podman-build - Build a container image using a Containerfile
podman build [options] [context]
podman image build [options] [context]
podman build Builds an image using instructions from
one or more Containerfiles or Dockerfiles and a specified build context
directory. A Containerfile uses the same syntax as a Dockerfile
internally. For this document, a file referred to as a Containerfile can
be a file named either 'Containerfile' or 'Dockerfile' exclusively. Any
file that has additional extension attached will not be recognized by
podman build .
unless 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 ending in .in are restricted to no comment
lines unless they are CPP commands. 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
locally 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 --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.
Add a custom host-to-IP mapping (host:ip) Multiple hostnames for the same IP can be separated by semicolons.
Add a line to /etc/hosts. The format is hostname:ip or hostname1;hostname2;hostname3:ip if you want to map multiple hostnames to the same ip without duplicating the --add-host parameter. The --add-host option can be set multiple times. Conflicts with the --no-hosts option.
Instead of building for a set of platforms specified using the --platform option, inspect the build's base images, and build for all of the platforms for which they are all available. Stages that use scratch as a starting point can not be inspected, so at least one non-scratch stage must be present for detection to work usefully.
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.
Set the architecture of the image to be built, and that of the base image to be pulled, if the build uses one, to the provided value instead of using the architecture of the build host. Unless overridden, subsequent lookups of the same image in the local storage matches this architecture, regardless of the host. (Examples: arm, arm64, 386, amd64, ppc64le, s390x)
Path of the authentication file. Default is
${XDG_RUNTIME_DIR}/containers/auth.json
on Linux, and
$HOME/.config/containers/auth.json
on Windows/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
authentication file by setting the REGISTRY_AUTH_FILE
environment variable. This can be done with export
REGISTRY_AUTH_FILE=path.
Specifies a build argument and its value, which is interpolated in instructions 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.
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 arguments 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
.
Specify an additional build context using its short name and its location. Additional build contexts can be referenced in the same manner as we access different stages in COPY instruction.
Valid values are:
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:
Repository to utilize as a potential cache source. When specified, Buildah tries to look for cache images in the specified repository and attempts 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.
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 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.
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.
When executing RUN instructions, run the command specified in the instruction with the specified capability added to its capability set. Certain capabilities are granted by default; this option can be used to add more.
When executing RUN instructions, run the command specified in the instruction with the specified capability removed from its capability set. The CAP_CHOWN, CAP_DAC_OVERRIDE, CAP_FOWNER, CAP_FSETID, CAP_KILL, CAP_NET_BIND_SERVICE, CAP_SETFCAP, CAP_SETGID, CAP_SETPCAP, and CAP_SETUID capabilities are granted by default; this option can be used to remove them.
If a capability is specified to both the --cap-add and --cap-drop options, it is dropped, regardless of the order in which the options were given.
Use certificates at path (*.crt, *.cert, *.key) to connect to the registry. (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)
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 already exist.
Sets the configuration for cgroup namespaces when handling
RUN
instructions. The configured value can be "" (the empty
string) or "private" to indicate that a new cgroup namespace is created,
or it can be "host" to indicate that the cgroup namespace in which
buildah
itself is being run is reused.
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 introduction of this option, this behavior was the default, but it is now disabled by default.
This option is added to be aligned with other containers CLIs. Podman doesn't communicate with a daemon or a remote server. Thus, compressing the data before sending it is irrelevant to Podman. (This option is not available with the remote Podman client, including Mac and Windows (excluding WSL2) machines)
Set additional flags to pass to the C Preprocessor cpp(1). Containerfiles 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 default CPPFLAGS by setting the BUILDAH_CPPFLAGS environment variable (e.g., export BUILDAH_CPPFLAGS="-DDEBUG").
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/podman/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.
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).
On some systems, changing the resource limits may not be allowed for non-root users. For more details, see https://github.com/containers/podman/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 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 containers. Default 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 container C0 is started with --cpu-shares=512 running one process, and another 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 |
On some systems, changing the resource limits may not be allowed for non-root users. For more details, see https://github.com/containers/podman/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.
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).
On some systems, changing the resource limits may not be allowed for non-root users. For more details, see https://github.com/containers/podman/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.
Memory nodes (MEMs) in which to allow execution (0-3, 0,1). Only effective 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.
On some systems, changing the resource limits may not be allowed for non-root users. For more details, see https://github.com/containers/podman/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.
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 authenticate against
those consider using a containers-auth.json(5)
file.
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 conventional contents, the root filesystem of the image will contain an encrypted disk image and configuration information for krun.
The value for options is a comma-separated list of key=value pairs, supplying configuration information which is needed for producing the additional 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 specified, 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 Encrypted Virtualization - Secure Nested Paging). If not specified, defaults to "SNP".
workload_id: A workload identifier which will be recorded in the container 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.
