The search target requires INDEX-9. Please run make index or make fetchindex

How do I search ports tree under FreeBSD operating system and fix this issue?

You can search FreeBSD ports tree by changing to the /usr/ports directory and typing the following command:

make search name=string

To fix this issue you need to cd into /usr/ports directory. Open a terminal or ssh session and type the followign command as root user:

cd /usr/ports
make index

OR

cd /usr/ports
make fetchindex
Sample outputs:

/usr/ports/INDEX-9.bz2                        100% of 1665 kB   54 kBps 00m00s

Now, try searching ports tree:
# make search name=apache
# make search name=lsof
Sample outputs:

Port:	lsof-4.87,8
Path:	/usr/ports/sysutils/lsof
Info:	Lists information about open files (similar to fstat(1))
Maint:	ler@lerctr.org
B-deps:	
R-deps:	
WWW:	http://people.freebsd.org/~abe/
 
Port:	p5-Unix-Lsof-0.0.5_1
Path:	/usr/ports/sysutils/p5-Unix-Lsof
Info:	Unix::Lsof -- a wrapper to the Unix lsof utility
Maint:	gjvc@gjvc.com
B-deps:	p5-IPC-Run3-0.045 perl-5.14.2_2
R-deps:	p5-IPC-Run3-0.045 perl-5.14.2_2
WWW:	http://search.cpan.org/dist/Unix-Lsof/