buildah-build

buildah-build(1) General Commands Manual buildah-build(1)

NAME

   buildah-build - Build an image using instructions from Containerfiles

SYNOPSIS

   buildah build [options] [context]

   buildah bud [options] [context]

DESCRIPTION

   Builds  an  image  using  instructions from one or more Containerfiles or Dockerfiles and a specified build context directory.  A Containerfile uses the same
   syntax as a Dockerfile internally.  For this document, a file referred to as a Containerfile can be a file named either 'Containerfile' or 'Dockerfile'.

   The build context directory can be specified as the http(s) URL of an archive, git repository or Containerfile.

   If no context directory is specified, then Buildah will assume the current working directory as build context, which should contain a Containerfile.

   Containerfiles ending with a ".in" suffix will be preprocessed via cpp(1).  This can be useful to decompose Containerfiles into several reusable  parts  that
   can  be used via CPP's #include directive.  Notice, a Containerfile.in file can still be used by other tools when manually preprocessing them via cpp -E. Any
   comments ( Lines beginning with # ) in included Containerfile(s) that are not preprocess commands, will be printed as warnings during builds.

   When the URL is an archive, the contents of the URL is downloaded to a temporary location and extracted before execution.

   When the URL is a Containerfile, the file is downloaded to a temporary location.

   When a Git repository is set as the URL, the repository is cloned locally and then used as the build context.  A non-default branch (or commit ID) and subdi‐
   rectory  of  the  cloned  git  repository  can  be used by including their names at the end of the URL in the form myrepo.git#mybranch:subdir, myrepo.git#my‐
   commit:subdir, or myrepo.git#:subdir if the subdirectory should be used from the default branch.

OPTIONS

   --add-host=[]

   Add a custom host-to-IP mapping (host:ip)

   Add a line to /etc/hosts. The format is hostname:ip. The --add-host option can be set multiple times. Conflicts with the --no-hosts option.

   --all-platforms

   Instead of building for a set of platforms specified using the --platform option, inspect the build's base images, and build for all  of  the  platforms  for
   which they are all available.  Stages that use scratch as a starting point can not be inspected, so at least one non-scratch stage must be present for detec‐
   tion to work usefully.

   --annotation annotation[=value]

   Add an image annotation (e.g. annotation=value) to the image metadata. Can be used multiple times.  If annotation is named, but neither = nor a value is pro‐
   vided, then the annotation is set to an empty value.

   Note: this information is not present in Docker image formats, so it is discarded when writing images in Docker formats.

   --arch="ARCH"

   Set  the  ARCH of the image to be built, and that of the base image to be pulled, if the build uses one, to the provided value instead of using the architec‐
   ture of the host. (Examples: arm, arm64, 386, amd64, ppc64le, s390x)

   --authfile path

   Path of the authentication file.  Default  is  ${XDG_\RUNTIME_DIR}/containers/auth.json.  If  XDG_RUNTIME_DIR  is  not  set,  the  default  is  /run/contain‐
   ers/$UID/auth.json. This file is created using buildah login.

   If the authorization state is not found there, $HOME/.docker/config.json is checked, which is set using docker login.

   Note:  You  can  also  override  the  default  path  of  the  authentication  file  by  setting  the  REGISTRY_AUTH_FILE  environment  variable.  export REG‐
   ISTRY_AUTH_FILE=path

   --build-arg arg=value

   Specifies a build argument and its value, which will be interpolated in instructions read from the Containerfiles in the same way that environment  variables
   are, but which will not be added to environment variable list in the resulting image's configuration.

   Please  refer  to  the  BUILD TIME VARIABLES ⟨#build-time-variables⟩ section for the list of variables that can be overridden within the Containerfile at run
   time.

   --build-context name=value

   Specify an additional build context using its short name and its location. Additional build contexts can be referenced in the same manner as we  access  dif‐
   ferent stages in COPY instruction.

   Valid  values  could  be:  *  Local  directory  –  e.g.  --build-context  project2=../path/to/project2/src  *  HTTP  URL  to a tarball – e.g. --build-context
   src=https://example.org/releases/src.tar *  Container  image  –  specified  with  a  container-image://  prefix,  e.g.  --build-context  alpine=container-im‐
   age://alpine:3.15, (also accepts docker://, docker-image://)

   On the Containerfile side, you can reference the build context on all commands that accept the “from” parameter.  Here’s how that might look:

          FROM [name]
          COPY --from=[name] ...
          RUN --mount=from=[name] …

   The value of [name] is matched with the following priority order:

          • Named build context defined with --build-context [name]=..

          • Stage defined with AS [name] inside Containerfile

          • Image [name], either local or in a remote registry

   --cache-from

   Repository  to utilize as a potential cache source. When specified, Buildah will try to look for cache images in the specified repository and will attempt to
   pull cache images instead of actually executing the build steps locally. Buildah will only attempt to pull previously cached images if they are considered as
   valid cache hits.

   Use the --cache-to option to populate a remote repository with cache content.

   Example

          # populate a cache and also consult it
          buildah build -t test --layers --cache-to registry/myrepo/cache --cache-from registry/myrepo/cache .

   Note: --cache-from option is ignored unless --layers is specified.

   --cache-to

   Set  this  flag  to  specify  a remote repository that will be used to store cache images. Buildah will attempt to push newly built cache image to the remote
   repository.

   Note: Use the --cache-from option in order to use cache content in a remote repository.

   Example

          # populate a cache and also consult it
          buildah build -t test --layers --cache-to registry/myrepo/cache --cache-from registry/myrepo/cache .

   Note: --cache-to option is ignored unless --layers is specified.

