Why are statically linked cgo binaries smaller than regularly compiled dynamically linked binaries?

<p>Let&#39;s take kubernetes&#39;s kubelet that has a bunch of cgo in things it depends on (or even in itself). I assume this is something that either a) I don&#39;t understand about Go b) I am doing wrong c) both.</p> <p>results show compiled and then stripped size</p> <p>With Go 1.6 normally I see</p> <pre><code>$ go build ./cmd/kubelet/kubelet.go ; ls -l kubelet ; strip kubelet ; ls -l kubelet -rwxr-xr-x 1 compsciphd compsciphd 170777248 Jan 3 15:02 kubelet -rwxr-xr-x 1 compsciphd compsciphd 120943000 Jan 3 15:02 kubelet </code></pre> <p>and if I statically link it via ldflag options, I see</p> <pre><code>$ go build --ldflags &#39;-extldflags &#34;-static&#34;&#39; ./cmd/kubelet/kubelet.go ; ls -l kubelet ; strip kubelet ; ls -l kubelet -rwxr-xr-x 1 compsciphd compsciphd 133684544 Jan 3 15:06 kubelet -rwxr-xr-x 1 compsciphd compsciphd 83362544 Jan 3 15:06 kubelet </code></pre> <p>And if I do the same with Go 1.7, I see similar results (though smaller binaries overall as to be expected)</p> <p>with normal go build</p> <pre><code>$ /usr/lib/go-1.7/bin/go build ./cmd/kubelet/kubelet.go ; ls -l kubelet ; strip kubelet ; ls -l kubelet -rwxr-xr-x 1 compsciphd compsciphd 119859816 Jan 3 15:08 kubelet -rwxr-xr-x 1 compsciphd compsciphd 72698056 Jan 3 15:08 kubelet </code></pre> <p>with ldflags to link statically</p> <pre><code>$ /usr/lib/go-1.7/bin/go build --ldflags &#39;-extldflags &#34;-static&#34;&#39; ./cmd/kubelet/kubelet.go ; ls -l kubelet ; strip kubelet ; ls -l kubelet -rwxr-xr-x 1 compsciphd compsciphd 105767304 Jan 3 15:10 kubelet -rwxr-xr-x 1 compsciphd compsciphd 58116640 Jan 3 15:10 kubelet </code></pre>