Warning: Unknown: Releasing SysV semaphore id 58 key 0x152b in request cleanup in Unknown on line 0


This is not an error from WordPress, but from the WP Super Cache Plugin you forgot you installed. The error comes when from the cache directory is not writable.

Change the permissions on the wp-content/cache directory to allow the web user to write and the error will disappear.

The solution is obvious if you check the source code on the page when the error appears. WP Super Cache spits out the error, but it is hidden in HTML comment tags. Your source code will look something like this:

<!-- Dynamic Page Served (once) in 0.297 seconds -->
<!-- File not cached! Super Cache Couldn't write to: wp-content/cache/wp-cache-2876abde8ce3a2aa817c8289ea85486e.html -->

87
<br />
<b>Warning</b>: Unknown: Releasing SysV semaphore id 58 key 0x152b in request cleanup in <b>Unknown</b> on line <b>0</b><br />

What you need:

• iCal client like Sunbird or Lightning from Mozilla
• Apache web server with WebDav installed

How to do it:

1. Install WebDav and password protect a public directory on your web server.
2. Touch a .ics file for your calendar. I called mine matt.ics
3. chmod the directory so the web user can create files and modify the .ics file
4. Install and configure an iCal client that can publish via WebDav. Sunbird is excellent for this.
5. Remove your local calendar from Sunbird
6. Add a calendar to Sunbird using the URL to your empty .ics file
7. Add an event to your calendar. Sunbird should modify the .ics file on your web server. You will probably be prompted for the username and password on the first try.
8. Add that calendar to as many clients as you want. They can all share the calendar. Create more calendars! Party!