   --cache-ttl duration

   Limit the use of cached images to only consider images with created timestamps less than duration ago.  For example if --cache-ttl=1h is  specified,  Buildah
   will  only  consider  intermediate cache images which are created under the duration of one hour, and intermediate cache images outside this duration will be
   ignored.

   Note: Setting --cache-ttl=0 manually is equivalent to using --no-cache in the implementation since this would effectively mean that user is  not  willing  to
   use cache at all.

   --cap-add=CAP_xxx

   When  executing  RUN instructions, run the command specified in the instruction with the specified capability added to its capability set.  Certain capabili‐
   ties are granted by default; this option can be used to add more.

   --cap-drop=CAP_xxx

   When executing RUN instructions, run the command specified in the instruction with the specified capability removed from its  capability  set.   The  CAP_AU‐
   DIT_WRITE,  CAP_CHOWN, CAP_DAC_OVERRIDE, CAP_FOWNER, CAP_FSETID, CAP_KILL, CAP_MKNOD, CAP_NET_BIND_SERVICE, CAP_SETFCAP, CAP_SETGID, CAP_SETPCAP, CAP_SETUID,
   and CAP_SYS_CHROOT capabilities are granted by default; this option can be used to remove them.

   If a capability is specified to both the --cap-add and --cap-drop options, it will be dropped, regardless of the order in which the options were given.

   --cert-dir path

   Use certificates at path (*.crt, *.cert, *.key) to connect to the registry.  The default certificates directory is /etc/containers/certs.d.

   --cgroup-parent=""

   Path to cgroups under which the cgroup for the container will be created. If the path is not absolute, the path is considered to be relative to  the  cgroups
   path of the init process. Cgroups will be created if they do not already exist.

   --cgroupns how

   Sets the configuration for cgroup namespaces when handling RUN instructions.  The configured value can be "" (the empty string) or "private" to indicate that
   a new cgroup namespace should be created, or it can be "host" to indicate that the cgroup namespace in which buildah itself is being run should be reused.

   --compress

   This option is added to be aligned with other containers CLIs.  Buildah doesn't send a copy of the context directory to a daemon or a remote  server.   Thus,
   compressing the data before sending it is irrelevant to Buildah.

   --cpp-flag=""

   Set  additional  flags  to  pass to the C Preprocessor cpp(1).  Containerfiles ending with a ".in" suffix will be preprocessed via cpp(1). This option can be
   used to pass additional flags to cpp.  Note: You can also set default CPPFLAGS by setting the  BUILDAH_CPPFLAGS  environment  variable  (e.g.,  export  BUIL‐
   DAH_CPPFLAGS="-DDEBUG").

   --cpu-period=0

   Set  the  CPU  period for the Completely Fair Scheduler (CFS), which is a duration in microseconds. Once the container's CPU quota is used up, it will not be
   scheduled to run until the current period ends. Defaults to 100000 microseconds.

   On some systems, changing the CPU limits may not be allowed for non-root users. For more  details,  see  https://github.com/containers/podman/blob/main/trou‐
   bleshooting.md#26-running-containers-with-cpu-limits-fails-with-a-permissions-error

   --cpu-quota=0

   Limit the CPU CFS (Completely Fair Scheduler) quota

   Limit  the  container's CPU usage. By default, containers run with the full CPU resource. This flag tells the kernel to restrict the container's CPU usage to
   the quota you specify.

   On some systems, changing the CPU limits may not be allowed for non-root users. For more  details,  see  https://github.com/containers/podman/blob/main/trou‐
   bleshooting.md#26-running-containers-with-cpu-limits-fails-with-a-permissions-error

   --cpu-shares, -c=0

   CPU shares (relative weight)

   By default, all containers get the same proportion of CPU cycles. This proportion can be modified by changing the container's CPU share weighting relative to
   the weighting of all other running containers.

   To modify the proportion from the default of 1024, use the --cpu-shares flag to set the weighting to 2 or higher.

   The proportion will only apply when CPU-intensive processes are running.  When tasks in one container are idle, other containers can use  the  left-over  CPU
   time. The actual amount of CPU time will vary depending on the number of containers running on the system.

   For  example,  consider  three containers, one has a cpu-share of 1024 and two others have a cpu-share setting of 512. When processes in all three containers
   attempt to use 100% of CPU, the first container would receive 50% of the total CPU time. If you add a fourth container with a cpu-share of  1024,  the  first
   container only gets 33% of the CPU. The remaining containers receive 16.5%, 16.5% and 33% of the CPU.

   On  a  multi-core system, the shares of CPU time are distributed over all CPU cores. Even if a container is limited to less than 100% of CPU time, it can use
   100% of each individual CPU core.

   For example, consider a system with more than three cores. If you start one container {C0} with -c=512 running one process, and another container  {C1}  with
   -c=1024 running two processes, this can result in the following division of CPU shares:

          PID    container    CPU  CPU share
          100    {C0}         0    100% of CPU0
          101    {C1}         1    100% of CPU1
          102    {C1}         2    100% of CPU2

   --cpuset-cpus=""

   CPUs in which to allow execution (0-3, 0,1)

   --cpuset-mems=""

   Memory nodes (MEMs) in which to allow execution (0-3, 0,1). Only effective on NUMA systems.

   If  you  have  four  memory nodes on your system (0-3), use --cpuset-mems=0,1 then processes in your container will only use memory from the first two memory
   nodes.

   --creds creds

   The [username[:password]] to use to authenticate with the registry if required.  If one or both values are not supplied, a command line  prompt  will  appear
   and the value can be entered.  The password is entered without echo.

