Gfilui

I work on remote servers, and its a painfull process to go into Rescue Mode everytime I screw something up when it comes to network configuraitons.

Are there a way to implement something like:

Netplan apply /customscript.yaml

That I can use when I troubleshoot network configurations.
So the server gets its "defaults" if I do a cold reboot.

There is a new way to do this in Bionic: netplan try.

In your case, netplan try --config-file foo.yaml should do what you want.

The manpage isn't very helpful as it mostly describes the config file format, but --help gives you a pretty good outline of the tool:

ubuntu@netplan:~$ netplan try --help
usage: /usr/sbin/netplan try [-h] [--debug] [--config-file CONFIG_FILE]
 [--timeout TIMEOUT]

Try to apply a new netplan config to running system, with automatic rollback

optional arguments:
 -h, --help show this help message and exit
 --debug Enable debug messages
 --config-file CONFIG_FILE
 Apply the config file in argument in addition to
 current configuration.
 --timeout TIMEOUT Maximum number of seconds to wait for the user's
 confirmation

First I created a sh script, placed it in /etc/netplan/ and named it backup.sh

#!/bin/sh

# -q quiet
# -c nb of pings to perform

ping -q -c5 aa.bb.cc.dd > /dev/null

if [ $? -eq 0 ]
then
 : #do absolutly nothing! server can ping its external IP.
else 
 # restore, working config to netplan.
 cp -f /etc/netplan/02-netcfg.yaml /etc/netplan/01-netcfg.yaml 
 # apply network config.
 netplan apply
fi

This script revert the changes I have made, to a working configuration setup that I have stored in 02-netcfg.yaml If i cant ping the server IP. I have masked my server IP address whit aa.bb.cc.dd So you have to replace that whit the IP you want to ping, in order to execute the "else" in the if.

Then i set this script to run everytime the server restart, as well as enable a Cron job for it that runs every 3 minutes when i work on network configurations.