podman-create man page

podman-create — Create a new container

Synopsis

podman create [options] image [command [arg ...]]

Description

Creates a writable container layer over the specified image and prepares it for running the specified command. The container ID is then printed to STDOUT. This is similar to podman run -d except the container is never started. You can then use the podman start container command to start the container at any point.

The initial status of the container created with podman create is 'created'.

Options

--add-host=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=key=value
Add an annotation to the container. The format is key=value. The --annotation option can be set multiple times.
--attach, -a=location
Attach to STDIN, STDOUT or STDERR.

In foreground mode (the default when -d is not specified), podman run can start the process in the container and attach the console to the process's standard input, output, and standard error. It can even pretend to be a TTY (this is what most commandline executables expect) and pass along signals. The -a option can be set for each of stdin, stdout, and stderr.

--authfile=path
Path of the authentication file. Default is ${XDG_\RUNTIME_DIR}/containers/auth.json

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 (Not available for remote commands)

--blkio-weight=weight
Block IO weight (relative weight) accepts a weight value between 10 and 1000.
--blkio-weight-device=weight
Block IO weight (relative device weight, format: DEVICE_NAME:WEIGHT).
--cap-add=capability
Add Linux capabilities
--cap-drop=capability
Drop Linux capabilities
--cgroupns=mode
Set the cgroup namespace mode for the container, by default host is used.
   host: use the host's cgroup namespace inside the container.
   container:: join the namespace of the specified container.
   private: create a new cgroup namespace.
   ns:: join the namespace at the specified path.
--cgroup-parent=path
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.
--cidfile=id
Write the container ID to the file
--conmon-pidfile=path
Write the pid of the conmon process to a file. conmon runs in a separate process than Podman, so this is necessary when using systemd to restart Podman containers.
--cpu-count=limit
Limit the number of CPUs available for execution by the container.

On Windows Server containers, this is approximated as a percentage of total CPU usage.

On Windows Server containers, the processor resource controls are mutually exclusive, the order of precedence is CPUCount first, then CPUShares, and CPUPercent last.

--cpu-period=limit
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=limit
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-rt-period=microseconds
Limit the CPU real-time period in microseconds

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

--cpu-rt-runtime=microseconds
Limit the CPU real-time runtime in microseconds

Limit the containers Real Time CPU usage. This flag tells the kernel to limit the amount of time in a given CPU period Real Time tasks may consume. Ex: Period of 1,000,000us and Runtime of 950,000us means that this container could consume 95% of available CPU and leave the remaining 5% to normal priority tasks.

The sum of all runtimes across containers cannot exceed the amount allotted to the parent cgroup.

--cpu-shares=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 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    containerCPUCPU share
100    {C0}0100% of CPU0
101    {C1}1100% of CPU1
102    {C1}2100% of CPU2
--cpus=number
Number of CPUs. The default is 0.0 which means no limit.
--cpuset-cpus=cpus
CPUs in which to allow execution (0-3, 0,1)
--cpuset-mems=nodes
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.

--detach, -d=true|false
Detached mode: run the container in the background and print the new container ID. The default is false.

At any time you can run podman ps in the other shell to view a list of the running containers. You can reattach to a detached container with podman attach.

When attached in the tty mode, you can detach from the container (and leave it running) using a configurable key sequence. The default sequence is ctrl-p,ctrl-q. Configure the keys sequence using the --detach-keys option, or specifying it in the libpod.conf file: see libpod.conf(5) for more information.

--detach-keys=sequence
Override the key sequence for detaching a container. Format is a single character [a-Z] or a comma separated sequence of ctrl-<value>, where <value> is one of: a-z, @, ^, [, \\, ], ^ or _.
--device=device
Add a host device to the container. The format is <device-on-host>[:<device-on-container>][:<permissions>] (e.g. --device=/dev/sdc:/dev/xvdc:rwm)
--device-read-bps=path
Limit read rate (bytes per second) from a device (e.g. --device-read-bps=/dev/sda:1mb)
--device-read-iops=path
Limit read rate (IO per second) from a device (e.g. --device-read-iops=/dev/sda:1000)
--device-write-bps=path
Limit write rate (bytes per second) to a device (e.g. --device-write-bps=/dev/sda:1mb)
--device-write-iops=path
Limit write rate (IO per second) to a device (e.g. --device-write-iops=/dev/sda:1000)
--dns=dns
Set custom DNS servers. Invalid if using --dns and --network that is set to 'none' or 'container:'.

