podman-build(1) - Man pages

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' exclusively. Any file that has ad-
ditional extension attached will not be recognized by podman build . un-
less a -f flag is used to specify the file.

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

When invoked with -f and a path to a Containerfile, with no explicit
CONTEXT directory, Podman uses the Containerfile's parent directory as
its build context.

Containerfiles ending with a ".in" suffix are preprocessed via CPP(1).
This can be useful to decompose Containerfiles into several reusable
parts that can be used via CPP's #include directive. Containerfiles end-
ing in .in are restricted to no comment lines unless they are CPP com-
mands. Note, 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. A URL is treated as a Git repository
if it has a git:// prefix or a .git suffix.

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
--external command to see these containers.

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

OPTIONS
--add-host=hostname[;hostname[;...]]:ip
Add a custom host-to-IP mapping to the container's /etc/hosts file.

The option takes one or multiple semicolon-separated hostnames to be
mapped to a single IPv4 or IPv6 address, separated by a colon. It can
also be used to overwrite the IP addresses of hostnames Podman adds to
/etc/hosts by default (also see the --name and --hostname options). This
option can be specified multiple times to add additional mappings to
/etc/hosts. It conflicts with the --no-hosts option and conflicts with
no_hosts=true in containers.conf.

Instead of an IP address, the special flag host-gateway can be given.
This resolves to an IP address the container can use to connect to the
host. The IP address chosen depends on your network setup, thus there's
no guarantee that Podman can determine the host-gateway address automat-
ically, which will then cause Podman to fail with an error message. You
can overwrite this IP address using the host_containers_internal_ip op-
tion in containers.conf.

The host-gateway address is also used by Podman to automatically add the
host.containers.internal and host.docker.internal hostnames to
/etc/hosts. You can prevent that by either giving the --no-hosts op-
tion, or by setting host_containers_internal_ip="none" in contain-
ers.conf. If no host-gateway address was configured manually and Podman
fails to determine the IP address automatically, Podman will silently
skip adding these internal hostnames to /etc/hosts. If Podman is running
in a virtual machine using podman machine (this includes Mac and Windows
hosts), Podman will silently skip adding the internal hostnames to
/etc/hosts, unless an IP address was configured manually; the internal
hostnames are resolved by the gvproxy DNS resolver instead.

Podman will use the /etc/hosts file of the host as a basis by default,
i.e. any hostname present in this file will also be present in the
/etc/hosts file of the container. A different base file can be config-
ured using the base_hosts_file config in containers.conf.

--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=value
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 matches this archi-
tecture, 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 on Linux, and $HOME/.config/containers/auth.json on Win-
dows/macOS. The file is created by 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 is interpolated in in-
structions read from the Containerfiles in the same way that environment
variables are, but which are not added to environment variable list in
the resulting image's configuration.

--build-arg-file=path
Specifies a file containing lines of build arguments of the form
arg=value. The suggested file name is argfile.conf.

Comment lines beginning with # are ignored, along with blank lines. All
others must be of the arg=value format passed to --build-arg.

If several arguments are provided via the --build-arg-file and --build-
arg options, the build arguments are merged across all of the provided
files and command line arguments.

Any file provided in a --build-arg-file option is read before the argu-
ments supplied via the --build-arg option.

When a given argument name is specified several times, the last instance
is the one that is passed to the resulting builds. This means --build-
arg values always override those in a --build-arg-file.

--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 are:

• 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 ma-
cOS and Windows) 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, reference the build context on all commands
that accept the “from” parameter. Here’s how that might look:

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

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

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

• Stage defined with AS [name] inside Containerfile

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

--cache-from=image
Repository to utilize as a potential cache source. When specified, Buil-
dah tries to look for cache images in the specified repository and at-
tempts to pull cache images instead of actually executing the build
steps locally. Buildah only attempts 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=image
Set this flag to specify a remote repository that is used to store cache
images. Buildah attempts to push newly built cache image to the remote
repository.

Note: Use the --cache-from option in order to use cache content in a re-
mote 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 considers intermediate cache images which are created
under the duration of one hour, and intermediate cache images outside
this duration is ignored.

Note: Setting --cache-ttl=0 manually is equivalent to using --no-cache
in the implementation since this means that the user does not want 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, and CAP_SE-
TUID capabilities are granted by default; this option can be used to re-
move them.

