podman-pod-create - Create a new pod
podman pod create [options] [name]
Creates an empty pod, or unit of multiple containers, and prepares it to have containers added to it. The pod can be created with a specific name. If a name is not given a random name is generated. 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.
The operator can identify a pod in three ways: UUID long identifier (âf78375b1c487e03c9438c729345e54db9d20cfa2ac1fc3494b6eb60872e74778â) UUID short identifier (âf78375b1c487â) Name (âjonahâ)
podman generates a UUID for each pod, and if a name is not assigned to the container with --name then a random string name is generated for it. This name is useful to identify a pod.
Note: resource limit related flags work by setting the limits explicitly in the pod’s cgroup parent for all containers joining the pod. A container can override the resource limits when joining a pod. For example, if a pod was created via podman pod create --cpus=5, specifying podman container create --pod=<pod_id|pod_name> --cpus=4 causes the container to use the smaller limit. Also, containers which specify their own cgroup, such as --cgroupns=host, do NOT get the assigned pod level cgroup resources.
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. Conflicts with the --no-hosts option.
The /etc/hosts file is shared between all containers in the pod.
Block IO relative weight. The weight is a value between 10 and 1000.
This option is not supported on cgroups V1 rootless systems.
Block IO relative device weight.
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 (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:
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.
Set the total number of CPUs delegated to the pod. Default is 0.000 which indicates that there is no limit on computation power.
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.
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.
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.
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.
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.
Set custom DNS servers in the /etc/resolv.conf file that is shared between all containers in the pod. A special option, "none" is allowed which disables creation of /etc/resolv.conf for the pod.
Set custom DNS options in the /etc/resolv.conf file that is shared between all containers in the pod.
Set custom DNS search domains in the /etc/resolv.conf file that is shared between all containers in the pod.
Set the exit policy of the pod when the last container exits. Supported policies are:
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.
Print usage statement.
Set a hostname to the pod.
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.
The command that is run to start the infra container. Default: "/pause".
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.
The custom image that is used for the infra container. Unless specified, Podman builds a custom local image which does not require pulling down an image.
The name that is used for the pod’s infra container.
Specify a static IPv4 address for the pod, for example 10.88.64.128. This option can only be used if the pod is joined to only a single network - i.e., --network=network-name is used at most once - and if the pod is not joining another container’s network namespace via --network=container:id. The address must be within the network’s IP address pool (default 10.88.0.0/16).
To specify multiple static IP addresses per pod, set multiple networks using the --network option with a static IP address specified for each using the ip mode for that option.
Specify a static IPv6 address for the pod, for example fd46:db93:aa76:ac37::10. This option can only be used if the pod is joined to only a single network - i.e., --network=network-name is used at most once - and if the pod is not joining another container’s network namespace via --network=container:id. The address must be within the network’s IPv6 address pool.
To specify multiple static IPv6 addresses per pod, set multiple networks using the --network option with a static IPv6 address specified for each using the ip6 mode for that option.
Add metadata to a pod.
Read in a line-delimited file of labels.
Pod network interface MAC address (e.g. 92:d0:c6:0a:29:33) This option can only be used if the pod is joined to only a single network - i.e., --network=network-name is used at most once - and if the pod is not joining another container’s network namespace via --network=container:id.
Remember that the MAC address in an Ethernet network must be unique. The IPv6 link-local address is based on the device’s MAC address according to RFC4862.
To specify multiple static MAC addresses per pod, set multiple networks using the --network option with a static MAC address specified for each using the mac mode for that option.
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.
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.
Assign a name to the pod.
Set the network mode for the pod.
Valid mode values are:
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bridge[:OPTIONS,...]: Create a network stack on the default bridge. This is the default for rootful containers. It is possible to specify these additional options: |
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alias=name: Add network-scoped alias for the container. | |||
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ip=IPv4: Specify a static ipv4 address for this container. | ||
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ip=IPv6: Specify a static ipv6 address for this container. | ||
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mac=MAC: Specify a static mac address for this container. | ||
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interface_name: Specify a name for the created network interface inside the container. |
For example to set a static ipv4 address and a static mac address, use --network bridge:ip=10.88.0.10,mac=44:33:22:11:00:99.