This option can be used to override the DNS configuration passed to the container. Typically this is necessary when the host DNS configuration is invalid for the container (e.g., 127.0.0.1). When this is the case the --dns flags is necessary for every run.

The special value none can be specified to disable creation of /etc/resolv.conf in the container by Podman. The /etc/resolv.conf file in the image will be used without changes.

--dns-option=option
Set custom DNS options. Invalid if using --dns-option and --network that is set to 'none' or 'container:'.
--dns-search=domain
Set custom DNS search domains. Invalid if using --dns-search and --network that is set to 'none' or 'container:'. (Use --dns-search=. if you don't wish to set the search domain)
--entrypoint="command" | '["command", "arg1", ...]'
Overwrite the default ENTRYPOINT of the image

This option allows you to overwrite the default entrypoint of the image. The ENTRYPOINT of an image is similar to a COMMAND because it specifies what executable to run when the container starts, but it is (purposely) more difficult to override. The ENTRYPOINT gives a container its default nature or behavior, so that when you set an ENTRYPOINT you can run the container as if it were that binary, complete with default options, and you can pass in more options via the COMMAND. But, sometimes an operator may want to run something else inside the container, so you can override the default ENTRYPOINT at runtime by using a --entrypoint and a string to specify the new ENTRYPOINT.

You need to specify multi option commands in the form of a json string.

--env, -e=env
Set environment variables

This option allows arbitrary environment variables that are available for the process to be launched inside of the container.  If an environment variable is specified without a value, Podman will check the host environment for a value and set the variable only if it is set on the host.  If an environment variable ending in * is specified, Podman will search the host environment for variables starting with the prefix and will add those variables to the container.  If an environment variable with a trailing ***** is specified, then a value must be supplied.

See Environment ⟨#environment⟩ note below for precedence and examples.

--env-host=true|false
Use host environment inside of the container. See Environment note below for precedence.
--env-file=file
Read in a line delimited file of environment variables. See Environment note below for precedence.
--expose=port
Expose a port, or a range of ports (e.g. --expose=3300-3310) to set up port redirection on the host system.
--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.

The following example maps uids 0-2000 in the container to the uids 30000-31999 on the host and gids 0-2000 in the container to the gids 30000-31999 on the host. --gidmap=0:30000:2000

--group-add=group
Add additional groups to run as
--health-cmd="command" | '["command", "arg1", ...]'
Set or alter a healthcheck command for a container. The command is a command to be executed inside your container that determines your container health.  The command is required for other healthcheck options to be applied.  A value of none disables existing healthchecks.

Multiple options can be passed in the form of a JSON array; otherwise, the command will be interpreted as an argument to /bin/sh -c.

--health-interval=interval
Set an interval for the healthchecks (a value of disable results in no automatic timer setup) (default "30s")
--health-retries=retries
The number of retries allowed before a healthcheck is considered to be unhealthy.  The default value is 3.
--health-start-period=period
The initialization time needed for a container to bootstrap. The value can be expressed in time format like 2m3s.  The default value is 0s
--health-timeout=timeout
The maximum time allowed to complete the healthcheck before an interval is considered failed.  Like start-period, the value can be expressed in a time format such as 1m22s.  The default value is 30s.
--hostname=name
Container host name

Sets the container host name that is available inside the container.

--help
Print usage statement
--http-proxy=true|false
By default proxy environment variables are passed into the container if set for the podman process.  This can be disabled by setting the --http-proxy option to false.  The environment variables passed in include http_proxy, https_proxy, ftp_proxy, no_proxy, and also the upper case versions of those.  This option is only needed when the host system must use a proxy but the container should not use any proxy.  Proxy environment variables specified for the container in any other way will override the values that would have been passed thru from the host.  (Other ways to specify the proxy for the container include passing the values with the --env flag, or hard coding the proxy environment at container build time.)

