buildah-build(1) General Commands Manual buildah-build(1)
NAME
buildah-build - Build an image using instructions from Containerfiles
SYNOPSIS
buildah build [options] [context]
buildah bud [options] [context]
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 'Contain-
erfile' 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 cur-
rent working directory as build context, which should contain a Contain-
erfile.
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 lo-
cally and then used as the build context. A non-default branch (or com-
mit ID) and subdirectory of the cloned git repository can be used by in-
cluding their names at the end of the URL in the form myrepo.git#my-
branch:subdir, myrepo.git#mycommit:subdir, or myrepo.git#:subdir if the
subdirectory should be used from the default branch.
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 op-
tion can be set multiple times. Conflicts with the --no-hosts option.
--all-platforms
Instead of building for a set of platforms specified using the --plat-
form option, inspect the build's base images, and build for all of the
platforms for which they are all available. Stages that use scratch as
a starting point can not be inspected, so at least one non-scratch stage
must be present for detection to work usefully.
--annotation annotation[=value]
Add an image annotation (e.g. annotation=value) to the image metadata.
Can be used multiple times. If annotation is named, but neither = nor a
value is provided, then the annotation is set to an empty value.
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}/contain-
ers/auth.json. See containers-auth.json(5) for more information. This
file is created 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 REG-
ISTRY_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 environ-
ment 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 Container-
file at run time.
--build-arg-file path
Specifies a file containing lines of build arguments of the form
arg=value. The suggested file name is argfile.conf.
Comment lines beginning with # are ignored, along with blank lines. All
others should be of the arg=value format passed to --build-arg.
If several arguments are provided via the --build-arg-file and --build-
arg options, the build arguments will be merged across all of the pro-
vided files and command line arguments.
Any file provided in a --build-arg-file option will be read before the
arguments supplied via the --build-arg option.
When a given argument name is specified several times, the last instance
is the one that is passed to the resulting builds. This means --build-
arg values always override those in a --build-arg-file.
--build-context name=value
Specify an additional build context using its short name and its loca-
tion. Additional build contexts can be referenced in the same manner as
we access different stages in COPY instruction.
Valid values could be: * Local directory – e.g. --build-context
project2=../path/to/project2/src * HTTP URL to a tarball – e.g. --build-
context src=https://example.org/releases/src.tar * Container image –
specified with a container-image:// prefix, e.g. --build-context
alpine=container-image://alpine:3.15, (also accepts docker://, docker-
image://)
On the Containerfile side, you can reference the build context on all
commands that accept the “from” parameter. Here’s how that might look:
FROM [name]
COPY --from=[name] ...
RUN --mount=from=[name] …
The value of [name] is matched with the following priority order:
• Named build context defined with --build-context [name]=..
• Stage defined with AS [name] inside Containerfile
• Image [name], either local or in a remote registry
--cache-from
Repository to utilize as a potential list of cache sources. When speci-
fied, Buildah will try to look for cache images in the specified reposi-
tories and will attempt to pull cache images instead of actually execut-
ing the build steps locally. Buildah will only attempt to pull previ-
ously cached images if they are considered as valid cache hits.
Use the --cache-to option to populate a remote repository or reposito-
ries with cache content.
Example
# populate a cache and also consult it
buildah build -t test --layers --cache-to registry/myrepo/cache --cache-from registry/myrepo/cache .
Note: --cache-from option is ignored unless --layers is specified.
Note: Buildah's --cache-from option is designed differently than Docker
and BuildKit's --cache-from option. Buildah's distributed cache mecha-
nism pulls intermediate images from the remote registry itself, unlike
Docker and BuildKit where the intermediate image is stored in the image
itself. Buildah's approach is similar to kaniko, which does not inflate
the size of the original image with intermediate images. Also, interme-
diate images can truly be kept distributed across one or more remote
registries using Buildah's caching mechanism.
--cache-to
Set this flag to specify list of remote repositories that will be used
to store cache images. Buildah will attempt to push newly built cache
image to the remote repositories.
Note: Use the --cache-from option in order to use cache content in a re-
mote repository.
Example
# populate a cache and also consult it
buildah build -t test --layers --cache-to registry/myrepo/cache --cache-from registry/myrepo/cache .
Note: --cache-to option is ignored unless --layers is specified.
Note: Buildah's --cache-to option is designed differently than Docker
and BuildKit's --cache-to option. Buildah's distributed cache mechanism
push intermediate images to the remote registry itself, unlike Docker
and BuildKit where the intermediate image is stored in the image itself.
Buildah's approach is similar to kaniko, which does not inflate the size
of the original image with intermediate images. Also, intermediate im-
ages can truly be kept distributed across one or more remote registries
using Buildah's caching mechanism.