If a capability is specified to both the --cap-add and --cap-drop op-
tions, it is 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) For details, see containers-
certs.d(5). (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 is created. If
the path is not absolute, the path is considered to be relative to the
cgroups path of the init process. Cgroups are created if they do not al-
ready 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 is created, or it can be "host"
to indicate that the cgroup namespace in which buildah itself is being
run is reused.

--compat-volumes
Handle directories marked using the VOLUME instruction (both in this
build, and those inherited from base images) such that their contents
can only be modified by ADD and COPY instructions. Any changes made in
those locations by RUN instructions will be reverted. Before the intro-
duction of this option, this behavior was the default, but it is now
disabled by default.

--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 (ex-
cluding WSL2) machines)

--cpp-flag=flags
Set additional flags to pass to the C Preprocessor cpp(1). Container-
files ending with a ".in" suffix is preprocessed via cpp(1). This option
can be used to pass additional flags to cpp.Note: You can also set de-
fault CPPFLAGS by setting the BUILDAH_CPPFLAGS environment variable
(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/containers/pod-
man/blob/main/troubleshooting.md#26-running-containers-with-resource-
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 is 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 weight-
ing relative to the combined weight of all the running containers. De-
fault weight is 1024.

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

For example, consider three containers, one has a cpu-share of 1024 and
two others have a cpu-share setting of 512. When processes in all three
containers attempt to use 100% of CPU, the first container receives 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 only uses 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
appears and the value can be entered. The password is entered without
echo.

Note that the specified credentials are only used to authenticate
against target registries. They are not used for mirrors or when the
registry gets rewritten (see containers-registries.conf(5)); to authen-
ticate against those consider using a containers-auth.json(5) file.

--cw=options
Produce an image suitable for use as a confidential workload running in
a trusted execution environment (TEE) using krun (i.e., crun built with
the libkrun feature enabled and invoked as krun). Instead of the con-
ventional contents, the root filesystem of the image will contain an en-
crypted disk image and configuration information for krun.

The value for options is a comma-separated list of key=value pairs, sup-
plying configuration information which is needed for producing the addi-
tional data which will be included in the container image.

Recognized keys are:

attestation_url: The location of a key broker / attestation server. If
a value is specified, the new image's workload ID, along with the
passphrase used to encrypt the disk image, will be registered with the
server, and the server's location will be stored in the container image.
At run-time, krun is expected to contact the server to retrieve the
passphrase using the workload ID, which is also stored in the container
image. If no value is specified, a passphrase value must be specified.

cpus: The number of virtual CPUs which the image expects to be run with
at run-time. If not specified, a default value will be supplied.

firmware_library: The location of the libkrunfw-sev shared library. If
not specified, buildah checks for its presence in a number of hard-coded
locations.

memory: The amount of memory which the image expects to be run with at
run-time, as a number of megabytes. If not specified, a default value
will be supplied.

passphrase: The passphrase to use to encrypt the disk image which will
be included in the container image. If no value is specified, but an
attestation_url value is specified, a randomly-generated passphrase will
be used. The authors recommend setting an attestation_url but not a
passphrase.

slop: Extra space to allocate for the disk image compared to the size of
the container image's contents, expressed either as a percentage (..%)
or a size value (bytes, or larger units if suffixes like KB or MB are
present), or a sum of two or more such specifications. If not speci-
fied, buildah guesses that 25% more space than the contents will be
enough, but this option is provided in case its guess is wrong.

type: The type of trusted execution environment (TEE) which the image
should be marked for use with. Accepted values are "SEV" (AMD Secure
Encrypted Virtualization - Encrypted State) and "SNP" (AMD Secure En-
crypted Virtualization - Secure Nested Paging). If not specified, de-
faults to "SNP".

workload_id: A workload identifier which will be recorded in the con-
tainer image, to be used at run-time for retrieving the passphrase which
was used to encrypt the disk image. If not specified, a semi-random
value will be derived from the base image's image ID.

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

--decryption-key=key[:passphrase]
The [key[:passphrase]] to be used for decryption of images. Key can
point to keys and/or certificates. Decryption is 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 is resolved first. The
container only stores the major and minor numbers of the host device.

Podman may load kernel modules required for using the specified device.
The devices that Podman loads 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 fails. 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 storage
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 con-
tainer 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 is 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 is 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 are only be accepted from
the last specified file.

