Ubuntu Manpage: buildah-build - Build an image using instructions from Containerfiles

NAME

       buildah-build - Build an image using instructions from Containerfiles

SYNOPSIS

       buildah build [options] [context]

       buildah bud [options] [context]

       buildah build-using-dockerfile [options] [context]

       build has aliases bud and build-using-dockerfile.

DESCRIPTION

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 Buildah will assume the current working
directory as build context, which should contain a 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. Any comments ( Lines beginning with # ) in
included Containerfile(s) that are not preprocess commands, will be printed as warnings
during builds.

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 file 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.

--arch="ARCH"

Set the ARCH 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 host.
(Examples: arm, arm64, 386, amd64, ppc64le, s390x)

--authfile path

Path of the authentication file. Default is ${XDG_\RUNTIME_DIR}/containers/auth.json. If
XDG_RUNTIME_DIR is not set, the default is /run/containers/$UID/auth.json. This file is
created using using buildah 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.

Please refer to the BUILD TIME VARIABLES ⟨#build-time-variables⟩ section for the list of
variables that can be overridden within the Containerfile at run time.

--cache-from

Images to utilise as potential cache sources. Buildah does not currently support
--cache-from so this is a NOOP.

--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. The 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. Buildah doesn't send a
copy of the context directory to a daemon or a remote server. Thus, compressing the data
before sending it is irrelevant to Buildah.

--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=0

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/main/troubleshooting.md#26-running-containers-with-cpu-limits-fails-with-a-permissions-error

--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.

--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=device

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 Buildah. This flag is a NOOP and provided solely for scripting
compatibility.

--dns=[]

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 Buildah. The /etc/resolv.conf file in the image will be used without changes.

--dns-option=[]

Set custom DNS options

--dns-search=[]

Set custom DNS search domains

--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 local file is specified as the Containerfile and it does not exist, the context
directory will be prepended to the local file value.

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

--force-rm bool-value

Always remove intermediate containers after a build, even if the build fails (default
false).

--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=true

By default proxy environment variables are passed into the container if set for the
buildah process. This can be disabled by setting the --http-proxy option to false. The
environment variables passed in include http_proxy, https_proxy, ftp_proxy, no_proxy, and
also the upper case versions of those.

--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 file

Path to an alternative .containerignore (.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 buildah
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, with --no-new-keyring
added to its create invocation, reusing the host's network and UTS namespaces, and
creating private IPC, PID, mount, and user namespaces; the default for unprivileged
users), and chroot (an internal wrapper that leans more toward chroot(1) than container
technology, reusing the host's control group, network, IPC, and PID namespaces, and
creating private mount and UTS namespaces, and creating user namespaces only when they're
required for ID mapping).

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

--jobs N

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 on 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 container engines, like Podman, to run the
container with just these capabilities. The container engine 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, container engines should print
an error message and will run the container with the default capabilities.

--layers bool-value

Cache intermediate images during the build process (Default is false).

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 "listName"

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

--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.

--network, --net=mode

Sets the configuration for network namespaces when handling RUN instructions.

Valid mode values are:

• none: no networking;

• host: use the 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="OS"

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 host.

--pid how

Sets the configuration for PID namespaces when handling RUN instructions. The configured
value can be "" (the empty string) or "private" to indicate that a new PID namespace
should be created, or it can be "host" to indicate that the PID namespace in which buildah
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 buildah bud 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 flag is enabled, attempt to pull the latest image from the registries listed in
registries.conf if a local image does not exist or the image is newer than the one in
storage. Raise an error if the image is not in any listed registry and is not present
locally.

If the flag is disabled (with --pull=false), do not pull the image from the registry,
unless there is no local image. Raise an error if the image is not in any registry and is
not present locally.

Defaults to true.

--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 bool-value

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. Default is runc, or crun when machine is configured to
use cgroups V2.

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

--runtime-flag flag

Adds global flags for the container rutime. To list the supported flags, please consult
the manpages of the selected container runtime.

Note: Do not pass the leading -- to the flag. To pass the runc flag --log-format json to
buildah build, the option given would be --runtime-flag log-format=json.

--secret=id=id,src=path

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

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

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

--security-opt=[]

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
"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

--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.

--sign-by fingerprint

Sign the built image using the GPG key that matches the specified fingerprint.

--squash

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

--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=secret,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 component, 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 to remain the same. All files committed to the layers of the image will be
created with the timestamp.

--tls-verify bool-value

Require HTTPS and verification of certificates when talking to container registries
(defaults to true). TLS verification cannot be used when talking to an insecure registry.

--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)
"nofile": maximum number of open files (1048576); when run by root
"nproc": maximum number of processes (ulimit -u)
"nproc": maximum number of processes (1048576); when run by root
"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 "private" to indicate that a new user namespace
should be created, it can be "host" to indicate that the user namespace in which buildah
itself is being run should be reused, or it can be the path to an user namespace which is
already in use by another process.

--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,
buildah will assume that the specified group name is also a suitable user name to use as
the default setting for this option.

Users can specify the maps directly using --userns-uid-map described in the buildah(1) man
page.

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

--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,
buildah will assume that the specified user name is also a suitable group name to use as
the default setting for this option.

Users can specify the maps directly using --userns-gid-map described in the buildah(1) man
page.

--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 buildah 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 pulled.

