of stuff by default. So, for example, to default to using UTF8 encoding and Localization as well as basic stuff like signal handlers. I cheerily set up my SIGDIE handler in my initApp() method to handle stuff like checking if headers need sending before dumping the error message back to the browser and moved on.

After getting the basic thing working a little I decided to approach Localization (L10N). I’ve never tried this before and I have to be honest the suggestions on how to do this in Perl … err.. lack. I found myself hitting the same few articles time and time again. Heck even Bugzilla’s roadmap uses the same list of articles quoted else where (TJP13, Locale::Maketext::Lexicon, and the Cpanel.net roadmap for the future of Cpanel), but as with most things Perl trying and poking seems to get you somewhere.

In my case it got me more than I’d bargained for because in trying to make my app flexible the localization is optional, and more so, tried to make the use of Locale::Maketext::Lexicon optional so you can use other modules if you prefer. This meant that I was a prime candidate for the “use base” bug.

If you haven’t come across this bug then its pretty simple. There’s a bug in base.pm in which the die signal handler entry in %SIG is local()ized for part of import(). This is great because its localized and the author makes an attempt to restore it afterward to ensure it was reset correctly. Unfortunately it goes horribly wrong. And I’ve just wasted another couple of hours tracking this crap down only to discover that because this is a relatively new machine I hadn’t patched base.pm on it unlike my other servers … *grr*.

If you don’t know the bug a solution is documented on the perl5 mailing list. The code block in question is this:

 85             my $sigdie;
 86             {
 87                 local $SIG{__DIE__};
 88                 eval "require $base";
 89                 # Only ignore "Can't locate" errors from our eval require.
 90                 # Other fatal errors (syntax etc) must be reported.
 91                 die if $@ && $@ !~ /^Can't locate .*? at \(eval /;
 92                 unless (%{"$base\::"}) {
 93                     require Carp;
 94                     Carp::croak(<<ERROR);
 95 Base class package "$base" is empty.
 96     (Perhaps you need to 'use' the module which defines that package first.)
 97 ERROR
 98                 }
 99                 $sigdie = $SIG{__DIE__};
100             }
101             # Make sure a global $SIG{__DIE__} makes it out of the localization.
102             $SIG{__DIE__} = $sigdie if defined $sigdie;

The general idea here is that base.pm doesn’t want a custom SIGDIE handler interfering with what’s going on and so overrides it and tries to reset it. The bug is that this doesn’t happen. What happens is that your signal handler is always removed. Why? Well that’s because line 87 causes SIGDIE to be defined, but to be defined with no value. It seems that this is the default for signal handlers, even though it doesn’t appear to happen for other variables, including hashes:

#!/usr/bin/perl
use strict;
use warnings;
use vars qw(%A);

print "\$A{B} def: ", defined($A{B}) ? 'Yes' : 'No', "\n";
$A{B} = 1;
print "\$A{B} def: ", defined($A{B}) ? 'Yes' : 'No', "\n";
local($A{B});
print "\$A{B} def: ", defined($A{B}) ? 'Yes' : 'No', "\n";

print "\$SIG{__DIE__} def: ", defined($SIG{__DIE__}) ? 'Yes' : 'No', "\n";
$SIG{__DIE__} = 'IGNORE';
print "\$SIG{__DIE__} def: ", defined($SIG{__DIE__}) ? 'Yes' : 'No', "\n";
local($SIG{__DIE__});
print "\$SIG{__DIE__} def: ", defined($SIG{__DIE__}) ? 'Yes' : 'No', "\n";

This outputs the following. Can you spot the problem?

$A{B} def: No
$A{B} def: Yes
$A{B} def: No
$SIG{__DIE__} def: No
$SIG{__DIE__} def: Yes
$SIG{__DIE__} def: Yes

That’s right. In a normal hash once we localize a hash variable then we end up with it not being defined, irregardless of whether or not the original var was defined. This doesn’t hold true for %SIG. In the case of %SIG localizing it causes the elements to be defined. ALWAYS.

