TYPO3 Core

Please also check the error log of your webserver

I found the problem: Wrong PHP settings apparently prevent TYPO3 creating files.

With my server setup the install tool complains about some PHP settings being low (e.g. PHP upload_max_filesize = 2 MB). It suggests to change it to higher values. I copy pasted these without thinking and didn't remove the "B" in "MB". I ended up with the following wrong config in .htaccess:

php_value upload_max_filesize 10MB
php_value max_execution_time 240
php_value post_max_size 10MB

Correctly written file size values should only have a "M" instead of "MB".

With this wrong configuration the install tool didn't complain about low values anymore and offered to continue to step two. However that didn't work as explained in the opening comment.

I suggest the superfluous "B" in error message

PHP Maximum upload filesize too small
PHP upload_max_filesize = 2 MB

Maximum size for POST requests is smaller than maximum upload filesize in PHP
upload_max_filesize=10M
post_max_size=8M

Still it would be very nice if the install tool would not fail silently if execution of a step doesn't work.

I agree the message can be improved.

But still this seems to be not a TYPO3 issue. I guess TYPO3 is not even executed, but rather a HTTP 500 error is issues by the webserver, due to wrong .htaccess configuration.

In this case the webserver error log should hold a message telling this. Can you confirm that?

Furthermore the installation will NOT fail because of any of those options mentioned above.

You're right: Installation won't fail. I was just very eager to get rid of those warnings.

Server logs complain about the POST content exceeding the upload limit of 10 bytes. Apparently "MB" is parsed as nothing, thus rendering the limit to 10 bytes.

[Wed Jul 30 20:33:05.278330 2014] [:error] [pid 5299] [client ::1:56677] PHP Warning:  Unknown: POST Content-Length of 66 bytes exceeds the limit of 10 bytes in Unknown on line 0, referer: http://localhost/t/typo3/sysext/install/Start/Install.php

So the issue seems to be that TYPO3 never gets the POST variables. There is nothing that can fix that in TYPO3. Sorry for bothering you and thanks for the help.

Although ... thinking about it again: Why does the install tool stop complaining about a low value of the upload limit? 10 bytes is clearly less than 10 MB, so there should still be a warning.

Of course that might be due to a lot of things going wrong with such a bad configuration.

I guess that is because TYPO3 parses the option and receives the 10MB value, which it obviously treats "correctly" as 10MB.

If I remember correctly, we take the number and the first character behind it.
Obviously, and I didn't know that either, PHP is stupid enough to hand through the unvalidated php.ini options instead of reporting the actual values in use.

So, I leave it as open question, if the CMS should be held responsible for sanitizing values that should actually be done by the underlying architecture.