Netplan pre-up-down post-up-down scripts

netplan network ubuntu

From Ubuntu 18, the network IFUPDOWN has been replaced by NETPLAN. Netplan doesn’t provide up/down hook scripts. But we can do it using networkd-dispatcher.

Below is a table mapping networking states and hooks available:

HOOK	IFUPDOWN	NETWORKD-DISPATCHER	NETWORKMANAGER
pre-up	if-pre-up.d		pre-up
configuring		configuring.d
configured		configured.d
up	if-up.d	routable.d	up
post-up	if-post-up.d	routable.d
degraded		degraded.d
pre-down	if-pre-down.d		pre-down
down	if-down.d	off.d	down
post-down	if-post-down.d	off.d
no-carrier		nocarrier.d

Note that in networkd-dispatcher, the hooks run asychronous; that is they will not block transition into another state.

Example for an ifupdown legacy hook for post-up/post-down states
The following is an example of using networkd-dispatcher to run existing ifup hooks via a script installed in /etc/networkd-dispatcher/routable.d/50-ifup-hooks:

#!/bin/sh

for d in up post-up; do
    hookdir=/etc/network/if-${d}.d
    [ -e $hookdir ] && /bin/run-parts $hookdir
done
exit 0

Similarly, here is an example of an ifdown hook installed in /etc/networkd-dispatcher/off.d/50-ifdown-hooks:

#!/bin/sh

for d in down post-down; do
    hookdir=/etc/network/if-${d}.d
    [ -e $hookdir ] && /bin/run-parts $hookdir
done
exit 0

Refer:
https://netplan.io/faq#use-pre-up-post-up-etc-hook-scripts

Written on September 12, 2019