installation warning

Hi, I tried to install Contao 2.10.4. The contao-check told me that I have to use the so called safe mode hack:
Create directory • Error Error creating directory "contao-check"
Create file • Error Error creating file "contao-check.txt"

I changed the permissions of tmp, /log, /html directions to 777 and inserted
$GLOBALS['TL_CONFIG']['useFTP'] = true;
$GLOBALS['TL_CONFIG']['ftpHost'] = 'mydoman.de';
$GLOBALS['TL_CONFIG']['ftpPath'] = '/';
$GLOBALS['TL_CONFIG']['ftpUser'] = 'xyz';
$GLOBALS['TL_CONFIG']['ftpPass'] = 'xyz';

into the localconfig.php. Starting the install.php I got the message:
Warning: Unknown: open(/tmp/sess_cd571e99377283420160d1c872b50579, O_RDWR) failed: Permission denied (13) in Unknown on line 0
#0 [internal function]: __error(2, 'Unknown: open(/...', 'Unknown', 0, Array)
#1 {main}
Warning: Unknown: Failed to write session data (files). Please verify that the current setting of session.save_path is correct (/tmp) in Unknown on line 0
#0 [internal function]: __error(2, 'Unknown: Failed...', 'Unknown', 0, Array)
#1 {main}

I could not use the "Check FTP connection" to check the FTPpath. I think the path is OK. What went wrong?
carolus