Akeeba Kickstart starts, but can't extract the archive, throws an AJAX Error, Invalid Archive Header or other error

Server protection

If you get a 502 Bad Gateway error or the extraction halts mysteriously after a very short while (about 10 seconds or less) you may be hitting a server limitation. Hosts using the Apache web server usually have installed and configured mod_evasive, a tool which blocks similar requests coming too fast from the same remote client. While this is a good protection against Denial of Service attacks it can get in the way of extracting a backup archive: Kickstart is hitting a similar URL for each of its extractions steps. Moreover, some hosts may go a step further and apply CPU usage limits. If a script, like Kickstart, uses too much CPU they will block your requests and / or your IP address for a while. Again that's very good for preventing Denial of Service attacks but not very good for extracting backup archives, something which is by its nature a CPU-intensive process.

There is a workaround for that but the exact values depend on your server. On Kickstart's main page, under advanced settings, set the minimum execution time to 7 seconds and the maximum to 10. If that still fails, try setting the minimum time to 7 seconds and the maximum to 3 (yes, the maximum is less than the minimum, that's on purpose). These settings modify the amount of time Kickstart will be spending on each request and its duty cycle (how much work it will do and how much time it will sit around doing nothing). These tricks work around the protections of your server. If all else fails you can always extract the backup archive manually on your computer, using Kickstart running on a local web server (e.g. XAMPP, WAMPserver, MAMP, …) or under CLI, and upload everything to your server. This is much slower but it always works.

Free space

The most common issue of all is, surprisingly, not having enough disk space. In order to restore a backup archive you need to have at least as much space as kickstart.php, your backup archive and all of the extracted files occupy. As a rule of thumb, you need about 2.5 times as much disk space as your backup archive. In other words, if you have a 100Mb archive file, make sure your site has at least 250Mb of free space before uploading Kickstart and the backup archive to it.


Some hosts claim "unlimited" disk space. Sadly, this is never the case. Most hosts have "hidden" limits, such as the amount of files you can host under one account. If you go over that limit, you'll get extraction errors. Another thing is that you "unlimited" host is physically bound to the size of their hard drives. If their hard drive was close to completely filling up, trying to extract your site will also lead to a restoration failure. Moreover, we have seen hosts with "unlimited" space which actually give you a finite and small amount of space (e.g. 1GB) and you have to explain why you need more to get another chunk of free space (if you successfully convince them). If nothing else helps with this kind of errors, do contact your host and ask them if you are hitting a file count limitation or their hard drive is full.

Moreover, some hosts have a limitation on the maximum file size PHP can create. For example, Strato allows PHP to create files of only up to 10MB. Trying to extract bigger files from the archive will lead to such an error. Do note that you might be able to upload large files, such as your site's backup archive, through FTP. However, if you try to extract a large file from the archive (e.g. a large non-split database dump, a large video or music file, etc) it will fail. Your ONLY way to perform the restoration is to extract the archive on your local computer and upload all the extracted files by SFTP / FTP. All you'll have to do next is visiting the restoration URL which is in the form of Please refer to Akeeba Backup's documentation (the chapter on restoring your site) for more information.

Missing or corrupt backup archive parts

If you have a multi-part archive (files named .jpa, .j01, .j02, etc or .zip, .z01, .z02 etc) remember to upload all of the archive parts, otherwise the extraction will, of course, fail. More specifically, the extraction might continue up to the point where Kickstart determines that a part file is missing. Then, it will tell you that the archive is invalid, corrupt or archive parts are missing (older versions will just show INVALID_HEADER without further information). Moreover, make sure that all backup archives have been downloaded from a live server and/or uploaded to a live server using FTP in Binary transfer mode. Any other way to transfer them will most likely corrupt them, making restoration impossible. We suggest using FileZilla to do that. As soon as you connect to your site and right before downloading/uploading any files click on the Transfer, Transfer Type, Binary menu item.

Mixed ownership

You may end up with wrong or mixed file and directory permissions (this situation is also known as "mixed onwership" or "permissions hell"). This is very easy to happen if you are restoring to a host with an existing installation of Joomla! which doesn't use per-account web server process ownership through FastCGI or suPHP, i.e. the majority of cheap shared hosting. You might want to try using the FTP or Hybrid file writing mode.

If this still doesn't work for you, try removing all existing files and directories from your server before restoring the backup archive. It's very easy to mix up ownerships and permissions on a shared host, effectively entering into a mixed ownership situation which is virtually impossible to work around unless you have root privileges on an SSH console or, more easily, removing all files from the account. Do note that removing files might require using both an FTP program and your host's control panel, or raising a ticket with your host.

File and folder permissions

If you are restoring on a Windows server or local WAMP/XAMPP/other local server solution and you receive an error message like "Could not create test/info/N:/ folder", take a good look at the error message. If the file name contains a colon (:), slash (/), question mark (?), asterisk (*), vertical bar (|), quotation mark ("), less than (<) or greater than (>) please note that these characters are invalid in filenames on Windows, even though they are valid on Linux, macOS, and pretty much every other Operating System. You can still use Kickstart to extract the archive by selecting the "Ignore most errors" option. This feature will skip over files which cannot be extracted.

If that doesn't work, please indicate the type of server you are restoring to

  • A local server, for example XAMPP, MAMP, WAMPServer, Zend Server CE, Uniform Server, etc.

  • A live server, e.g. a shared host, dedicated box, cloud host, VPS or any other server directly accessible from the Internet

Troubleshooting on a local server

If you are on a local host, be advised that permissions or Windows ACL may be interfering with Kickstart's operation.

If you are on a Linux machine, change the permissions of the root of your to-be-restored website to 0777. For example, if you're trying to restore to /var/www/mysite you have to issue a command like chmod -Rf 0777 /var/www/mysite after you have put Kickstart and the archive in there, but before launching Kickstart

If you are on a Mac OS X machine, use the Finder to find your site's root. Right-click or Control-click on it and select Get Info. Scroll down to the Sharing & Permissions slider and expand it if it's not already expanded. Find the row where the Name column reads everyone and set the Privilege to Read & Write.

If you are on a Windows XP Home machine, use Windows explorer to find your site's root. Right click on it, select Properties and clear (unselect - it must be blank, not gray!) the Read Only checkbox. Click OK and, if prompted, tell Windows to apply this to all files and subdirectories.

If you are on a Windows XP Professional, Vista (all versions) or 7 (all versions) machine, use Windows explorer to find your site's root. Right click on it, select Properties and click on the Security tab. Click on the Edit... button. If you can't see a user named Everyone, you will have to click on the Add... button, type Everyone in the big text box and click OK. Now click on the Everyone user and then take a look at the list of checkboxes below. Click the Accept checkbox on the Full Control row (the topmost one). Click on OK, then again on OK.


If you are restoring a backup taken on Linux / Mac OS X on a Windows machnie there is another possibility. You may have a filename which is valid under Linux / Mac OS X but not on Windows such as "index.php?something". In this example the question mark is an allowed filename character on Linux but not on Windows. In such cases you can extract the backup archive using Akeeba eXtract Wizard or Akeeba Kickstart as long as you check the Ignore most errors checkbox. This will tell eXtract or Kickstart to ignore files which cannot be opened for writing. But beware! This will also skip files with legitimate filenames which are attempted to be extracted on unwritable directories. So, our suggestion is to first try adjusting the Security privileges and only if all else fails should you resort to using the Ignore most errors checkbox.