podman-pod-clone - Man Page

Create a copy of an existing pod

Synopsis

podman pod clone [options] pod name

Description

podman pod clone creates a copy of a pod, recreating the identical config for the pod and for all of its containers. Users can modify the pods new name and select pod details within the infra container

Options

--blkio-weight=weight

Block IO relative weight. The weight is a value between 10 and 1000.

This option is not supported on cgroups V1 rootless systems.

--blkio-weight-device=device:weight

Block IO relative device weight.

--cgroup-parent=path

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

--cpu-shares, -c=shares

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 combined weight of all the running containers. Default weight is 1024.

The proportion only applies 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 varies 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 receives 50% of the total CPU time. If a fourth container is added 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 the container C0 is started with --cpu-shares=512 running one process, and another container C1 with --cpu-shares=1024 running two processes, this can result in the following division of CPU shares:

PIDcontainerCPUCPU share
100C00100% of CPU0
101C11100% of CPU1
102C12100% of CPU2

On some systems, changing the resource limits may not be allowed for non-root users. For more details, see https://github.com/containers/podman/blob/main/troubleshooting.md#26-running-containers-with-resource-limits-fails-with-a-permissions-error

This option is not supported on cgroups V1 rootless systems.

--cpus

Set a number of CPUs for the pod that overrides the original pods CPU limits. If none are specified, the original pod's Nano CPUs are used.

--cpuset-cpus=number

CPUs in which to allow execution. Can be specified as a comma-separated list (e.g. 0,1), as a range (e.g. 0-3), or any combination thereof (e.g. 0-3,7,11-15).

On some systems, changing the resource limits may not be allowed for non-root users. For more details, see https://github.com/containers/podman/blob/main/troubleshooting.md#26-running-containers-with-resource-limits-fails-with-a-permissions-error

This option is not supported on cgroups V1 rootless systems.

If none are specified, the original pod's CPUset is used.

--cpuset-mems=nodes

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

If there are four memory nodes on the system (0-3), use --cpuset-mems=0,1 then processes in the container only uses memory from the first two memory nodes.

On some systems, changing the resource limits may not be allowed for non-root users. For more details, see https://github.com/containers/podman/blob/main/troubleshooting.md#26-running-containers-with-resource-limits-fails-with-a-permissions-error

This option is not supported on cgroups V1 rootless systems.

--destroy

Remove the original pod that we are cloning once used to mimic the configuration.

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

Add a host device to the pod. Optional permissions parameter can be used to specify device permissions by combining 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 is resolved first. The pod only stores the major and minor numbers of the host device.

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

In rootless mode, the new device is bind mounted in the container from the host rather than Podman creating it within the container space. Because the bind mount retains its SELinux label on SELinux systems, the container can get permission denied when accessing the mounted device. Modify SELinux settings to allow containers to use all device labels via the following command:

$ sudo setsebool -P  container_use_devices=true

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.

--device-read-bps=path:rate

Limit read rate (in bytes per second) from a device (e.g. --device-read-bps=/dev/sda:1mb).

On some systems, changing the resource limits may not be allowed for non-root users. For more details, see https://github.com/containers/podman/blob/main/troubleshooting.md#26-running-containers-with-resource-limits-fails-with-a-permissions-error

This option is not supported on cgroups V1 rootless systems.

--device-write-bps=path:rate

Limit write rate (in bytes per second) to a device (e.g. --device-write-bps=/dev/sda:1mb).

On some systems, changing the resource limits may not be allowed for non-root users. For more details, see https://github.com/containers/podman/blob/main/troubleshooting.md#26-running-containers-with-resource-limits-fails-with-a-permissions-error

This option is not supported on cgroups V1 rootless systems.

--gidmap=pod_gid:host_gid:amount

GID map for the user namespace. Using this flag runs all containers in the pod with user namespace enabled. It conflicts with the --userns and --subgidname flags.

--gpus=ENTRY

GPU devices to add to the container ('all' to pass all GPUs) Currently only Nvidia devices are supported.

--help, -h

Print usage statement.

--hostname=name

Set a hostname to the pod.

--infra-command=command

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

--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-name=name

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

--label, -l=key=value

Add metadata to a pod.

--label-file=file

Read in a line-delimited file of labels.

--memory, -m=number[unit]

Memory limit. A unit can be b (bytes), k (kibibytes), m (mebibytes), or g (gibibytes).

