awg's blog

Reverting to a Specific Revision with SVN

Suppose you've edited a file, checked it into SVN, then realized it's completely broken. SVN won't let you revert to a specific revision directly, so you can do something like: svn up -rX; mv file file.old; svn up; mv file.old file; svn ci file; where X is the last correct revision of the file in question.

There's an easier way to do it, though: svn diff -rX file | patch -R file; svn ci file

This gets a diff between your (incorrect) version and the last correct version, then applies the patch (in reverse) to the file so you get the old version back.

Just a handy trick.

Eclipse and the Mystical Error 13

This is less of a rant and more of a how-to. But also a bit of a rant, since there's no reason why I should have had to figure out how to do this.

What I wanted to do: Install Eclipse on our new database server and X-Forward it to my desktop, so I can compile some stuff we want to run on the DB server the same way I would compile it on my desktop. The database server is a 64-bit box running 64-bit Fedora.

What I expected to do: Install Java using the RPM from Sun's website (I don't trust Fedora's Java). Install Eclipse from the tarball on Eclipse's site (I don't trust Fedora's Eclipse). SSH into the server with -X and run eclipse.

What happened: Installing Java went fine, as expected. But then I tried to X-Forward something from that machine, and it didn't work. Of course, the server didn't have an X server on it, but we expected that as long as it had the X client libraries, we should be able to X-Forward without any trouble. As it turns out, you also need the xauth package. Of course, no one has documented this anywhere. But, once I had yum installed xorg-x11-xauth, it worked fine. Then came installing eclipse. Easy enough, un-tar the package in to /opt, and run it. I got a nice dialog box with an exceptionally informative error: Error 13. Thanks, Java.

As it turns out, one of the many causes of Error 13 is telling the 64-bit Java that your application is 32-bit. Magic portability my ass! And the kicker is: Eclipse doesn't link to a 64-bit version anywhere on their website. The only way to get it seems to be copying the location of the 32-bit version and rummaging through the directory where it's kept to find the 64-bit version. For your reference, the Europa version can be found here (courtesy of Waterloo's CS club).

So, there are three things to rant about here:

1. Java's error reporting: Error 13 wouldn't even be so bad if it were documented, but it's not.
2. The fact that even though Java claims to provide magic portability, you need to download a special 64-bit version of a Java app to make it run on a 64-bit system.
3. The fact that Eclipse knows about this, and even provides a 64-bit version, but doesn't link to that version on their website (which is a generally un-navigatable mess).

Slashdot Silliness: Eee Violates the GPL?

Slashdot has a story today about the new Asus Eee PC and how it may violoate the GPL.

Now, I'm something of an open-source zealot. I've been using Linux as my primary/only OS since 1998ish, I've organized Linux installfests, and I generally try to be supportive of open source things. But this Eee complaint is just silly.

It's entirely possible that Asus has violated the GPL. But, who cares? To me, the important thing is that they've released a really cool device that openly uses Linux. It's a Linux device that normal, non-geeky people will buy and use. And they'll know they're using Linux (unlike a Linksys router, which may use Linux, but most people who buy one will never know it). The GPL zealots are being stupid and counterproductive: instead of seeing the upside - a Linux device that's cool and easy to use, and might make people want to try Linux on their other computers - they bitch and complain about the fact that a tiny bit of the code may break the GPL. Way to advance the cause, guys.

Stupid Password Systems

I'm going to rant about password systems today. Now, I'm not complaining about what everyone else has already complained about online: requiring 8 characters, requiring special characters, not allowing dictionary words, etc. These are all perfectly good rules: you don't want your passwords to be weak. Sure, they make it hard for people to remember their passwords, but that's just something people are going to have to get used to if they want to trust software with important information. Forcing people to change their passwords every 6 months is silly, and leads to more problems, but I'm not even going to complain about that today.

What I'm going to complain about today is systems that make you dumb down your password. You know, they don't allow special characters, or they truncate your password to 8 characters. It's ridiculous. Proper passwords, where any character is allowed, are just not that hard to implement. So why does anyone do anything else? All it does is make users angry.

Example time! I do my banking at Presidents Choice Financial. When I first went to set up my PC Financial account, they got me to choose a password for online banking. I was happy to notice that the system at the banking pavillion let me choose a good password (one of the ones I usually use for secure things). Then I got home and tried to login. "Invalid character in password" it said. What? You mean the password I picked at the bank isn't allowed? It sure would have been nice if the system at the bank had told me that, so I could have picked a different password. I ended up having to call tech support and get them to change my password for me.

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