--cache-ttl duration
Limit the use of cached images to only consider images with created
timestamps less than duration ago. For example if --cache-ttl=1h is
specified, Buildah will only consider intermediate cache images which
are created under the duration of one hour, and intermediate cache im-
ages outside this duration will be ignored.
Note: Setting --cache-ttl=0 manually is equivalent to using --no-cache
in the implementation since this would effectively mean that user is not
willing to use cache at all.
--cap-add=CAP_xxx
When executing RUN instructions, run the command specified in the in-
struction with the specified capability added to its capability set.
Certain capabilities are granted by default; this option can be used to
add more.
--cap-drop=CAP_xxx
When executing RUN instructions, run the command specified in the in-
struction with the specified capability removed from its capability set.
The CAP_CHOWN, CAP_DAC_OVERRIDE, CAP_FOWNER, CAP_FSETID, CAP_KILL,
CAP_NET_BIND_SERVICE, CAP_SETFCAP, CAP_SETGID, CAP_SETPCAP, and CAP_SE-
TUID capabilities are granted by default; this option can be used to re-
move them. The list of default capabilities is managed in contain-
ers.conf(5).
If a capability is specified to both the --cap-add and --cap-drop op-
tions, 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 reg-
istry and retrieve contents from HTTPS locations for ADD instructions.
The default certificates directory is /etc/containers/certs.d.
--cgroup-parent=""
Path to cgroups under which the cgroup for the container will be cre-
ated. 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.
--cgroupns how
Sets the configuration for cgroup namespaces when handling RUN instruc-
tions. The configured value can be "" (the empty string) or "private"
to indicate that a new cgroup namespace should be created, or it can be
"host" to indicate that the cgroup namespace in which buildah itself is
being run should be reused.
--compat-volumes
Handle directories marked using the VOLUME instruction (both in this
build, and those inherited from base images) such that their contents
can only be modified by ADD and COPY instructions. Any changes made in
those locations by RUN instructions will be reverted. Before the intro-
duction of this option, this behavior was the default, but it is now
disabled by default.
--compress
This option is added to be aligned with other containers CLIs. 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.
--cpp-flag=""
Set additional flags to pass to the C Preprocessor cpp(1). Container-
files ending with a ".in" suffix will be preprocessed via cpp(1). This
option can be used to pass additional flags to cpp. Note: You can also
set default CPPFLAGS by setting the BUILDAH_CPPFLAGS environment vari-
able (e.g., export BUILDAH_CPPFLAGS="-DDEBUG").
--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/pod-
man/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 tells the kernel to restrict the con-
tainer's CPU usage to the quota you specify.
On some systems, changing the CPU limits may not be allowed for non-root
users. For more details, see https://github.com/containers/pod-
man/blob/main/troubleshooting.md#26-running-containers-with-cpu-limits-
fails-with-a-permissions-error
--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 weight-
ing 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 remain-
ing 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 con-
tainer {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 effec-
tive 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 with-
out echo.
--cw options
Produce an image suitable for use as a confidential workload running in
a trusted execution environment (TEE) using krun (i.e., crun built with
the libkrun feature enabled and invoked as krun). Instead of the con-
ventional contents, the root filesystem of the image will contain an en-
crypted disk image and configuration information for krun.
The value for options is a comma-separated list of key=value pairs, sup-
plying configuration information which is needed for producing the addi-
tional data which will be included in the container image.
Recognized keys are:
attestation_url: The location of a key broker / attestation server. If
a value is specified, the new image's workload ID, along with the
passphrase used to encrypt the disk image, will be registered with the
server, and the server's location will be stored in the container image.
At run-time, krun is expected to contact the server to retrieve the
passphrase using the workload ID, which is also stored in the container
image. If no value is specified, a passphrase value must be specified.
cpus: The number of virtual CPUs which the image expects to be run with
at run-time. If not specified, a default value will be supplied.
firmware_library: The location of the libkrunfw-sev shared library. If
not specified, buildah checks for its presence in a number of hard-coded
locations.
memory: The amount of memory which the image expects to be run with at
run-time, as a number of megabytes. If not specified, a default value
will be supplied.
passphrase: The passphrase to use to encrypt the disk image which will
be included in the container image. If no value is specified, but an
attestation_url value is specified, a randomly-generated passphrase will
be used. The authors recommend setting an attestation_url but not a
passphrase.
slop: Extra space to allocate for the disk image compared to the size of
the container image's contents, expressed either as a percentage (..%)
or a size value (bytes, or larger units if suffixes like KB or MB are
present), or a sum of two or more such specifications. If not speci-
fied, buildah guesses that 25% more space than the contents will be
enough, but this option is provided in case its guess is wrong.
type: The type of trusted execution environment (TEE) which the image
should be marked for use with. Accepted values are "SEV" (AMD Secure
Encrypted Virtualization - Encrypted State) and "SNP" (AMD Secure En-
crypted Virtualization - Secure Nested Paging). If not specified, de-
faults to "SNP".
workload_id: A workload identifier which will be recorded in the con-
tainer image, to be used at run-time for retrieving the passphrase which
was used to encrypt the disk image. If not specified, a semi-random
value will be derived from the base image's image ID.
