path: root/docs/podman-build.1.md

% podman-build(1)

## NAME
podman\-build - Build a container image using a Dockerfile

## SYNOPSIS
**podman build** [*options*] *context*

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

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

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

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

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

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

## OPTIONS

**--add-host**=[]

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

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

**--annotation** *annotation*

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

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

**--authfile** *path*

Path of the authentication file. Default is ${XDG\_RUNTIME\_DIR}/containers/auth.json, which is set using `podman login`.
If the authorization state is not found there, $HOME/.docker/config.json is checked, which is set using `docker login`. (Not available for remote commands)

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

**--build-arg** *arg=value*

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

**--cache-from**

Images to utilize as potential cache sources. Podman does not currently support caching so this is a NOOP.

**--cap-add**=*CAP\_xxx*

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

**--cap-drop**=*CAP\_xxx*

When executing RUN instructions, run the command specified in the instruction
with the specified capability removed from its capability set.
The CAP\_AUDIT\_WRITE, CAP\_CHOWN, CAP\_DAC\_OVERRIDE, CAP\_FOWNER,
CAP\_FSETID, CAP\_KILL, CAP\_MKNOD, CAP\_NET\_BIND\_SERVICE, CAP\_SETFCAP,
CAP\_SETGID, CAP\_SETPCAP, CAP\_SETUID, and CAP\_SYS\_CHROOT capabilities are
granted by default; this option can be used to remove them.

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

**--cert-dir** *path*

Use certificates at *path* (\*.crt, \*.cert, \*.key) to connect to the registry.
Default certificates directory is _/etc/containers/certs.d_. (Not available for remote commands)

**--cgroup-parent**=""

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

**--compress**

This option is added to be aligned with other containers CLIs.
Podman doesn't communicate with a daemon or a remote server.
Thus, compressing the data before sending it is irrelevant to Podman.

**--cni-config-dir**=*directory*

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

**--cni-plugin-path**=*directory[:directory[:directory[...]]]*

List of directories in which the CNI plugins which will be used for configuring
network namespaces can be found.

**--cpu-period**=*0*

Limit the CPU CFS (Completely Fair Scheduler) period

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

**--cpu-quota**=*0*

Limit the CPU CFS (Completely Fair Scheduler) quota

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

**--cpu-shares, -c**=*0*

CPU shares (relative weight)

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

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

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

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

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

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

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

**--cpuset-cpus**=""

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

**--cpuset-mems**=""

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

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

**--creds** *creds*

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

**--disable-content-trust**

This is a Docker specific option to disable image verification to a Docker
registry and is not supported by Podman.  This flag is a NOOP and provided
soley for scripting compatibility.

**--file, -f** *Dockerfile*

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

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

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

**--force-rm** *bool-value*

Always remove intermediate containers after a build, even if the build is unsuccessful.

**--format**

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

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

**--iidfile** *ImageIDfile*

Write the image ID to the file.

**--ipc** *how*

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

**--isolation** *type*

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

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

**--label** *label*

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

**--layers**

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

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

**--logfile** *filename*

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

**--memory, -m**=""
Memory limit (format: <number>[<unit>], 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.

**--net** *how*
**--network** *how*

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

**--no-cache**

Do not use existing cached images for the container build. Build from the start with a new set of cached layers.

**--pid** *how*

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

**--pull**

When the flag is enabled, attempt to pull the latest image from the registries
listed in registries.conf if a local image does not exist or the image is newer
than the one in storage. Raise an error if the image is not in any listed
registry and is not present locally.

If the flag is disabled (with *--pull=false*), do not pull the image from the
registry, use only the local version. Raise an error if the image is not
present locally.

Defaults to *true*.

**--pull-always**

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

**--quiet, -q**

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

**--rm** *bool-value*

Remove intermediate containers after a successful build (default true).

**--runtime** *path*

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

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

**--runtime-flag** *flag*

Adds global flags for the container rutime. To list the supported flags, please
consult the manpages of the selected container runtime (`runc` is the default
runtime, the manpage to consult is `runc(8)`).