If a build context is not specified, and at least one Containerfile is a
local file, the directory in which it resides is used as the build con-
text.

Specifying the option -f - causes the Containerfile contents to 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 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 work as ex-
pected. For example, oci-archive:/x.tar references /x.tar on the remote
machine instead of on the client. When using podman remote clients it is
best to restrict use to containers-storage, and docker:// transports.

--group-add=group | keep-groups
Assign additional groups to the primary user running within the con-
tainer process.

• keep-groups is a special flag that tells Podman to keep the
supplementary group access.

Allows container to use the user's supplementary group access. If file
systems or devices are only accessible by the rootless user's group,
this flag tells the OCI runtime to pass the group access into the con-
tainer. Currently only available with the crun OCI runtime. Note: keep-
groups is exclusive, other groups cannot be specified with this flag.
(Not available for remote commands, including Mac and Windows (excluding
WSL2) machines)

--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 seman-
tics 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 currently defaults to
/usr/share/containers/oci/hooks.d and /etc/containers/oci/hooks.d in or-
der of increasing precedence. Using these defaults is deprecated. Mi-
grate to explicitly setting --hooks-dir.

--http-proxy
By default proxy environment variables are passed into the container if
set for the Podman process. This can be disabled by setting the value to
false. The environment variables passed in include http_proxy,
https_proxy, ftp_proxy, no_proxy, and also the upper case versions of
those. This option is only needed when the host system must use a proxy
but the container does not use any proxy. Proxy environment variables
specified for the container in any other way overrides the values that
have been passed through from the host. (Other ways to specify the proxy
for the container include passing the values with the --env flag, or
hard coding the proxy environment at container build time.) When used
with the remote client it uses the proxy environment variables that are
set on the server process.

Defaults to true.

--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 triggers an error.

--ipc=how
Sets the configuration for IPC namespaces when handling RUN instruc-
tions. The configured value can be "" (the empty string) or "container"
to indicate that a new IPC namespace is created, or it can be "host" to
indicate that the IPC namespace in which podman itself is being run is
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 name-
spaces 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 is 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 con-
tainer image tells Podman to run the container with just these capabili-
ties. Podman launches the container with just the specified capabili-
ties, 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 prints
an error message and runs the container with the default capabilities.

--layer-label=label[=value]
Add an intermediate image label (e.g. label=value) to the intermediate
image metadata. It can be used multiple times.

If label is named, but neither = nor a value is provided, then the label
is set to an empty value.

--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 is 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 is added. Creates the mani-
fest 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 con-
tainer's memory is not limited. The actual limit may be rounded up to a
multiple of the operating system's page size (the value is 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 must 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 instruc-
tions.

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.

• slirp4netns[:OPTIONS,...]: use slirp4netns(1) to create a user
network stack. It is possible to specify these additional op-
tions, they can also be set with network_cmd_options in con-
tainers.conf:

• allow_host_loopback=true|false: Allow slirp4netns to reach
the host loopback IP (default is 10.0.2.2 or the second IP
from slirp4netns cidr subnet when changed, see the cidr op-
tion below). The default is false.

• mtu=MTU: Specify the MTU to use for this network. (Default is
65520).

• cidr=CIDR: Specify ip range to use for this network. (Default
is 10.0.2.0/24).

• enable_ipv6=true|false: Enable IPv6. Default is true. (Re-
quired for outbound_addr6).

• outbound_addr=INTERFACE: Specify the outbound interface slirp
binds to (ipv4 traffic only).

• outbound_addr=IPv4: Specify the outbound ipv4 address slirp
binds to.

• outbound_addr6=INTERFACE: Specify the outbound interface
slirp binds to (ipv6 traffic only).

• outbound_addr6=IPv6: Specify the outbound ipv6 address slirp
binds to.