--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, or devices under a directory, to the environment of
any RUN instructions run during the build. The optional permissions pa-
rameter can be used to specify device permissions, using any one or more
of r for read, w for write, and m for mknod(2).
Example: --device=/dev/sdc:/dev/xvdc:rwm.
Note: if host-device is a symbolic link then it will be resolved first.
The container will only store the major and minor numbers of the host
device.
The device to share can also be specified using a Container Device In-
terface (CDI) specification (https://github.com/cncf-tags/container-de-
vice-interface).
Note: if the user only has access rights via a group, accessing the de-
vice from inside a rootless container will fail. The crun(1) runtime of-
fers 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 Con-
tainer registry and is not supported by Buildah. This flag is a NOOP
and provided solely for scripting compatibility.
--dns=[]
Set custom DNS servers. Invalid if using --dns with --network=none.
This option can be used to override the DNS configuration passed to the
container. Typically this is necessary when the host DNS configuration
is invalid for the container (e.g., 127.0.0.1). When this is the case
the --dns flag is necessary for every run.
The special value none can be specified to disable creation of /etc/re-
solv.conf in the container by Buildah. The /etc/resolv.conf file in the
image will be used without changes.
--dns-option=[]
Set custom DNS options. Invalid if using --dns-option with --net-
work=none.
--dns-search=[]
Set custom DNS search domains. Invalid if using --dns-search with --net-
work=none.
--env env[=value]
Add a value (e.g. env=value) to the built image. Can be used multiple
times. If neither = nor a *value* are specified, but env is set in the
current environment, the value from the current environment will be
added to the image. The value of env can be overridden by ENV instruc-
tions in the Containerfile. To remove an environment variable from the
built image, use the --unsetenv option.
--file, -f Containerfile
Specifies a Containerfile which contains instructions for building the
image, either a local file or an http or https URL. If more than one
Containerfile is specified, FROM instructions will only be accepted from
the last 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 BUIL-
DAH_FORMAT environment variable. export BUILDAH_FORMAT=docker
--from
Overrides the first FROM instruction within the Containerfile. If there
are multiple FROM instructions in a Containerfile, only the first is
changed.
--group-add=group | keep-groups
Assign additional groups to the primary user running within the con-
tainer process.
• keep-groups is a special flag that tells Buildah to keep the
supplementary group access.
Allows container to use the user's supplementary group access. If file
systems or devices are only accessible by the rootless user's group,
this flag tells the OCI runtime to pass the group access into the con-
tainer. Currently only available with the crun OCI runtime. Note: keep-
groups is exclusive, other groups cannot be specified with this flag.
--help, -h
Print usage statement
--hooks-dir path
Each *.json file in the path configures a hook for buildah build con-
tainers. For more details on the syntax of the JSON files and the seman-
tics of hook injection, see oci-hooks(5). Buildah currently support both
the 1.0.0 and 0.1.0 hook schemas, although the 0.1.0 schema is depre-
cated.
This option may be set multiple times; paths from later options have
higher precedence (oci-hooks(5) discusses directory precedence).
For the annotation conditions, buildah uses any annotations set in the
generated OCI configuration.
For the bind-mount conditions, only mounts explicitly requested by the
caller via --volume are considered. Bind mounts that buildah inserts by
default (e.g. /dev/shm) are not considered.
If --hooks-dir is unset for root callers, Buildah will currently default
to /usr/share/containers/oci/hooks.d and /etc/containers/oci/hooks.d in
order of increasing precedence. Using these defaults is deprecated, and
callers should migrate to explicitly setting --hooks-dir.
--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 in-
clude http_proxy, https_proxy, ftp_proxy, no_proxy, and also the upper
case versions of those.
--identity-label bool-value
Adds default identity label io.buildah.version if set. (default true).
--ignorefile file
Path to an alternative .containerignore (.dockerignore) file.
--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.
--ipc how
Sets the configuration for IPC namespaces when handling RUN instruc-
tions. The configured value can be "" (the empty string) or "container"
to indicate that a new IPC namespace should be created, or it can be
"host" to indicate that the IPC namespace in which buildah itself is be-
ing 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[=value]
Add an image label (e.g. label=value) to the image metadata. Can be used
multiple times. If label is named, but neither = nor a value is pro-
vided, then the label is set to an empty value.