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.
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. Because 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 device 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.
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.
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.
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/resolv.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.
Set custom DNS options to be used during the build.
Set custom DNS search domains to be used during the build.
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.
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 context.
Specifying the option -f -
causes the Containerfile
contents to be read from stdin.
Always remove intermediate containers after a build, even if the build fails (default true).
Control the format for the built image's manifest and configuration data. Recognized formats include oci (OCI image-spec v1.0, the default) and docker (version 2, using schema format 2 for the manifest).
Note: You can also override the default format by setting the
BUILDAH_FORMAT environment variable.
export BUILDAH_FORMAT=docker
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 expected. 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.
Assign additional groups to the primary user running within the container 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
container. 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)
Print usage statement
Each *.json file in the path configures a hook for buildah build containers. For more details on the syntax of the JSON files and the semantics of hook 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 order of increasing precedence. Using these defaults is deprecated. Migrate to explicitly setting --hooks-dir.
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.
Adds default identity label io.buildah.version
if set.
(default true).
Path to an alternative .containerignore file.
Write the built image's ID to the file. When --platform
is specified more than once, attempting to use this option triggers an
error.
Sets the configuration for IPC namespaces when handling
RUN
instructions. The configured value can be "" (the empty
string) or "container" to indicate that a new IPC namespace 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.
Controls what type of isolation is used for running processes as part
of RUN
instructions. Recognized types include oci
(OCI-compatible runtime, the default), rootless (OCI-compatible
runtime invoked using a modified configuration and its --rootless option
enabled, with --no-new-keyring --no-pivot added to its
create invocation, with network and UTS namespaces disabled,
and IPC, PID, and user namespaces enabled; the default for unprivileged
users), and chroot (an internal wrapper that leans more toward
chroot(1) than container technology).
Note: You can also override the default isolation type by setting the
BUILDAH_ISOLATION environment variable.
export BUILDAH_ISOLATION=oci
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.
Add an image label (e.g. label=value) to the image metadata. Can be used multiple times.
Users can set a special LABEL io.containers.capabilities=CAP1,CAP2,CAP3 in a Containerfile that specifies the list of Linux capabilities required for the container to run properly. This label specified in a container image tells Podman to run the container with just these capabilities. Podman launches the container with just the specified capabilities, as long as this list of capabilities is a subset of the default list.
If the specified capabilities are not in the default set, Podman prints an error message and runs the container with the default capabilities.
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.
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
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.
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.
Name of the manifest list to which the image is added. Creates the manifest list if it does not exist. This option is useful for building multi architecture images.
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 is very large, that's millions of trillions).
This option is not supported on cgroups V1 rootless systems.
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.
Sets the configuration for network namespaces when handling
RUN
instructions.
Valid mode values are:
--network mynet
to join the
network with the name mynet. Only supported for rootful users.network_cmd_options
in containers.conf:
65520
).10.0.2.0/24
).outbound_addr6
).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.Do not use existing cached images for the container build. Build from the start with a new set of cached layers.
Do not create the /etc/hostname file in the container for RUN instructions.
By default, Buildah manages the /etc/hostname file, adding the container's own hostname. When the --no-hostname option is set, the image's /etc/hostname will be preserved unmodified if it exists.
Do not create /etc/hosts for the container. By default, Podman manages /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 is preserved unmodified.
This option conflicts with --add-host.
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.
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.
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.
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 image's required OS version is kept, if the base image specified one. This option is typically only meaningful when the image's OS is Windows, and is typically set in Windows base images, so using this option is usually unnecessary.
Output destination (format: type=local,dest=path)
The --output (or -o) option extends the default behavior of building a container image by allowing users to export the contents of the image as files on the local filesystem, which can be useful for generating local binaries, code generation, etc. (This option is not available with the remote Podman client, including Mac and Windows (excluding WSL2) machines)
The value for --output is a comma-separated sequence of key=value pairs, defining the output type and options.
Supported keys are: - dest: Destination
path for exported output. Valid value is absolute or relative path,
-
means the standard output. - type:
Defines the type of output to be used. Valid values is documented
below.
Valid type values are: - local: write the resulting build files to a directory on the client-side. - tar: write the resulting files as a single tarball (.tar).
If no type is specified, the value defaults to
local. Alternatively, instead of a comma-separated
sequence, the value of --output can be just a
destination (in the dest format) (e.g.
--output some-path
, --output -
) where
--output some-path
is treated as if
type=local and --output -
is treated as if
type=tar.
Sets the configuration for PID namespaces when handling
RUN
instructions. The configured value can be "" (the empty
string) or "container" to indicate that a new PID namespace 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.
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 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 are
able to succeed without the help of emulation provided by packages like
qemu-user-static
.
Pull image policy. The default is missing.
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.