• pasta[:OPTIONS,...]: use pasta(1) to create a user-mode net-
working stack.
This is the default for rootless containers and only supported
in rootless mode.
By default, IPv4 and IPv6 addresses and routes, as well as the
pod interface name, are copied from the host. If port forward-
ing isn't configured, ports are forwarded dynamically as ser-
vices are bound on either side (init namespace or container
namespace). Port forwarding preserves the original source IP
address. Options described in pasta(1) can be specified as
comma-separated arguments.
In terms of pasta(1) options, --config-net is given by default,
in order to configure networking when the container is started,
and --no-map-gw is also assumed by default, to avoid direct ac-
cess from container to host using the gateway address. The lat-
ter can be overridden by passing --map-gw in the pasta-specific
options (despite not being an actual pasta(1) option).
Also, -t none and -u none are passed to disable automatic port
forwarding based on bound ports. Similarly, -T none and -U none
are given to disable the same functionality from container to
host.
Some examples:

• pasta:--map-gw: Allow the container to directly reach the
host using the gateway address.

• pasta:--mtu,1500: Specify a 1500 bytes MTU for the tap inter-
face in the container.

• pasta:--ipv4-only,-a,10.0.2.0,-n,24,-g,10.0.2.2,--dns-for-
ward,10.0.2.3,-m,1500,--no-ndp,--no-dhcpv6,--no-dhcp, equiva-
lent to default slirp4netns(1) options: disable IPv6, assign
10.0.2.0/24 to the tap0 interface in the container, with
gateway 10.0.2.3, enable DNS forwarder reachable at 10.0.2.3,
set MTU to 1500 bytes, disable NDP, DHCPv6 and DHCP support.

• pasta:-I,tap0,--ipv4-only,-a,10.0.2.0,-n,24,-g,10.0.2.2,--dns-
forward,10.0.2.3,--no-ndp,--no-dhcpv6,--no-dhcp, equivalent
to default slirp4netns(1) options with Podman overrides: same
as above, but leave the MTU to 65520 bytes

• pasta:-t,auto,-u,auto,-T,auto,-U,auto: enable automatic port
forwarding based on observed bound ports from both host and
container sides

• pasta:-T,5201: enable forwarding of TCP port 5201 from con-
tainer to host, using the loopback interface instead of the
tap interface for improved performance

--no-cache
Do not use existing cached images for the container build. Build from
the start with a new set of cached layers.

--no-hostname
Do not create the /etc/hostname file in the containers.

By default, Podman manages the /etc/hostname file, adding the con-
tainer's own hostname. When the --no-hostname option is set, the im-
age's /etc/hostname will be preserved unmodified if it exists.

--no-hosts
Do not modify the /etc/hosts file in the container.

Podman assumes control over the container's /etc/hosts file by default
and adds entries for the container's name (see --name option) and host-
name (see --hostname option), the internal host.containers.internal and
host.docker.internal hosts, as well as any hostname added using the
--add-host option. Refer to the --add-host option for details. Passing
--no-hosts disables this, so that the image's /etc/hosts file is kept
unmodified. The same can be achieved globally by setting no_hosts=true
in containers.conf.

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 matches this OS, regardless of the host.

--os-feature=feature
Set the name of a required operating system feature for the image which
is 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 is listed in the image.

--os-version=version
Set the exact required operating system version for the image which is
built. By default, if the image is not based on scratch, the base im-
age'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) ma-
chines)

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 di-
rectory on the client-side. - tar: write the resulting files as a sin-
gle 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 instruc-
tions. The configured value can be "" (the empty string) or "container"
to indicate that a new PID namespace is created, or it can be "host" to
indicate that the PID namespace in which podman itself is being run is
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, when using 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 matches this
platform, regardless of the host.

If --platform is set, then the values of the --arch, --os, and --variant
options is 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 is 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 combina-
tions 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 are unable to succeed without the
help of emulation provided by packages like qemu-user-static.

--pull=policy
Pull image policy. The default is missing.

• always: Always pull the image and throw an error if the pull
fails.

• missing: Only pull the image when it does not exist in the lo-
cal containers storage. Throw an error if no image is found
and the pull fails.

• never: Never pull the image but use the one from the local con-
tainers storage. Throw an error when no image is 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 lo-
cal 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 pulling or pushing images between the registry
and local storage in case of failure. Default is 3.

--retry-delay=duration
Duration of delay between retry attempts when pulling or pushing images
between the registry and local storage in case of failure. The default
is to start at two seconds and then exponentially back off. The delay is
used when this value is set, and no exponential back off occurs.

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

--runtime=path
The path to an alternate OCI-compatible runtime, which is 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 runtime. 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 is --runtime-flag
log-format=json.