Users can set a special LABEL io.containers.capabilities=CAP1,CAP2,CAP3
in a Containerfile that specifies the list of Linux capabilities re-
quired for the container to run properly. This label specified in a con-
tainer image tells container engines, like Podman, which recognize this
label 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 en-
gines should print an error message and will run the container with the
default capabilities.
--layer-label label[=value]
Add an intermediate image label (e.g. label=value) to the metadata in
intermediate images, i.e., any images built for non-final stages and for
non-final instructions in stages when --layers is true. It can be used
multiple times. If label is named, but neither = nor a value is pro-
vided, then the label is set to an empty value.
--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.
--logsplit bool-value
If --logfile and --platform is specified following flag allows end-users
to split log file for each platform into different files with naming
convention as ${logfile}_${platform-os}_${platform-arch}.
--manifest listName
Name of the manifest list to which the built image will be added. Cre-
ates the manifest list if it does not exist. This option is useful for
building multi architecture images. If listName does not include a reg-
istry name component, the registry name localhost will be prepended to
the list name.
--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 con-
tainer's memory is not limited. The actual limit may be rounded up to a
multiple of the operating system's page size (the value 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 (--mem-
ory) 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 (kilo-
bytes), 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 instruc-
tions.
Valid mode values are:
• none: no networking. Invalid if using --dns, --dns-opt, or
--dns-search;
• 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)
• <network name|ID>: Join the network with the given name or ID,
e.g. use --network mynet to join the network with the name
mynet. Only supported for rootful users.
• slirp4netns[:OPTIONS,...]: use slirp4netns(1) to create a user
network stack. This is the default for rootless containers. It
is possible to specify these additional options, they can also
be set with network_cmd_options in containers.conf:
• allow_host_loopback=true|false: Allow slirp4netns to reach
the host loopback IP (default is 10.0.2.2 or the second IP
from slirp4netns cidr subnet when changed, see the cidr op-
tion below). The default is false.
• mtu=MTU: Specify the MTU to use for this network. (Default is
65520).
• cidr=CIDR: Specify ip range to use for this network. (Default
is 10.0.2.0/24).
• enable_ipv6=true|false: Enable IPv6. Default is true. (Re-
quired for outbound_addr6).
• outbound_addr=INTERFACE: Specify the outbound interface slirp
binds to (ipv4 traffic only).
• outbound_addr=IPv4: Specify the outbound ipv4 address slirp
binds to.
• outbound_addr6=INTERFACE: Specify the outbound interface
slirp binds to (ipv6 traffic only).
• outbound_addr6=IPv6: Specify the outbound ipv6 address slirp
binds to.
• pasta[:OPTIONS,...]: use pasta(1) to create a user-mode net-
working stack.
This is only supported in rootless mode.
By default, IPv4 and IPv6 addresses and routes, as well as the
pod interface name, are copied from the host. If port forward-
ing isn't configured, ports are forwarded dynamically as ser-
vices are bound on either side (init namespace or container
namespace). Port forwarding preserves the original source IP
address. Options described in pasta(1) can be specified as
comma-separated arguments.
In terms of pasta(1) options, --config-net is given by default,
in order to configure networking when the container is started,
and --no-map-gw is also assumed by default, to avoid direct ac-
cess from container to host using the gateway address. The lat-
ter can be overridden by passing --map-gw in the pasta-specific
options (despite not being an actual pasta(1) option).
Also, -t none and -u none are passed to disable automatic port
forwarding based on bound ports. Similarly, -T none and -U none
are given to disable the same functionality from container to
host.
Some examples:
• pasta:--map-gw: Allow the container to directly reach the
host using the gateway address.
• pasta:--mtu,1500: Specify a 1500 bytes MTU for the tap inter-
face in the container.
• pasta:--ipv4-only,-a,10.0.2.0,-n,24,-g,10.0.2.2,--dns-for-
ward,10.0.2.3,-m,1500,--no-ndp,--no-dhcpv6,--no-dhcp, equiva-
lent to default slirp4netns(1) options: disable IPv6, assign
10.0.2.0/24 to the tap0 interface in the container, with
gateway 10.0.2.3, enable DNS forwarder reachable at 10.0.2.3,
set MTU to 1500 bytes, disable NDP, DHCPv6 and DHCP support.
• pasta:-I,tap0,--ipv4-only,-a,10.0.2.0,-n,24,-g,10.0.2.2,--dns-
forward,10.0.2.3,--no-ndp,--no-dhcpv6,--no-dhcp, equivalent
to default slirp4netns(1) options with Podman overrides: same
as above, but leave the MTU to 65520 bytes
• pasta:-t,auto,-u,auto,-T,auto,-U,auto: enable automatic port
forwarding based on observed bound ports from both host and
container sides
• pasta:-T,5201: enable forwarding of TCP port 5201 from con-
tainer to host, using the loopback interface instead of the
tap interface for improved performance
--no-cache
Do not use existing cached images for the container build. Build from
the start with a new set of cached layers.
