NTOP prefsCache.db failed: Can't be writer

When i start ntop service, it fails with following error.

[root@localhost bin]# ./ntop -i -d -L -u ntop -P /usr/local/ntop -w 3000 --interface eth0 --skip-version-check yes
Tue Jun 12 12:27:06 2012  NOTE: Interface merge enabled by default
Tue Jun 12 12:27:06 2012  Initializing gdbm databases
Tue Jun 12 12:27:06 2012  **ERROR** ....open of /usr/local/ntop/prefsCache.db failed: Can't be writer
Tue Jun 12 12:27:06 2012  Possible solution: please use '-P '
Tue Jun 12 12:27:06 2012  **FATAL_ERROR** GDBM open failed, ntop shutting down...
Tue Jun 12 12:27:06 2012  CLEANUP[t3086178000]: ntop caught signal 2 [state=2]
Tue Jun 12 12:27:06 2012  ntop is now quitting...


Solution :-

As we can see in error, ntop enable to write in database file.

After check, found this file owned by root user.

-rw-r----- 1 root root  16K Jun 12 12:25 prefsCache.db


#killall ntop

Now this db file must written by ntop user, following command has been used to change ownsership.

[root@localhost ntop]# chown ntop:ntop prefsCache.db

Now seems likes this.

root@localhost ntop]# ls -ltrh

-rw-r----- 1 ntop ntop  16K Jun 12 12:25 prefsCache.db



Now just run service again, and it should work.

if again trough same error, kill service 2-3 time & run again.

P.S :- check staus through ps like
#ps -aux | grep ntop

Enjoy.