--sbom=preset
Generate SBOMs (Software Bills Of Materials) for the output image by
scanning the working container and build contexts using the named combi-
nation of scanner image, scanner commands, and merge strategy. Must be
specified with one or more of --sbom-image-output, --sbom-image-purl-
output, --sbom-output, and --sbom-purl-output. Recognized presets, and
the set of options which they equate to:

• "syft", "syft-cyclonedx":
--sbom-scanner-image=ghcr.io/anchore/syft
--sbom-scanner-command="/syft scan -q dir:{ROOTFS} --output
cyclonedx-json={OUTPUT}"
--sbom-scanner-command="/syft scan -q dir:{CONTEXT} --output
cyclonedx-json={OUTPUT}"
--sbom-merge-strategy=merge-cyclonedx-by-component-name-and-
version

• "syft-spdx":
--sbom-scanner-image=ghcr.io/anchore/syft
--sbom-scanner-command="/syft scan -q dir:{ROOTFS} --output
spdx-json={OUTPUT}"
--sbom-scanner-command="/syft scan -q dir:{CONTEXT} --output
spdx-json={OUTPUT}"
--sbom-merge-strategy=merge-spdx-by-package-name-and-version-
info

• "trivy", "trivy-cyclonedx":
--sbom-scanner-image=ghcr.io/aquasecurity/trivy
--sbom-scanner-command="trivy filesystem -q {ROOTFS} --format
cyclonedx --output {OUTPUT}"
--sbom-scanner-command="trivy filesystem -q {CONTEXT} --format
cyclonedx --output {OUTPUT}"
--sbom-merge-strategy=merge-cyclonedx-by-component-name-and-
version

• "trivy-spdx":
--sbom-scanner-image=ghcr.io/aquasecurity/trivy
--sbom-scanner-command="trivy filesystem -q {ROOTFS} --format
spdx-json --output {OUTPUT}"
--sbom-scanner-command="trivy filesystem -q {CONTEXT} --format
spdx-json --output {OUTPUT}"
--sbom-merge-strategy=merge-spdx-by-package-name-and-version-
info

--sbom-image-output=path
When generating SBOMs, store the generated SBOM in the specified path in
the output image. There is no default.

--sbom-image-purl-output=path
When generating SBOMs, scan them for PURL (package URL
⟨https://github.com/package-url/purl-spec/blob/master/PURL-SPECIFICA-
TION.rst⟩) information, and save a list of found PURLs to the specified
path in the output image. There is no default.

--sbom-merge-strategy=method
If more than one --sbom-scanner-command value is being used, use the
specified method to merge the output from later commands with output
from earlier commands. Recognized values include:

• cat
Concatenate the files.

• merge-cyclonedx-by-component-name-and-version
Merge the "component" fields of JSON documents, ignoring val-
ues from
documents when the combination of their "name" and "version"
values is
already present. Documents are processed in the order in
which they are
generated, which is the order in which the commands that gen-
erate them
were specified.

• merge-spdx-by-package-name-and-versioninfo
Merge the "package" fields of JSON documents, ignoring values
from
documents when the combination of their "name" and "version-
Info" values is
already present. Documents are processed in the order in
which they are
generated, which is the order in which the commands that gen-
erate them
were specified.

--sbom-output=file
When generating SBOMs, store the generated SBOM in the named file on the
local filesystem. There is no default.

--sbom-purl-output=file
When generating SBOMs, scan them for PURL (package URL
⟨https://github.com/package-url/purl-spec/blob/master/PURL-SPECIFICA-
TION.rst⟩) information, and save a list of found PURLs to the named file
in the local filesystem. There is no default.

--sbom-scanner-command=image
Generate SBOMs by running the specified command from the scanner image.
If multiple commands are specified, they are run in the order in which
they are specified. These text substitutions are performed:
- {ROOTFS}
The root of the built image's filesystem, bind mounted.
- {CONTEXT}
The build context and additional build contexts, bind mounted.
- {OUTPUT}
The name of a temporary output file, to be read and merged with
others or copied elsewhere.

--sbom-scanner-image=image
Generate SBOMs using the specified scanner image.

--secret=id=id[,src=envOrFile][,env=ENV][,type=file | env]
Pass secret information to be used in the Containerfile for building im-
ages in a safe way that will not end up stored in the final image, or be
seen in other stages. The value of the secret will be read from an en-
vironment variable or file named by the "id" option, or named by the
"src" option if it is specified, or from an environment variable speci-
fied by the "env" option. See EXAMPLES ⟨#examples⟩. The secret will be
mounted in the container at /run/secrets/id by default.