--no-hostname
Do not create the /etc/hostname file in the container for RUN instruc-
tions.
By default, Buildah manages the /etc/hostname file, adding the con-
tainer's own hostname. When the --no-hostname option is set, the im-
age's /etc/hostname will be preserved unmodified if it exists.
--no-hosts
Do not create the /etc/hosts file in the container for RUN instructions.
By default, Buildah manages /etc/hosts, adding the container's own IP
address. --no-hosts disables this, and the image's /etc/hosts will be
preserved unmodified. Conflicts with the --add-host option.
--omit-history bool-value
Omit build history information in the built image. (default false).
This option is useful for the cases where end users explicitly want to
set --omit-history to omit the optional History from built images or
when working with images built using build tools that do not include
History information in their images.
--os="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.
--os-feature feature
Set the name of a required operating system feature for the image which
will be built. By default, if the image is not based on scratch, the
base image's required OS feature list is kept, if the base image speci-
fied any. This option is typically only meaningful when the image's OS
is Windows.
If feature has a trailing -, then the feature is removed from the set of
required features which will be listed in the image.
--os-version version
Set the exact required operating system version for the image which will
be built. By default, if the image is not based on scratch, the base
image's required OS version is kept, if the base image specified one.
This option is typically only meaningful when the image's OS is Windows,
and is typically set in Windows base images, so using this option is
usually unnecessary.
--output, -o=""
Output destination (format: type=local,dest=path)
The --output (or -o) option extends the default behavior of building a
container image by allowing users to export the contents of the image as
files on the local filesystem, which can be useful for generating local
binaries, code generation, etc.
The value for --output is a comma-separated sequence of key=value pairs,
defining the output type and options.
Supported keys are: - dest: Destination path for exported output. Valid
value is absolute or relative path, - means the standard output. -
type: Defines the type of output to be used. Valid values is documented
below.
Valid type values are: - local: write the resulting build files to a di-
rectory on the client-side. - tar: write the resulting files as a sin-
gle tarball (.tar).
If no type is specified, the value defaults to local. Alternatively,
instead of a comma-separated sequence, the value of --output can be just
a destination (in the **dest** format) (e.g. --output some-path, --out-
put -) where --output some-path is treated as if type=local and --output
- is treated as if type=tar.
Note: The --tag option can also be used to change the file image format
to supported containers-transports(5).
--pid how
Sets the configuration for PID namespaces when handling RUN instruc-
tions. 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 be-
ing 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, linux/arm64,
linux/amd64).
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 combina-
tions are listed as values for $GOOS and $GOARCH at
https://golang.org/doc/install/source#environment, and can also be found
by running go tool dist list.
The buildah build command allows building images for all Linux architec-
tures, even non-native architectures. When building images for a differ-
ent architecture, the RUN instructions require emulation software in-
stalled on the host provided by packages like qemu-user-static. Note: it
is always preferred to build images on the native architecture if possi-
ble.
NOTE: The --platform option may not be used in combination with the
--arch, --os, or --variant options.
--pull
Pull image policy. The default is missing.
• always: Pull base and SBOM scanner images from the registries
listed in registries.conf. Raise an error if a base or SBOM
scanner image is not found in the registries, even if an image
with the same name is present locally.
• missing: SBOM scanner images only if they could not be found in
the local containers storage. Raise an error if no image could
be found and the pull fails.
• never: Do not pull base and SBOM scanner images from reg-
istries, use only the local versions. Raise an error if the
image is not present locally.
• newer: Pull base and SBOM scanner images from the registries
listed in registries.conf if newer. Raise an error if a base
or SBOM scanner image is not found in the registries when image
with the same name 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.
--retry attempts
Number of times to retry in case of failure when performing push/pull of
images to/from registry.
Defaults to 3.
--retry-delay duration
Duration of delay between retry attempts in case of failure when per-
forming push/pull of images to/from registry.
Defaults to 2s.
--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 BUIL-
DAH_RUNTIME environment variable. export BUILDAH_RUNTIME=/usr/bin/crun
--runtime-flag flag
Adds global flags for the container runtime. To list the supported
flags, please consult the manpages of the selected container runtime.
Note: Do not pass the leading -- to the flag. To pass the runc flag
--log-format json to buildah build, the option given would be --runtime-
flag log-format=json.
