0ct0pu5/moby
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity

Merge pull request #21885 from triccardi-systran/20612-improve-build-cache-miss-documentation

Browse source 
Improve build cache miss doc for `ARG` and `RUN`
This commit is contained in:
Vincent Demeester 2016-04-13 15:23:14 +02:00
commit edfe4e9fba
1 changed files with 3 additions and 2 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

5
docs/reference/builder.md
View file

@ -1174,8 +1174,9 @@ To use these, simply pass them on the command line using the `--build-arg
`ARG` variables are not persisted into the built image as `ENV` variables are.
However, `ARG` variables do impact the build cache in similar ways. If a
Dockerfile defines an `ARG` variable whose value is different from a previous
build, then a "cache miss" occurs upon first use of the `ARG` variable. The
declaration of the `ARG` variable does not count as a use.
build, then a "cache miss" occurs upon its first usage, not its definition. In
particular, all `RUN` instructions following an `ARG` instruction use the `ARG`
variable implicitly (as an environment variable), thus can cause a cache miss.
For example, consider these two Dockerfile: