Category Archives: Web

Refresh owncloud file cache

I came across an issue with owncloud where I had manually placed files in my user directory but the files were not showing up in owncloud. I found from here that you can access the owncloud console directly and trigger a re-scan of your files.

To trigger a re-scan, open up a terminal session to your owncloud server and run the following command:

php /path/of/owncloud/console.php files:scan --all

This will trigger a re-scan of all files for all users. You can replace –all with a userid if you just want to scan a specific user’s folder instead.

Fix Apache “Could not reliably determine name” error

For too many years now I have been too lazy to investigate the Apache error message I get whenever I restart the service:

 ... waiting apache2: Could not reliably determine the server's fully qualified domain name, using 127.0.1.1 for ServerName

I finally decided to investigate it today and found this post which describes a simple fix: create /etc/apache2/conf.d/name and add the ServerName variable to it.

sudo vim /etc/apache2/conf.d/name
ServerName jeppson.org

Change ServerName to be whatever you would like, and you’re good to go.

Fix subsonic after 5.0 upgrade

Subsonic is a great media streaming program that I’ve used for a few years now. It was originally designed for streaming your private music collection but has since moved to allowing you to stream your video collection as well. It’s great for those of us who can’t bring their entire audio/visual library with them but would still like access to said library wherever they are.

I run subsonic behind an apache reverse proxy configuration similar to this one to allow it to run on the same server as other websites over port 80 and allow for HTTPS (When I set up my subsonic server years ago it had no native support for HTTPS.  The only way to have HTTPS was through another web server such as apache.)

After downloading and installing the Subsonic 5.0 upgrade I ran into a couple of issues, detailed below.

Issue #1

I have experienced several times over the years – upgrading causes /etc/default/subsonic to be replaced with a default, clean version. This is a problem if you have a few customizations to your subsonic setup, in my case context-path and port. (My experience is with Debian. I don’t know if other distros perform in a similar manner or not)

Resolution

Before you upgrade subsonic, make a backup copy of /etc/default/subsonic, then restore that copy after upgrade. If you forgot to make a backup first, edit the new /etc/default/subsonic file and check the following

  • Make sure the –port and –https-port arguments are correct
  • Re-add –context-path if you had it configured before. In my setup, I have configured –context-path=/subsonic to make my apache rewrite rules easier to manage.

Issue #2

The video streaming function broke entirely. This was due to the fact that it was trying to reference a local IP address to stream the videos, despite my apache proxypass rule. This problem will only surface itself if you are running Subsonic behind a reverse proxy.

Resolution

After a few days of searching I finally came across this helpful post. To get video to work, simply add

 ProxyPreserveHost on

to the apache configuration file you used for your reverse proxy, then restart apache. This will fix the video streaming function but you will notice your HTTPS icon change (if you configured HTTPS), notifying you that some content on the page is not encrypted. This is due to subsonic streaming the video in plain HTTP instead of HTTPS.

Unfortunately the fix to that appears to require at least Apache 2.4.5. Since I have an earlier version, I was greeted with this lovely message:

Syntax error on line 15 of /etc/apache2/sites-enabled/subsonic:
Invalid command 'SSLProxyCheckPeerName', perhaps misspelled or defined by a module not included in the server configuration

Since I did not want to upgrade my version of apache, I simply decided to accept the risk of my video streams possibly being intercepted.

Success.

WordPress wp-admin links are incorrect after site move

I’ve been scouring the internet for months for this particular issue.  It must not be very common. Ever since I moved my site from one source (local IP address) to another (web facing URL) I have had issues with bad links (things pointing to the old address instead of the new one.)

I have mostly resolved them (using methods from this post) but one vexing issue remained: links in wp-admin.php remained bad; specifically, the  column headers and pagination links in the All Posts section of managing the site – they all still pointed to the backend IP address instead of the domain name of the site.

I found a few bug reports mentioning this but no clear resolution. After investigating ticket 18944 I was put on the right track. One link from that ticket pointed me in the right direction, but the comment that really drove me to the resolution was the last one:

Any proxy configuration is “supported” by WordPress, you just need to remap the server vars based on whatever that particular proxy configuration is using.

This is proxy 101.

That made me realize that when I changed from a local IP to a public facing IP, I also went from direct access to the blog to being behind a reverse proxy. The issue I’ve been having is a proxy issue, not a site move issue. Thanks to the comment above, I learned I need to add a single line to wp-config.php:

$_SERVER[ 'HTTP_HOST' ]   = "jeppson.org";

Replace jeppson.org with the base URL of your site. That’s it! all links are correct now. Brilliant.

WordPress directing to old URL after upgrade to 4.0

I encountered an odd issue after upgrading one of my wordpress sites to version 4.0: the login page suddenly kept trying to redirect to its old address (I had changed addresses some time ago.)

I still don’t know how or why this happened, but after some googling the way to fix it was to follow instructions as outlined here.

wp-login.php can be used to (re-)set the URIs. Find this line:

require( dirname(__FILE__) . '/wp-load.php' );

and insert the following lines below:

//FIXME: do comment/remove these hack lines. (once the database is updated)
update_option('siteurl', 'http://your.domain.name/the/path' );
update_option('home', 'http://your.domain.name/the/path' );

You’re done. Test your site to make sure that it works right. If the change involves a new address for your site, make sure you let people know the new address, and consider adding some redirection instructions in your .htaccess file to guide visitors to the new location.

