on your kernel command line in the */etc/grub.conf* setup.
For any problems look in the */var/log/dmesg* and */var/log/messages* files.
# /sbin/chkconfig kdump on # /sbin/service kdump start # /usr/bin/reboot
Unless you know what kdumps are used for chances are most likely that you really don't need it.Sorry to disagree, but a VMCORE, produced by a kdump, is ultimately useful to technical support should an incident occur. Yes, it's beyond the ken of administrators, but they are not the intended audience.