--sbom preset
Generate SBOMs (Software Bills Of Materials) for the output image by
scanning the working container and build contexts using the named combi-
nation of scanner image, scanner commands, and merge strategy. Must be
specified with one or more of --sbom-image-output, --sbom-image-purl-
output, --sbom-output, and --sbom-purl-output. Recognized presets, and
the set of options which they equate to:
• "syft", "syft-cyclonedx":
--sbom-scanner-image=ghcr.io/anchore/syft
--sbom-scanner-command="/syft scan -q dir:{ROOTFS} --output
cyclonedx-json={OUTPUT}"
--sbom-scanner-command="/syft scan -q dir:{CONTEXT} --output
cyclonedx-json={OUTPUT}"
--sbom-merge-strategy=merge-cyclonedx-by-component-name-and-
version
• "syft-spdx":
--sbom-scanner-image=ghcr.io/anchore/syft
--sbom-scanner-command="/syft scan -q dir:{ROOTFS} --output
spdx-json={OUTPUT}"
--sbom-scanner-command="/syft scan -q dir:{CONTEXT} --output
spdx-json={OUTPUT}"
--sbom-merge-strategy=merge-spdx-by-package-name-and-version-
info
• "trivy", "trivy-cyclonedx":
--sbom-scanner-image=ghcr.io/aquasecurity/trivy
--sbom-scanner-command="trivy filesystem -q {ROOTFS} --format
cyclonedx --output {OUTPUT}"
--sbom-scanner-command="trivy filesystem -q {CONTEXT} --format
cyclonedx --output {OUTPUT}"
--sbom-merge-strategy=merge-cyclonedx-by-component-name-and-
version
• "trivy-spdx":
--sbom-scanner-image=ghcr.io/aquasecurity/trivy
--sbom-scanner-command="trivy filesystem -q {ROOTFS} --format
spdx-json --output {OUTPUT}"
--sbom-scanner-command="trivy filesystem -q {CONTEXT} --format
spdx-json --output {OUTPUT}"
--sbom-merge-strategy=merge-spdx-by-package-name-and-version-
info
--sbom-image-output path
When generating SBOMs, store the generated SBOM in the specified path in
the output image. There is no default.
--sbom-image-purl-output path
When generating SBOMs, scan them for PURL (package URL
⟨https://github.com/package-url/purl-spec/blob/master/PURL-SPECIFICA-
TION.rst⟩) information, and save a list of found PURLs to the specified
path in the output image. There is no default.
--sbom-merge-strategy method
If more than one --sbom-scanner-command value is being used, use the
specified method to merge the output from later commands with output
from earlier commands. Recognized values include:
• cat
Concatenate the files.
• merge-cyclonedx-by-component-name-and-version
Merge the "component" fields of JSON documents, ignoring val-
ues from
documents when the combination of their "name" and "version"
values is
already present. Documents are processed in the order in
which they are
generated, which is the order in which the commands that gen-
erate them
were specified.
• merge-spdx-by-package-name-and-versioninfo
Merge the "package" fields of JSON documents, ignoring values
from
documents when the combination of their "name" and "version-
Info" values is
already present. Documents are processed in the order in
which they are
generated, which is the order in which the commands that gen-
erate them
were specified.
--sbom-output file
When generating SBOMs, store the generated SBOM in the named file on the
local filesystem. There is no default.
--sbom-purl-output file
When generating SBOMs, scan them for PURL (package URL
⟨https://github.com/package-url/purl-spec/blob/master/PURL-SPECIFICA-
TION.rst⟩) information, and save a list of found PURLs to the named file
in the local filesystem. There is no default.
--sbom-scanner-command image
Generate SBOMs by running the specified command from the scanner image.
If multiple commands are specified, they are run in the order in which
they are specified. These text substitutions are performed:
- {ROOTFS}
The root of the built image's filesystem, bind mounted.
- {CONTEXT}
The build context and additional build contexts, bind mounted.
- {OUTPUT}
The name of a temporary output file, to be read and merged with
others or copied elsewhere.
--sbom-scanner-image image
Generate SBOMs using the specified scanner image.
--secret=id=id[,src=envOrFile][,env=ENV][,type=file|env]
Pass secret information to be used in the Containerfile for building im-
ages in a safe way that will not end up stored in the final image, or be
seen in other stages. The value of the secret will be read from an en-
vironment variable or file named by the "id" option, or named by the
"src" option if it is specified, or from an environment variable speci-
fied by the "env" option. The secret will be mounted in the container
at /run/secrets/*id* by default.
To later use the secret, use the --mount flag in a RUN instruction
within a Containerfile:
RUN --mount=type=secret,id=mysecret cat /run/secrets/mysecret
The location of the secret in the container can be overridden using the
"target", "dst", or "destination" option of the RUN --mount flag.
RUN --mount=type=secret,id=mysecret,target=/run/secrets/myothersecret
cat /run/secrets/myothersecret
Note: changing the contents of secret files will not trigger a rebuild
of layers that use said secrets.
