zrhoffman commented on a change in pull request #5252:
URL: https://github.com/apache/trafficcontrol/pull/5252#discussion_r524753211
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File path: infrastructure/cdn-in-a-box/optional/vnc/Dockerfile
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@@ -14,15 +14,22 @@
# KIND, either express or implied. See the License for the
# specific language governing permissions and limitations
# under the License.
-FROM docker.io/centos:7
+
+ARG CENTOS_VERSION=8
+FROM centos:${CENTOS_VERSION}
+ARG CENTOS_VERSION=8
Review comment:
Nope because `ENV` cannot come before the first `FROM`. If it does,
you'll get an error like `No build stage in current context`.
From [the
documentation](https://docs.docker.com/engine/reference/builder/#from):
> - `ARG` is the only instruction that may precede `FROM` in the
`Dockerfile`.
See [Understand how ARG and FROM
interact](https://docs.docker.com/engine/reference/builder/#understand-how-arg-and-from-interact).
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