install_restart_sshd.sh

#!/bin/bash -e

# Restart sshd using an appropriate method based on the currently running init daemon
# Note that systemd can return "running" or "degraded" (If a systemd unit has failed)
# This was observed on the RHEL 7.3 AMI, so it's added for completeness
# systemd is also not standardized in the name of the ssh service, nor in the places
# where the unit files are stored.

# Capture the return code and use that to determine if we have the command available
retval=0
which systemctl > /dev/null 2>&1 || retval=$?

if [[ "$retval" -eq "0" ]]; then
  if [[ ($(systemctl is-system-running) =~ running) || ($(systemctl is-system-running) =~ degraded) || ($(systemctl is-system-running) =~ starting) ]]; then
    if [ -f "/usr/lib/systemd/system/sshd.service" ] || [ -f "/lib/systemd/system/sshd.service" ]; then
      systemctl restart sshd.service
    else
      systemctl restart ssh.service
    fi
  fi
elif [[ $(/sbin/init --version) =~ upstart ]]; then
    if [ -f "/etc/init.d/sshd" ]; then
      service sshd restart
    else
      service ssh restart
    fi
else
  if [ -f "/etc/init.d/sshd" ]; then
    /etc/init.d/sshd restart
  else
    /etc/init.d/ssh restart
  fi
fi