Safely replacing /etc/s6-rc/compiled

[Jan Bramkamp]

Is there a way to update /etc/s6-rc/compiled without risking a broken 
system if the power fails midway through the update?
The best I can come up with is to use a symlink to a uniquely named 
compiled directory and a recompile wrapper along those lines:

    cd /etc/s6-rc
    s6-rc-compile .compiled-$SUFFIX source
    s6-rc-update $PWD/.compiled-$SUFFIX $* # TODO: avoid $*
    ln -s .compiled-$SUFFIX .compiled-${SUFFIX}.link
    mv .compiled-${SUFFIX}.link compiled
    # TODO: cleanup old .compiled-* dirs
    fsync compiled .