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)