Moving from a self hosted Wordpress blog to Blogger

October 21, 2012

I have a self hosted wordpress food blog hosted on an old silly domain that I’ve wanted to move away from for a while. I also want to stop paying hosting fees some time soon. Since I’m already looking at moving a lot of my day-to-day activities to the ‘cloud’ it made sense to pick a blogging platform that ties into a major cloud hub. Google’s Blogger was the obvious choice as I’m already using the Google Apps platform for my new domain paulcz.net.

Creating a blog on blogger is dead simple. I went ahead and created two: food.paulcz.net for the new food blog and tech.paulcz.net to start journalling random tech things. Transfering the blog content itself is quite simple, however, doing it in a way as to preserve links between posts, from other sites, and teaching the search engines how to find your new site requires a little more trickery.

I’m assuming you already have some technical know-how … this isn’t for the Octogenarians or Luddites in the audience. You’ll need access to a linux host and have a basic understanding of editing files in vim and navigating the linux command prompt as well as be able to navigate the Wordpress and Blogger interfaces.

These examples use my own blog so where you see food.paulcz.net please modify the text to your own blog URL if you want to use them. Some of the scripting is a bit silly and could be cleaner but they’re throwaway scripts and I didn’t want to spend too much time on them.

Step 1. Perform Initial Import/Export of blog.

Log into your wordpress blog and export the blog to an XMLfile ( wordpress_export.xml ). You should be able to do this by going to Dashboard -> Tools -> Export -> Download Export file.

Browse to http://wordpress2blogger.appspot.com/. This site will convert the file from Wordpress format to Blogger format. Upload and Convert your file, saving it to blogger_export.xml.

Log into blogger and create a new blog. if you’re using your own domain set up the address in basic settings and then go to Other Settings -> Import blog and select the blogger-export.xml file. You’ll also need to publish all the posts ( they don’t seem to publish by default ). You can do this 50 at a time from the Posts section.

Now if you have a small blog, or don’t have any intrasite links you’re basically done here. However A lot of my posts have links back to other posts and these are not converted. This means that there’s tons of links on my new blog posting back to my old blog.

Thankfully I don’t upload images to the blog, rather link to them on my picasa/google+ albums. This means I don’t have to deal with some wacky image stuff.

Step 2. Modify links to point to new site.

The first thing to do is get a list of all blog post links on your new Blogger site. This is pretty easy, you can do it via an RSS feed and some perl magic.

Browse to your new blog like so: http://food.paulcz.net/feeds/posts/default?start-index=1&max-results=999. This will give you a page showing your entire blog ( assuming you have less than 999 posts ). Save this file from your browser as default.xhtml.

now create a perl script called urls.pl … notice the URL ( with \ escaped characters ) .. you’ll need to modify this to match your new blogger url.

#!/usr/bin/perl
open (TXT,"< default.xhtml");
while (<TXT>) {
 chomp;
 /(http:\/\/food\.paulcz\.net\/\d\d\d\d.*?html)/;
 print $1 . "\n";
}

Then run the following:

perl urls.pl | uniq > blogger_urls.txt'
grep "<link>" wordpress_export.xml | sed "s/<link>//" | sed "s/<\/link>//" \
 | perl -e 'print reverse <>' > wordpress_posts.txt
cp blogger_export.xml blogger_munge.xml
vim -O wordpress_posts.txt blogger_urls.txt

This will extract a unique list of URLs of posts from both your new blogger and old wordpress sites. Chances are they won’t match up exactly and some hand editing will be required. That’s okay the last line above will open the files side-by-side in vim to allow you to clean this up. Hand edit each side to ensure that both URLs on the same line match the same a posts.

Once that is done we can write and run some more perl to create a shell script that will modify the blogger_munge.xml file ( copied from the original blogger_export.xml above ) replacing all your old links.

Create the following perl script named create_sed.pl

#!/usr/bin/perl
my @combined;
open(TXT, "< wordpress_posts.txt");
my @wordpress = <TXT>;
close TXT;
open(TXT, "< blogger_urls");
my @blogger = <TXT>;
chomp(@wordpress);
chomp(@blogger);
$size = $#blogger;
for ( $count=0;$count<=$size;$count++ ) {
 $string = $wordpress[$count] . "|" . $blogger[$count];
 push(@combined, $string);
}

foreach ( @combined ) {
 s/\//\\\//g;
 s/\./\\./g;
 s/\|/\//;
 print "sed -i \'s/$_/g\' blogger-munge.xml\n";
}

Now run create_sed.pl, and the resultant munge.sh script.

perl create_sed.pl  > munge.sh
sh munge.sh

now you have a blogger_munge.xml file that links back to its own articles. There may be some residual links back to your old site. If you’re a perfectionist you could hand edit the XML to fix this, but I’d say its now good enough.

Step 3. Re-Create your blogger blog.

Now you’ll want to delete your initial blogger blog and recreate it. Remember to set your URL again, then import the blogger_munge.xml file and republish all the posts.

Step 4. Set redirects from your old blog space.

Since we have the matching pairs of URLs it becomes quite simple to set up some permanent redirects from your apache config, or even better from inside a .htaccess file. Setting a permanent redirect not only redirects the user to the correct place, but in theory also informs a search engine ( on its next pass over your blog ) to update its database to the new location.

Links from around the web pointing at your old domain will continue to work for as long as the redirects work. At some point if you want to retire your old domain this will break those links… But there’s not a great deal you can do about that.

save the following perl snippet as rewrite.pl. remember to rewrite any strings specific to my domains to match your own:

#!/usr/bin/perl
my @combined;
my @wordpress;
open(TXT, "< wordpress_posts.txt");
while (<TXT>) {
 chomp;
 s/\/$//;  # remove trailing /
 my @temp = split "/";
 $last = pop @temp;
 push(@wordpress, $last);
}
close TXT;
open(TXT, "< blogger_urls");
my @blogger = <TXT>;
chomp(@blogger);
$size = $#blogger;
for ( $count=0;$count<=$size;$count++ ) {
 $string = $wordpress[$count] . "|" . $blogger[$count];
 push(@combined, $string);
}
print "rewriteEngine on\n";
foreach ( @combined ) {
 s/\|/ /;
 s/^http:\/\/*.?\///;
 print "rewriteRule $_ [R=permanent,L]\n";
}
print "rewriteRule ^.*\$ http://food.paulcz.net [R=permanent,L]\n";

Run the script and output to a file. The contents of this file can be added to a .htaccess file and will immediately start redirecting your traffic to the correct post on your new blog. Any hits that don’t match a mapped blog post will get redirected to the main page of your blog.

perl rewrite.pl > rewrite.txt

Inspect the file and if it looks correct you can append it to your .htaccess file. If you have other redirect rules already in your .htaccess file you’ll need to remove them or comment them out.

cat rewrite.txt >> /var/www/html/.htaccess

There’s no need to restart apache for a changed .htaccess file, so you can immediately test that the redirects are working …

Perfect! we’re working.

Step 5. More Things to do … ?

This has taken care of almost everything I care about. However I do want to be able to cancel my webhost subscription so I’ll need to try and find a cloud type service to perform the redirects for me. Heroku is probably the place I’ll go for that.