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% podman-pod-create(1)

NAME

podman-pod-create - Create a new pod

SYNOPSIS

podman pod create [options]

DESCRIPTION

Creates an empty pod, or unit of multiple containers, and prepares it to have containers added to it. The pod id is printed to STDOUT. You can then use podman create --pod <pod_id|pod_name> ... to add containers to the pod, and podman pod start <pod_id|pod_name> to start the pod.

OPTIONS

--add-host=host:ip

Add a host to the /etc/hosts file shared between all containers in the pod.

--cgroup-parent=path

Path to cgroups under which the cgroup for the pod 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.

--cpus=amount

Set the total number of CPUs delegated to the pod. Default is 0.000 which indicates that there is no limit on computation power.

--cpuset-cpus=amount

Limit the CPUs to support execution. First CPU is numbered 0. Unlike --cpus this is of type string and parsed as a list of numbers

Format is 0-3,0,1

Examples of the List Format:

0-4,9 # bits 0, 1, 2, 3, 4, and 9 set 0-2,7,12-14 # bits 0, 1, 2, 7, 12, 13, and 14 set

--device=host-device[:container-device][:permissions]

Add a host device to the pod. Optional permissions parameter can be used to specify device permissions It is a combination 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 pod will only store the major and minor numbers of the host device.

Note: the pod implements devices by storing the initial configuration passed by the user and recreating the device on each container added to the pod.

Podman may load kernel modules required for using the specified device. The devices that Podman will load modules for when necessary are: /dev/fuse.

--dns=ipaddr

Set custom DNS servers in the /etc/resolv.conf file that will be shared between all containers in the pod. A special option, "none" is allowed which disables creation of /etc/resolv.conf for the pod.

--dns-opt=option

Set custom DNS options in the /etc/resolv.conf file that will be shared between all containers in the pod.

--dns-search=domain

Set custom DNS search domains in the /etc/resolv.conf file that will be shared between all containers in the pod.

--gidmap=container_gid:host_gid:amount

GID map for the user namespace. Using this flag will run the container with user namespace enabled. It conflicts with the --userns and --subgidname flags.

--uidmap=container_uid:from_uid:amount

Run the container in a new user namespace using the supplied mapping. This option conflicts with the --userns and --subuidname options. This option provides a way to map host UIDs to container UIDs. It can be passed several times to map different ranges.

--subgidname=name

Name for GID map from the /etc/subgid file. Using this flag will run the container with user namespace enabled. This flag conflicts with --userns and --gidmap.

--subuidname=name

Name for UID map from the /etc/subuid file. Using this flag will run the container with user namespace enabled. This flag conflicts with --userns and --uidmap.

--help, -h

Print usage statement.

--hostname=name

Set a hostname to the pod

--infra

Create an infra container and associate it with the pod. An infra container is a lightweight container used to coordinate the shared kernel namespace of a pod. Default: true.

--infra-conmon-pidfile=file

Write the pid of the infra container's conmon process to a file. As conmon runs in a separate process than Podman, this is necessary when using systemd to manage Podman containers and pods.

--infra-command=command

The command that will be run to start the infra container. Default: "/pause".

--infra-image=image

The image that will be created for the infra container. Default: "k8s.gcr.io/pause:3.1".

--infra-name=name

The name that will be used for the pod's infra container.

--ip=ipaddr

Set a static IP for the pod's shared network.

--label=label, -l

Add metadata to a pod (e.g., --label com.example.key=value).

--label-file=label

Read in a line delimited file of labels.

--mac-address=address

Set a static MAC address for the pod's shared network.

--name=name, -n

Assign a name to the pod.

--network=mode, --net

Set network mode for the pod. Supported values are:

  • bridge: Create a network stack on the default bridge. This is the default for rootfull containers.
  • none: Create a network namespace for the container but do not configure network interfaces for it, thus the container has no network connectivity.
  • host: Do not create a network namespace, all containers in the pod will use the host's network. Note: the host mode gives the container full access to local system services such as D-bus and is therefore considered insecure.
  • network: Connect to a user-defined network, multiple networks should be comma-separated.
  • private: Create a new namespace for the container. This will use the bridge mode for rootfull containers and slirp4netns for rootless ones.
  • 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:
    • allow_host_loopback=true|false: Allow the slirp4netns to reach the host loopback IP (10.0.2.2, which is added to /etc/hosts as host.containers.internal for your convenience). 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 false. (Required for outbound_addr6).
    • outbound_addr=INTERFACE: Specify the outbound interface slirp should bind to (ipv4 traffic only).
    • outbound_addr=IPv4: Specify the outbound ipv4 address slirp should bind to.
    • outbound_addr6=INTERFACE: Specify the outbound interface slirp should bind to (ipv6 traffic only).
    • outbound_addr6=IPv6: Specify the outbound ipv6 address slirp should bind to.
    • port_handler=rootlesskit: Use rootlesskit for port forwarding. Default. Note: Rootlesskit changes the source IP address of incoming packets to a IP address in the container network namespace, usually 10.0.2.100. If your application requires the real source IP address, e.g. web server logs, use the slirp4netns port handler. The rootlesskit port handler is also used for rootless containers when connected to user-defined networks.
    • port_handler=slirp4netns: Use the slirp4netns port forwarding, it is slower than rootlesskit but preserves the correct source IP address. This port handler cannot be used for user-defined networks.

--network-alias=strings

Add a DNS alias for the pod. When the pod is joined to a CNI network with support for the dnsname plugin, the containers inside the pod will be accessible through this name from other containers in the network.

--no-hosts

Disable creation of /etc/hosts for the pod.

--pid=pid

Set the PID mode for the pod. The default is to create a private PID namespace for the pod. Requires the PID namespace to be shared via --share.

host: use the host’s PID namespace for the pod
ns: join the specified PID namespace
private: create a new namespace for the pod (default)

--pod-id-file=path

Write the pod ID to the file.

--publish=port, -p

Publish a port or range of ports from the pod to the host.

Format: ip:hostPort:containerPort | ip::containerPort | hostPort:containerPort | containerPort Both hostPort and containerPort can be specified as a range of ports. When specifying ranges for both, the number of container ports in the range must match the number of host ports in the range. Use podman port to see the actual mapping: podman port CONTAINER $CONTAINERPORT.

NOTE: This cannot be modified once the pod is created.

--replace

If another pod with the same name already exists, replace and remove it. The default is false.

--share=namespace

A comma-separated list of kernel namespaces to share. If none or "" is specified, no namespaces will be shared. The namespaces to choose from are ipc, net, pid, uts.

The operator can identify a pod in three ways: UUID long identifier (“f78375b1c487e03c9438c729345e54db9d20cfa2ac1fc3494b6eb60872e74778”) UUID short identifier (“f78375b1c487”) Name (“jonah”)

podman generates a UUID for each pod, and if a name is not assigned to the container with --name then a random string name will be generated for it. The name is useful any place you need to identify a pod.

--userns=mode

Set the user namespace mode for all the containers in a pod. It defaults to the PODMAN_USERNS environment variable. An empty value ("") means user namespaces are disabled.

Valid mode values are:

  • auto[:OPTIONS,...]: automatically create a namespace. It is possible to specify these options to auto:
    • 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 specified, 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.
  • host: run in the user namespace of the caller. The processes running in the container will have the same privileges on the host as any other process launched by the calling user (default).
  • keep-id: creates a user namespace where the current rootless user's UID:GID are mapped to the same values in the container. This option is ignored for containers created by the root user.

--volume, -v[=[[SOURCE-VOLUME|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. Similarly, -v SOURCE-VOLUME:/CONTAINER-DIR will mount the volume in the host to the container. If no such named volume exists, Podman will create one. The OPTIONS are a comma-separated list and can be: [1] (Note when using the remote client, the volumes will be mounted from the remote server, not necessarily the client machine.)

The options is a comma-separated list and can be:

  • rw|ro
  • z|Z
  • [r]shared|[r]slave|[r]private[r]unbindable
  • [r]bind
  • [no]exec
  • [no]dev
  • [no]suid
  • [O]
  • [U]

The CONTAINER-DIR must be an absolute path such as /src/docs. The volume will be mounted into the container at this directory.

Volumes may specify a source as well, as either a directory on the host or the name of a named volume. If no source is given, the volume will be created as an anonymously named volume with a randomly generated name, and will be removed when the pod is removed via the --rm flag or podman rm --volumes commands.