   --decryption-key key[:passphrase]

   The  [key[:passphrase]] to be used for decryption of images. Key can point to keys and/or certificates. Decryption will be tried with all keys. If the key is
   protected by a passphrase, it is required to be passed in the argument and omitted otherwise.

   --device=device

   Add a host device to the container. Optional permissions parameter can be used to specify device permissions, it is combination of r for read, w  for  write,
   and m for mknod(2).

   Example: --device=/dev/sdc:/dev/xvdc:rwm.

   Note: if _hostdevice is a symbolic link then it will be resolved first.  The container will only store the major and minor numbers of the host device.

   Note:  if  the  user  only has access rights via a group, accessing the device from inside a rootless container will fail. The crun(1) runtime offers a work‐
   around for this by adding the option --annotation run.oci.keep_original_groups=1.

   --disable-compression, -D

   Don't compress filesystem layers when building the image unless it is required by the location where the image is being written.  This is  the  default  set‐
   ting,  because  image layers are compressed automatically when they are pushed to registries, and images being written to local storage would only need to be
   decompressed again to be stored.  Compression can be forced in all cases by specifying --disable-compression=false.

   --disable-content-trust

   This is a Docker specific option to disable image verification to a Container registry and is not supported by Buildah.  This flag is  a  NOOP  and  provided
   solely for scripting compatibility.

   --dns=[]

   Set custom DNS servers.  Invalid if using --dns with --network=none.

   This option can be used to override the DNS configuration passed to the container. Typically this is necessary when the host DNS configuration is invalid for
   the container (e.g., 127.0.0.1). When this is the case the --dns flag is necessary for every run.

   The special value none can be specified to disable creation of /etc/resolv.conf in the container by Buildah. The /etc/resolv.conf file in the image  will  be
   used without changes.

   --dns-option=[]

   Set custom DNS options. Invalid if using --dns-option with --network=none.

   --dns-search=[]

   Set custom DNS search domains. Invalid if using --dns-search with --network=none.

   --env env[=value]

   Add  a value (e.g. env=value) to the built image.  Can be used multiple times.  If neither = nor a *value* are specified, but env is set in the current envi‐
   ronment, the value from the current environment will be added to the image.  To remove an environment variable from the built image, use the  --unsetenv  op‐
   tion.

   --file, -f Containerfile

   Specifies a Containerfile which contains instructions for building the image, either a local file or an http or https URL.  If more than one Containerfile is
   specified, FROM instructions will only be accepted from the first specified file.

   If a local file is specified as the Containerfile and it does not exist, the context directory will be prepended to the local file value.

   If you specify -f -, the Containerfile contents will be read from stdin.

   --force-rm bool-value

   Always remove intermediate containers after a build, even if the build fails (default false).

   --format

   Control the format for the built image's manifest and configuration data.  Recognized formats include oci (OCI image-spec v1.0, the default) and docker (ver‐
   sion 2, using schema format 2 for the manifest).

   Note: You can also override the default format by setting the BUILDAH_FORMAT environment variable.  export BUILDAH_FORMAT=docker

   --from

   Overrides the first FROM instruction within the Containerfile.  If there are multiple FROM instructions in a Containerfile, only the first is changed.

   --help, -h

   Print usage statement

   --hooks-dir path

   Each  *.json  file in the path configures a hook for buildah build containers. For more details on the syntax of the JSON files and the semantics of hook in‐
   jection. Buildah currently support both the 1.0.0 and 0.1.0 hook schemas, although the 0.1.0 schema is deprecated.

   This option may be set multiple times; paths from later options have higher precedence.

   For the annotation conditions, buildah uses any annotations set in the generated OCI configuration.

   For the bind-mount conditions, only mounts explicitly requested by the caller via --volume are considered. Bind mounts that buildah inserts by default  (e.g.
   /dev/shm) are not considered.

   If --hooks-dir is unset for root callers, Buildah will currently default to /usr/share/containers/oci/hooks.d and /etc/containers/oci/hooks.d in order of in‐
   creasing precedence. Using these defaults is deprecated, and callers should migrate to explicitly setting --hooks-dir.

   --http-proxy=true

   By default proxy environment variables are passed into the container if set for the buildah process.  This can be disabled by setting the --http-proxy option
   to false.  The environment variables passed in include http_proxy, https_proxy, ftp_proxy, no_proxy, and also the upper case versions of those.

   --identity-label bool-value

   Adds default identity label io.buildah.version if set. (default true).

   --ignorefile file

   Path to an alternative .containerignore (.dockerignore) file.

   --iidfile ImageIDfile

   Write the built image's ID to the file.  When --platform is specified more than once, attempting to use this option will trigger an error.

   --ipc how

   Sets  the configuration for IPC namespaces when handling RUN instructions.  The configured value can be "" (the empty string) or "container" to indicate that
   a new IPC namespace should be created, or it can be "host" to indicate that the IPC namespace in which buildah itself is being run should be  reused,  or  it
   can be the path to an IPC namespace which is already in use by another process.

   --isolation type

   Controls  what  type  of  isolation is used for running processes as part of RUN instructions.  Recognized types include oci (OCI-compatible runtime, the de‐
   fault), rootless (OCI-compatible runtime invoked using a modified configuration, with --no-new-keyring added to its create  invocation,  reusing  the  host's
   network  and  UTS namespaces, and creating private IPC, PID, mount, and user namespaces; the default for unprivileged users), and chroot (an internal wrapper
   that leans more toward chroot(1) than container technology, reusing the host's control group, network, IPC, and PID namespaces, and  creating  private  mount
   and UTS namespaces, and creating user namespaces only when they're required for ID mapping).

