Quote:
what all i can remove,which is unwanted
It matters what you are using, what type of install you did -
Entire Distribution plus OEM support, Entire Distribution, Developer System Support, End User System Support, or Core System Support.
Let's say you did the Entire distribution plus OEM support. You would have Apache loaded on the system ( in /usr/apache and /var/apache), Perl5 (in /usr/perl5), Man pages (one of the things I almost always remove IF I am running low on disk space in /usr (/usr/share/man)).
There are many other things such as newsyslog which can be changed to keep fewer copies of log files - other log files can be added to insure they are 'cut back' (see crontab for root or /usr/lib/newsyslog). Also look at /etc/cron.d/logchecker.
Another un-needed directory contains demo's for Openwindows - /usr/openwin/demo.
Another thing you can look at is moving log files off of /var and onto a different disk/partition by either using the ln command or mounting a new partition.
In the end, each system is different because of what it is used for so there isn't an 'easy' answer. You have to get to know what you can and CAN"T delete. Get a test system to learn what can or can't be changed/moved/deleted.