Number of times to retry pulling or pushing images between the registry and local storage in case of failure. Default is 3.
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.
Remove intermediate containers after a successful build (default true).
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
BUILDAH_RUNTIME environment variable.
export BUILDAH_RUNTIME=/usr/local/bin/runc
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.
Generate SBOMs (Software Bills Of Materials) for the output image by scanning the working container and build contexts using the named combination 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:
When generating SBOMs, store the generated SBOM in the specified path in the output image. There is no default.
When generating SBOMs, scan them for PURL (package URL) information, and save a list of found PURLs to the specified path in the output image. There is no default.
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:
When generating SBOMs, store the generated SBOM in the named file on the local filesystem. There is no default.
When generating SBOMs, scan them for PURL (package URL) information, and save a list of found PURLs to the named file in the local filesystem. There is no default.
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.
Generate SBOMs using the specified scanner image.
Pass secret information used in the Containerfile for building images
in a safe way that are not stored in the final image, or be seen in
other stages. The secret is 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 Options
apparmor=unconfined
: Turn off apparmor confinement
for the container
apparmor=alternate-profile
: Set the apparmor
confinement profile for the container
label=user:USER
: Set the label user for the
container processes
label=role:ROLE
: Set the label role for the
container processes
label=type:TYPE
: Set the label process type for the
container processes
label=level:LEVEL
: Set the label level for the
container processes
label=filetype:TYPE
: Set the label file type for
the container files
label=disable
: Turn off label separation for the
container
no-new-privileges
: Not supported
seccomp=unconfined
: Turn off seccomp confinement
for the container
seccomp=profile.json
: JSON file to be used as the
seccomp filter for the container.
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 conflicts with --ipc=host.
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 stages in multi-stage builds which don't affect the target stage. (Default: true).
Squash all of the image's new layers into a single new layer; any preexisting layers are not squashed.
Squash all of the new image's layers (including those inherited from a base image) into a single new layer.
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
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.
Specifies the name which is assigned to the resulting image if the build process completes successfully. If imageName does not include a registry name, the registry name localhost is prepended to the image name.
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.
Set the create timestamp to seconds since epoch to allow for deterministic builds (defaults to current time). By default, the created timestamp is changed and written into the image manifest with every commit, causing the image's sha256 hash to be different even if the sources are exactly the same otherwise. When --timestamp is set, the created timestamp is always set to the time specified and therefore not changed, allowing the image's sha256 hash to remain the same. All files committed to the layers of the image is created with the timestamp.
If the only instruction in a Containerfile is FROM
, this
flag has no effect.
Require HTTPS and verify certificates when contacting registries (default: true). If explicitly set to true, TLS verification is used. If set to false, TLS verification is not used. If not specified, TLS verification is used unless the target registry is listed as an insecure registry in containers-registries.conf(5)
Specifies resource limits to apply to processes launched when
processing RUN
instructions. This option can be specified
multiple times. Recognized resource types include: "core": maximum core
dump size (ulimit -c) "cpu": maximum CPU time (ulimit -t) "data":
maximum size of a process's data segment (ulimit -d) "fsize": maximum
size of new files (ulimit -f) "locks": maximum number of file locks
(ulimit -x) "memlock": maximum amount of locked memory (ulimit -l)
"msgqueue": maximum amount of data in message queues (ulimit -q) "nice":
niceness adjustment (nice -n, ulimit -e) "nofile": maximum number of
open files (ulimit -n) "nproc": maximum number of processes (ulimit -u)
"rss": maximum size of a process's (ulimit -m) "rtprio": maximum
real-time scheduling priority (ulimit -r) "rttime": maximum amount of
real-time execution between blocking syscalls "sigpending": maximum
number of pending signals (ulimit -i) "stack": maximum stack size
(ulimit -s)
Unset environment variables from the final image.
Unset the image label, causing the label not to be inherited from the base image.
Sets the configuration for user namespaces when handling
RUN
instructions. The configured value can be "" (the empty
string) or "container" to indicate that a new user namespace 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.
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 number of consecutive IDs which the map entry represents.
This option overrides the remap-gids setting in the options section of /etc/containers/storage.conf.
If this option is not specified, but a global --userns-gid-map setting is supplied, settings from the global option 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.
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
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 is when run rootful.
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 number of consecutive IDs which the map entry represents.
This option overrides the remap-uids setting in the options section of /etc/containers/storage.conf.
If this option is not specified, but a global --userns-uid-map setting is supplied, settings from the global option 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.
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 suitable user name to use as the
default setting for this option.
NOTE: When this option is specified by a rootless user, the specified mappings are relative to the rootless user namespace in the container, rather than being relative to the host as it is when run rootful.
Sets the configuration for UTS namespaces when handling
RUN
instructions. The configured value can be "" (the empty
string) or "container" to indicate that a new UTS namespace 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.
