You may get the above mentioned error while installing
Extensions from your
Joomla admin section.
One of the solutions is to check the
tmp_path in the
configuration.php file.
if
$tmp_path = '/public_html/tmp';
then you change it to :-
$tmp_path = '/home/username/public_html/tmp'; [i.e. the absolute path to the tmp directory under your account]
and Save the file.
This should resolve the issue and the Extensions can be installed successfully.
PS : Make sure that the
tmp directory is
writable.