--volume, -v[=[HOST-DIR:CONTAINER-DIR[:OPTIONS]]]

Create a bind mount. If you specify, -v /HOST-DIR:/CONTAINER-DIR, Buildah
bind mounts /HOST-DIR in the host to /CONTAINER-DIR in the Buildah
container. The OPTIONS are a comma delimited list and can be: [1] ⟨#Footnote1⟩

• [rw|ro]

• [U]

• [z|Z|O]

• [[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. Buildah bind-mounts the HOST-DIR to the path you specify. For
example, if you supply /foo as the host path, Buildah 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.

Write Protected Volume 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, Buildah does not change the owner and group of source volume directories
mounted into containers. If a container is created in a new user namespace, the UID and
GID in the container may correspond to another UID and GID on the host.

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

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, Buildah 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 Buildah to relabel file objects on the shared
volumes. The z option tells Buildah that two containers share the volume content. As a
result, Buildah labels the content with a shared content label. Shared volume labels allow
all containers to read/write content. The Z option tells Buildah to label the content
with a private unshared label. Only the current container can use a private volume.

Overlay Volume Mounts

The :O flag tells Buildah 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:

- 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 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 the 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 (the mount point where source dir is mounted on) it 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.

BUILD TIME VARIABLES

       The  ENV  instruction  in a Containerfile can be used to define variable values.  When the
       image is built, the values will persist in the container  image.   At  times  it  is  more
       convenient to change the values in the Containerfile via a command-line option rather than
       changing the values within the Containerfile itself.

       The following variables can be used in conjunction with the --build-arg option to override
       the corresponding values set in the Containerfile using the ENV instruction.

              • HTTP_PROXY

              • HTTPS_PROXY

              • FTP_PROXY

              • NO_PROXY

       Please  refer  to  the Using Build Time Variables ⟨#using-build-time-variables⟩ section of
       the Examples.

EXAMPLE

Build an image using local Containerfiles
buildah build .

buildah build -f Containerfile .

cat /Dockerfile | buildah build -f - .

buildah build -f Dockerfile.simple -f Dockerfile.notsosimple .

buildah build --timestamp=$(date '+%s') -t imageName .

buildah build -t imageName .

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

buildah build --tls-verify=false -t imageName .

buildah build --runtime-flag log-format=json .

buildah build -f Containerfile --runtime-flag debug .

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

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

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

buildah build --arch=arm --variant v7 -t imageName .

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

buildah build -v /home/test:/myvol:z,U -t imageName .

buildah build -v /var/lib/dnf:/var/lib/dnf:O -t imageName .

buildah build --layers -t imageName .

buildah build --no-cache -t imageName .

buildah build -f Containerfile --layers --force-rm -t imageName .

buildah build --no-cache --rm=false -t imageName .

buildah build --dns-search=example.com --dns=223.5.5.5 --dns-option=use-vc .

buildah build -f Containerfile.in -t imageName .

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

buildah build --arch amd64 --manifest myimage /tmp/mysrc

buildah build --arch s390x --manifest myimage /tmp/mysrc

buildah bud --platform linux/s390x,linux/ppc64le,linux/amd64 --manifest myimage /tmp/mysrc

buildah bud --platform linux/arm64 --platform linux/amd64 --manifest myimage /tmp/mysrc

Building an image using a URL
This will clone the specified GitHub repository from the URL and use it as context. The
Containerfile or Dockerfile at the root of the repository is used as the context of the
build. This only works if the GitHub repository is a dedicated repository.

buildah build github.com/scollier/purpletest

Note: You can set an arbitrary Git repository via the git:// scheme.

Building an image using a URL to a tarball'ed context
Buildah will fetch the tarball archive, decompress it and use its contents as the build
context. The Containerfile or 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 an -f PATH/Containerfile
option as well, the system will look for that file inside the contents of the tarball.

buildah build -f dev/Containerfile https://10.10.10.1/docker/context.tar.gz

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

Using Build Time Variables
Replace the value set for the HTTP_PROXY environment variable within the Containerfile.
buildah build --build-arg=HTTP_PROXY="http://127.0.0.1:8321"

ENVIRONMENT

       BUILD_REGISTRY_SOURCES

       BUILD_REGISTRY_SOURCES,  if  set,  is  treated  as  a  JSON object which contains lists of
       registry   names   under   the    keys    insecureRegistries,    blockedRegistries,    and
       allowedRegistries.

       When  pulling  an  image  from  a registry, if the name of the registry matches any of the
       items in the blockedRegistries list, the image pull  attempt  is  denied.   If  there  are
       registries  in the allowedRegistries list, and the registry's name is not in the list, the
       pull attempt is denied.

       TMPDIR The TMPDIR environment variable allows the user to specify  where  temporary  files
       are stored while pulling and pushing images.  Defaults to '/var/tmp'.

Files

.containerignore/.dockerignore
If the .containerignore/.dockerignore file exists in the context directory, buildah build
reads its contents. If both exist, then .containerignore is used. Use the --ignorefile
flag to override the ignore file path location. Buildah 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

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

Example .containerignore file:

# exclude this content for image
*/*.c
**/output*
src

*/*.c Excludes files and directories whose names ends with .c in any top level
subdirectory. For example, the source file include/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/.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.

policy.json (/etc/containers/policy.json)

Signature policy file. This defines the trust policy for container images. Controls
which container registries can be used for image, and whether or not the tool should trust
the images.

FOOTNOTES

       1:  The  Buildah  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,  Buildah
       will follow suit immediately.