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.
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:
[r]shared
|[r]slave
|[r]private
][1]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 using 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
suffixes :z
or :Z
to the volume mount. These
suffixes tell Podman to relabel file objects on the shared volumes. The
z
option tells Podman that two containers share the volume
content. As a result, Podman labels the content with a shared content
label. Shared volume labels allow all containers to read/write content.
The Z
option tells Podman to label the content with a
private unshared label. Only the current container can use a private
volume.
Note: Do not relabel system files and directories. Relabeling system
content might cause other confined services on the host machine to fail.
For these types of containers, disabling SELinux separation is
recommended. The option --security-opt label=disable
disables SELinux separation for the container. For example, if a user
wanted to volume mount their entire home directory into the build
containers, they need to disable SELinux separation.
$ podman build --security-opt label=disable -v $HOME:/home/user .
Overlay Volume Mounts
The :O
flag tells Podman to mount the directory from the
host as a temporary storage using the Overlay file system. The
RUN
command containers are allowed to modify contents
within the mountpoint and are stored in the container storage in a
separate directory. In Overlay FS terms the source directory 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 directory content, any changes from previous RUN
commands no longer exists.
One use case of the overlay
mount is sharing the package
cache from the host into the container to allow speeding up builds.
Note:
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.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 property.
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 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 is 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]
Use df <source-dir>
to determine the source mount
and then use
findmnt -o TARGET,PROPAGATION <source-mount-dir>
to
determine propagation properties of source mount, if
findmnt
utility is not available, the source mount point
can be determined by looking at the mount entry in
/proc/self/mountinfo
. Look at optional fields
and see if any propagation properties are specified.
shared:X
means the mount is shared
,
master:X
means the mount is slave
and if
nothing is there that means the mount is private
. [1]
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.
Build image using Containerfile with content from current directory:
$ podman build .
Build image using specified Containerfile with content from current directory:
$ podman build -f Containerfile.simple .
Build image using Containerfile from stdin with content from current directory:
$ cat $HOME/Containerfile | podman build -f - .
Build image using multiple Containerfiles with content from current directory:
$ podman build -f Containerfile.simple -f Containerfile.notsosimple .
Build image with specified Containerfile with content from $HOME
directory. Note cpp
is applied to Containerfile.in before
processing as Containerfile:
$ 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 containers 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 image using the specified architectures and link to a single manifest 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
The build context directory can be specified as a URL to a Containerfile, a Git repository, or URL to an archive. If the URL is a Containerfile, it is downloaded to a temporary location and used as the context. When a Git repository is set as the URL, the repository is cloned locally to a temporary location and then used as the context. Lastly, if the URL is an archive, it is downloaded to a temporary location and extracted before being used as the context.
Build image from Containerfile downloaded into temporary location used as the build context:
$ podman build https://10.10.10.1/podman/Containerfile
Podman clones the specified GitHub repository to a temporary location and uses it as the context. The Containerfile at the root of the repository is used and it only works if the GitHub repository is a dedicated repository.
Build image from specified git repository downloaded into temporary location 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
operation due to recent changes in their
security guidance
(https://github.blog/2021-09-01-improving-git-protocol-security-github/).
Use an https://
URL if the source repository is hosted on
GitHub.
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 'identity' (no compression).
If the file .containerignore or .dockerignore
exists in the context directory, podman build
reads its
contents. Use the --ignorefile
option to override the
.containerignore path location. Podman uses the content to exclude files
and directories from the context directory, when executing COPY and ADD
directives in the Containerfile/Dockerfile
The .containerignore and .dockerignore files use the same syntax; if both are in the context directory, podman build only uses .containerignore.
Users can specify a series of Unix shell globs in a .containerignore file to identify files/directories to exclude.
Podman supports a special wildcard string **
which
matches any number of directories (including zero). For example, **/*.go
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 content in it.
Lines starting with ! (exclamation mark) can be used to make exceptions to exclusions. The following is an example .containerignore file that uses this mechanism:
*.doc
!Help.doc
Exclude all doc files except Help.doc from the image.
This functionality is compatible with the handling of .containerignore files described here:
https://github.com/containers/common/blob/main/docs/containerignore.5.md
registries.conf
(/etc/containers/registries.conf
)
registries.conf is the configuration file which specifies which container registries is consulted when completing image names which do not include a registry or domain portion.
Using a useradd command within a Containerfile with a large UID/GID
creates 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.
podman(1), buildah(1), containers-certs.d(5), containers-registries.conf(5), crun(1), runc(8), useradd(8), podman-ps(1), podman-rm(1), Containerfile(5), containerignore(5)
See podman-troubleshooting(7) for solutions to common issues.
See podman-rootless(7) for rootless issues.
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>
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.