Installation error - permission problem?

I have attempted to install netjuke on Linux with PHP 4.3.1 and MySQL. 
I created my database and attempted the installation when it came to the
point of creating the inc-prefs.php file, it resulted in the following
errors.  Do I have a problem with permissions?


Warning: shell_exec() [function.shell-exec]: Cannot execute using
backquotes in Safe Mode in
/var/www/html/netjuke/installer/lib/inc-generate.php on line 164

Warning: shell_exec() [function.shell-exec]: Cannot execute using
backquotes in Safe Mode in
/var/www/html/netjuke/installer/lib/inc-generate.php on line 165

Warning: shell_exec() [function.shell-exec]: Cannot execute using
backquotes in Safe Mode in
/var/www/html/netjuke/installer/lib/inc-generate.php on line 166

Warning: shell_exec() [function.shell-exec]: Cannot execute using
backquotes in Safe Mode in
/var/www/html/netjuke/installer/lib/inc-generate.php on line 167

Warning: Cannot modify header information - headers already sent by
(output started at
/var/www/html/netjuke/installer/lib/inc-generate.php:164) in
/var/www/html/netjuke/installer/lib/inc-generate.php on line 529

Warning: Cannot modify header information - headers already sent by
(output started at
/var/www/html/netjuke/installer/lib/inc-generate.php:164) in
/var/www/html/netjuke/installer/lib/inc-generate.php on line 530



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