Normally this isn’t a problem because you don’t use these, and besides which the value is defined but zero. But in the way this is handled in base.pm, its a problem because of the strange way that SIGDIE is restored from the var $sigdie, but $sigdie is assigned to after the call to local():

 99                 $sigdie = $SIG{__DIE__};
100             }
101             # Make sure a global $SIG{__DIE__} makes it out of the localization.
102             $SIG{__DIE__} = $sigdie if defined $sigdie;

Thanks to above quirk with %SIG and local in this situation $sigdie (line 99) is ALWAYS defined, but because $sigdie is assigned to after local() is used, $sigdie doesn’t contain your signal handler, but instead contains “”. So we hit line 102 where the block is conditional on $sigdie being defined, which it always is, remember, and thus the code always assigns “” to $SIG{__DIE__} after loading the given module. As line 102 is outside of the block in which local() is used at this point %SIG is the actual %SIG (the global copy if you prefer). Therefore this assignation has the effect of wiping out any signal handler you may have installed despite the fact that it is trying to achieve exactly the opposite and restore the original signal handler.

The solution mentioned above is to use || undef on line 99. This has the effect of assigning undef to $sigdie because the signal handler is “”, or false, thus line 102 doesn’t pass the conditional and install this “” as the SIGDIE handler. It works, but I have to ask, why bother? It seems like the better way is to simply remove all of the $sigdie stuff and localize %SIG resetting it to its default, and then let the code exit the block. When it does the localized version of %SIG is removed and there’s no risk of clobbering an existing handler.

An alternative, if you must use $sigdie, is to assign the current SIGDIE handler as you’re declaring it, thus:

 85             my $sigdie = $SIG{__DIE__};
 86             {
 87                 local $SIG{__DIE__};

Then remove line 99 where the value is messed up:

 99                 $sigdie = $SIG{__DIE__};

Having just checked for updated modules the other day, I have to say, I’m very surprised that there isn’t a patched version of this which has been sent out to versions of Perl with broken versions. As I understand it 5.10 doesn’t suffer this problem, but since the stable version is still considered to be 5.8.8 it seems like it should be updated too. It would save people like me wasting a few hours trying to track down what’s going on with their code….

Colin.

Firebug’s Hidden Gems

Like many people who develop sites these days I find that Firebug is an indispensable part of my toolkit. It has evolved from “yet another web developer extension” into a tool which is an essential part of any developer’s toolkit – at least if they’re using anything but plain HTML. Its facilities for observing, testing and tweaking what’s going on in your web application are countless and as far as I’m aware, without compare.

If you haven’t tried it then you’re severely handicapping yourself so I would recommend that you install it and start playing. If you already have it, then you’ll know what I mean – the moment you end up on a computer without it, you feel like you need it installed. But even having used it for a good while (years?) now, I’m constantly amazed by the attention to detail the developers and contributors have paid.

For example I was just poking around with a test site trying out some CSS and discovered something new tonight. Like me you’re probably used to opening up Firebug to tweak the CSS styles to see how things will look without needing to reload the page. I should probably point out that if you’re not used to Firebug and you think it is just for looking at things, then you’re missing a good 50% of the picture… In fact lets try it.

Select an element on screen using the “Inspect” button in the HTML panel. You’ll see the DOM tree open up to that element. Want to try out a change, say a different background color? Select the “BODY” element and then right-click. Lots of options huh? Select “New Attribute” and you’ll get to add a new attribute to the element. So here’s a quick way of testing a new background, border, etc. – add the attribute “style”. Here’s a perfect example of the attention being paid. Instead of typing it all it, you enter only the name, and then hit “tab” and you’ll move on to entering the attribute’s value. You don’t need to worry about the equals symbol or quotes because FB fixes that for you, you just enter the value you want to use.