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

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

The location of the secret in the container can be overridden using the
"target", "dst", or "destination" option of the RUN --mount flag.

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

Note: changing the contents of secret files will not trigger a rebuild
of layers that use said secrets.

--security-opt=option
Security Options

• apparmor=unconfined : Turn off apparmor confinement for the
container

• apparmor=alternate-profile : Set the apparmor confinement pro-
file 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 container
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 : JSON file to be used as the seccomp
filter for the container.

--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 container. This option con-
flicts with --ipc=host.

--sign-by=fingerprint
Sign the image using a GPG key with the specified FINGERPRINT. (This op-
tion 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 preex-
isting 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 inter-
act from the terminal during the build.

--tag, -t=imageName
Specifies the name which is assigned to the resulting image if the build
process completes successfully. If imageName does not include a reg-
istry name, the registry name localhost is 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 is skipped.

--timestamp=seconds
Set the create timestamp to seconds since epoch to allow for determinis-
tic builds (defaults to current time). By default, the created timestamp
is changed and written into the image manifest with every commit, caus-
ing the image's sha256 hash to be different even if the sources are ex-
actly the same otherwise. When --timestamp is set, the created time-
stamp is always set to the time specified and therefore not changed, al-
lowing the image's sha256 hash to remain the same. All files committed
to the layers of the image is created with the timestamp.

If the only instruction in a Containerfile is FROM, this flag has no ef-
fect.

--tls-verify
Require HTTPS and verify certificates when contacting registries (de-
fault: true). If explicitly set to true, TLS verification is used. If
set to false, TLS verification is not used. If not specified, TLS veri-
fication is 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 processing
RUN instructions. This option can be specified multiple times. Recog-
nized 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.

--unsetlabel=label
Unset the image label, causing the label not to be inherited from the
base image.

--userns=how
Sets the configuration for user namespaces when handling RUN instruc-
tions. The configured value can be "" (the empty string) or "container"
to indicate that a new user namespace is created, it can be "host" to
indicate that the user namespace in which podman itself is being run is
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 to be used to set ownership, at the
filesystem level, on the working container's contents. Commands run
when handling RUN instructions defaults 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 is 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 is
set to use the same numeric values as the UID map.

--userns-gid-map-group=group
Specifies that a GID mapping to 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 defaults 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 assumes that the specified user name is also a suit-
able 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 is when run rootful.

--userns-uid-map=mapping
Directly specifies a UID mapping to be used to set ownership, at the
filesystem level, on the working container's contents. Commands run
when handling RUN instructions 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 is 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 is
set to use the same numeric values as the GID map.

--userns-uid-map-user=user
Specifies that a UID mapping to 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 defaults 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 assumes that the specified group name is also a suit-
able user name to use as the default setting for this option.

--uts=how
Sets the configuration for UTS namespaces when handling RUN instruc-
tions. The configured value can be "" (the empty string) or "container"
to indicate that a new UTS namespace to be created, or it can be "host"
to indicate that the UTS namespace in which podman itself is being run
is 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]]
Mount a host directory into containers when executing RUN instructions
during the build.

The OPTIONS are a comma-separated list and can be one or more of:

• [rw|ro]

• [z|Z|O]

• [U]

• [[r]shared|[r]slave|[r]private][1] ⟨#Footnote1⟩

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 specified path when processing RUN instructions.

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

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

Chowning Volume Mounts

By default, 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 modifies 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 us-
ing the content. By default, Podman does not change the labels set by
the OS.

To change a label in the container context, add one of these two suf-
fixes :z or :Z to the volume mount. These suffixes tell Podman to rela-
bel 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 con-
tainers 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 the host 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 dis-
able 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 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 is the lower, and the container storage directory is
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 direc-
tory 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 direc-
tory 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. Do not
modify the directory until the container finishes running.