Allows the memory available to a container to be constrained. 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 is very large, that's millions of trillions).

This option is not supported on cgroups V1 rootless systems.

--memory-swap=number[unit]

A limit value equal to memory plus swap. A unit can be b (bytes), k (kibibytes), m (mebibytes), or g (gibibytes).

Must be used with the -m (--memory) flag. The argument value must be larger than that of
-m (--memory) By default, it is set to double the value of --memory.

Set number to -1 to enable unlimited swap.

This option is not supported on cgroups V1 rootless systems.

--name, -n

Set a custom name for the cloned pod. The default if not specified is of the syntax: <ORIGINAL_NAME>-clone

--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)

--restart=policy

Restart policy to follow when containers exit. Restart policy does not take effect if a container is stopped via the podman kill or podman stop commands.

Valid policy values are:

  • no                       : Do not restart containers on exit
  • never                    : Synonym for no; do not restart containers on exit
  • on-failure[:max_retries] : Restart containers when they exit with a non-zero exit code, retrying indefinitely or until the optional max_retries count is hit
  • always                   : Restart containers when they exit, regardless of status, retrying indefinitely
  • unless-stopped           : Identical to always

Podman provides a systemd unit file, podman-restart.service, which restarts containers after a system reboot.

When running containers in systemd services, use the restart functionality provided by systemd. In other words, do not use this option in a container unit, instead set the Restart= systemd directive in the [Service] section. See podman-systemd.unit(5) and systemd.service(5).

Default restart policy for all the containers in a pod.

--security-opt=option

Security Options

  • apparmor=unconfined : Turn off apparmor confinement for the pod
  • apparmor=alternate-profile : Set the apparmor confinement profile for the pod
  • label=user:USER: Set the label user for the pod processes
  • label=role:ROLE: Set the label role for the pod processes
  • label=type:TYPE: Set the label process type for the pod processes
  • label=level:LEVEL: Set the label level for the pod processes
  • label=filetype:TYPE: Set the label file type for the pod files
  • label=disable: Turn off label separation for the pod

Note: Labeling can be disabled for all pods/containers by setting label=false in the containers.conf (/etc/containers/containers.conf or $HOME/.config/containers/containers.conf) file.

  • label=nested: Allows SELinux modifications within the container. Containers are allowed to modify SELinux labels on files and processes, as long as SELinux policy allows. Without nested, containers view SELinux as disabled, even when it is enabled on the host. Containers are prevented from setting any labels.
  • mask=/path/1:/path/2: The paths to mask separated by a colon. A masked path cannot be accessed inside the containers within the pod.
  • no-new-privileges: Disable container processes from gaining additional privileges.
  • seccomp=unconfined: Turn off seccomp confinement for the pod.
  • seccomp=profile.json: JSON file to be used as a seccomp filter. Note that the io.podman.annotations.seccomp annotation is set with the specified value as shown in podman inspect.
  • proc-opts=OPTIONS : Comma-separated list of options to use for the /proc mount. More details for the possible mount options are specified in the proc(5) man page.
  • 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/virtual/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.

Note: Labeling can be disabled for all containers by setting label=false in the containers.conf(5) file.

--shm-size=number[unit]

Size of /dev/shm. A unit can be b (bytes), k (kibibytes), m (mebibytes), or g (gibibytes). If the unit is omitted, the system uses bytes. If the size is omitted, the default is 64m. When size is 0, there is no limit on the amount of memory used for IPC by the pod. This option conflicts with --ipc=host.

--shm-size-systemd=number[unit]

Size of systemd-specific tmpfs mounts such as /run, /run/lock, /var/log/journal and /tmp. A unit can be b (bytes), k (kibibytes), m (mebibytes), or g (gibibytes). If the unit is omitted, the system uses bytes. If the size is omitted, the default is 64m. When size is 0, the usage is limited to 50% of the host's available memory.

--start

When set to true, this flag starts the newly created pod after the clone process has completed. All containers within the pod are started.

--subgidname=name

Run the container in a new user namespace using the map with name in the /etc/subgid file. If running rootless, the user needs to have the right to use the mapping. See subgid(5). This flag conflicts with --userns and --gidmap.

--subuidname=name

Run the container in a new user namespace using the map with name in the /etc/subuid file. If running rootless, the user needs to have the right to use the mapping. See subuid(5). This flag conflicts with --userns and --uidmap.

