# merge ro and rw file systems
    if [ "x$UNIONTYPE" = "xaufs" ]; then
                mount -t aufs -o br:/cow/${KEY}=rw:/rofs=ro aufsroot ${rootmnt}
    else
                mount -t unionfs -o dirs=/cow/${KEY}=rw:/rofs=ro,debug=1 unionfs ${rootmnt}
    fi