[Freeswitch-users] config ramdisk on CentOS 5.5

i'm trying tuning the FS to max performance on centos 5.5, and referred to http://wiki.freeswitch.org/wiki/Performance_testing_and_configurations#FreeS... #1, i configure the DB of FS to ramdisk , when i run "tmpfs /opt/freeswitch/db tmpfs defaults 0 0", it output: "-bash: tmpfs: command not found" #2, i run "ethtool -g eth0", the output is below, what value i should config for RX and TX for max performance... Ring parameters for eth0: Pre-set maximums: RX: 4096 RX Mini: 0 RX Jumbo: 0 TX: 4096 Current hardware settings: RX: 256 RX Mini: 0 RX Jumbo: 0 TX: 256 Apprecited if anyone help how to configure it... thanks! Regards, Charles