A few days ago one of my previous client has contacted me and complained about not being able to auto-update two of his WordPress-based websites. I thought it was some file permission problem, probably the directory the update script was going to be saved was not writable, so I’ve told him to set the permissions of the upgrade folder to 777 and try updating his WordPress again, but didn’t solve the problem…
Then I took a look at his site and saw that the WordPress update is starting, is downloading the necessary package, but gets stuck at extracting the archive and throws the following exception:
PCLZIP_ERR_BAD_FORMAT (-10): Unable to find End of Central Dir Record signature
File permissions… was my second though too, I actually thought that the download failed too, so there wasn’t any archive to extract, that’s why it threw that error message. Logged in in CPanel to check the file permissions and saw that there was no more free disk space. After removing some unnecessary files from the server (~10-15 megs), everything was fine, the WordPress update did successfully run.
99% of all times I would have used an FTP client to modify the file permissions, but luckily I was too lazy to set up a new connection and wanted to use CPanel instead, otherwise I’m not sure I would have spotted the source of the error. So if you are getting the same error message and have tried all possible solutions without any success, then check if you still have some free space on the disk your WordPress is installed on.