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<network name or ID>[:OPTIONS,...]: Connect to a user-defined network; this is the network name or ID from a network created by podman network create. Using the network name implies the bridge network mode. It is possible to specify the same options described under the bridge mode above. Use the --network option multiple times to specify additional networks. For backwards compatibility it is also possible to specify networks comma separated on the first --network argument, however this prevents you from using the options described under the bridge section above. | ||
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none: Create a network namespace for the container but do not configure network interfaces for it, thus the container has no network connectivity. | ||
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container:id: Reuse another container’s network stack. | ||
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host: Do not create a network namespace, the container uses 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. | ||
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ns:path: Path to a network namespace to join. | ||
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private: Create a new namespace for the container. This uses the bridge mode for rootful containers and slirp4netns for rootless ones. | ||
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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: |
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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. | |||
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mtu=MTU: Specify the MTU to use for this network. (Default is 65520). | ||
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cidr=CIDR: Specify ip range to use for this network. (Default is 10.0.2.0/24). | ||
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enable_ipv6=true|false: Enable IPv6. Default is true. (Required for outbound_addr6). | ||
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outbound_addr=INTERFACE: Specify the outbound interface slirp binds to (ipv4 traffic only). | ||
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outbound_addr=IPv4: Specify the outbound ipv4 address slirp binds to. | ||
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outbound_addr6=INTERFACE: Specify the outbound interface slirp binds to (ipv6 traffic only). | ||
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outbound_addr6=IPv6: Specify the outbound ipv6 address slirp binds to. | ||
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port_handler=rootlesskit: Use rootlesskit for port forwarding. Default. Note: Rootlesskit changes the source IP address of incoming packets to an IP address in the container network namespace, usually 10.0.2.100. If the 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. | ||
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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. | ||
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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 if,
respectively, no TCP or UDP port forwarding from host to
container is configured, 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:
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pasta:--map-gw: Allow the container to directly reach the host using the gateway address. | ||
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pasta:--mtu,1500: Specify a 1500 bytes MTU for the tap interface in the container. | ||
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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. | ||
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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 | ||
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pasta:-t,auto,-u,auto,-T,auto,-U,auto: enable automatic port forwarding based on observed bound ports from both host and container sides | ||
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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 |
NOTE: For backward compatibility reasons, if there is an existing network named pasta, Podman uses it instead of the pasta mode."?
Invalid if using --dns, --dns-option, or --dns-search with --network set to none or container:id.
Add a network-scoped alias for the pod, setting the alias for all networks that the container joins. To set a name only for a specific network, use the alias option as described under the --network option. If the network has DNS enabled (podman network inspect -f {{.DNSEnabled}} <name>), these aliases can be used for name resolution on the given network. This option can be specified multiple times. NOTE: When using CNI a pod only has access to aliases on the first network that it joins. This limitation does not exist with netavark/aardvark-dns.
Do not create /etc/hosts for the pod. By default, Podman manages /etc/hosts, adding the container’s own IP address and any hosts from --add-host. --no-hosts disables this, and the image’s /etc/hosts is preserved unmodified.
This option conflicts with --add-host.
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
hostâs PID namespace for the pod
ns: join the specified PID namespace
private: create a new namespace for the pod (default)
Write the pod ID to the file.
Publish a container’s port, or range of ports, within this pod to the host.
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.
If host IP is set to 0.0.0.0 or not set at all, the port is bound on all IPs on the host.
By default, Podman publishes TCP ports. To publish a UDP port instead, give udp as protocol. To publish both TCP and UDP ports, set --publish twice, with tcp, and udp as protocols respectively. Rootful containers can also publish ports using the sctp protocol.
Host port does not have to be specified (e.g. podman run -p 127.0.0.1::80). If it is not, the container port is randomly assigned a port on the host.