--security-opt=[]
Security Options
"apparmor=unconfined" : Turn off apparmor confinement for the con-
tainer
"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
"mask=/path/1:/path/2": The paths to mask separated by a colon. A masked
path cannot be accessed inside the container.
"no-new-privileges" : Disable container processes from gaining addi-
tional privileges
"seccomp=unconfined" : Turn off seccomp confinement for the container
"seccomp=profile.json : JSON configuration for a seccomp filter
"unmask=ALL or /path/1:/path/2, or shell expanded paths (/proc/*): Paths
to unmask separated by a colon. If set to ALL, it unmasks all the paths
that are masked or made read-only by default.
The default masked paths are /proc/acpi, /proc/kcore, /proc/keys,
/proc/latency_stats, /proc/sched_debug, /proc/scsi, /proc/timer_list,
/proc/timer_stats, /sys/firmware, and /sys/fs/selinux, /sys/devices/vir-
tual/powercap. The default paths that are read-only are /proc/asound,
/proc/bus, /proc/fs, /proc/irq, /proc/sys, /proc/sysrq-trigger,
/sys/fs/cgroup.
--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 fin-
gerprint.
--skip-unused-stages bool-value
Skip stages in multi-stage builds which don't affect the target stage.
(Default is true).
--squash
Squash all layers, including those from base image(s), into one single
layer. (Default is false).
By default, Buildah preserves existing base-image layers and adds only
one new layer on a build. The --layers option can be used to preserve
intermediate build layers.
--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. Sometimes 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.
The --tag option supports all transports from containers-transports(5).
If no transport is specified, the containers-storage (i.e., local stor-
age) transport is used.
buildah build --tag=oci-archive:./foo.ociarchive .
buildah build -t quay.io/username/foo .
--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. Com-
mands after the target stage will be skipped.
--timestamp seconds
Set the create timestamp to seconds since epoch to allow for determinis-
tic builds (defaults to current time). By default, the created time-
stamp 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 time-
stamp is always set to the time specified and therefore not changed, al-
lowing 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) and retrieving content from HTTPS loca-
tions for ADD instructions. TLS verification cannot be used when talk-
ing 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. Recog-
nized resource types include:
"core": maximum core dump size (ulimit -c)
"cpu": maximum CPU time (ulimit -t)
"data": maximum size of a process's data segment (ulimit -d)
"fsize": maximum size of new files (ulimit -f)
"locks": maximum number of file locks (ulimit -x)
"memlock": maximum amount of locked memory (ulimit -l)
"msgqueue": maximum amount of data in message queues (ulimit -q)
"nice": niceness adjustment (nice -n, ulimit -e)
"nofile": maximum number of open files (ulimit -n)
"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)
--unsetenv env
Unset environment variables from the final image.
--unsetlabel label
Unset the image label, causing the label not to be inherited from the
base image.
--userns how
Sets the configuration for user namespaces when handling RUN instruc-
tions. The configured value can be "" (the empty string) , "private" or
"auto" 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.
auto: automatically create a unique user namespace.
The --userns=auto flag, requires that the user name containers and a
range of subordinate user ids that the build container is allowed to use
be specified in the /etc/subuid and /etc/subgid files.
Example: containers:2147483647:2147483648.
Buildah allocates unique ranges of UIDs and GIDs from the containers
subordinate user ids. The size of the ranges is based on the number of
UIDs required in the image. The number of UIDs and GIDs can be overrid-
den with the size option.
Valid auto options:
• gidmapping=CONTAINER_GID:HOST_GID:SIZE: to force a GID mapping
to be present in the user namespace.
• size=SIZE: to specify an explicit size for the automatic user
namespace. e.g. --userns=auto:size=8192. If size is not speci-
fied, auto will estimate a size for the user namespace.
• uidmapping=CONTAINER_UID:HOST_UID:SIZE: to force a UID mapping
to be present in the user namespace.
--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 colon-separated 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.
--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 be-
ing 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 op-
tion.
Users can specify the maps directly using --userns-gid-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-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 colon-separated 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.
--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.
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.
--uts how
Sets the configuration for UTS namespaces when handling RUN instruc-
tions. The configured value can be "" (the empty string) or "container"
to indicate that a new UTS namespace should be created, or it can be
"host" to indicate that the UTS namespace in which buildah itself is be-
ing 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]]]
Mount a host directory into containers when executing RUN instructions
during the build. The OPTIONS are a comma delimited list and can be:
• [rw|ro]
• [U]
• [z|Z|O]
• [[r]shared|[r]slave|[r]private] [1] ⟨#Footnote1⟩
The CONTAINER-DIR must be an absolute path such as /src/docs. The HOST-
DIR must be an absolute path as well. 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 an-
other 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 us-
ing 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 la-
bels the content with a shared content label. Shared volume labels allow
all containers to read/write content. The Z option tells Buildah to la-
bel the content with a private unshared label. Only the current con-
tainer can use a private volume.