--sysctl=name=value

Configure namespaced kernel parameters for all containers in the pod.

For the IPC namespace, the following sysctls are allowed:

  • kernel.msgmax
  • kernel.msgmnb
  • kernel.msgmni
  • kernel.sem
  • kernel.shmall
  • kernel.shmmax
  • kernel.shmmni
  • kernel.shm_rmid_forced
  • Sysctls beginning with fs.mqueue.*

Note: if the ipc namespace is not shared within the pod, the above sysctls are not allowed.

For the network namespace, only sysctls beginning with net.* are allowed.

Note: if the network namespace is not shared within the pod, the above sysctls are not allowed.

--uidmap=container_uid:from_uid:amount

Run all containers in the pod 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.

--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.

Rootless user --userns=Key mappings:

KeyHost UserContainer User
""$UID0 (Default User account mapped to root user in container.)
keep-id$UID$UID (Map user account to same UID within container.)
auto$UIDnil (Host User UID is not mapped into container.)
nomap$UIDnil (Host User UID is not mapped into container.)

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 estimates the 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 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 not allowed for containers created by the root user.
  • nomap: creates a user namespace where the current rootless user's UID:GID are not mapped into the container. This option is not allowed for containers created by the root user.

--uts=mode

Set the UTS namespace mode for the pod. The following values are supported:

  • host: use the host's UTS namespace inside the pod.
  • private: create a new namespace for the pod (default).
  • ns:[path]: run the pod in the given existing UTS namespace.

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

Create a bind mount. If -v /HOST-DIR:/CONTAINER-DIR is specified, Podman bind mounts /HOST-DIR from the host into /CONTAINER-DIR in the Podman container. Similarly, -v SOURCE-VOLUME:/CONTAINER-DIR mounts the named volume from the host into the container. If no such named volume exists, Podman creates one. If no source is given, the volume is created as an anonymously named volume with a randomly generated name, and is removed when the pod is removed via the --rm flag or the podman rm --volumes command.

(Note when using the remote client, including Mac and Windows (excluding WSL2) machines, the volumes are mounted from the remote server, not necessarily the client machine.)

The OPTIONS is a comma-separated list and can be one or more of:

  • rw|ro
  • z|Z
  • [O]
  • [U]
  • [no]copy
  • [no]dev
  • [no]exec
  • [no]suid
  • [r]bind
  • [r]shared|[r]slave|[r]private[r]unbindable [1] ⟨#Footnote1⟩
  • idmap[=options]

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

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 returns an error. Users must pre-create the source files or directories.

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

Specify multiple -v options to mount one or more volumes into a pod.

Write Protected Volume Mounts

Add :ro or :rw option to mount a volume in 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. Chowning walks the file system under the volume and changes the UID/GID on each file. If the volume has thousands of inodes, this process takes a long time, delaying the start of the pod.

Warning use with caution since this modifies 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, 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 or more 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. Relabeling walks the file system under the volume and changes the label on each file, if the volume has thousands of inodes, this process takes a long time, delaying the start of the pod. If the volume was previously relabeled with the z option, Podman is optimized to not relabel a second time. If files are moved into the volume, then the labels can be manually change with the chcon -Rt container_file_t PATH command.

Note: Do not relabel system files and directories. Relabeling system content might cause other confined services on the machine to fail.  For these types of containers we recommend disabling SELinux separation.  The option --security-opt label=disable disables SELinux separation for the pod. For example if a user wanted to volume mount their entire home directory into a pod, they need to disable SELinux separation.

$ podman pod clone --security-opt label=disable -v $HOME:/home/user fedora touch /home/user/file

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 is the lower, and the container storage directory is the upper. Modifications to the mount point are destroyed when the pod finishes executing, similar to a tmpfs mount point being unmounted.

For advanced users, the overlay option also supports custom non-volatile upperdir and workdir for the overlay mount. Custom upperdir and workdir can be fully managed by the users themselves, and Podman does not remove it on lifecycle completion. Example :O,upperdir=/some/upper,workdir=/some/work

Subsequent executions of the container sees 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 pod infra container label. Usually containers can read/execute container_share_t and can read/write container_file_t. If unable to change the labels on a source volume, SELinux container separation must be disabled for the pod or infra container to work.

