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podman-build(1) General Commands Manual 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 Con-
tainerfiles 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 ei-
ther '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 cur-
rent 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 lo-
cally 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 pod-
man build crashes or users kill the podman build process, these exter-
nal 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
--add-host=host:ip
Add a custom host-to-IP mapping (host:ip)

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

--all-platforms
Instead of building for a set of platforms specified using the --plat-
form 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 im-
age to be pulled, if the build uses one, to the provided value instead
of using the architecture of the build host. Unless overridden, subse-
quent lookups of the same image in the local storage will match this
architecture, regardless of the host. (Examples: arm, arm64, 386,
amd64, ppc64le, s390x)

--authfile=path
Path of the authentication file. Default is ${XDG_RUNTIME_DIR}/contain-
ers/auth.json, which is set using podman login. If the authorization
state is not found there, $HOME/.docker/config.json is checked, which
is set using docker login.

Note: There is also the option to override the default path of the au-
thentication file by setting the REGISTRY_AUTH_FILE environment vari-
able. This can be done with export REGISTRY_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 environ-
ment 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 loca-
tion. 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://exam-
ple.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. Heres 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
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 im-
ages 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 in-
struction 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 in-
struction 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 op-
tions, 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 reg-
istry. (Default: /etc/containers/certs.d) Please refer to containers-
certs.d(5) for details. (This option is not available with the remote
Podman client, including Mac and Windows (excluding WSL2) machines)

--cgroup-parent=path
Path to cgroups under which the cgroup for the container will be cre-
ated. If the path is not absolute, the path is considered to be rela-
tive 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 instruc-
tions. 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, compress-
ing 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). Container-
files 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 vari-
able (e.g., export BUILDAH_CPPFLAGS="-DDEBUG").

--cpu-period=limit
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 resource limits may not be allowed for
non-root users. For more details, see https://github.com/contain-
ers/podman/blob/main/troubleshooting.md#26-running-containers-with-re-
source-limits-fails-with-a-permissions-error

This option is not supported on cgroups V1 rootless systems.

--cpu-quota=limit
Limit the CPU Completely Fair Scheduler (CFS) quota.

Limit the container's CPU usage. By default, containers run with the
full CPU resource. The limit is a number in microseconds. If a number
is provided, the container will be allowed to use that much CPU time
until the CPU period ends (controllable via --cpu-period).

This option is not supported on cgroups V1 rootless systems.

--cpu-shares, -c=shares
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 combined weight of all the running contain-
ers. Default weight is 1024.

The proportion will only apply when CPU-intensive processes are run-
ning. When tasks in one container are idle, other containers can use
the left-over CPU time. The actual amount of CPU time will vary depend-
ing 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 re-
ceive 50% of the total CPU time. If a fourth container is added 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 the con-
tainer C0 is started with --cpu-shares=512 running one process, and an-
other container C1 with --cpu-shares=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 |
+-----+-----------+-----+--------------+

This option is not supported on cgroups V1 rootless systems.

--cpuset-cpus=number
CPUs in which to allow execution. Can be specified as a comma-separated
list (e.g. 0,1), as a range (e.g. 0-3), or any combination thereof
(e.g. 0-3,7,11-15).

This option is not supported on cgroups V1 rootless systems.

--cpuset-mems=nodes
Memory nodes (MEMs) in which to allow execution (0-3, 0,1). Only effec-
tive on NUMA systems.

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

This option is not supported on cgroups V1 rootless systems.

--creds=[username[:password]]
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 en-
tered 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=host-device[:container-device][:permissions]
Add a host device to the container. Optional permissions parameter can
be used to specify device permissions by combining r for read, w for
write, and m for mknod(2).

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

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

Podman may load kernel modules required for using the specified device.
The devices that Podman will load modules for when necessary are:
/dev/fuse.

In rootless mode, the new device is bind mounted in the container from
the host rather than Podman creating it within the container space. Be-
cause the bind mount retains its SELinux label on SELinux systems, the
container can get permission denied when accessing the mounted device.
Modify SELinux settings to allow containers to use all device labels
via the following command:

$ sudo setsebool -P container_use_devices=true

Note: if the user only has access rights via a group, accessing the de-
vice from inside a rootless container will fail. The crun(1) 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 stor-
age 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 Podman. This option is a
NOOP and provided solely for scripting compatibility.

--dns=ipaddr
Set custom DNS servers.

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/re-
solv.conf in the container by Podman. The /etc/resolv.conf file in the
image will be used without changes.

This option cannot be combined with --network that is set to none.

Note: this option takes effect only during RUN instructions in the
build. It does not affect /etc/resolv.conf in the final image.

--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 de-
fault) and docker (version 2, using schema format 2 for the manifest).

Note: You can also override the default format by setting the BUIL-
DAH_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 re-
mote podman clients, it is best to restrict yourself to containers-
storage: and docker:// transports.

--help, -h
Print usage statement

--hooks-dir=path
Each *.json file in the path configures a hook for buildah build con-
tainers. For more details on the syntax of the JSON files and the se-
mantics of hook injection. 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 de-
fault to /usr/share/containers/oci/hooks.d and /etc/contain-
ers/oci/hooks.d in order of increasing precedence. Using these defaults
is deprecated, and callers should migrate to explicitly setting
--hooks-dir.

--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 instruc-
tions. The configured value can be "" (the empty string) or "con-
tainer" 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 name-
space 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 run-
time, 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 re-
quired for the container to run properly. This label specified in a
container image tells Podman to run the container with just these capa-
bilities. Podman launches the container with just the specified capa-
bilities, as long as this list of capabilities is a subset of the de-
fault 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 ca-
pabilities.

