path: root/docs/source/markdown/podman-build.1.md.in

% podman-build 1

## NAME
podman\-build - Build a container image using a Containerfile

## SYNOPSIS
**podman build** [*options*] [*context*]

**podman image build** [*options*] [*context*]

## DESCRIPTION
**podman build** 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 Podman will assume the current
working directory as the build context, which should contain the 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`.

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 Containerfile is downloaded to a temporary
location.

When a Git repository is set as the URL, the repository is cloned locally and
then set as the context.

NOTE: `podman build` uses code sourced from the `Buildah` project to build
container images.  This `Buildah` code creates `Buildah` containers for the
`RUN` options in container storage. In certain situations, when the
`podman build` crashes or users kill the `podman build` process, these external
containers can be left in container storage. Use the `podman ps --all --storage`
command to see these containers. External containers can be removed with the
`podman rm --storage` command.

`podman buildx build` command is an alias of `podman build`.  Not all `buildx build` features are available in Podman. The `buildx build` option is provided for scripting compatibility.

## OPTIONS

@@option add-host

#### **--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 detection to work usefully.

#### **--annotation**=*annotation*

Add an image *annotation* (e.g. annotation=*value*) to the image metadata. Can
be used multiple times.

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

#### **--arch**=*arch*

Set the architecture 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
architecture of the build host. Unless overridden, subsequent lookups of the
same image in the local storage will match this architecture, regardless of the
host. (Examples: arm, arm64, 386, amd64, ppc64le, s390x)

@@option authfile

#### **--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.

#### **--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
different stages in COPY instruction.

Valid values could be:

* Local directory – e.g. --build-context project2=../path/to/project2/src (This option is not available with the remote Podman client. On Podman machine setup (i.e macOS and Winows) path must exists on the machine VM)
* 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-image://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:

```dockerfile
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

