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  newline-separated  list  of  patterns
       similar  to  the  file  globs  of  Unix  shells. For the purposes of matching, the root of the context is
       considered 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 located 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 before 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 wildcard 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 because !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 instructions 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)