   Note: You can also override the default isolation type by setting the BUILDAH_ISOLATION environment variable.  export BUILDAH_ISOLATION=oci

   --jobs N

   Run  up to N concurrent stages in parallel.  If the number of jobs is greater than 1, stdin will be read from /dev/null.  If 0 is specified, then there is no
   limit on the number of jobs that run in parallel.

   --label label[=value]

   Add an image label (e.g. label=value) to the image metadata. Can be used multiple times.  If label is named, but neither = nor a value is provided, then  the
   label is set to an empty value.

   Users  can  set  a  special LABEL io.containers.capabilities=CAP1,CAP2,CAP3 in a Containerfile that specifies the list of Linux capabilities required for the
   container to run properly. This label specified in a container image tells container engines, like Podman, to run the container with just these capabilities.
   The container engine launches the container with just the specified capabilities, as long as this list of capabilities is a subset of the default list.

   If  the  specified capabilities are not in the default set, container engines should print an error message and will run the container with the default capa‐
   bilities.

   --layers bool-value

   Cache intermediate images during the build process (Default is false).

   Note: You can also override the default value of layers by setting the BUILDAH_LAYERS environment variable. export BUILDAH_LAYERS=true

   --logfile filename

   Log output which would be sent to standard output and standard error to the specified file instead of to standard output and standard error.

   --logsplit bool-value

   If --logfile and --platform is specified following flag allows end-users to split log file for each platform into different files with naming  convention  as
   ${logfile}_${platform-os}_${platform-arch}.

   --manifest listName

   Name  of the manifest list to which the built image will be added.  Creates the manifest list if it does not exist.  This option is useful for building multi
   architecture images.  If listName does not include a registry name component, the registry name localhost will be prepended to the list name.

   --memory, -m=""

   Memory limit (format: [], where unit = b, k, m or g)

   Allows you to constrain the memory available to a container. If the host supports swap memory, then the -m memory setting can be larger than physical RAM. If
   a  limit  of 0 is specified (not using -m), the container's memory is not limited. The actual limit may be rounded up to a multiple of the operating system's
   page size (the value would be very large, that's millions of trillions).

   --memory-swap="LIMIT"

   A limit value equal to memory plus swap. Must be used with the  -m (--memory) flag. The swap LIMIT should always be larger than -m (--memory) value.  By  de‐
   fault, the swap LIMIT will be set to double the value of --memory.

   The  format  of LIMIT is <number>[<unit>]. Unit can be b (bytes), k (kilobytes), m (megabytes), or g (gigabytes). If you don't specify a unit, b is used. Set
   LIMIT to -1 to enable unlimited swap.

   --network, --net=mode

   Sets the configuration for network namespaces when handling RUN instructions.

   Valid mode values are:

          • none: no networking. Invalid if using --dns, --dns-opt, or --dns-search;

          • host: use the host network stack. Note: the host mode gives the container full access to local system services such as D-bus and is  therefore  con‐
            sidered insecure;

          • ns:path: path to a network namespace to join;

          • private: create a new namespace for the container (default)

          • <network  name|ID>: Join the network with the given name or ID, e.g. use --network mynet to join the network with the name mynet. Only supported for
            rootful users.

   --no-cache

   Do not use existing cached images for the container build. Build from the start with a new set of cached layers.

   --no-hosts

   Do not create /etc/hosts for the container.

   By default, Buildah manages /etc/hosts, adding the container's own IP address.  --no-hosts disables this, and the image's /etc/hosts will be preserved unmod‐
   ified. Conflicts with the --add-host option.

   --omit-history bool-value

   Omit build history information in the built image. (default false).

   This option is useful for the cases where end users explicitly want to set --omit-history to omit the optional History from built images or when working with
   images built using build tools that do not include History information in their images.

   --os="OS"

   Set the OS of the image to be built, and that of the base image to be pulled, if the build uses one, instead of using the current  operating  system  of  the
   host.

   --os-feature feature

   Set  the  name  of a required operating system feature for the image which will be built.  By default, if the image is not based on scratch, the base image's
   required OS feature list is kept, if the base image specified any.  This option is typically only meaningful when the image's OS is Windows.

   If feature has a trailing -, then the feature is removed from the set of required features which will be listed in the image.

   --os-version version

   Set the exact required operating system version for the image which will be built.  By default, if the image is not based on scratch, the  base  image's  re‐
   quired OS version is kept, if the base image specified one.  This option is typically only meaningful when the image's OS is Windows, and is typically set in
   Windows base images, so using this option is usually unnecessary.

   --output, -o=""

   Output destination (format: type=local,dest=path)

   The --output (or -o) option extends the default behavior of building a container image by allowing users to export the contents of the image as files on  the
   local filesystem, which can be useful for generating local binaries, code generation, etc.

   The value for --output is a comma-separated sequence of key=value pairs, defining the output type and options.

   Supported keys are: - dest: Destination path for exported output. Valid value is absolute or relative path, - means the standard output.  - type: Defines the
   type of output to be used. Valid values is documented below.

   Valid type values are: - local: write the resulting build files to a directory on the client-side.  - tar: write the resulting  files  as  a  single  tarball
   (.tar).

   If  no type is specified, the value defaults to local.  Alternatively, instead of a comma-separated sequence, the value of --output can be just a destination
   (in the **dest** format) (e.g.--output some-path,--output -) where--output some-pathis treated as if **type=local** and--output -` is treated as if type=tar.

   --pid how

   Sets the configuration for PID namespaces when handling RUN instructions.  The configured value can be "" (the empty string) or "private" to indicate that  a
   new  PID namespace should be created, or it can be "host" to indicate that the PID namespace in which buildah itself is being run should be reused, or it can
   be the path to a PID namespace which is already in use by another process.

