Failed to reload sysctl

On Debian 9-10 systems, we have noticed the error as below,

Failed to reload sysctl: net.ipv6.conf.all.disable_ipv6 = 1

This errors out at the TASK [opsview_host : Set sysctl config settings]

while running the setup-everything.yml playbook, which basically consists of the below 3 playbooks:

- import_playbook: setup-hosts.yml
- import_playbook: setup-infrastructure.yml
- import_playbook: setup-opsview.yml

In order to fix this failure:

• You have to delete all lines referencing IPv6 /etc/sysctl.conf EXCEPT the below:

net.ipv6.conf.all.disable_ipv6 = 1

OR (Alternative Fix)

• Enter the command in the terminal:

sysctl -w net.ipv6.conf.all.disable_ipv6=1

This should fix your playbook failure.