debugging - How can I inspect the file system of a failed `docker build`? - Stack Overflow

debugging - How can I inspect the file system of a failed `docker build`? - Stack Overflow

Everytime docker successfully executes a RUN command from a Dockerfile, a new layer in the image filesystem is committed. Conveniently you can use those layers ids as images to start a new container.

Take the following Dockerfile:

FROM base  RUN echo 'foo' > /tmp/foo.txt  RUN echo 'bar' >> /tmp/foo.txt  

and build it:

$ docker build --force-rm -t so-26220957 .  Sending build context to Docker daemon 3.584 kB  Sending build context to Docker daemon  Step 0 : FROM base   ---> b750fe79269d  Step 1 : RUN echo 'foo' > /tmp/foo.txt   ---> Running in d37d756f6e55   ---> de1d48805de2  Removing intermediate container d37d756f6e55  Step 2 : RUN echo 'bar' >> /tmp/foo.txt   ---> Running in a180fdacd268   ---> 40fd00ee38e1  Removing intermediate container a180fdacd268  Successfully built 40fd00ee38e1  

You can now start a new container from b750fe79269d, de1d48805de2 and 40fd00ee38e1:

$ docker run --rm b750fe79269d cat /tmp/foo.txt  cat: /tmp/foo.txt: No such file or directory    $ docker run --rm de1d48805de2 cat /tmp/foo.txt  foo    $ docker run --rm 40fd00ee38e1 cat /tmp/foo.txt  foo  bar  

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