   --platform="OS/ARCH[/VARIANT]"

   Set the OS/ARCH of the built image (and its base image, if your build uses one) to the provided value instead of using the current operating system  and  ar‐
   chitecture of the host (for example linux/arm).

   The  --platform  flag  can be specified more than once, or given a comma-separated list of values as its argument.  When more than one platform is specified,
   the --manifest option should be used instead of the --tag option.

   OS/ARCH pairs are those used by the Go Programming Language.  In several cases the ARCH value for a platform differs from one produced by other tools such as
   the  arch  command.  Valid OS and architecture name combinations are listed as values for $GOOS and $GOARCH at https://golang.org/doc/install/source#environ‐
   ment, and can also be found by running go tool dist list.

   While buildah bud is happy to use base images and build images for any platform that exists, RUN instructions will not be able to succeed without the help of
   emulation provided by packages like qemu-user-static.

   NOTE: The --platform option may not be used in combination with the --arch, --os, or --variant options.

   --pull

   When  the  flag  is enabled or set explicitly to true (with --pull=true), attempt to pull the latest image from the registries listed in registries.conf if a
   local image does not exist or the image is newer than the one in storage. Raise an error if the image is not in any listed registry and is  not  present  lo‐
   cally.

   If  the flag is disabled (with --pull=false), do not pull the image from the registry, use only the local version. Raise an error if the image is not present
   locally.

   If the pull flag is set to always (with --pull=always), pull the image from the first registry it is found in as listed in registries.conf.  Raise  an  error
   if not found in the registries, even if the image is present locally.

   If the pull flag is set to never (with --pull=never), Do not pull the image from the registry, use only the local version. Raise an error if the image is not
   present locally.

   Defaults to true.

   --quiet, -q

   Suppress output messages which indicate which instruction is being processed, and of progress when pulling images from a registry, and when writing the  out‐
   put image.

   --retry attempts

   Number of times to retry in case of failure when performing push/pull of images to/from registry.

   Defaults to 3.

   --retry-delay duration

   Duration of delay between retry attempts in case of failure when performing push/pull of images to/from registry.

   Defaults to 2s.

   --rm bool-value

   Remove intermediate containers after a successful build (default true).

   --runtime path

   The  path  to an alternate OCI-compatible runtime, which will be used to run commands specified by the RUN instruction. Default is runc, or crun when machine
   is configured to use cgroups V2.

   Note: You can also override the default runtime by setting the BUILDAH_RUNTIME environment variable.  export BUILDAH_RUNTIME=/usr/bin/crun

   --runtime-flag flag

   Adds global flags for the container rutime. To list the supported flags, please consult the manpages of the selected container runtime.

   Note: Do not pass the leading -- to the flag. To pass the runc flag --log-format json to buildah build, the option given  would  be  --runtime-flag  log-for‐
   mat=json.

   --secret=id=id,src=path

   Pass secret information to be used in the Containerfile for building images in a safe way that will not end up stored in the final image, or be seen in other
   stages.  The secret will be mounted in the container at the default location of /run/secrets/id.

   To later use the secret, use the --mount flag in a RUN instruction within a Containerfile:

   RUN --mount=type=secret,id=mysecret cat /run/secrets/mysecret

   --security-opt=[]

   Security Options

   "apparmor=unconfined" : Turn off apparmor confinement for the container
     "apparmor=your-profile" : Set the apparmor confinement profile for the container

   "label=user:USER"   : Set the label user for the container
     "label=role:ROLE"   : Set the label role for the container
     "label=type:TYPE"   : Set the label type for the container
     "label=level:LEVEL" : Set the label level for the container
     "label=disable"     : Turn off label confinement for the container
     "no-new-privileges" : Not supported

   "seccomp=unconfined" : Turn off seccomp confinement for the container
     "seccomp=profile.json :  White listed syscalls seccomp Json file to be used as a seccomp filter

   --shm-size=""

   Size of /dev/shm. The format is <number><unit>. number must be greater than 0.  Unit is optional and can be b (bytes), k (kilobytes), m(megabytes), or g (gi‐
   gabytes).  If you omit the unit, the system uses bytes. If you omit the size entirely, the system uses 64m.

   --sign-by fingerprint

   Sign the built image using the GPG key that matches the specified fingerprint.

   --skip-unused-stages bool-value

   Skip stages in multi-stage builds which don't affect the target stage. (Default is true).

   --squash

   Squash all of the image's new layers into a single new layer; any preexisting layers are not squashed.

   --ssh=default|id[=socket>|[,]

   SSH agent socket or keys to expose to the build.  The socket path can be left empty to use the value of default=$SSH_AUTH_SOCK

   To later use the ssh agent, use the --mount flag in a RUN instruction within a Containerfile:

   RUN --mount=type=secret,id=id mycmd

   --stdin

   Pass stdin into the RUN containers. Sometimes commands being RUN within a Containerfile want to request information from the user. For example apt asking for
   a confirmation for install.  Use --stdin to be able to interact from the terminal during the build.

   --tag, -t imageName

   Specifies the name which will be assigned to the resulting image if the build process completes successfully.  If imageName does not include a registry  name
   component, the registry name localhost will be prepended to the image name.

   --target stageName

   Set  the  target build stage to build.  When building a Containerfile with multiple build stages, --target can be used to specify an intermediate build stage
   by name as the final stage for the resulting image.  Commands after the target stage will be skipped.

   --timestamp seconds

   Set the create timestamp to seconds since epoch to allow for deterministic builds (defaults to current time).  By default, the created timestamp  is  changed
   and  written  into  the image manifest with every commit, causing the image's sha256 hash to be different even if the sources are exactly the same otherwise.
   When --timestamp is set, the created timestamp is always set to the time specified and therefore not changed, allowing the image's sha256 to remain the same.
   All files committed to the layers of the image will be created with the timestamp.