If a volume source is specified, it must be a path on the host or the name of a named volume. Host paths are allowed to be absolute or relative; relative paths are resolved relative to the directory Podman is run in. If the source does not exist, Podman will return an error. Users must pre-create the source files or directories.

Any source that does not begin with a . or / will be treated as the name of a named volume. If a volume with that name does not exist, it will be created. Volumes created with names are not anonymous, and they are not removed by the --rm option and the podman rm --volumes command.

You can specify multiple -v options to mount one or more volumes into a pod.

Write Protected Volume Mounts

You can add :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, Podman does not change the owner and group of source volume directories mounted into containers. If a pod 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 Podman to use the correct host UID and GID based on the UID and GID within the pod, to change recursively the owner and group of the source volume.

Warning use with caution since this will modify the host filesystem.

Labeling Volume Mounts

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

To change a label in the pod 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 pods 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 pod can use a private volume.

Overlay Volume Mounts

The :O flag tells Podman to mount the directory from the host as a temporary storage using the overlay file system. The pod processes can modify content within the mountpoint which is stored in the container storage in a separate directory. In overlay 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 pod finishes executing, similar to a tmpfs mount point being unmounted.

Subsequent executions of the container will see the original source directory content, any changes from previous pod executions 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 conflicts with other options listed above.

Content mounted into the container is labeled with the private label. On SELinux systems, labels in the source directory must be readable by the infra container label. Usually containers can read/execute container_share_t and can read/write container_file_t. If you cannot change the labels on a source volume, SELinux container separation must be disabled for the infra container/pod to work. - The source directory mounted into the pod with an overlay mount should not be modified, it can cause unexpected failures. It is recommended that you do not modify the directory until the container finishes running.

Mounts propagation

By default bind mounted volumes are private. That means any mounts done inside pod will not be visible on host and vice versa. One can change this behavior by specifying a volume mount propagation property. Making a volume shared mounts done under that volume inside pod will be visible on host and vice versa. Making a volume slave enables only one way mount propagation and that is mounts done on host under that volume will be visible inside container but not the other way around. [1]

To control mount propagation property of a volume one can use the [r]shared, [r]slave, [r]private or the [r]unbindable propagation flag. Propagation property can be specified only for bind mounted volumes and not for internal volumes or named volumes. For mount propagation to work the source mount point (the 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 point has to be either shared or slave. [1]

If you want to recursively mount a volume and all of its submounts into a pod, then you can use the rbind option. By default the bind option is used, and submounts of the source directory will not be mounted into the pod.

Mounting the volume with the nosuid options means that SUID applications on the volume will not be able to change their privilege. By default volumes are mounted with nosuid.

Mounting the volume with the noexec option means that no executables on the volume will be able to executed within the pod.

Mounting the volume with the nodev option means that no devices on the volume will be able to be used by processes within the pod. By default volumes are mounted with nodev.

If the <source-dir> is a mount point, then "dev", "suid", and "exec" options are ignored by the kernel.

Use df <source-dir> to figure out the source mount and then use findmnt -o TARGET,PROPAGATION <source-mount-dir> to figure out propagation properties of source mount. If findmnt utility is not available, then one can look at the mount entry for the source mount point in /proc/self/mountinfo. Look at optional fields and see if any propagation properties are specified. shared:X means mount is shared, master:X means mount is slave and if nothing is there that means mount is private. [1]

To change propagation properties of a mount point use mount command. For example, if one wants to bind mount source directory /foo one can do mount --bind /foo /foo and mount --make-private --make-shared /foo. This will convert /foo into a shared mount point. Alternatively one can directly change propagation properties of source mount. Say / is source mount for /foo, then use mount --make-shared / to convert / into a shared mount.

Note: if the user only has access rights via a group, accessing the volume from inside a rootless pod will fail.

EXAMPLES

$ podman pod create --name test

$ podman pod create --infra=false

$ podman pod create --infra-command /top

$ podman pod create --publish 8443:443

$ podman pod create --network slirp4netns:outbound_addr=127.0.0.1,allow_host_loopback=true

$ podman pod create --network slirp4netns:cidr=192.168.0.0/24

SEE ALSO

podman-pod(1)

HISTORY

July 2018, Originally compiled by Peter Hunt [email protected]