Comment 1 for bug 1575572

This issue was originally reported by a customer, who investigated it as follows:

#####

"If you run up a 16.04 cloud image using EC2 compatible user-data containing a simple shell script.

#!/bin/sh

sudo DEBIAN_FRONTEND=noninteractive apt-get -q -y update
sudo DEBIAN_FRONTEND=noninteractive apt-get install -q -y apache2
sudo nc -k -l -d 443&

then the apache2 daemon will rarely start - if ever.

(You get the same problem running the equivalent 'cloud-config' script).

This is because 'cloud-init' runs the script when the run level is 'unknown', and the 'invoke-rc.d' script has no case for handling 'unknown' run levels - so it defaults to not starting anything.

I've seen this a few times with packages that have old style SysV init scripts and that start a daemon automatically in the 'postinst' script.

cloud-init should defer running scripts and cloud-config installs until systemd has achieved a defined run level - or the SysV backward compatibility needs improving so that it can deal with systemd being between run levels."

###

I could consistently reproduce across 20+ tests using the user data supplied by the customer; either:

#cloud-config
packages:
- apache2
runcmd:
- "nc -k -l -d 443&"

or:

#!/bin/sh

output_runlevel() {
echo -n "Current runlevel is "
sudo /sbin/runlevel
}
output_runlevel
sudo DEBIAN_FRONTEND=noninteractive apt-get -q -y update
#sudo sed -ie 's/set +e$/& -x/' /usr/sbin/invoke-rc.d
output_runlevel
sudo DEBIAN_FRONTEND=noninteractive apt-get install -q -y apache2
output_runlevel
sudo nc -k -l -d 443&

Apache 2 is correctly installed, but never started (nc is started as expected):

$ sudo systemctl status apache2; sudo netstat -A inet -lnp | grep 443
● apache2.service - LSB: Apache2 web server
Loaded: loaded (/etc/init.d/apache2; bad; vendor preset: enabled)
Drop-In: /lib/systemd/system/apache2.service.d
└─apache2-systemd.conf
Active: inactive (dead)
Docs: man:systemd-sysv-generator(8)
tcp 0 0 0.0.0.0:443 0.0.0.0:* LISTEN 2657/nc

Runlevel output is as per the customer's description (unknown). Edited excerpt from cloud-init-output.log on a VM that ran the script:

[snip]
Reading package lists...
Current runlevel is unknown # <-- output of output_runlevel(), as per above
Reading package lists...
Building dependency tree...
Reading state information...
The following additional packages will be installed:
  apache2-bin apache2-data apache2-utils libapr1 libaprutil1
[snip]