   --tls-verify bool-value

   Require  HTTPS  and verification of certificates when talking to container registries (defaults to true).  TLS verification cannot be used when talking to an
   insecure registry.

   --ulimit type=soft-limit[:hard-limit]

   Specifies resource limits to apply to processes launched when processing RUN instructions.  This option can be specified multiple times.  Recognized resource
   types include:
     "core": maximum core dump size (ulimit -c)
     "cpu": maximum CPU time (ulimit -t)
     "data": maximum size of a process's data segment (ulimit -d)
     "fsize": maximum size of new files (ulimit -f)
     "locks": maximum number of file locks (ulimit -x)
     "memlock": maximum amount of locked memory (ulimit -l)
     "msgqueue": maximum amount of data in message queues (ulimit -q)
     "nice": niceness adjustment (nice -n, ulimit -e)
     "nofile": maximum number of open files (ulimit -n)
     "nofile": maximum number of open files (1048576); when run by root
     "nproc": maximum number of processes (ulimit -u)
     "nproc": maximum number of processes (1048576); when run by root
     "rss": maximum size of a process's (ulimit -m)
     "rtprio": maximum real-time scheduling priority (ulimit -r)
     "rttime": maximum amount of real-time execution between blocking syscalls
     "sigpending": maximum number of pending signals (ulimit -i)
     "stack": maximum stack size (ulimit -s)

   --unsetenv env

   Unset environment variables from the final image.

   --userns how

   Sets  the configuration for user namespaces when handling RUN instructions.  The configured value can be "" (the empty string) , "private" or "auto" to indi‐
   cate that a new user namespace should be created, it can be "host" to indicate that the user namespace in which buildah itself is being run should be reused,
   or it can be the path to an user namespace which is already in use by another process.

   auto: automatically create a unique user namespace.

   The --userns=auto flag, requires that the user name containers and a range of subordinate user ids that the build container is allowed to use be specified in
   the /etc/subuid and /etc/subgid files.

   Example: containers:2147483647:2147483648.

   Buildah allocates unique ranges of UIDs and GIDs from the containers subordinate user ids. The size of the ranges is based on the number of UIDs required  in
   the image. The number of UIDs and GIDs can be overridden with the size option.

   Valid auto options:

          • gidmapping=CONTAINER_GID:HOST_GID:SIZE: to force a GID mapping to be present in the user namespace.

          • size=SIZE:  to specify an explicit size for the automatic user namespace. e.g. --userns=auto:size=8192. If size is not specified, auto will estimate
            a size for the user namespace.

          • uidmapping=CONTAINER_UID:HOST_UID:SIZE: to force a UID mapping to be present in the user namespace.

   --userns-gid-map-group group

   Specifies that a GID mapping which should be used to set ownership, at the filesystem level, on the working container's contents, can be found in entries  in
   the  /etc/subgid file which correspond to the specified group.  Commands run when handling RUN instructions will default to being run in their own user name‐
   spaces, configured using the UID and GID maps.  If --userns-uid-map-user is specified, but --userns-gid-map-group is not specified, buildah will assume  that
   the specified user name is also a suitable group name to use as the default setting for this option.

   Users can specify the maps directly using --userns-gid-map described in the buildah(1) man page.

   NOTE: When this option is specified by a rootless user, the specified mappings are relative to the rootless usernamespace in the container, rather than being
   relative to the host as it would be when run rootful.

   --userns-uid-map-user user

   Specifies that a UID mapping which should be used to set ownership, at the filesystem level, on the working container's contents, can be found in entries  in
   the  /etc/subuid  file which correspond to the specified user.  Commands run when handling RUN instructions will default to being run in their own user name‐
   spaces, configured using the UID and GID maps.  If --userns-gid-map-group is specified, but --userns-uid-map-user is not specified, buildah will assume  that
   the specified group name is also a suitable user name to use as the default setting for this option.

   Users can specify the maps directly using --userns-uid-map described in the buildah(1) man page.

   NOTE: When this option is specified by a rootless user, the specified mappings are relative to the rootless usernamespace in the container, rather than being
   relative to the host as it would be when run rootful.

   --uts how

   Sets the configuration for UTS namespaces when handling RUN instructions.  The configured value can be "" (the empty string) or "container" to indicate  that
   a  new  UTS  namespace should be created, or it can be "host" to indicate that the UTS namespace in which buildah itself is being run should be reused, or it
   can be the path to a UTS namespace which is already in use by another process.

   --variant=""

   Set the architecture variant of the image to be pulled.

   --volume, -v[=[HOST-DIR:CONTAINER-DIR[:OPTIONS]]]

   Mount a host directory into containers when executing RUN instructions during the build.  The OPTIONS are a comma delimited list and can be: [1] ⟨#Footnote1⟩

          • [rw|ro]

          • [U]

          • [z|Z|O]

          • [[r]shared|[r]slave|[r]private]

   The CONTAINER-DIR must be an absolute path such as /src/docs. The HOST-DIR must be an absolute path as well. Buildah bind-mounts the HOST-DIR to the path you
   specify.  For  example, if you supply /foo as the host path, Buildah copies the contents of /foo to the container filesystem on the host and bind mounts that
   into the container.

   You can specify multiple  -v options to mount one or more mounts to a container.

   Write Protected Volume Mounts

   You can add the :ro or :rw suffix to a volume to mount it read-only or read-write mode, respectively. By default, the volumes are  mounted  read-write.   See
   examples.

