Code Inspections in Dockerfile

A single quoted string in JSON array format

Reports a single quoted string in JSON array format.

JSON array form, must use double-quotes (") around words not single-quotes ('). Otherwise, Docker build will fail.

Examples:

# all the commands below will fail
RUN ['/bin/bash', '-c', 'echo hello']
ADD ['binaryA.jar', 'binary2.jar', 'destination/']
COPY ['binaryA.jar', 'binary2.jar', 'destination/']

After the quick-fix is applied:

RUN ["/bin/bash", "-c", "echo hello"]
ADD ["binaryA.jar", "binary2.jar", "destination/"]
COPY ["binaryA.jar", "binary2.jar", "destination/"]

Warning

Invalid destination for ''ADD''/''COPY'' commands

Reports invalid destination directories in ADD and COPY commands.

According to the Dockerfile specification, if multiple sources are specified, then the destination must be a directory, and it must end with a slash '/'. Otherwise, Docker build will fail.

Examples:

# all the commands below will fail
ADD textA.txt textB.txt relativeDir
ADD ["binaryA.jar", "binary2.jar", "destination"]
COPY text3.txt text4.txt /absolute/path

After the quick-fix is applied:

ADD textA.txt textB.txt relativeDir/
ADD ["binaryA.jar", "binary2.jar", "destination/"]
COPY text3.txt text4.txt /absolute/path/

Warning

Invalid spaces in ''key=value'' pair

Reports incorrect spacing for key-value pairs in ARG, ENV, and LABEL commands.

While it is not explicitly specified in the Dockerfile specification, some combinations of spacing for key-value pairs are not allowed. Docker build will fail after reaching the problem instruction.

Examples:

• The ARG command does not allow any spaces around '='

• ENV and LABEL do not allow spaces after '='

# all the commands below will fail
ARG answer = 42
ARG version= "1.0.0"
LABEL "maintained.by"= someone@gmail.com
ENV JAVA_HOME= "/docker-java-home"

After the quick-fix is applied:

ARG answer=2
ARG version="1.0.0"
LABEL "maintained.by"=someone@gmail.com
ENV JAVA_HOME="/docker-java-home"

Error

Missing continuation character for ''RUN'' command

Reports missing continuation characters in RUN command.

In the shell form of RUN command you should use a '\' (backslash) to continue a single RUN instruction onto the next line. Otherwise, Docker build will fail.

Examples:

# the command below will fail
RUN /bin/bash -c 'source $HOME/.bashrc;
    echo $HOME'

After the quick-fix is applied:

RUN /bin/bash -c 'source $HOME/.bashrc; \
    echo $HOME'

Error

Wrong number of arguments

Reports invalid number of arguments for the Dockerfile commands.

Docker build will fail after reaching the instruction with an invalid number of arguments.

Error