What is the difference between iface eth0 inet manual and iface eth0 inet static?

iface eth0 inet static: Defines a static IP address for eth0

iface eth0 inet manual :To create a network interface without an IP address at all. Usually used by interfaces that are bridge or aggregation members, or have a VLAN device configured on them

For more information read:

• https://wiki.debian.org/NetworkConfiguration

Take a look on the file /usr/share/doc/ifupdown/examples/network-interfaces.gz, you can know more about manual and some cases to use:

# Set up an interface to read all the traffic on the network. This # configuration can be useful to setup Network Intrusion Detection# sensors in 'stealth'-type configuration. This prevents the NIDS# system to be a direct target in a hostile network since they have# no IP address on the network. Notice, however, that there have been# known bugs over time in sensors part of NIDS (for example see # DSA-297 related to Snort) and remote buffer overflows might even be# triggered by network packet processing.# # auto eth0# iface eth0 inet manual#   up ifconfig $IFACE 0.0.0.0 up#       up ip link set $IFACE promisc on#       down ip link set $IFACE promisc off#       down ifconfig $IFACE down# Set up an interface which will not be allocated an IP address by# ifupdown but will be configured through external programs. This# can be useful to setup interfaces configured through other programs,# like, for example, PPPOE scripts.## auto eth0# iface eth0 inet manual#       up ifconfig $IFACE 0.0.0.0 up#       up /usr/local/bin/myconfigscript#       down ifconfig $IFACE down