The alternative to editing this inline is to use the Sub-Panels on the right of the HTML Panel. When you view the DOM tree you’ll see that the sub-panels on the right update. They show the Style, Layout and DOM for the selected element. Here again is an example of the detail. The Style sub-panel shows by default the CSS rules applicable to this element. It strikes through rules which have been superseded as well as the source file and line number. This is extremely handy for working out why your DIV tag has a bright blue background instead of bright red. But by checking an option in the “Options” menu you can see the additional rules set by Firefox (this may be a 1.3 track setting) and view the computed style rules.

Okay so yes, this was available in the DOM inspector, but the packaging is nicer, and it is combined with the particularly useful Layout tab which allows you to see, and modify, the settings for the layout characteristics – border, padding, margin, height, width and top/left offsets. If you haven’t discovered it yet (or read the manual, may be its all in there?), then you can click on any of the numbers in the Layout tab and edit them. Did you also discover (read about?) how when you hit tab you move on to the next number in the square? And how you can tab all the way around from offset to margin to border to padding in a loop? Oh and of course how if you shift-tab you tab backwards in reverse order? Yeah, that’s the kind of attention that I’m talking about.

Well if you found all of that and think that’s cool then there’s the surprise I found tonight back on the “Style” tab. I knew that instead of editing the style attribute you could also edit the styles for an element from with in the Style tab – if you didn’t then select your element and right click in the style sub-panel and you’ll see a host of options for editing the style, adding new properties, editing the existing properties etc.

So here’s the cool bit… Can’t remember what the CSS property is called? No problem they’ve thought of that too. Type whatever you can think it starts with and hit up/down. You’ll scroll through all of the properties that FB knows about. This includes all of the new CSS3 and -moz extensions that FFx supports. If that wasn’t handy enough hit tab to go on to editing the value… and you can do the same thing.

This was the “easter egg” I found tonight, having FB be intelligent enough that I was able to scroll through appropriate values for an attribute (handy with some of the obscure/new -moz… attributes).

For example; If your value is numeric then up will increment and down will decrement, seems reasonable. But if it is a known CSS attribute then you’ll be stepped through a list of possible options. For example, can’t remember what border styles are supported? No problem add an attribute “border-style” tab into the value field and scroll through them all with up/down. Can’t remember the (256?) named web colours? Again, if its a recognized colour attribute then you can scroll up/down through a list of known colours.

If that isn’t good enough try it with a combination attribute such as “border”. Try editing a standard CSS value like “border: 1px solid black”. If you edit this value and hit up/down then the border width will increment/decrement. Okay so you’re not impressed because its only doing it because it starts with a number. So double-click on the border-style (in this case “solid”) and yeah, you can scroll through a list of known border-styles. When you’ve found something you like you can repeat this with colour attribute. If the auto-complete of the names, the tab/shift-tab support wasn’t enough then this while not commonly used, just makes it a much nicer experience.

A huge thank you to Joe Hewitt, John J Barton, and everyone else for this amazing extension.

Colin.

Perl 6 and the “Vaporware” Label

Perusing Perlbuzz, as I tend to do on a rainy saturday afternoon, I was intrigued by Andy Lester’s latest post “Perl 6 isn’t exactly vaporware” in which he comments on the vaporware label that is often used around Perl 6.

I must say that I found it quite interesting to see Andy calling for an early adopter’s release of Rakudo because as he notes,

but the fact still stands that Perl 6 is vapor enough for most organizations wanting to do anything useful.

A while ago I moved this blog to my own site on perladmin.oreally.co.uk. Posting about the move I tried to explain what I was hoping to achieve with the blog – to do my part in building attention to Perl. As part of this I made the observation that I believe one of the reasons that industry interest has turned away from Perl is because, in part, that we keep being promised that P6 is coming, but there is no usable implementation.

The comments I received about the post concentrated only on this part of the post and it was noted that by “bashing” Perl 6 in this way I was only adding to the problem. I suppose that a comment such as this from someone who claims to support Perl could be construed as in-fighting, but this was not the intent of my comment. Rather I was pointing out what I believe to be a very simple flaw in our collective front; that by talking about how great this language will be, but never having anything substantial in circulation, we look bad. Think about the disparaging comments that circulated about Microsoft and its repeated resetting of release dates for various versions of Windows and Office.

