Command explanations --noninteractive : This switch is used to avoid the configuration routine asking for confirmation of the directories to install to (which we pass using switches to configure anyways). --with-GCOPTS="$CFLAGS" : This switch causes libtiff to be built using the options we have set in $CFLAGS (which most other packages handle automatically). --with-DIR_MAN=/usr/share/man : This is used because despite the fact we pass --prefix=/usr, the configure routine tries to install the man pages in /usr/local/man instead of the correct place.