Overlay Volume Mounts
The :O flag tells Buildah to mount the directory from the host as a tem-
porary storage using the Overlay file system. The RUN command containers
are allowed to modify contents within the mountpoint and are stored in
the container storage in a separate directory. In Overlay FS terms the
source directory 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 direc-
tory content, any changes from previous RUN commands no longer exist.
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 must be
readable by the container label. If not, SELinux container sep-
aration 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 con-
tainer 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 prop-
erty.
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 prop-
erties of source mount, if findmnt utility is not available, the source
mount point can be determined by looking at the mount entry in
/proc/self/mountinfo. Look at optional fields and see if any propagation
properties are specified. shared:X means the mount is shared, master:X
means the mount is slave and if nothing is there that means the mount is
private. [1] ⟨#Footnote1⟩
To change propagation properties of a mount point use the mount command.
For example, to bind mount the source directory /foo do mount --bind
/foo /foo and mount --make-private --make-shared /foo. This 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 con-
tainer 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 us-
ing the ENV instruction.
• HTTP_PROXY
• HTTPS_PROXY
• FTP_PROXY
• NO_PROXY
Please refer to the Using Build Time Variables ⟨#using-build-time-vari-
ables⟩ section of the Examples.
EXAMPLE
Build an image using local Containerfiles
buildah build .
buildah build -f Containerfile .
cat ~/Containerfile | buildah build -f - .
buildah build -f Containerfile.simple -f Containerfile.notsosimple .
buildah build --timestamp=$(date '+%s') -t imageName .
buildah build -t imageName .
buildah build --tls-verify=true -t imageName -f Containerfile.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 Container-
file.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 --cpp-flag="-DDEBUG" -t imageName .
buildah build --network mynet .
buildah build --env LANG=en_US.UTF-8 -t imageName .
buildah build --env EDITOR -t imageName .
buildah build --unsetenv LANG -t imageName .
buildah build --os-version 10.0.19042.1645 -t imageName .
buildah build --os-feature win32k -t imageName .
buildah build --os-feature win32k- -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 build --platform linux/arm64 --platform linux/amd64 --manifest
myimage /tmp/mysrc
buildah bud --all-platforms --manifest myimage /tmp/mysrc
Building an image using (--output) custom build output
buildah build -o out .
buildah build --output type=local,dest=out .
buildah build --output type=tar,dest=out.tar .
buildah build -o - . > out.tar
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 reposi-
tory is used as the context of the build. This only works if the GitHub
repository is a dedicated repository.
buildah build https://github.com/containers/PodmanHello.git
Note: Github does not support using git:// for performing clone opera-
tion due to recent changes in their security guidance
(https://github.blog/2021-09-01-improving-git-protocol-security-
github/). Use an https:// URL if the source repository is hosted on
Github.
Building an image using a URL to a tarball'ed context
Buildah will fetch the tarball archive, decompress it and use its con-
tents 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/buildah/con-
text.tar.gz
Note: supported compression formats are 'xz', 'bzip2', 'gzip' and 'iden-
tity' (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 con-
tains lists of registry names under the keys insecureRegistries, blocke-
dRegistries, 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 direc-
tory, buildah build reads its contents. If both exist, then .container-
ignore 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 .containerig-
nore/.dockerignore file to identify files/directories to exclude.
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 end with .c in any top
level subdirectory. For example, the source file include/rootless.c.
**/output* Excludes files and directories starting with output from any
directory.
src Excludes files named src and the directory src as well as any con-
tent in it.
Lines starting with ! (exclamation mark) can be used to make exceptions
to exclusions. The following is an example .containerignore/.dockerig-
nore file that uses this mechanism:
*.doc
!Help.doc
Exclude all doc files except Help.doc from the image.
This functionality is compatible with the handling of .containerignore
files described here:
https://github.com/containers/common/blob/main/docs/containerignore.5.md
registries.conf (/etc/containers/registries.conf)
registries.conf is the configuration file which specifies which con-
tainer registries 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 im-
ages. Controls which container registries can be used for image, and
whether or not the tool should trust the images.
SEE ALSO
buildah(1), cpp(1), buildah-login(1), docker-login(1), namespaces(7),
pid_namespaces(7), containers-policy.json(5), containers-reg-
istries.conf(5), user_namespaces(7), crun(1), runc(8), contain-
ers.conf(5), oci-hooks(5), containers-transports(5), containers-
auth.json(5)
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.
buildah April 2017 buildah-build(1)
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