I’m not, of course, knocking Perl 6, its hard working designers or developers, or any such thing. Indeed quite the opposite I’m trying to say how I think Perl can be improved after all more interest in Perl means more, and sustained, interesting in Perl 6. Having tried to explain my thoughts, I was amused to read Andy’s post stating exactly the same point that I was trying to get across – that I think Perl is already the best solution to many problems, and that the descriptions we get of Perl 6 make me curious and want to use it, but that I cannot because it isn’t yet available in a form which is stable enough for general use.

Of further interest to those in the Perl community who have a similar view to mine are some of the comments posted in response to Andy’s posting. Indeed the second commenter asks

Have you actually looked at the November source code? It’s full of ugly workarounds and quirky hacks to work around Rakudo bugs

This is a rather disconcerting comment is further strengthened as the author makes mention of some of the issues and while supporters can easily wave off most of them the comment author provides one example as:

3. List assignment. my ($x, $y) = 1, 2; doesn’t work right now

If something like this doesn’t work then it seems to be a long way from being usable. Now your definition of usable may be different from mine, but in my definition it means I can write my apps using it. It doesn’t, of course, mean that I don’t want/like Perl 6 or its designers or developers. I don’t have anything against it, I just don’t think that it is ready and both Andy’s post and the associated comments appear to emphasize that point.

So while it is being developed IMO that the rest of us can help rebuild the love for Perl by concentrating on what Perl can do right now and just accept that Perl 6 isn’t going to be in a cinema near you soon. So lets go Team Perl! :)

Colin.

Incidentally, this is being posted here rather than on my own site, perladmin.oreally.co.uk, because its currently being moved to a new server. It was previously hosted on a box thrown together from junk in 1999. As you might imagine it was slow when receiving any real level of traffic but it was finally withdrawn from service due to its power usage. As a sign of the times, RedBus – the London, England, data center in which the box was hosted – has recently changed its billing calculations to include power consumption and as such a 9 year old box was not a good thing to have around for free and so it needed to be pulled. As a comparison cabinet space and bandwidth, the usual billing metric for data centers, is all but free. The migration has yet to be completed due to various complicating factors. Until then I’ll likely be posting through wordpress again.

Google Search Trends for Scripting Languages

I was poking around on Google earlier and ended up on their search trends page. One of the examples they provided was to compare the searches for the four major script languages, Perl, PHP, Ruby and Python so I decided to see what the data was like for that.

There are no major surprises, sadly, but as you might expect PHP has more searches, but the most noticeable issue after this is that searches for all four languages have decreased since 2004 when the data was first collected.

Will the tightening economy make Perl more attractive?

Based purely on speculation and my own view of the universe, rather than on any material evidence, I was wondering if the tightening of economies around the world may not end up being beneficial for Perl.

Don’t get me wrong. I’m not suggesting something insane like Perl makes you keep your job. But rather I’m speculating that it might help simply because Perl isn’t used soley for the web. So take, for example, the situation where a company has a dedicated web developer and a site written in something other than Perl. If they also have a dedicated Sysadmin then you can bet that much of the stuff in the back end is written in either Perl or Python. Since Perl has been around longer, its more likely to be that.

To be fair, your web developer might be mightily skilled at design and PHP. They may be totally XHTML 1.0/strict and CSS2.1 + firefox/safari proprietary extensions compliant. They may have “mad Javascript skillz”, and they may even be pretty fun to hang out with – say Dex of 17, Chr of 16 and Int of 16. Your sysadmin character is likewise highly skilled at (whatever the hell it is that non-sysadmins think we do and get paid for, because yeah, we can do that :-). Okay, so your techie might have the social skills of a somewhat evolved baboon, easily distracted by shiny objects (or “hi tech gadgets” as we call them now), and the sole demand for raman noodles, but they too are pretty good at their job. Lets call it Chr 12, Dex 15, but an Int of 17 and Wis 17.

