Shutdown/reboot hangs forever if an autossh process is started by rc.local

[Ivan Kozik]

If an autossh process is started by /etc/rc.local, a xenial system is no longer able to shut down. It seems to hang forever, not just for a few minutes.

Repro steps:

As root:

# Set up an autossh tunnel (in this example, from localhost to localhost):
apt-get install autossh openssh-server
ssh-keygen
cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys
chmod 0600 ~/.ssh/authorized_keys
ssh root@localhost true
  "yes", accept the fingerprint

# Test that autossh works:
autossh -f -L 127.0.0.2:22:127.0.0.1:22 root@localhost -N
ps auxw | grep autossh
  autossh should be listed

# Add to /etc/rc.local before exit line:
autossh -f -L 127.0.0.2:22:127.0.0.1:22 root@localhost -N &

# Enable rc-local service if necessary:
systemctl enable rc-local.service

Reboot.

After booted into system, `shutdown -r now`. Observe that systemd always hangs forever during shutdown.

# lsb_release -rd
Description: Ubuntu 16.04.1 LTS
Release: 16.04

# dpkg -l | grep systemd
ii libpam-systemd:amd64 229-4ubuntu13 amd64 system and service manager - PAM module
ii libsystemd0:amd64 229-4ubuntu13 amd64 systemd utility library
ii libsystemd0:i386 229-4ubuntu13 i386 systemd utility library
ii systemd 229-4ubuntu13 amd64 system and service manager
ii systemd-sysv 229-4ubuntu13 amd64 system and service manager - SysV links

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.