```bash
# 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

```bash
# 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**

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.

#### **--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 capabilities 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\_CHOWN, CAP\_DAC\_OVERRIDE, CAP\_FOWNER,
CAP\_FSETID, CAP\_KILL, 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.

@@option cert-dir

@@option cgroup-parent

#### **--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.
Podman doesn't communicate with a daemon or a remote server.
Thus, compressing the data before sending it is irrelevant to Podman. (This option is not available with the remote Podman client, including Mac and Windows (excluding WSL2) machines)

#### **--cpp-flag**=*flags*

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 BUILDAH_CPPFLAGS="-DDEBUG").

@@option cpu-period

@@option cpu-quota

@@option cpu-shares

@@option cpuset-cpus

@@option cpuset-mems

@@option creds

#### **--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.

@@option 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)](https://github.com/containers/crun/tree/main/crun.1.md)** runtime offers a
workaround 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 setting,
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**.

@@option disable-content-trust

#### **--dns**=*dns*

Set custom DNS servers to be used during the build.

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`
option is necessary for every run.

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

#### **--dns-option**=*option*

Set custom DNS options to be used during the build.

#### **--dns-search**=*domain*

Set custom DNS search domains to be used during the build.

#### **--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
environment, the value from the current environment will be added to the image.
To remove an environment variable from the built image, use the `--unsetenv`
option.

#### **--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 build context is not specified, and at least one Containerfile is a
local file, the directory in which it resides will be used as the build
context.

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

#### **--force-rm**

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

#### **--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* (version 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.

With the remote podman client, not all container transports will work as
expected. For example, oci-archive:/x.tar will reference /x.tar on the remote
machine instead of on the client. If you need to support remote podman clients,
it is best to restrict yourself to containers-storage: and docker://
transports.

#### **--help**, **-h**

Print usage statement

#### **--http-proxy**

Pass through HTTP Proxy environment variables.

#### **--identity-label**

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

#### **--ignorefile**

Path to an alternative .containerignore 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 `podman` 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
default), *rootless* (OCI-compatible runtime invoked using a modified
configuration and its --rootless option enabled, with *--no-new-keyring
--no-pivot* added to its *create* invocation, with network and UTS namespaces
disabled, and IPC, PID, and user namespaces enabled; the default for
unprivileged users), and *chroot* (an internal wrapper that leans more toward
chroot(1) than container technology).

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

#### **--jobs**=*number*

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 in the number of jobs that run in parallel.

#### **--label**=*label*

Add an image *label* (e.g. label=*value*) to the image metadata. Can be used
multiple times.

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
Podman to run the container with just these capabilities. Podman 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, Podman will
print an error message and will run the container with the default capabilities.

#### **--layers**

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

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.
This option is not supported on the remote client, including Mac and Windows
(excluding WSL2) machines.

#### **--logsplit**=*bool-value*

If `--logfile` and `--platform` are specified, the `--logsplit` option allows
end-users to split the log file for each platform into different files in the
following format: `${logfile}_${platform-os}_${platform-arch}`.
This option is not supported on the remote client, including Mac and Windows
(excluding WSL2) machines.

#### **--manifest**=*manifest*

Name of the manifest list to which the image will be added. Creates the manifest list
if it does not exist. This option is useful for building multi architecture images.

@@option memory

@@option memory-swap

#### **--network**=*mode*, **--net**

Sets the configuration for network namespaces when handling `RUN` instructions.

Valid _mode_ values are:

- **none**: no networking.
- **host**: use the Podman host network stack. Note: the host mode gives the
container full access to local system services such as D-bus and is therefore
considered 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.

@@option no-hosts

This option conflicts with **--add-host**.

#### **--omit-history**

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**=*string*

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
build host. Unless overridden, subsequent lookups of the same image in the
local storage will match this OS, regardless 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
required 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-opts*

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. (This option is not available with the remote Podman client, including Mac and Windows (excluding WSL2) machines)

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-path` is treated as if **type=local** and `--output -` is treated as if **type=tar**.

#### **--pid**=*pid*

Sets the configuration for PID namespaces when handling `RUN` instructions.
The configured value can be "" (the empty string) or "container" to indicate
that a new PID namespace should be created, or it can be "host" to indicate
that the PID namespace in which `podman` 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
architecture of the host (for example `linux/arm`).  Unless overridden,
subsequent lookups of the same image in the local storage will match this
platform, regardless of the host.

If `--platform` is set, then the values of the `--arch`, `--os`, and
`--variant` options will be overridden.

The `--platform` option 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#environment,
and can also be found by running `go tool dist list`.

While `podman build` 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`.

#### **--pull**=*policy*

Pull image policy. The default is **always**.

- **always**, **true**: Always pull the image and throw an error if the pull fails.
- **missing**: Pull the image only if it could not be found in the local containers storage.  Throw an error if no image could be found and the pull fails.
- **never**, **false**: Never pull the image but use the one from the local containers storage.  Throw an error if no image could be found.
- **newer**: Pull if the image on the registry is newer than the one in the local containers storage.  An image is considered to be newer when the digests are different.  Comparing the time stamps is prone to errors.  Pull errors are suppressed if a local image was found.

#### **--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
output image.

#### **--rm**

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.

Note: You can also override the default runtime by setting the BUILDAH\_RUNTIME
environment variable.  `export BUILDAH_RUNTIME=/usr/local/bin/runc`

#### **--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 option in a `RUN` instruction within a `Containerfile`:

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

