Ubuntu Manpage: podman-build - Build a container image using a Containerfile

Provided by: podman_3.4.4+ds1-1ubuntu1.22.04.3_amd64

NAME

       podman-build - Build a container image using a Containerfile

SYNOPSIS

       podman build [options] [context]

       podman image build [options] [context]

DESCRIPTION

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

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

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

Containerfiles ending with a ".in" suffix will be preprocessed via CPP(1). This can be
useful to decompose Containerfiles into several reusable parts that can be used via CPP's
#include directive. Notice, a Containerfile.in file can still be used by other tools when
manually preprocessing them via cpp -E.

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

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

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

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

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

OPTIONS

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

Add a line to /etc/hosts. The format is hostname:ip. The --add-host option can be set
multiple times.

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

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

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

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

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

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

--cache-from
Images to utilize as potential cache sources. Podman does not currently support caching so
this is a NOOP. (This option is not available with the remote Podman client)

--cap-add=CAP_xxx
When executing RUN instructions, run the command specified in the instruction with the
specified capability added to its capability set. Certain capabilities are granted by
default; this option can be used to add more.

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

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

--cert-dir=path
Use certificates at path (*.crt, *.cert, *.key) to connect to the registry. (Default:
/etc/containers/certs.d) Please refer to containers-certs.d(5) for details. (This option
is not available with the remote Podman client)

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

--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)

--cni-config-dir=directory
Location of CNI configuration files which will dictate which plugins will be used to
configure network interfaces and routing for containers created for handling RUN
instructions, if those containers will be run in their own network namespaces, and
networking is not disabled.

--cni-plugin-path=directory[:directory[:directory[...]]]
List of directories in which the CNI plugins which will be used for configuring network
namespaces can be found.

--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 CPU limits may not be allowed for non-root users. For more
details, see
https://github.com/containers/podman/blob/master/troubleshooting.md#26-running-containers-
with-cpu-limits-fails-with-a-permissions-error

--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 you provide a number, the container will be
allowed to use that much CPU time until the CPU period ends (controllable via --cpu-
period).

--cpu-shares, -c=shares
CPU shares (relative weight)

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

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

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

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

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

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

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

--cpuset-cpus=num
CPUs in which to allow execution (0-3, 0,1)

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

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

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

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

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

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

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

Note: if the user only has access rights via a group, accessing the device from inside a
rootless container will fail. The crun(1) runtime offers a workaround for this by adding
the option

--annotation run.oci.keep_original_groups=1.
--disable-compression, -D
Don't compress filesystem layers when building the image unless it is required by the
location where the image is being written. This is the default setting, because image
layers are compressed automatically when they are pushed to registries, and images being
written to local storage would only need to be decompressed again to be stored.
Compression can be forced in all cases by specifying --disable-compression=false.

--disable-content-trust
This is a Docker specific option to disable image verification to a Docker registry and is
not supported by Podman. This flag is a NOOP and provided solely for scripting
compatibility. (This option is not available with the remote Podman client)

--dns=dns
Set custom DNS servers to be used during the build.

This option can be used to override the DNS configuration passed to the container.
Typically this is necessary when the host DNS configuration is invalid for the container
(e.g., 127.0.0.1). When this is the case the --dns 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 will be used without changes.

--dns-option=option
Set custom DNS options to be used during the build.

--dns-search=domain
Set custom DNS search domains to be used during the build.

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

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

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

--force-rm=true|false
Always remove intermediate containers after a build, even if the build fails (default
true).

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

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

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

-h, --help

Print usage statement

--http-proxy
Pass through HTTP Proxy environment variables.

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

--ignorefile
Path to an alternative .dockerignore file.

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

--isolation=type
Controls what type of isolation is used for running processes as part of RUN instructions.
Recognized types include oci (OCI-compatible runtime, the default), rootless (OCI-
compatible runtime invoked using a modified configuration and its --rootless flag enabled,
with --no-new-keyring --no-pivot added to its create invocation, with network and UTS
namespaces disabled, and IPC, PID, and user namespaces enabled; the default for
unprivileged users), and chroot (an internal wrapper that leans more toward chroot(1) than
container technology).

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

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

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

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

If the specified capabilities are not in the default set, Podman will print an error
message and will run the container with the default capabilities.

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

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

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

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

--memory, -m=LIMIT
Memory limit (format: <number>[<unit>], where unit = b (bytes), k (kilobytes), m
(megabytes), or g (gigabytes))

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

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

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

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

Valid mode values are:

• none: no networking.

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

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

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

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

--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.

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

--platform="OS/ARCH[/VARIANT][,...]"
Set the OS/ARCH of the built image (and its base image, if your build uses one) to the
provided value instead of using the current operating system and architecture of the host
(for example linux/arm). If --platform is set, then the values of the --arch, --os, and
--variant options will be overridden.

