Current Disk Usage
Filesystem Size Used Avail Use% Mounted on
/dev/hda2 7.7G 179M 7.2G 3% /
/dev/hda1 76M 13M 60M 18% /boot
/dev/hda8 84G 7.0G 73G 9% /home
none 505M 0 505M 0% /dev/shm
/dev/hda7 1012M 35M 926M 4% /tmp
/dev/hda5 7.7G 2.2G 5.2G 30% /var
/dev/hda6 7.7G 7.4G 0 100% /usr



root@server [/usr]# ls
./ dict/ include/ local/ quota.user* tmp@
../ doc/ kerberos/ lost+found/ sbin/ usr@
aquota.user* etc/ lib/ mailscanner/ share/ X11R6/
bin/ games/ libexec/ man/ src/
root@server [/usr]#


what can i delete in that partition/folder ?
what is taking all the space ?

I would try:

cd /usr
du --max-depth 1 -h

And see which are the biggest (it could take a while to run as it's totalling everything it sees).

When you find a very large directory, cd to it and run the du again. Keep going until you find the problem file/dir. It could be a really large, trash log file or something...