Provided by: buildah_1.39.3+ds1-1syncable1_amd64 
NAME
buildah-from - Creates a new working container, either from scratch or using a specified image as a
starting point.
SYNOPSIS
buildah from [options] image
DESCRIPTION
Creates a working container based upon the specified image name. If the supplied image name is "scratch"
a new empty container is created. Image names use a "transport":"details" format.
Multiple transports are supported:
dir:path
An existing local directory path containing the manifest, layer tarballs, and signatures in individual
files. This is a non-standardized format, primarily useful for debugging or noninvasive image inspection.
docker://docker-reference (Default)
An image in a registry implementing the "Docker Registry HTTP API V2". By default, uses the
authorization state in $XDG_RUNTIME_DIR/containers/auth.json, which is set using (buildah login). See
containers-auth.json(5) for more information. If the authorization state is not found there,
$HOME/.docker/config.json is checked, which is set using (docker login).
If docker-reference does not include a registry name, localhost will be consulted first, followed by
any registries named in the registries configuration.
docker-archive:path
An image is retrieved as a podman load formatted file.
docker-daemon:docker-reference
An image docker-reference stored in the docker daemon's internal storage. docker-reference must
include either a tag or a digest. Alternatively, when reading images, the format can also be docker-
daemon:algo:digest (an image ID).
oci:path:tag**
An image tag in a directory compliant with "Open Container Image Layout Specification" at path.
oci-archive:path:tag
An image tag in a directory compliant with "Open Container Image Layout Specification" at path.
DEPENDENCIES
Buildah resolves the path to the registry to pull from by using the /etc/containers/registries.conf file,
containers-registries.conf(5). If the buildah from command fails with an "image not known" error, first
verify that the registries.conf file is installed and configured appropriately.
RETURN VALUE
The container ID of the container that was created. On error 1 is returned.
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.
--arch="ARCH"
Set the ARCH of the image to be pulled 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. 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 REGISTRY_AUTH_FILE=path
--cap-add=CAP_xxx
Add the specified capability to the default set of capabilities which will be supplied for subsequent
buildah run invocations which use this container. Certain capabilities are granted by default; this
option can be used to add more.
--cap-drop=CAP_xxx
Remove the specified capability from the default set of capabilities which will be supplied for
subsequent buildah run invocations which use this container. The CAP_CHOWN, CAP_DAC_OVERRIDE,
CAP_FOWNER, CAP_FSETID, CAP_KILL, CAP_NET_BIND_SERVICE, CAP_SETFCAP, CAP_SETGID, CAP_SETPCAP, and
CAP_SETUID capabilities are granted by default; this option can be used to remove them. The list of
default capabilities is managed in containers.conf(5).
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.
--cgroupns how
Sets the configuration for IPC namespaces when the container is subsequently used for buildah run. 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.
--cidfile ContainerIDFile
Write the container ID to the file.
--cpu-period=0
Limit the CPU CFS (Completely Fair Scheduler) period
Limit the container's CPU usage. This flag tells the kernel to restrict the container's CPU usage to the
period you specify.
--cpu-quota=0
Limit the CPU CFS (Completely Fair Scheduler) quota
Limit the container's CPU usage. By default, containers run with the full CPU resource. This flag tells
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, or devices under a directory, to the environment of subsequent buildah run invocations
for the new working container. The optional permissions parameter 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 Interface (CDI) specification
(https://github.com/cncf-tags/container-device-interface).
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.
--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
--format, -f oci | docker
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
--group-add=group | keep-groups
Assign additional groups to the primary user running within the container 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 container. Currently only available with the crun OCI runtime. Note: keep-groups is exclusive, other
groups cannot be specified with this flag.
--http-proxy
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.
Defaults to true
--ipc how
Sets the configuration for IPC namespaces when the container is subsequently used for buildah run. 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 under buildah run. 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
--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.
--name name
A name for the working container
--network=mode, --net=mode
Sets the configuration for network namespaces when the container is subsequently used for buildah run.
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 option
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. (Required 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 networking 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 forwarding isn't configured, ports are forwarded dynamically as services
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
access from container to host using the gateway address. The latter 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 interface in the container.
• pasta:--ipv4-only,-a,10.0.2.0,-n,24,-g,10.0.2.2,--dns-forward,10.0.2.3,-m,1500,--no-ndp,--no-
dhcpv6,--no-dhcp, equivalent 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 container to host, using the loopback
interface instead of the tap interface for improved performance
--os="OS"
Set the OS of the image to be pulled to the provided value instead of using the current operating system
of the host.
--pid how
Sets the configuration for PID namespaces when the container is subsequently used for buildah run. The
configured value can be "" (the empty string) or "container" to indicate that a new PID namespace should
be created, or it can be "host" to indicate that the PID namespace in which 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 image to be pulled to the provided value instead of using the current operating
system and architecture of the host (for example linux/arm).
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 from is happy to pull an image for any platform that exists, buildah run will not be able
to run binaries provided by that image without the help of emulation provided by packages like qemu-user-
static.
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 registries, 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
If an image needs to be pulled from the registry, suppress progress output.