Do not modify the source directory mounted into the pod with an overlay mount, it can cause unexpected failures. Only modify the directory after the container finishes running.

Mounts propagation

By default, bind-mounted volumes are private. That means any mounts done inside the pod are not visible on the host and vice versa. One can change this behavior by specifying a volume mount propagation property. When a volume is shared, mounts done under that volume inside the pod are visible on host and vice versa. Making a volume slave[1] ⟨#Footnote1⟩ enables only one-way mount propagation: mounts done on the host under that volume are visible inside the container but not the other way around.

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] ⟨#Footnote1⟩

To recursively mount a volume and all of its submounts into a pod, use the rbind option. By default the bind option is used, and submounts of the source directory is not mounted into the pod.

Mounting the volume with a copy option tells podman to copy content from the underlying destination directory onto newly created internal volumes. The copy only happens on the initial creation of the volume. Content is not copied up when the volume is subsequently used on different containers. The copy option is ignored on bind mounts and has no effect.

Mounting volumes with the nosuid options means that SUID executables on the volume can not be used by applications 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 can be executed within the pod.

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

If the HOST-DIR is a mount point, then dev, suid, and exec options are ignored by the kernel.

Use df HOST-DIR to figure out the source mount, then use findmnt -o TARGET,PROPAGATION source-mount-dir to figure out propagation properties of source mount. If findmnt(1) utility is not available, then one can look at the mount entry for the source mount point in /proc/self/mountinfo. Look at the "optional fields" and see if any propagation properties are specified. In there, shared:N means the mount is shared, master:N means mount is slave, and if nothing is there, the mount is private. [1] ⟨#Footnote1⟩

To change propagation properties of a mount point, use mount(8) 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 converts /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 fails.

Idmapped mount

If idmap is specified, create an idmapped mount to the target user namespace in the container. The idmap option supports a custom mapping that can be different than the user namespace used by the container. The mapping can be specified after the idmap option like: idmap=uids=0-1-10#10-11-10;gids=0-100-10. For each triplet, the first value is the start of the backing file system IDs that are mapped to the second value on the host.  The length of this mapping is given in the third value. Multiple ranges are separated with #.

--volumes-from=CONTAINER[:OPTIONS]

Mount volumes from the specified container(s). Used to share volumes between containers and pods. The options is a comma-separated list with the following available elements:

  • rw|ro
  • z

Mounts already mounted volumes from a source container onto another pod. CONTAINER may be a name or ID. To share a volume, use the --volumes-from option when running the target container. Volumes can be shared even if the source container is not running.

By default, Podman mounts the volumes in the same mode (read-write or read-only) as it is mounted in the source container. This can be changed by adding a ro or rw option.

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 container from using the content. By default, Podman does not change the labels set by the OS.

To change a label in the pod context, add z to the volume mount. This suffix tells Podman to relabel file objects on the shared volumes. The z option tells Podman that two entities 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.

If the location of the volume from the source container overlaps with data residing on a target pod, then the volume hides that data on the target.

Examples

Clone the specified pod to a new pod.

# podman pod clone pod-name
6b2c73ff8a1982828c9ae2092954bcd59836a131960f7e05221af9df5939c584

Clone the specified pod to a new pod with a new name.

# podman pod clone pod-name --name=cloned-pod
d0cf1f782e2ed67e8c0050ff92df865a039186237a4df24d7acba5b1fa8cc6e7
6b2c73ff8a1982828c9ae2092954bcd59836a131960f7e05221af9df5939c584

Clone and remove the specified pod to a new pod, modifying its cpus.

# podman pod clone --destroy --cpus=5 d0cf1
6b2c73ff8a1982828c9ae2092954bcd59836a131960f7e05221af9df5939c584

Clone the specified pod to a new named pod.

# podman pod clone 2d4d4fca7219b4437e0d74fcdc272c4f031426a6eacd207372691207079551de new_name
5a9b7851013d326aa4ac4565726765901b3ecc01fcbc0f237bc7fd95588a24f9

See Also

podman-pod-create(1)

History

May 2022, Originally written by Charlie Doern cdoern@redhat.com ⟨mailto:cdoern@redhat.com⟩

Footnotes

1: The Podman 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 needs to 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, Podman will follow suit immediately.

Referenced By

podman-pod(1).

The man page docker-pod-clone(1) is an alias of podman-pod-clone(1).