By default bind mounted volumes are private. That means any mounts done
inside containers are 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 completed
inside the container on that volume is visible to both the host and con-
tainer. 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 is visible only inside of the container. To control the mount
propagation property of volume use the :[r]shared, :[r]slave or :[r]pri-
vate 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 propagation
properties are specified. shared:X means the mount is shared, master:X
means the mount is slave and if nothing is there that means the mount is
private. [1] ⟨#Footnote1⟩

To change propagation properties of a mount point use the mount command.
For example, to bind mount the source directory /foo do mount --bind
/foo /foo and mount --make-private --make-shared /foo. This converts
/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
Build image using Containerfile with content from current directory:

$ podman build .

Build image using specified Containerfile with content from current di-
rectory:

$ podman build -f Containerfile.simple .

Build image using Containerfile from stdin with content from current di-
rectory:

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

Build image using multiple Containerfiles with content from current di-
rectory:

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

Build image with specified Containerfile with content from $HOME direc-
tory. Note cpp is applied to Containerfile.in before processing as Con-
tainerfile:

$ podman build -f Containerfile.in $HOME

Build image with the specified tag with Containerfile and content from
current directory:

$ podman build -t imageName .

Build image ignoring registry verification for any images pulled via the
Containerfile:

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

Build image with the specified logging format:

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

Build image using debug mode for logging:

$ podman build --runtime-flag debug .

Build image using specified registry attributes when pulling images from
the selected Containerfile:

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

Build image using specified resource controls when running containers
during the build:

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

Build image using specified SELinux labels and cgroup config running
containers during the build:

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

Build image with read-only and SELinux relabeled volume mounted from the
host into running containers during the build:

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

Build image with overlay volume mounted from the host into running con-
tainers during the build:

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

Build image using layers and then removing intermediate containers even
if the build fails.

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

Build image ignoring cache and not removing intermediate containers even
if the build succeeds:

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

Build image using the specified network when running containers during
the build:

$ podman build --network mynet .

Build an image using a secret stored in an environment variable or file
named mysecret to be used with the instruction RUN --mount=type=se-
cret,id=mysecret cat /run/secrets/mysecret:

$ podman build --secret=id=mysecret .

Build an image using a secret stored in an environment variable named
MYSECRET to be used with the instruction RUN --mount=type=secret,id=my-
secret cat /run/secrets/mysecret:

$ podman build --secret=id=mysecret,env=MYSECRET .
$ podman build --secret=id=mysecret,src=MYSECRET,type=env .

Build an image using a secret stored in a file named .mysecret to be
used with the instruction RUN --mount=type=secret,id=mysecret cat
/run/secrets/mysecret:

$ podman build --secret=id=mysecret,src=.mysecret .
$ podman build --secret=id=mysecret,src=.mysecret,type=file .

Building a multi-architecture image using the --manifest option (requires
emulation software)
Build image using the specified architectures and link to a single mani-
fest on successful completion:

$ podman build --arch arm --manifest myimage /tmp/mysrc
$ podman build --arch amd64 --manifest myimage /tmp/mysrc
$ podman build --arch s390x --manifest myimage /tmp/mysrc

Similarly build using a single command

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

Build image using multiple specified architectures and link to single
manifest on successful completion:

$ 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 Container-
file, 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 lo-
cally 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 ex-
tracted before being used as the context.

Building an image using a URL to a Containerfile
Build image from Containerfile downloaded into temporary location used
as the build context:

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

Building an image using a Git repository
Podman clones the specified GitHub repository to a temporary location
and uses it as the context. The Containerfile at the root of the reposi-
tory is used and it only works if the GitHub repository is a dedicated
repository.

Build image from specified git repository downloaded into temporary lo-
cation used as the build context:

$ podman build -t hello https://github.com/containers/PodmanHello.git
$ podman run hello

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 fetches the archive file, decompresses it, and uses its contents
as the build context. The Containerfile at the root of the archive and
the rest of the archive are used as the context of the build. Passing
the -f PATH/Containerfile option as well tells the system to 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 'iden-
tity' (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 .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 only uses .containerig-
nore.

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 excludes 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 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/containerignore.5.md

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

registries.conf is the configuration file which specifies which con-
tainer registries is consulted when completing image names which do not
include a registry or domain portion.

Troubleshooting
lastlog sparse file
Using a useradd command within a Containerfile with a large UID/GID cre-
ates 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 the container image.

When using the useradd command within the build script, 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)

Troubleshooting
See podman-troubleshooting(7) for solutions to common issues.

See podman-rootless(7) for rootless issues.

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 needs to 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)

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