Doxygen Documentation
 

When I want to use and compile doxygen doc.,after typing in the terminal :"./Allwmake doc" I encountered with this error:
///////////////////////////////////////////
****terminal:
chmod: changing permissions of '/opt/openfoam5': Operation not permitted
chmod: changing permissions of '/opt/openfoam5/doc': Operation not permitted
chmod: changing permissions of 'Doxygen': Operation not permitted
error: Failed to open temporary file /opt/openfoam5/doc/Doxygen/doxygen_objdb_18333.tmp
Exiting...

Done doxygen

note : I've installed doxygen and graphviz formerly.

It seems you need to run your command with sudo to install in the /opt folder... You could, if you don't want to sudo, build the doxygen documents without going to /opt

I've already install doxygen with sudo apt install but when I want to compile it in doc folder (opt/openFOAM), this error will be appeared.
Do you mean to execute "./Allwmake" with sudo ?!