#### **--security-opt**=*option*

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 processes
- `label=role:ROLE`     : Set the label role for the container processes
- `label=type:TYPE`     : Set the label process type for the container processes
- `label=level:LEVEL`   : Set the label level for the container processes
- `label=filetype:TYPE` : Set the label file type for the container files
- `label=disable`       : Turn off label separation 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*

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

#### **--sign-by**=*fingerprint*

Sign the image using a GPG key with the specified FINGERPRINT. (This option is not available with the remote Podman client, including Mac and Windows (excluding WSL2) machines,)

#### **--squash**

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

#### **--squash-all**

Squash all of the new image's layers (including those inherited from a base
image) into a single new layer.

#### **--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 option in a `RUN` instruction within a `Containerfile`:

`RUN --mount=type=ssh,id=id mycmd`

#### **--stdin**

Pass stdin into the RUN containers. Sometime 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, 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 hash to remain the
same. All files committed to the layers of the image will be created with the
timestamp.

If the only instruction in a Containerfile is `FROM`, this flag has no effect.

#### **--tls-verify**

Require HTTPS and verify certificates when talking to container registries
(defaults to true). (This option is not available with the remote Podman client, including Mac and Windows (excluding WSL2) machines)

#### **--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)
  "nproc": maximum number of processes (ulimit -u)
  "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) or "container" to indicate
that a new user namespace should be created, it can be "host" to indicate that
the user namespace in which `podman` itself is being run should be reused, or
it can be the path to a user namespace which is already in use by another
process.

#### **--userns-gid-map**=*mapping*

Directly specifies a GID mapping which should be used to set ownership, at the
filesystem level, on the working container's contents.
Commands run when handling `RUN` instructions will default to being run in
their own user namespaces, configured using the UID and GID maps.

Entries in this map take the form of one or more triples of a starting
in-container GID, a corresponding starting host-level GID, and the number of
consecutive IDs which the map entry represents.

This option overrides the *remap-gids* setting in the *options* section of
/etc/containers/storage.conf.

If this option is not specified, but a global --userns-gid-map setting is
supplied, settings from the global option will be used.

If none of --userns-uid-map-user, --userns-gid-map-group, or --userns-gid-map
are specified, but --userns-uid-map is specified, the GID map will be set to
use the same numeric values as the UID map.

#### **--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 namespaces, configured using the UID and GID maps.
If --userns-uid-map-user is specified, but --userns-gid-map-group is not
specified, `podman` will assume that the specified user name is also a
suitable group name to use as the default setting for this option.

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

#### **--userns-uid-map**=*mapping*

Directly specifies a UID mapping which should be used to set ownership, at the
filesystem level, on the working container's contents.
Commands run when handling `RUN` instructions will default to being run in
their own user namespaces, configured using the UID and GID maps.

Entries in this map take the form of one or more triples of a starting
in-container UID, a corresponding starting host-level UID, and the number of
consecutive IDs which the map entry represents.

This option overrides the *remap-uids* setting in the *options* section of
/etc/containers/storage.conf.

If this option is not specified, but a global --userns-uid-map setting is
supplied, settings from the global option will be used.

If none of --userns-uid-map-user, --userns-gid-map-group, or --userns-uid-map
are specified, but --userns-gid-map is specified, the UID map will be set to
use the same numeric values as the GID map.

#### **--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 namespaces, configured using the UID and GID maps.
If --userns-gid-map-group is specified, but --userns-uid-map-user is not
specified, `podman` will assume that the specified group name is also a
suitable user name to use as the default setting for this option.

**NOTE:** When this option is specified by a rootless user, the specified
mappings are relative to the rootless user namespace 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 `podman` 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**=*variant*

Set the architecture variant 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 architecture variant of the build host.

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

Create a bind mount. If you specify `-v /HOST-DIR:/CONTAINER-DIR`, Podman
bind mounts `/HOST-DIR` in the host to `/CONTAINER-DIR` in the Podman
container. (This option is not available with the remote Podman client,
including Mac and Windows (excluding WSL2) machines)

The `OPTIONS` are a comma-separated list and can be: <sup>[[1]](#Footnote1)</sup>

   * [rw|ro]
   * [z|Z|O]
   * [U]
   * [`[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. Podman bind-mounts the `HOST-DIR` to the
path you specify. For example, if you supply `/foo` as the host path,
Podman 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.

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, Podman does not change the owner and group of source volume
directories mounted. When running using user namespaces, the UID and GID inside
the namespace may correspond to another UID and GID on the host.

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

**Warning** use with caution since this will modify the host filesystem.

  `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, Podman 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 Podman to relabel file
objects on the shared volumes. The `z` option tells Podman that two containers
share the volume content. As a result, Podman labels the content with a shared
content label. Shared volume labels allow all containers to read/write content.
The `Z` option tells Podman to label the content with a private unshared label.
Only the current container can use a private volume.

Note: Do not relabel system files and directories. Relabeling system content
might cause other confined services on your machine to fail.  For these types
of containers, disabling SELinux separation is recommended.  The option
`--security-opt label=disable` disables SELinux separation for the container.
For example, if a user wanted to volume mount their entire home directory into the build containers, they need to disable SELinux separation.

	   $ podman build --security-opt label=disable -v $HOME:/home/user .

  `Overlay Volume Mounts`

   The `:O` flag tells Podman 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 exists.

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

  Note:

     - Overlay mounts are not currently supported in rootless mode.
     - 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 needs to 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 containers 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 volume use the `:[r]shared`, `:[r]slave` or `:[r]private`
propagation flag. For mount propagation to work on the source mount point (mount
point where source dir is mounted on) 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. <sup>[[1]](#Footnote1)</sup>

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`. <sup>[[1]](#Footnote1)</sup>

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 directly. For instance if `/` is the source
mount for `/foo`, then use `mount --make-shared /` to convert `/` into a
`shared` mount.

## EXAMPLES

### Build an image using local Containerfiles