This worked for me – I could now log in with the correct URL.

 

Configure SSMTP to use SSL/TLS connections

SSMTP is a very simple SMTP mail program which is used to send e-mails to a target server. It’s not a fully feature e-mail server but simply passes e-mails on. I first became acquainted with it because it’s the only mail server you can install on Citrix Xenserver. I now use it with all my servers because it’s very easy to configure.

Simply install it via command line:

sudo apt-get install ssmtp

There is only one config file to worry about: /etc/ssmtp/ssmtp.conf. To configure it to use an SSL connection (for gmail or if, like me, your ISP blocks port 25), add the following options, changing the brackets with your mailserver, username, and password.

mailhub=<mailserver>:587
UseSTARTTLS=YES
AuthUser=<username>
AuthPass=<password>
AuthMethod=DIGEST-MD5

If you just pasted the above config into your ssmtp.conf be sure to check the resulting config file for duplicate entries.

It’s as simple as that. All outgoing mail will be sent to the server specified above.

Configure WordPress to report true IP addresses when behind a reverse proxy

Placing WordPress behind a Web Application Firewall (reverse proxy) greatly enhances the security of your site; however, it can also be quite a pain.

My most recent experience with hosting WordPress behind a reverse proxy is that all traffic is reported as coming from that reverse proxy regardless of where it truly came from. This is a problem for site statistics, or for my specific example, seeing the source IP address of comment spam.

The fix, fortunately, is fairly simple. It requires tweaking the PHP code just a little bit to use the X_FORWARDED_FOR header, if it exists. Simply add the following to the top of your wp-config.php file (in the base install directory of your WordPress installation)

/** Reverse Proxy configuration
Configures WordPress to show correct source IP addresses when it's behind a reverse proxy
*/
if(isset($_SERVER['HTTP_X_FORWARDED_FOR'])) {
        $list = explode(',',$_SERVER['HTTP_X_FORWARDED_FOR']);
        $_SERVER['REMOTE_ADDR'] = $list[0];
  }

That’s all! Future traffic should properly report source IP addresses from that point on. Thanks to the WordPress support forum for helping me find this fix.

Fix images in wordpress posts after address change

In my experiments with WordPress I have discovered an annoying complication when it comes to changing servers. When you change the address of your wordpress site, links to images and other files inside posts are not updated to point to the new wordpress URL. Links to the posts themselves are all updated but for whatever reason WordPress ignores post content.

What this means is if you transform a staging server (say, http://server) into a “production” server (say, http://jeppson.org) posts containing links to any files on that server will now be (silently!) broken. The files are all still there, the posts just point to the old address instead of the new one.

There are numerous plugins for WordPress that can take care of this; however I am averse to installing random WordPress plugins due to security concerns. Fortunately, the fix for this vexing problem is a fairly simple one. It requires executing a command on the MySQL database hosting the wordpress site.

The table we are interested in is the <prefix>_posts table. <prefix> was defined when the wordpress site was set up. If you don’t remember what that prefix was, take a peek at /wp-config.php line 62

Capture

The field we are interested in is post_content – this is where all the links to pictures in your various posts resides. From here execute the update command and use the replace function to find all instances of the old URL and update them with the new URL

Capture

That’s it! Your images should now re-appear. The two commands I used in my specific example are below.  Be sure to replace the following :

  • wordpress with the name of your wordpress database
  • nm_posts with the name of your site’s post table,
  • http://server with your original wordpress URL and
  • http://jeppson.org with your new wordpress URL
mysql -u root -p wordpress
update nm_posts set post_content = replace(post_content, 'http://server' , 'http://jeppson.org');

 


 

Update: I’ve discovered a very handy script that will take care of this for you: wp-cli

To do the same thing as above with less steps, simply download wp-cli

curl -O https://raw.githubusercontent.com/wp-cli/builds/gh-pages/phar/wp-cli.phar

Make the script executable and move it to /usr/bin

chmod +x wp-cli.phar
sudo mv wp-cli.phar /usr/local/bin/wp

Navigate to the directory of your wordpress install and run wp search-replace

cd /var/www/wordpress
wp search-replace 'http://server' 'http://jeppson.org'

Easy.

Capture

Changing permalink structure in WordPress

After installing a fresh installation of WordPress on LAMP (Linux, Apache, MySQL, and PHP) I decided to change the new site’s permalink structure. The default structure on WordPress is so boring and uninformative  – sitename/?p=(number). I prefer the blogger method – sitename/year/month/postname.

Changing the structure should be pretty straightforward; However, when I clicked that option and clicked save, every post greeted me with a wonderful 404 error page.

Screenshot from 2014-08-01 20:33:54

If you are running apache it turns out there are a few extra things you need to do that aren’t mentioned in WordPress’s 5 minute install guide. Detailed instructions are found here.

  1. Enable the mod-rewrite apache plugin
  2. Ensure the directory of your wordpress installation has a Directory entry and that AllowOverride All is enabled
  3. Restart apache

After this, everything worked. The reason behind needing this change is WordPress modifies the .htaccess file for its installation folder with a simple rule:

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ – [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>

All it does is transparently prepend index.php to any web request it receives. Index.php is smart enough to direct pages wherever it needs to after that. If you don’t want to mess with enabling mod_rewrite, you can simply change your site structure to have /index.php/ before everything else. It will accomplish the same thing, only now index.php will show up in all your site URLs.