.containerignore(28) Container User Manuals .containerignore(28)
NAME
.containerignore(.dockerignore) - files to ignore buildah or podman
build context directory
INTRODUCTION
Before container engines build an image, they look for a file named
.containerignore or .dockerignore in the root context directory. If one
of these file exists, the CLI modifies the context to exclude files and
directories that match patterns specified in the file. This avoids
adding them to images using the ADD or COPY instruction.
The CLI interprets the .containerignore or .dockerignore file as a new-
line-separated list of patterns similar to the file globs of Unix
shells. For the purposes of matching, the root of the context is consid-
ered to be both the working and the root directory. For example, the
patterns /foo/bar and foo/bar both exclude a file or directory named bar
in the foo subdirectory of PATH or in the root of the git repository lo-
cated at URL. Neither excludes anything else.
If a line in .containerignore or .dockerignore file starts with # in
column 1, then this line is considered as a comment and is ignored be-
fore interpreted by the CLI.
EXAMPLES
Here is an example .containerignore file:
# comment
*/temp*
*/*/temp*
temp?
This file causes the following build behavior: Rule Behavior
# comment Ignored.
*/temp* Exclude files and directories whose names start with temp in any immediate subdirectory of the root.
For example, the plain file /somedir/temporary.txt is excluded, as is the directory /somedir/temp.
*/*/temp* Exclude files and directories starting with temp from any subdirectory that is two levels below the
root. For example, /somedir/subdir/temporary.txt is excluded.
temp? Exclude files and directories in the root directory whose names are a one-character extension of temp. For example, /tempa and /tempb are excluded.
Matching is done using Go’s filepath.Match rules. A preprocessing step
removes leading and trailing whitespace and eliminates . and .. elements
using Go’s filepath.Clean. Lines that are blank after preprocessing are
ignored.
Beyond Go’s filepath.Match rules, Docker also supports a special wild-
card string ** that matches any number of directories (including zero).
For example, */.go will exclude all files that end with .go that are
found in all directories, including the root of the build context.
Lines starting with ! (exclamation mark) can be used to make exceptions
to exclusions. The following is an example .containerignore file that
uses this mechanism:
*.md
!README.md
All markdown files except README.md are excluded from the context.
The placement of ! exception rules influences the behavior: the last
line of the .containerignore that matches a particular file determines
whether it is included or excluded. Consider the following example:
*.md
!README*.md
README-secret.md
No markdown files are included in the context except README files other
than README-secret.md.
Now consider this example:
*.md
README-secret.md
!README*.md
All of the README files are included. The middle line has no effect be-
cause !README*.md matches README-secret.md and comes last.
You can even use the .containerignore file to exclude the Containerfile
or Dockerfile and .containerignore files. These files are still sent to
the daemon because it needs them to do its job. But the ADD and COPY in-
structions do not copy them to the image.
Finally, you may want to specify which files to include in the context,
rather than which to exclude. To achieve this, specify * as the first
pattern, followed by one or more ! exception patterns.
SEE ALSO
buildah-build(1), podman-build(1), docker-build(1)
HISTORY
*Sep 2021, Compiled by Dan Walsh (dwalsh at redhat dot com) based on
docker.com .dockerignore documentation.
Sep 2021 .containerignore(28)
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