PREUN

/bin/sh

 
if [ $1 -eq 0 ] && [ -x "/usr/lib/systemd/systemd-update-helper" ]; then 
    # Package removal, not upgrade 
    /usr/lib/systemd/systemd-update-helper remove-system-units fdns || : 
fi

POSTIN

/bin/sh

 
if [ $1 -eq 1 ] && [ -x "/usr/lib/systemd/systemd-update-helper" ]; then 
    # Initial installation 
    /usr/lib/systemd/systemd-update-helper install-system-units fdns || : 
fi