In a tightening economy, which would you fire, your Sysadmin or your Web designer?

You see people may believe that “Perl whatever’s“, but it doesn’t. Its actually pretty useful at doing things. At getting the data from your database to your Apache config, to your BIND zone files, to your password files and your websites. Its also pretty handy at quietly monitor the entire network 24/7, and record all of your important information, and parsing your log files.

PHP … not really quite the so handy in that arena. And I do remember a very intelligent developer (of C) friend of mine some 10 years ago back in PHP v3 days trying to admin her box with PHP scripts. More of the kind of thing that developers do when they’re bored than having any practical purpose.

And lets face it. You can let the servers run themselves, or you can let the web site run itself. Which is more likely to break. The fast moving always on, always doing things servers or the website?

I’m not saying that knowing Perl will save your job. I’m certainly not wishing any PHP/Ruby/Python devs lose their jobs. Please guys not spams, we like you, really. I’m just speculating that because Perl isn’t used solely for developing webapps, being a Perl dev might not be a bad thing right now.

I moved my Blog to perladmin.oreally.co.uk

I moved my blog to WordPress hosted on my own box. It can now be accessed via the URL http://perladmin.oreally.co.uk/

As for why? Well I’ve played with wordpress on and off for a while, but I never really liked the previous versions that much and had given up several revisions ago. I decided to try looking at it again this time around and really prefered the interface. I’m still not at all convinced about much of the rest of it, particularly it being written in PHP since I have issues with that on several levels, but it is what it is. I decided to try it on line via this site with wordpress.com.

Interestingly enough Google must love this place because for certain searches the site is coming up in first place. Which is surprising, if not troubling since its a new site and if I can do it, any spammer can. I’ve even had people start stealing the content already, and there’s barely anything here…

But what I didn’t like is that I couldn’t customize it the way I wanted to. My PHP is limited but I know enough to hack on the code a little and wanted to try doing that on WP 2.6.2 as I have on earlier versions. I also wanted to try a different theme than the half dozen offered, and even something as simple as changing the CSS couldn’t be done without a paid update. This seemed a little much to ask for something so relatively simple, so I decided to move it off to my own box.

I’m not sure how well it will work since my box is about 10 years old, but hopefully it will be upgraded soon, and I have other options if needed :-)

So come on over to the new site, see if you like it:

http://perladmin.oreally.co.uk/

Colin.

Why does IPTables not log when it is started/stopped?

I have to say that it is very strange that iptables doesn’t log when it is started, stopped, restarted or even when a rule is added. Given how big of a part in the security scene iptables plays, you’d think that by default it would send a notice to syslog, probably at daemon.notice level, when it is stopped and started. After all this is one fairly important tool. Not the only (hopefully) but usually a pretty important one and in many cases it really is the only thing between a server and the bad guys (yes, I know, that it shouldn’t be the only thing..).

I mention this because I just came back from lunch to find my SSH connection wouldn’t respond to input. This has happened occasionally, but as far as I’ve been able to tell (by piecing together information afterwards), it has invariably been because iptables was restarted.

Now me, I just add the new rule to the firewall and if it works and I want to keep it, add it to the config file separately. I don’t believe in restarting iptables because if you f*ck up the new rule and restart the firewall you’re not only screwed then, but if you reboot the server too. For a remote connection that’s bad news. At least if you screw up the rule you know that you did the moment that you add it to the firewall, so if it comes to remotely rebooting the box you know it will come back up without a problem. And yes, I did do that once. It was a case of

“I’ll just update the firewall rules before I leave this morni… oh er.. oh, what did I type? Sh*t!”.