   Chowning Volume Mounts

   By  default,  Buildah does not change the owner and group of source volume directories mounted into containers. If a container is created in a new user name‐
   space, the UID and GID in the container may correspond to another UID and GID on the host.

   The :U suffix tells Buildah to use the correct host UID and GID based on the UID and GID within the container, to change the owner and group  of  the  source
   volume.

   Labeling Volume Mounts

   Labeling  systems  like  SELinux require that proper labels are placed on volume content mounted into a container. Without a label, the security system might
   prevent the processes running inside the container from using the content. By default, Buildah does not change the labels set by the OS.

   To change a label in the container context, you can add either of two suffixes :z or :Z to the volume mount. These suffixes tell Buildah to relabel file  ob‐
   jects  on  the shared volumes. The z option tells Buildah that two containers share the volume content. As a result, Buildah labels the content with a shared
   content label. Shared volume labels allow all containers to read/write content.  The Z option tells Buildah to label the content with a private unshared  la‐
   bel.  Only the current container can use a private volume.

   Overlay Volume Mounts

   The  :O  flag tells Buildah to mount the directory from the host as a temporary storage using the Overlay file system. The RUN command containers are allowed
   to modify contents within the mountpoint and are stored in the container storage in a separate directory.  In Overlay FS terms the source directory  will  be
   the  lower,  and  the  container storage directory will be the upper. Modifications to the mount point are destroyed when the RUN command finishes executing,
   similar to a tmpfs mount point.

   Any subsequent execution of RUN commands sees the original source directory content, any changes from previous RUN commands no longer exist.

   One use case of the overlay mount is sharing the package cache from the host into the container to allow speeding up builds.

   Note:

           - The `O` flag is not allowed to be specified with the `Z` or `z` flags. Content mounted into the container is labeled with the private label.
             On SELinux systems, labels in the source directory must be readable by the container label. If not, SELinux container separation must be disabled for the container to work.
           - Modification of the directory volume mounted into the container with an overlay mount can cause unexpected failures.  It is recommended that you do not modify the directory until the container finishes running.

   By default bind mounted volumes are private. That means any mounts done inside container will not be visible on the host and vice versa. This behavior can be
   changed by specifying a volume mount propagation property.

   When  the mount propagation policy is set to shared, any mounts completed inside the container on that volume will be visible to both the host and container.
   When the mount propagation policy is set to slave, one way mount propagation is enabled and any mounts completed on the host for that volume will be  visible
   only  inside  of  the  container.  To control the mount propagation property of the volume use the :[r]shared, :[r]slave or :[r]private propagation flag. The
   propagation property can be specified only for bind mounted volumes and not for internal volumes or named volumes. For  mount  propagation  to  work  on  the
   source  mount  point  (the  mount point where source dir is mounted on) it has to have the right propagation properties. For shared volumes, the source mount
   point has to be shared. And for slave volumes, the source mount has to be either shared or slave. [1] ⟨#Footnote1⟩

   Use df <source-dir> to determine the source mount and then use findmnt -o TARGET,PROPAGATION <source-mount-dir> to determine propagation properties of source
   mount,  if findmnt utility is not available, the source mount point can be determined by looking at the mount entry in /proc/self/mountinfo. Look at optional
   fields and see if any propagation properties are specified.  shared:X means the mount is shared, master:X means the mount is slave and if  nothing  is  there
   that means the mount is private. [1] ⟨#Footnote1⟩

   To  change  propagation properties of a mount point use the mount command. For example, to bind mount the source directory /foo do mount --bind /foo /foo and
   mount --make-private --make-shared /foo. This will convert /foo into a shared mount point.  The propagation properties of the source mount can be changed di‐
   rectly. For instance if / is the source mount for /foo, then use mount --make-shared / to convert / into a shared mount.

BUILD TIME VARIABLES

   The  ENV  instruction in a Containerfile can be used to define variable values.  When the image is built, the values will persist in the container image.  At
   times it is more convenient to change the values in the Containerfile via a command-line option rather than changing the values within the Containerfile  it‐
   self.

   The  following  variables  can be used in conjunction with the --build-arg option to override the corresponding values set in the Containerfile using the ENV
   instruction.

          • HTTP_PROXY

          • HTTPS_PROXY

          • FTP_PROXY

          • NO_PROXY

   Please refer to the Using Build Time Variables ⟨#using-build-time-variables⟩ section of the Examples.

EXAMPLE Build an image using local Containerfiles

   buildah build .

   buildah build -f Containerfile .

   cat ~/Containerfile | buildah build -f - .

   buildah build -f Containerfile.simple -f Containerfile.notsosimple .

   buildah build --timestamp=$(date '+%s') -t imageName .

   buildah build -t imageName .

   buildah build --tls-verify=true -t imageName -f Containerfile.simple .

   buildah build --tls-verify=false -t imageName .

   buildah build --runtime-flag log-format=json .

   buildah build -f Containerfile --runtime-flag debug .

   buildah build --authfile /tmp/auths/myauths.json --cert-dir ~/auth --tls-verify=true --creds=username:password -t imageName -f Containerfile.simple .

   buildah build --memory 40m --cpu-period 10000 --cpu-quota 50000 --ulimit nofile=1024:1028 -t imageName .

   buildah build --security-opt label=level:s0:c100,c200 --cgroup-parent /path/to/cgroup/parent -t imageName .

   buildah build --arch=arm --variant v7 -t imageName .

   buildah build --volume /home/test:/myvol:ro,Z -t imageName .

   buildah build -v /home/test:/myvol:z,U -t imageName .

   buildah build -v /var/lib/dnf:/var/lib/dnf:O -t imageName .

   buildah build --layers -t imageName .

   buildah build --no-cache -t imageName .

   buildah build -f Containerfile --layers --force-rm -t imageName .

   buildah build --no-cache --rm=false -t imageName .

   buildah build --dns-search=example.com --dns=223.5.5.5 --dns-option=use-vc .

   buildah build -f Containerfile.in --cpp-flag="-DDEBUG" -t imageName .

   buildah build --network mynet .

   buildah build --env LANG=en_US.UTF-8 -t imageName .

   buildah build --env EDITOR -t imageName .

   buildah build --unsetenv LANG -t imageName .

   buildah build --os-version 10.0.19042.1645 -t imageName .

   buildah build --os-feature win32k -t imageName .

   buildah build --os-feature win32k- -t imageName .