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

**--security-opt**=[]

Security Options

  "label=user:USER"   : Set the label user for the container
  "label=role:ROLE"   : Set the label role for the container
  "label=type:TYPE"   : Set the label type for the container
  "label=level:LEVEL" : Set the label level for the container
  "label=disable"     : Turn off label confinement for the container
  "no-new-privileges" : Not supported

  "seccomp=unconfined" : Turn off seccomp confinement for the container
  "seccomp=profile.json :  White listed syscalls seccomp Json file to be used as a seccomp filter

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

**--shm-size**=""

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

**--squash**

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

**--tag, -t** *imageName*

Specifies the name which will be assigned to the resulting image if the build
process completes successfully.
If _imageName_ does not include a registry name, the registry name *localhost* will be prepended to the image name.

**--target** *stageName*

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

**--tls-verify** *bool-value*

Require HTTPS and verify certificates when talking to container registries (defaults to true). (Not available for remote commands)

**--ulimit**=*type*=*soft-limit*[:*hard-limit*]

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

**--userns** *how*

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

**--userns-uid-map** *mapping*

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

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

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

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

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

**--userns-gid-map** *mapping*

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

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

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

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

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

**--userns-uid-map-user** *user*

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

**--userns-gid-map-group** *group*

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

**--uts** *how*

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

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

   Create a bind mount. If you specify, ` -v /HOST-DIR:/CONTAINER-DIR`, podman
   bind mounts `/HOST-DIR` in the host to `/CONTAINER-DIR` in the podman
   container. The `OPTIONS` are a comma delimited list and can be:

   * [rw|ro]
   * [z|Z]
   * [`[r]shared`|`[r]slave`|`[r]private`]

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

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

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

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

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

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

When the mount propagation policy is set to `shared`, any mounts completed inside
the container on that volume will be visible to both the host and container. When
the mount propagation policy is set to `slave`, one way mount propagation is enabled
and any mounts completed on the host for that volume will be visible only inside of the container.
To control the mount propagation property of volume use the `:[r]shared`,
`:[r]slave` or `:[r]private` propagation flag. The propagation property can
be specified only for bind mounted volumes and not for internal volumes or
named volumes. For mount propagation to work on the source mount point (mount point
where source dir is mounted on) has to have the right propagation properties. For
shared volumes, the source mount point has to be shared. And for slave volumes,
the source mount has to be either shared or slave.

Use `df <source-dir>` to determine the source mount and then use
`findmnt -o TARGET,PROPAGATION <source-mount-dir>` to determine propagation
properties of source mount, if `findmnt` utility is not available, the source mount point
can be determined by looking at the mount entry in `/proc/self/mountinfo`. Look
at `optional fields` and see if any propagaion properties are specified.
`shared:X` means the mount is `shared`, `master:X` means the mount is `slave` and if
nothing is there that means the mount is `private`.

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

## EXAMPLES

### Build an image using local Dockerfiles

```
$ podman build .

$ podman build -f Dockerfile.simple .

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

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

$ podman build -f Dockerfile.in ~

$ podman build -t imageName .

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

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

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

$ podman build --runtime-flag debug .

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

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

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

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

$ podman build --layers -t imageName .

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

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

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

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

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

#### Building an image using a URL to a Dockerfile

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

```
$ podman build https://10.10.10.1/podman/Dockerfile
```

#### Building an image using a Git repository

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

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

#### Building an image using a URL to an archive

  Podman will fetch the archive file, decompress it, and use its contents as the build context. The Dockerfile at the root of the archive and the rest of the archive will get used as the context of the build. If you pass `-f PATH/Dockerfile` option as well, the system will look for that file inside the contents of the archive.

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

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

## Files

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

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

## Troubleshooting

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

### Solution

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

## SEE ALSO
podman(1), buildah(1), containers-registries.conf(5), useradd(8)

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

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