--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.

--memory, -m=number[unit]
Memory limit. A unit can be b (bytes), k (kibibytes), m (mebibytes), or
g (gibibytes).

Allows the memory available to a container to be constrained. 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).

This option is not supported on cgroups V1 rootless systems.

--memory-swap=number[unit]
A limit value equal to memory plus swap. A unit can be b (bytes), k
(kibibytes), m (mebibytes), or g (gibibytes).

Must be used with the -m (--memory) flag. The argument value should
always be larger than that of
-m (--memory) By default, it is set to double the value of --memory.

Set number to -1 to enable unlimited swap.

This option is not supported on cgroups V1 rootless systems.

--network=mode, --net
Sets the configuration for network namespaces when handling RUN in-
structions.

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.

--no-hosts
Do not create /etc/hosts for the container. By default, Podman will
manage /etc/hosts, adding the container's own IP address and any hosts
from --add-host. --no-hosts disables this, and the image's /etc/hosts
will be preserved unmodified.

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 speci-
fied 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 op-
tion 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-pathis treated as if **type=local**
and--output -` is treated as if type=tar.

--pid=pid
Sets the configuration for PID namespaces when handling RUN instruc-
tions. The configured value can be "" (the empty string) or "con-
tainer" 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 --vari-
ant 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 sev-
eral 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-sta-
tic.

--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.

--retry=attempts
Number of times to retry in case of failure when performing pull of im-
ages from registry. Default is 3.

--retry-delay=duration
Duration of delay between retry attempts in case of failure when per-
forming pull of images from registry. Default is 2s.

--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 BUIL-
DAH_RUNTIME environment variable. export BUILDAH_RUNTIME=/usr/lo-
cal/bin/runc

--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 --run-
time-flag log-format=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 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 con-
tainer processes

• label=level:LEVEL : Set the label level for the container
processes

• label=filetype:TYPE : Set the label file type for the con-
tainer files

• label=disable : Turn off label separation for the con-
tainer

• no-new-privileges : Not supported

• seccomp=unconfined : Turn off seccomp confinement for the con-
tainer

• seccomp=profile.json : White listed syscalls seccomp Json
file to be used as a seccomp filter

--shm-size=number[unit]
Size of /dev/shm. A unit can be b (bytes), k (kibibytes), m
(mebibytes), or g (gibibytes). If the unit is omitted, the system uses
bytes. If the size is omitted, the default is 64m. When size is 0,
there is no limit on the amount of memory used for IPC by the con-
tainer. This option conflicts with --ipc=host.

--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,)

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

--squash
Squash all of the image's new layers into a single new layer; any pre-
existing 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 im-
age 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 interme-
diate 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 determin-
istic builds (defaults to current time). By default, the created time-
stamp 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 time-
stamp is always set to the time specified and therefore not changed,
allowing the image's sha256 hash to remain the same. All files commit-
ted 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 contacting registries (de-
fault: true). If explicitly set to true, TLS verification will be
used. If set to false, TLS verification will not be used. If not
specified, TLS verification will be used unless the target registry is
listed as an insecure registry in containers-registries.conf(5)

--ulimit=type=soft-limit[:hard-limit]
Specifies resource limits to apply to processes launched when process-
ing 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 instruc-
tions. The configured value can be "" (the empty string) or "con-
tainer" 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 num-
ber 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 be-
ing 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 num-
ber 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 be-
ing 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 op-
tion.

--uts=how
Sets the configuration for UTS namespaces when handling RUN instruc-
tions. The configured value can be "" (the empty string) or "con-
tainer" 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 con-
tainer. (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: [1] <#Footnote1>

• [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 la-
bels the content with a shared content label. Shared volume labels al-
low all containers to read/write content. The Z option tells Podman to
label the content with a private unshared label. Only the current con-
tainer 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 recom-
mended. The option --security-opt label=disable disables SELinux sepa-
ration 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 tem-
porary storage using the Overlay file system. The RUN command contain-
ers 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 di-
rectory will be the upper. Modifications to the mount point are de-
stroyed when the RUN command finishes executing, similar to a tmpfs
mount point.

Any subsequent execution of RUN commands sees the original source di-
rectory content, any changes from previous RUN commands no longer ex-
ists.

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 run-
ning.

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 prop-
erty.

When the mount propagation policy is set to shared, any mounts com-
pleted 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. [1] <#Footnote1>

Use df <source-dir> to determine the source mount and then use findmnt
-o TARGET,PROPAGATION <source-mount-dir> to determine propagation prop-
erties 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 propaga-
tion 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 com-
mand. 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 Container-
file, a Git repository, or URL to an archive. If the URL is a Contain-
erfile, it is downloaded to a temporary location and used as the con-
text. 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 loca-
tion 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 opera-
tion 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 di-
rectory, podman build reads its contents. Use the --ignorefile option
to override the Podman uses the content to exclude files and directo-
ries 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 .con-
tainerignore.

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/root-
less.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 con-
tent 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/containerig-
nore.5.md

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

registries.conf is the configuration file which specifies which con-
tainer 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), buildah(1), containers-certs.d(5), containers-reg-
istries.conf(5), crun(1), runc(8), useradd(8), podman-ps(1), podman-
rm(1), Containerfile(5), containerignore(5)

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
1: 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.

podman-build(1)

Want to link to this manual page? Use this URL:
<https://man.freebsd.org/cgi/man.cgi?query=podman-build&sektion=1&manpath=FreeBSD+13.2-RELEASE+and+Ports>

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