Building an multi-architecture image using the --manifest option (requires emulation software)

   buildah build --arch arm --manifest myimage /tmp/mysrc

   buildah build --arch amd64 --manifest myimage /tmp/mysrc

   buildah build --arch s390x --manifest myimage /tmp/mysrc

   buildah bud --platform linux/s390x,linux/ppc64le,linux/amd64 --manifest myimage /tmp/mysrc

   buildah bud --platform linux/arm64 --platform linux/amd64 --manifest myimage /tmp/mysrc

   buildah bud --all-platforms --manifest myimage /tmp/mysrc

Building an image using (--output) custom build output

   buildah build -o out .

   buildah build --output type=local,dest=out .

   buildah build --output type=tar,dest=out.tar .

   buildah build -o - . > out.tar

Building an image using a URL

   This will clone the specified GitHub repository from the URL and use it as context. The Containerfile or Dockerfile at the root of the repository is used  as
   the context of the build. This only works if the GitHub repository is a dedicated repository.

   buildah build https://github.com/scollier/purpletest

   Note:   Github   does   not   support   using   git://   for   performing   clone   operation   due   to   recent   changes   in   their   security  guidance
   (https://github.blog/2021-09-01-improving-git-protocol-security-github/). Use an https:// URL if the source repository is hosted on Github.

Building an image using a URL to a tarball'ed context

   Buildah will fetch the tarball archive, decompress it and use its contents as the build context.  The Containerfile or Dockerfile at the root of the  archive
   and  the  rest  of  the archive will get used as the context of the build. If you pass an -f PATH/Containerfile option as well, the system will look for that
   file inside the contents of the tarball.

   buildah build -f dev/Containerfile https://10.10.10.1/buildah/context.tar.gz

   Note: supported compression formats are 'xz', 'bzip2', 'gzip' and 'identity' (no compression).

Using Build Time Variables Replace the value set for the HTTP_PROXY environment variable within the Containerfile.

   buildah build --build-arg=HTTP_PROXY="http://127.0.0.1:8321"

ENVIRONMENT

   BUILD_REGISTRY_SOURCES

   BUILD_REGISTRY_SOURCES, if set, is treated as a JSON object which contains lists of registry names under the keys insecureRegistries, blockedRegistries,  and
   allowedRegistries.

   When  pulling an image from a registry, if the name of the registry matches any of the items in the blockedRegistries list, the image pull attempt is denied.
   If there are registries in the allowedRegistries list, and the registry's name is not in the list, the pull attempt is denied.

   TMPDIR The TMPDIR environment variable allows the user to specify where temporary files are stored while pulling and pushing images.  Defaults to '/var/tmp'.

Files .containerignore/.dockerignore

   If the .containerignore/.dockerignore file exists in the context directory, buildah build reads its contents. If both exist, then .containerignore  is  used.
   Use  the  --ignorefile  flag to override the ignore file path location. Buildah uses the content to exclude files and directories from the context directory,
   when executing COPY and ADD directives in the Containerfile/Dockerfile

   Users can specify a series of Unix shell globals in a

   Buildah supports a special wildcard string ** which matches any number of directories (including zero). For example, */.go will exclude all  files  that  end
   with .go that are found in all directories.

   Example .containerignore file:

          # exclude this content for image
          */*.c
          **/output*
          src

   */*.c Excludes files and directories whose names end with .c in any top level subdirectory. For example, the source file include/rootless.c.

   **/output* Excludes files and directories starting with output from any directory.

   src Excludes files named src and the directory src as well as any content in it.

   Lines  starting  with ! (exclamation mark) can be used to make exceptions to exclusions. The following is an example .containerignore/.dockerignore file that
   uses this mechanism:

          *.doc
          !Help.doc

   Exclude all doc files except Help.doc from the image.

   This functionality is compatible with the handling of .containerignore files described here:

   https://github.com/containers/buildah/blob/main/docs/containerignore.5.md

   registries.conf (/etc/containers/registries.conf)

   registries.conf is the configuration file which specifies which container registries should be consulted when completing image names which do not  include  a
   registry or domain portion.

   policy.json (/etc/containers/policy.json)

   Signature  policy  file.   This defines the trust policy for container images.  Controls which container registries can be used for image, and whether or not
   the tool should trust the images.

SEE ALSO

   buildah(1), cpp(1), buildah-login(1), docker-login(1), namespaces(7), pid_namespaces(7), containers-policy.json(5), containers-registries.conf(5), user_name‐
   spaces(7), crun(1), runc(8)

FOOTNOTES

   1:  The Buildah project is committed to inclusivity, a core value of open source. The master and slave mount propagation terminology used here is problematic
   and divisive, and should be changed. However, these terms are currently used within the Linux kernel and must be used as-is at this  time.  When  the  kernel
   maintainers rectify this usage, Buildah will follow suit immediately.

buildah April 2017 buildah-build(1)