Was getting the error

script 'nexus' missing LSB tags and overrides

Luckily I found that someone had already done the work :)

http://mrexception.blogspot.com/2011/12/make-nexus-startup-script-lsb-compliant.html

From that post - add the following to the top of the file:

    ### BEGIN INIT INFO
    # Provides:          nexus
    # Required-Start:    $remote_fs $syslog $network
    # Required-Stop:     $remote_fs $syslog $network
    # Default-Start:     2 3 4 5
    # Default-Stop:      0 1 6
    # Short-Description: Nexus Maven Proxy
    # Description:       Nexus Maven Proxy
    ### END INIT INFO