But my colleague believes that you should add it to the config file and restart because that way you’re only entering it once. Which is nice, and does indeed have its merits because there’s less chance of a typo, getting the order wrong, etc., but it also means you need to stop and restart iptables. Aside from the risk of locking yourself out of the server to me that’s a royal pain. You lose any temporary rules, and you worst of all you lose the connection tracking. Which means my nice and quiet SSH session which was working before lunch and has my open Vim session in it … is now not working because its state is not new or established or related, and thus not a valid connection state as far as iptables is concerned and thus the packets are blocked, and the connection gets dropped. *grr*

More irritatingly though is that I can’t *know* that that’s what happened because iptables doesn’t log when it stopped or started. Which is pretty crazy really if you think about the fact that every daemon under the sun logs that kind of information. It never occurred to me before, but its true, at least on my box.

Incidentally, if you’re looking to fiddle with the firewall remotely, a few good tricks are;

1. Add a rule to allow your SSH connection through as a first rule. E.g.iptables -I INPUT 1 -p tcp --dport 22 -s <your ip> -j ACCEPT
2. Use a sleep; undo system. This works for both the command line and restarting iptables. For example;
   1. Add a rule on the command line, knowing the rule number you’ll give it, and then set it to undo a moment later;iptables -I INPUT 23 <what you want to happen>; \
sleep 10; \
iptables -D INPUT 23
   2. Restart iptables, then stop it again if it doesn’t work;/etc/init.d/iptables restart; sleep 10; /etc/init.d/iptables stop

The second tip uses the a chain of commands which do whatever might go wrong, sleep and then undo it. The reason for this is that it will execute a command and then move on to the next command in the list, so if you submit the commands like this, where you must include the semi-colons between the commands, (don’t forget the \’s in the first case, or just ignore them and don’t hit return) , then the shell will execute them one after another like this … do “fiddle with firewall command”, sleep, and do “undo fiddle command”. In the even that you don’t do anything, the firewall will be restarted and then ten seconds later, stopped. This is good because in the event that you f*ck up the firewall rules and can’t type, 10s later you’ll be able to type again because the firewall has been taken down again.

But the best part of this trick is that in the event that you can type you do … you wait a second or so, and then type Ctrl-C to interupt the currently running command. This will be the sleep command, so you’ll interrupt that and interrupt the list of commands to execute so your last command, the “undo” command, is never run. So if you can’t get into the box it unsets its firewall. If you can get in then you kill the sleep command before it finishes thus the “undo” is never executed.

As a tip, if you’re not sure when to hit Ctrl-C, add a command echo “Sleeping” into the list just before the sleep command. If you don’t see that then the firewall was messed up. If you do see it then your changes worked, and you can kill the rest of the commands with Ctrl-C.

Colin.

Virtualbox 2.0 is out

For those who have never used it, Virtualbox is Virtual Machine software from Sun Microsystems, who bought the previous owners, innoTek Gmbh. While my experience with VM software is not extensive, I’ve used a few programs on a Windows host and I’m pretty impressed with Virtualbox. VMWare was, by comparision much much slower, although this may have changed in more recent editions. I also hated how tightly into the OS VMWare wove itself. Uninstalling it has broken several computers of mine and resulted in days of trying to unbreak its grip on my network adapter. (Trying to remove the virtual adapters from the MAC bridge when VMWare was no longer installed). In comparision to VB, MS Virtual PC appears to be lacking features – or at least an interface, and plainly has no design to support anything but Windows with boot options of “Windows 95, 98, NT, 2000, XP, Vista and OTHER”. It isn’t surprising, given that they sell Windows, but I can’t help but wonder how effective it can really be for non-windows, which at the moment is my thing since I’m running Windows as the host OS.

Virtualbox gives a nice range of features and appears pretty fast. 2.0 is no exception, appearing to most fix a few gotchas which never bit me. My only complaint about it is that aperiodically I’ve found that the clipboard will break. This is from Windows as a HostOS to CentOS and Fedora 8 as guest OS’s. You’ll be typing along and suddenly the clipboard won’t work, for Windows or in the guestOS and you end up needing to restart the Vbox to clear it.

