podman/docs/podman-build.1.md

% podman-build "1"

NAME

podman-build - Build a container image using a Dockerfile.

SYNOPSIS

podman build [options [...]] context

DESCRIPTION

podman build Builds an image using instructions from one or more Dockerfiles and a specified build context directory.

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

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 Dockerfile, the Dockerfile 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.

OPTIONS

--add-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.

--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.

--build-arg arg=value

Specifies a build argument and its value, which will be interpolated in instructions read from the Dockerfiles 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.

--cert-dir path

Use certificates at path (*.crt, *.cert, *.key) to connect to the registry. Default certificates directory is /etc/containers/certs.d.

--cgroup-parent=""

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.

--cpu-period=0

Limit the CPU CFS (Completely Fair Scheduler) period

Limit the container's CPU usage. This flag tell the kernel to restrict the container's CPU usage to the period you specify.

--cpu-quota=0

Limit the CPU CFS (Completely Fair Scheduler) quota

Limit the container's CPU usage. By default, containers run with the full CPU resource. This flag tell the kernel to restrict the container's CPU usage to the quota you specify.

--cpu-shares, -c=0

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=""

CPUs in which to allow execution (0-3, 0,1)

--cpuset-mems=""

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.

--file, -f Dockerfile

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

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

--force-rm

Always remove intermediate containers after a build. Podman does not currently support caching so this is a NOOP.

--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).

--iidfile ImageIDfile

Write the image ID to the file.

--isolation [Not Supported]

Podman is not currently supported on Windows, and does not have a daemon. If you want to override the container isolation you can choose a different OCI Runtime, using the --runtime flag.

--label label

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

--memory, -m="" Memory limit (format: [], where unit = b, k, m or g)

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.

--no-cache

Do not use caching for the container build. Podman does not currently support caching so this is a NOOP.

--pull

Pull the image if it is not present. If this flag is disabled (with --pull=false) and the image is not present, the image will not be pulled. Defaults to true.

--pull-always

Pull the image even if a version of the image is already present.

--quiet, -q

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

--rm

Remove intermediate containers after a successful build. Podman does not currently support caching so this is a NOOP.

--runtime path

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

--runtime-flag flag

Adds global flags for the container rutime. To list the supported flags, please consult the manpages of the selected container runtime (runc is the default runtime, the manpage to consult is runc(8)). Note: Do not pass the leading -- to the flag. To pass the runc flag --log-format json to podman build, the option given would be --runtime-flag log-format=json.

--security-opt=[]

Security Options

"label=user:USER" : Set the label user for the container "label=role:ROLE" : Set the label role for the container "label=type:TYPE" : Set the label type for the container "label=level:LEVEL" : Set the label level for the container "label=disable" : Turn off label confinement 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

"apparmor=unconfined" : Turn off apparmor confinement for the container "apparmor=your-profile" : Set the apparmor confinement profile for the container

--shm-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.

--signature-policy signaturepolicy

Pathname of a signature policy file to use. It is not recommended that this option be used, as the default behavior of using the system-wide default policy (frequently /etc/containers/policy.json) is most often preferred.

--squash

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

--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.

--tls-verify bool-value

Require HTTPS and verify certificates when talking to container registries (defaults to true).

--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": maximimum 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)

--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. The OPTIONS are a comma delimited list and can be:

• [rw|ro]
• [z|Z]
• [[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.

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.

By default bind mounted volumes are private. That means any mounts done inside container 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.

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 propagaion 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.

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 Dockerfiles

podman build .

podman build -f Dockerfile.simple .

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

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 ~/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 .

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

The build context directory can be specified as a URL to a Dockerfile, a Git repository, or URL to an archive. If the URL is a Dockerfile, 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 Dockerfile

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

podman build https://10.10.10.1/podman/Dockerfile

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 Dockerfile 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 Dockerfile 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/Dockerfile option as well, the system will look for that file inside the contents of the archive.

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

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

Files

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

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

SEE ALSO

podman(1), buildah(1)

HISTORY

• December 2017, Originally compiled by Tom Sweeney tsweeney@redhat.com
• May 2018, Minor revisions added by Joe Doss joe@solidadmin.com