--retry attempts
Number of times to retry in case of failure when performing pull of images from registry.
Defaults to 3.
--retry-delay duration
Duration of delay between retry attempts in case of failure when performing pull of images from registry.
Defaults to 2s.
--security-opt=[]
Security Options
"label=user:USER" : Set the label user for the container
"label=role:ROLE" : Set the label role for the container
"label=type:TYPE" : Set the label type for the container
"label=level:LEVEL" : Set the label level for the container
"label=disable" : Turn off label confinement for the container
"no-new-privileges" : Not supported
"seccomp=unconfined" : Turn off seccomp confinement for the container
"seccomp=profile.json : White listed syscalls seccomp Json file to be used as a seccomp filter
"apparmor=unconfined" : Turn off apparmor confinement for the container
"apparmor=your-profile" : Set the apparmor confinement profile for the container
--shm-size=""
Size of /dev/shm. The format is <number><unit>. number must be greater than 0. Unit is optional and can
be b (bytes), k (kilobytes), m(megabytes), or g (gigabytes). If you omit the unit, the system uses
bytes. If you omit the size entirely, the system uses 64m.
--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 during buildah run. 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 the container is subsequently used for buildah run. The
configured value can be "" (the empty string) or "container" to indicate that a new user namespace should
be created, it can be "host" to indicate that the user namespace in which 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-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 mapping
Directly specifies a GID mapping which should be used to set ownership, at the filesystem level, on the
container's contents. Commands run using buildah run will default to being run in their own user
namespaces, configured using the UID and GID maps.
Entries in this map take the form of one or more triples of a starting in-container GID, a corresponding
starting host-level GID, and the number of consecutive IDs which the map entry represents.
This option overrides the remap-gids setting in the options section of /etc/containers/storage.conf.
If this option is not specified, but a global --userns-gid-map setting is supplied, settings from the
global option will be used.
If none of --userns-uid-map-user, --userns-gid-map-group, or --userns-gid-map are specified, but
--userns-uid-map is specified, the GID map will be set to use the same numeric values as the UID map.
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
container's contents, can be found in entries in the /etc/subgid file which correspond to the specified
group. Commands run using buildah run 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.
--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 mapping
Directly specifies a UID mapping which should be used to set ownership, at the filesystem level, on the
container's contents. Commands run using buildah run will default to being run in their own user
namespaces, configured using the UID and GID maps.
Entries in this map take the form of one or more triples of a starting in-container UID, a corresponding
starting host-level UID, and the number of consecutive IDs which the map entry represents.
This option overrides the remap-uids setting in the options section of /etc/containers/storage.conf.
If this option is not specified, but a global --userns-uid-map setting is supplied, settings from the
global option will be used.
If none of --userns-uid-map-user, --userns-gid-map-group, or --userns-uid-map are specified, but
--userns-gid-map is specified, the UID map will be set to use the same numeric values as the GID map.
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-user user
Specifies that a UID mapping which should be used to set ownership, at the filesystem level, on the
container's contents, can be found in entries in the /etc/subuid file which correspond to the specified
user. Commands run using buildah run 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.
--uts how
Sets the configuration for UTS namespaces when the container is subsequently used for buildah run. 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:
• [rw|ro]
• [U]
• [z|Z|O]
• [[r]shared|[r]slave|[r]private|[r]unbindable] [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 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 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 need 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, [r]private or [r]unbindablepropagation 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.
EXAMPLE
buildah from --pull imagename
buildah from --pull docker://myregistry.example.com/imagename
buildah from docker-daemon:imagename:imagetag
buildah from --name mycontainer docker-archive:filename
buildah from oci-archive:filename
buildah from --name mycontainer dir:directoryname
buildah from --pull-always --name "mycontainer" myregistry.example.com/imagename
buildah from --tls-verify=false myregistry/myrepository/imagename:imagetag
buildah from --creds=myusername:mypassword --cert-dir ~/auth myregistry/myrepository/imagename:imagetag
buildah from --authfile=/tmp/auths/myauths.json myregistry/myrepository/imagename:imagetag
buildah from --memory 40m --cpu-shares 2 --cpuset-cpus 0,2 --security-opt label=level:s0:c100,c200
myregistry/myrepository/imagename:imagetag
buildah from --ulimit nofile=1024:1028 --cgroup-parent /path/to/cgroup/parent
myregistry/myrepository/imagename:imagetag
buildah from --volume /home/test:/myvol:ro,Z myregistry/myrepository/imagename:imagetag
buildah from -v /home/test:/myvol:z,U myregistry/myrepository/imagename:imagetag
buildah from -v /var/lib/yum:/var/lib/yum:O myregistry/myrepository/imagename:imagetag
buildah from --arch=arm --variant v7 myregistry/myrepository/imagename:imagetag
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
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.
SEE ALSO
buildah(1), buildah-pull(1), buildah-login(1), docker-login(1), namespaces(7), pid_namespaces(7),
containers-policy.json(5), containers-registries.conf(5), user_namespaces(7), containers.conf(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 March 2017 buildah-from(1)