I’ve yet to see any information explaining what is happening, but what I suspect is happening is that an event is being lost on the client end and this ties up the entire clipboard because Windows doesn’t get the acknowledgement that the event was processed. I did once see an error message from the Xserver about it dropping events so this seems to be a reasonable guess.

My solution to this has been to work around it and instead of using X directly on the console of the Vbox to connect to it via Nomachine’s NX client. This no only gives me the equivalent of “screen” under X, with the ability to disconnect and reconnect later, but I’ve never had the clipboard cross-over screw up. Which is really handy.

So if you haven’t already tried it but you’d like to, or you’d like to try VM’s and don’t know where to start, or you’re looking to try Linux, but are too addicted to your Windows apps to be logged out of your computer, Virtualbox will be great for you.

As for choice in Linuxes, well I’ve going with Fedora 8 and CentOS 5.2. Personally I’ve been concerned about the direction of Fedora, especially with its “pump a new version out every few months” attitude, (as opposed to putting out something decent). I did try Fedora 9 from the live CD and it sucked, especially when compaired to F8. F8 has, so far, been a pinnacle in the Fedora for me. By comparison CentOS 5.2 appears to have a very strong stable base, and ever bit as usable for a desktop OS as a server OS. As a quick comparison when running under Virtualbox in order to be able to have a graphical resolution which matches my windows box (which is only 1280px by 1024px, so nothing to write home about) Fedora 8 requires you allocate 32Mb of memory for graphics, but CentOS 5.2 requires only 16Mb. I think it says something about F8.

Colin.

Nomachine NX Client Times out “Negotiating Link Parameters”

I use NX Client from Nomachine to connect to one of my boxes, or more accurately, to a copy of CentOS 5.2 I’m running in a VirtualBox virtualbox that I run on my Windows box. Its kinda wierd, but cool in some respects as half of my computer is now running CentOS; pretty much literally since half the RAM can be used by it and since I connect via NX client it sits in a window which lives on a second monitor.

This is a cool setup. Its a way to wean myself from Windows, to run a test environment with yet another web browser (ok, so its Firefox, but still), while at the same time playing with VM’s (and X11 as I used to do). It also gives me a great excuse to use NX which is, it must be said, far better than the other free Xserver for Windows, Xming. I think its the compression or something, or maybe that its a dedicated protocol server and client, and Xming is implementing X11 directly. Whatever, Xming is often slow and sometimes iffy (to the point where I never felt comfortable purchasing the latest version). It is particularly bad at handling network issues I’ve found, where it will infrequently just hang the connection, causing you to lose all of your window placements.

Not so with NX which appears to be the equivalent of screen for X. Disconnect? Okay, I’ll just sit here and suspend your session and wait for you to come back. This feature alone is amazingly useful, but combined wtih the built-in compression it works very well. Part of the high quality compression is that they compress the data in the connection protocol, X11, VNC, or Radmin, instead of compressing the stream of data, as happens with say SSH compression. Although I haven’t tried it, you can apparently still use X sessions over a dialup line. I know its considerably easier to bring up my X session at home over a cable modem link with NX that it is with Xming, which crawls on anything but having a text window open.

One issue I do have with NX is that its is really complicated to setup. I spent a good couple of hours installing things and repeated logging into my box, with numerous updates to the local SELinux config to allow NX under SSH to launch various things, including being able to write a log to /var/log. That’s exactly the kinda of crap people won’t deal with in general. If you’re having this problem then I fully recommend running this command:

audit2allow -l -r < /var/log/audit/audit.log

After each failed login. This gets audit2allow to list only the allow rules which are needed for the failures since the last reload of the SELinux policy (-l) and (-r) output them with the corresponding require { } structure.

Beyond that, which I got on my FC8 system, even using FC8 RPM’s (but not on my CentOS 5.2, with both the CentOS and NX RPM’s) the only issue I’ve found with NX is that occassionally it seems to get confused. When you open your client connection it will go through the normal setup, the window will open and it will resume the session, but the final Windows dialog box will sit there saying

“Negotiating Link Parameters”

It will do this for about 30s to a minute, mean while the session is up and running and usable. At the end of what seems to be a timeout period, it seems to give up. At that point it closes both the dialog box and the entire NX client window. Once this happens you can try as many times as you like and it will just repeat.