Use podman port to see the actual mapping: podman port $CONTAINER $CONTAINERPORT.
Note that the network drivers macvlan and ipvlan do not support port forwarding, it will have no effect on these networks.
Note: You must not publish ports of containers in the pod individually, but only by the pod itself.
Note: This cannot be modified once the pod is created.
If another pod with the same name already exists, replace and remove it. The default is false.
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:
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no : Do not restart containers on exit | ||
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never : Synonym for no; do not restart containers on exit | ||
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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 | ||
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always : Restart containers when they exit, regardless of status, retrying indefinitely | ||
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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 Options
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apparmor=unconfined : Turn off apparmor confinement for the pod | ||
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apparmor=alternate-profile : Set the apparmor confinement profile for the pod | ||
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label=user:USER: Set the label user for the pod processes | ||
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label=role:ROLE: Set the label role for the pod processes | ||
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label=type:TYPE: Set the label process type for the pod processes | ||
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label=level:LEVEL: Set the label level for the pod processes | ||
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label=filetype:TYPE: Set the label file type for the pod files | ||
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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.
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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. | ||
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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. | ||
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no-new-privileges: Disable container processes from gaining additional privileges. | ||
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seccomp=unconfined: Turn off seccomp confinement for the pod. | ||
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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. | ||
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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. | ||
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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.
A comma-separated list of kernel namespaces to share. If none or "" is specified, no namespaces are shared, and the infra container is not created unless explicitly specified via --infra=true. The namespaces to choose from are cgroup, ipc, net, pid, uts. If the option is prefixed with a "+", the namespace is appended to the default list. Otherwise, it replaces the default list. Defaults match Kubernetes default (ipc, net, uts)
This boolean determines whether or not all containers entering the pod use the pod as their cgroup parent. The default value of this option is true. Use the --share option to share the cgroup namespace rather than a cgroup parent in a pod.
Note: This option conflicts with the --share=cgroup option since that option sets the pod as the cgroup parent but enters the container into the same cgroupNS as the infra container.
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.
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.
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.
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.
Configure namespaced kernel parameters for all containers in the pod.
For the IPC namespace, the following sysctls are allowed:
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kernel.msgmax |
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kernel.msgmnb |
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kernel.msgmni |
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kernel.sem |
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kernel.shmall |
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kernel.shmmax |
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kernel.shmmni |
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kernel.shm_rmid_forced |
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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.
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.
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:
Valid mode values are:
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auto[:OPTIONS,...]: automatically create a namespace. It is possible to specify these options to auto: | ||
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gidmapping=CONTAINER_GID:HOST_GID:SIZE to force a GID mapping to be present in the user namespace. | ||
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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. | ||
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uidmapping=CONTAINER_UID:HOST_UID:SIZE to force a UID mapping to be present in the user namespace. | ||
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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). | ||
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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. | ||
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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. |
Set the UTS namespace mode for the pod. The following values are supported:
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host: use the host’s UTS namespace inside the pod. |
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private: create a new namespace for the pod (default). |
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ns:[path]: run the pod in the given existing UTS namespace. |
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: [1] ⟨#Footnote1⟩
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rw|ro |
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z|Z |
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[O] |
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[U] |
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[no]copy |
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[no]dev |
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[no]exec |
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[no]suid |
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[r]bind |
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[r]shared|[r]slave|[r]private[r]unbindable |
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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 create --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 is not 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 the pod is 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 is visible inside container but not the other way around. [1] ⟨#Footnote1⟩
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 #.
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.
$ podman pod create --name test
$ podman pod create mypod
$ podman pod create --infra=false
$ podman pod create --infra-command /top toppod
$ 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
$ podman pod create --network pasta
$ podman pod create --network net1:ip=10.89.1.5 --network net2:ip=10.89.10.10
podman(1), podman-pod(1), podman-kube-play(1), containers.conf(1), cgroups(7)
July 2018, Originally compiled by Peter Hunt [email protected] ⟨mailto:[email protected]⟩
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.