diff --git a/docs/reference/builder.md b/docs/reference/builder.md index 652cdb6881..7e02ecebc9 100644 --- a/docs/reference/builder.md +++ b/docs/reference/builder.md @@ -708,23 +708,24 @@ backslashes as you would in command-line parsing. A few usage examples: LABEL description="This text illustrates \ that label-values can span multiple lines." -An image can have more than one label. To specify multiple labels, -Docker recommends combining labels into a single `LABEL` instruction where -possible. Each `LABEL` instruction produces a new layer which can result in an -inefficient image if you use many labels. This example results in a single image -layer. +An image can have more than one label. You can specify multiple labels on a +single line. Prior to Docker 1.10, this decreased the size of the final image, +but this is no longer the case. You may still choose to specify multiple labels +in a single instruction, in one of the following two ways: - LABEL multi.label1="value1" multi.label2="value2" other="value3" +```none +LABEL multi.label1="value1" multi.label2="value2" other="value3" +``` -The above can also be written as: +```none +LABEL multi.label1="value1" \ + multi.label2="value2" \ + other="value3" +``` - LABEL multi.label1="value1" \ - multi.label2="value2" \ - other="value3" - -Labels are additive including `LABEL`s in `FROM` images. If Docker -encounters a label/key that already exists, the new value overrides any previous -labels with identical keys. +Labels included in base or parent images (images in the `FROM` line) are +inherited by your image. If a label already exists but with a different value, +the most-recently-applied value overrides any previously-set value. To view an image's labels, use the `docker inspect` command.