```
$ podman build .

$ podman build -f Containerfile.simple .

$ cat $HOME/Containerfile | podman build -f - .

$ podman build -f Containerfile.simple -f Containerfile.notsosimple .

$ podman build -f Containerfile.in $HOME

$ podman build -t imageName .

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

$ podman build --tls-verify=false -t imageName .

$ podman build --runtime-flag log-format=json .

$ podman build --runtime-flag debug .

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

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

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

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

$ podman build -v /var/lib/yum:/var/lib/yum:O -t imageName .

$ podman build --layers -t imageName .

$ podman build --no-cache -t imageName .

$ podman build --layers --force-rm -t imageName .

$ podman build --no-cache --rm=false -t imageName .

$ podman build --network mynet .
```

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

```
$ podman build --arch arm --manifest myimage /tmp/mysrc

$ podman build --arch amd64 --manifest myimage /tmp/mysrc

$ podman build --arch s390x --manifest myimage /tmp/mysrc

$ podman build --platform linux/s390x,linux/ppc64le,linux/amd64 --manifest myimage /tmp/mysrc

$ podman build --platform linux/arm64 --platform linux/amd64 --manifest myimage /tmp/mysrc
```

### Building an image using a URL, Git repo, or archive

  The build context directory can be specified as a URL to a Containerfile, a
Git repository, or URL to an archive. If the URL is a Containerfile, it is
downloaded to a temporary location and used as the context. When a Git
repository is set as the URL, the repository is cloned locally to a temporary
location and then used as the context. Lastly, if the URL is an archive, it is
downloaded to a temporary location and extracted before being used as the
context.

#### Building an image using a URL to a Containerfile

  Podman will download the Containerfile to a temporary location and then use
it as the build context.

```
$ podman build https://10.10.10.1/podman/Containerfile
```

#### Building an image using a Git repository

  Podman will clone the specified GitHub repository to a temporary location and
use it as the context. The Containerfile at the root of the repository will be
used and it only works if the GitHub repository is a dedicated repository.

```
$ podman 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 an archive

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

```
$ podman build -f dev/Containerfile https://10.10.10.1/podman/context.tar.gz
```

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

## Files

### .containerignore/.dockerignore

If the file *.containerignore* or *.dockerignore* exists in the context directory,
`podman build` reads its contents. Use the `--ignorefile` option to override the
.containerignore path location.
Podman uses the content to exclude files and directories from the context
directory, when executing COPY and ADD directives in the
Containerfile/Dockerfile

The .containerignore and .dockerignore files use the same syntax; if both
are in the context directory, podman build will only use .containerignore.

Users can specify a series of Unix shell globs in a .containerignore file to
identify files/directories to exclude.

Podman 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 ends 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 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/common/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.

## Troubleshooting

### lastlog sparse file

If you are using a useradd command within a Containerfile with a large UID/GID,
it will create a large sparse file `/var/log/lastlog`.  This can cause the
build to hang forever.  Go language does not support sparse files correctly,
which can lead to some huge files being created in your container image.

If you are using `useradd` within your build script, you should pass the
`--no-log-init or -l` option to the `useradd` command.  This option tells
useradd to stop creating the lastlog file.

## SEE ALSO
**[podman(1)](podman.1.md)**, **[buildah(1)](https://github.com/containers/buildah/blob/main/docs/buildah.1.md)**, **[containers-certs.d(5)](https://github.com/containers/image/blob/main/docs/containers-certs.d.5.md)**, **[containers-registries.conf(5)](https://github.com/containers/image/blob/main/docs/containers-registries.conf.5.md)**, **[crun(1)](https://github.com/containers/crun/blob/main/crun.1.md)**, **[runc(8)](https://github.com/opencontainers/runc/blob/master/man/runc.8.md)**, **[useradd(8)](https://www.unix.com/man-page/redhat/8/useradd)**, **[podman-ps(1)](podman-ps.1.md)**, **[podman-rm(1)](podman-rm.1.md)**, **[Containerfile(5)](https://github.com/containers/common/blob/main/docs/Containerfile.5.md)**, **[containerignore(5)](https://github.com/containers/common/blob/main/docs/containerignore.5.md)**

## HISTORY
Aug 2020, Additional options and .containerignore added by Dan Walsh `<dwalsh@redhat.com>`

May 2018, Minor revisions added by Joe Doss `<joe@solidadmin.com>`

December 2017, Originally compiled by Tom Sweeney `<tsweeney@redhat.com>`

## FOOTNOTES
<a name="Footnote1">1</a>: The Podman 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,
Podman will follow suit immediately.