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

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

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

--pull
When the option is specified or set to "true", pull the image. Raise an error if the
image could not be pulled, even if the image is present locally.

If the option is disabled (with --pull=false) or not specified, pull the image from the
registry only if the image is not present locally. Raise an error if the image is not
found in the registries and is not present locally.

--pull-always
Pull the image from the first registry it is found in as listed in registries.conf. Raise
an error if not found in the registries, even if the image is present locally.

--pull-never
Do not pull the image from the registry, use only the local version. Raise an error if the
image is not present locally.

--quiet, -q
Suppress output messages which indicate which instruction is being processed, and of
progress when pulling images from a registry, and when writing the output image.

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

--runtime=path
The path to an alternate OCI-compatible runtime, which will be used to run commands
specified by the RUN instruction.

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

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

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

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

--security-opt=option
Security Options

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

• apparmor=your-profile : Set the apparmor confinement profile for the container

• label=user:USER : Set the label user for the container processes

• label=role:ROLE : Set the label role for the container processes

• label=type:TYPE : Set the label process type for the container processes

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

• label=filetype:TYPE : Set the label file type for the container files

• label=disable : Turn off label separation for the container

• no-new-privileges : Not supported

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

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

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

--sign-by=fingerprint
Sign the image using a GPG key with the specified FINGERPRINT. (This option is not
available with the remote Podman client)

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

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

--ssh=default|id[=socket>|[,]
SSH agent socket or keys to expose to the build. The socket path can be left empty to use
the value of default=$SSH_AUTH_SOCK

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

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

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

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

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

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

--tls-verify=true|false
Require HTTPS and verify certificates when talking to container registries (defaults to
true). (This option is not available with the remote Podman client)

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

--variant=""
Set the architecture variant of the image to be built, and that of the base image to be
pulled, if the build uses one, to the provided value instead of using the architecture
variant of the build host.

--volume, -v[=[HOST-DIR:CONTAINER-DIR[:OPTIONS]]]
Create a bind mount. If you specify, -v /HOST-DIR:/CONTAINER-DIR, Podman
bind mounts /HOST-DIR in the host to /CONTAINER-DIR in the Podman
container. (This option is not available with the remote Podman client)

The OPTIONS are a comma-separated list and can be: [1] ⟨#Footnote1⟩

• [rw|ro]

• [z|Z|O]

• [U]

• [[r]shared|[r]slave|[r]private]

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

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

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

Chowning Volume Mounts

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

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

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

Labeling Volume Mounts

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

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

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

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

Overlay Volume Mounts

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

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

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

Note:

- Overlay mounts are not currently supported in rootless mode.
- The `O` flag is not allowed to be specified with the `Z` or `z` flags.

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

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

When the mount propagation policy is set to shared, any mounts completed inside the
container on that volume will be visible to both the host and container. When the mount
propagation policy is set to slave, one way mount propagation is enabled and any mounts
completed on the host for that volume will be visible only inside of the container. To
control the mount propagation property of volume use the :[r]shared, :[r]slave or
:[r]private propagation flag. The propagation property can be specified only for bind
mounted volumes and not for internal volumes or named volumes. For mount propagation to
work on the source mount point (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 properties of source mount,
if findmnt utility is not available, the source mount point can be determined by looking
at the mount entry in /proc/self/mountinfo. Look at optional fields and see if any
propagation properties are specified. shared:X means the mount is shared, master:X means
the mount is slave and if nothing is there that means the mount is private. [1]
⟨#Footnote1⟩

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

EXAMPLES

   Build an image using local Containerfiles
              $ podman build .

              $ podman build -f Containerfile.simple .

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

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

              $ podman build -f Dockerfile.in $HOME

              $ podman build -t imageName .

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

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

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

              $ podman build --runtime-flag debug .

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

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

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

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

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

              $ podman build --layers -t imageName .

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

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

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

   Building a multi-architecture image using the --manifest option (requires emulation software)
              $ podman build --arch arm --manifest myimage /tmp/mysrc

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

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

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

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

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

   Building an image using a URL to a Containerfile
       Podman  will  download  the  Containerfile  to a temporary location and then use it as the
       build context.

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

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

              $ podman build git://github.com/scollier/purpletest

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

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

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

Files

.dockerignore
If the file .dockerignore exists in the context directory, buildah copy reads its
contents. Use the --ignorefile flag to override .dockerignore 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

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

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

Example .dockerignore 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 .dockerignore file that uses this mechanism:

*.doc
!Help.doc

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

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

https://docs.docker.com/engine/reference/builder/#dockerignore-file

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

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

Troubleshooting

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

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

HISTORY

       Aug 2020, Additional options and .dockerignore added by Dan Walsh <dwalsh@redhat.com>

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

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

FOOTNOTES

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

                                                                                podman-build(1)()