I’ve found that the only answer to this is to open up task manager with alt-ctrl-delete, and to kill all “NX” processes. Once you do that it works again.

Col.

Google Releases Updates for Chrome

Google’s new browser Chrome has been getting varied reviews. It seems the usefulness of the browser depends on your point of view, where those in the tech industry are, kinda like me, a little “neh” about it, others in the mainstream media are raving about it. It is being called all sorts of things including a replacement OS and other such nonsense. Which might be nice, if it were possible…

It also has a few issues. I couldn’t help but notice that they had to fix the carpet bombing flaw which affected other browsers, and they had a few issues with other sites that they’ve now fixed.

I couldn’t help but notice the blog post for beta-0214929, which included fixes for such minor sites as

• http://search.daum.net/
• http://search.empas.com/
• http://meta.ua/
• http://search.naver.com/
• and http://search.yahoo.com/

Hmm. Google’s new Terminator of browsers, designed to hunt down and kill other browser because it integrates with Google Gears and other stuff Google offers (which is like everything) conveniently didn’t work with a few minor search engines… Well that’s okay, it was only a few little ones. Oh, and Yahoo!. Well isn’t that a coincident :p

I wouldn’t be surprised if the internal name for this project is the Googlenator…

I also thought it was interesting to note that the “Links to this Blog Post” contained a rather notable entry:

Screenshot of Google

… Ahh but they allow it, so they must be “open”. :p

Col.

Bad Lunch Combination

Mountain Dew and Bananas… ick.

Its sort of my fault, well okay, completely, but I was starting to doze off in that afternoon lull, so I decided to get a soda… you know, the old coders and caffeine thing. I also decided a banana would go help perk me up too as it has lots of good stuff. A quick Google search shows that the good stuff includes Vitamin B to help calm the nervous system, and fibre to well.. “help”. Which means that they’re the idea fruit for programmers everywhere :-)

Google Chrome; A second look

Following on from my previous post about Google Chrome, Googles WebKit based new browser I think I have some answers to my issues.

The first issue was that the background colours on my select lists were black. It turns out that this is due to the use of the CSS directive background-color: transparent;. Both this and background-color: inherit; appear to cause select elements to have a black background. I don’t see any obvious reason why I had this so I’ve removed it. I suspect that this might have been added for an IE fix – but if that’s the case its okay because I’m already using IE conditional comments to load IE only style sheets.

Google’s Chrome Web browser; A First Look

So I decided to try out Google’s new web browser, Google Chrome (”Chrome”)

… so far I’m not sure on my opinion. I was, I think, hoping to be blown away. I was hoping that it would be Safari in Firefox’s clothing, and frankly it isn’t. It is just “okay” which is a little disappointing from the company that gave us Google Maps, Google Earth, and lets face it a search engine which at its inception was unique in not being part of a portal.

How WP Changed My Program

I was just playing with the widgets and I like that when you add them to the widget list that you can then edit them in situ. It is a really clean way of dealing with the extra info for a widget which I’m just incorporating into my company’s app (which I’m sure I’ll continually refer to as “my application” or “my app”) because we have something similar using drag-and-drop to indicate the active components. In my case though the extra info is prompted for later and its very long winded. Making the widgets editable in situ like this would make it much clearer.

My only issue with making this change is that this is still in embedded HTML not templates… so lots of code repeating :p

Hello .. er .. World

So having unsuccessfully tried to operate a blog once before I’ve decided to try again.

When I started blogging a couple of years ago I found it to be extremely awkward to do. This is, in part, because I cannot stand those blogs where people post pointless and bland commentaries about nothing exciting, or indeed interesting. Its not that I don’t like blogs. Some blogs are very interesting – although I don’t follow any with any degree of regularity – as they let you see interesting perspectives.