For example, to disable passing these environment variables from host to container:

--http-proxy=false
Defaults to true
--image-volume, builtin-volume=bind|tmpfs|ignore
Tells podman how to handle the builtin image volumes. The options are: 'bind', 'tmpfs', or 'ignore' (default 'bind'). bind: A directory is created inside the container state directory and bind mounted into the container for the volumes. tmpfs: The volume is mounted onto the container as a tmpfs, which allows the users to create content that disappears when the container is stopped. ignore: All volumes are just ignored and no action is taken.
--init
Run an init inside the container that forwards signals and reaps processes.
--init-path=path
Path to the container-init binary.
--interactive, i=true|false
Keep STDIN open even if not attached. The default is false.
--ip6=ip
Not implemented
--ip=ip
Specify a static IP address for the container, for example '10.88.64.128'. Can only be used if no additional CNI networks to join were specified via '--network=', and if the container is not joining another container's network namespace via '--network=container:'. The address must be within the default CNI network's pool (default 10.88.0.0/16).
--ipc=ipc
Default is to create a private IPC namespace (POSIX SysV IPC) for the container
               'container:': reuses another container shared memory, semaphores and message queues
               'host': use the host shared memory,semaphores and message queues inside the container.  Note: the host mode gives the container full access to local shared memory and is therefore considered insecure.
               'ns:' path to an IPC namespace to join.
--kernel-memory=number[unit]
Kernel memory limit (format: <number>[<unit>], where unit = b, k, m or g)

Constrains the kernel memory available to a container. If a limit of 0 is specified (not using --kernel-memory), the container's kernel memory is not limited. If you specify a limit, it may be rounded up to a multiple of the operating system's page size and the value can be very large, millions of trillions.

--label, -l=label
Add metadata to a container (e.g., --label com.example.key=value)
--label-file=file
Read in a line delimited file of labels
--link-local-ip=ip
Not implemented
--log-driver="k8s-file
"

Logging driver for the container.  Currently available options are k8s-file and journald, with json-file aliased to k8s-file for scripting compatibility.

--log-opt=path
Logging driver specific options.  Used to set the path to the container log file.  For example:

--log-opt path=/var/log/container/mycontainer.json

--mac-address=address
Container MAC address (e.g. 92:d0:c6:0a:29:33)

Remember that the MAC address in an Ethernet network must be unique. The IPv6 link-local address will be based on the device's MAC address according to RFC4862.

Not currently supported

--memory, -m=limit
Memory limit (format: [], where unit = b, k, m or g)

Allows you to constrain the memory available to a container. If the host supports swap memory, then the -m memory setting can be larger than physical RAM. If a limit of 0 is specified (not using -m), the container's memory is not limited. The actual limit may be rounded up to a multiple of the operating system's page size (the value would be very large, that's millions of trillions).

--memory-reservation=limit
Memory soft limit (format: [], where unit = b, k, m or g)

After setting memory reservation, when the system detects memory contention or low memory, containers are forced to restrict their consumption to their reservation. So you should always set the value below --memory, otherwise the hard limit will take precedence. By default, memory reservation will be the same as memory limit.

--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.

--memory-swappiness=number
Tune a container's memory swappiness behavior. Accepts an integer between 0 and 100.
--mount=type=TYPE,TYPE-SPECIFIC-OPTION[,...]
Attach a filesystem mount to the container

Current supported mount TYPES are bind, and tmpfs.

   e.g.

   type=bind,source=/path/on/host,destination=/path/in/container

   type=tmpfs,tmpfs-size=512M,destination=/path/in/container

   Common Options:

          · src, source: mount source spec for bind and volume. Mandatory for bind.

          · dst, destination, target: mount destination spec.

          · ro, read-only: true or false (default).

   Options specific to bind:

          · bind-propagation: shared, slave, private, rshared, rslave, or rprivate(default). See also mount(2).
          . bind-nonrecursive: do not setup a recursive bind mount.  By default it is recursive.

   Options specific to tmpfs:

          · tmpfs-size: Size of the tmpfs mount in bytes. Unlimited by default in Linux.

          · tmpfs-mode: File mode of the tmpfs in octal. (e.g. 700 or 0700.) Defaults to 1777 in Linux.
--name=name
Assign a name to the container

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

podman generates a UUID for each container, and if a name is not assigned to the container with --name then it will generate a random string name. The name is useful any place you need to identify a container. This works for both background and foreground containers.

--network, --net="bridge
"

Set the Network mode for the container. Invalid if using --dns, --dns-option, or --dns-search with --network that is set to 'none' or 'container:'.
               'bridge': create a network stack on the default bridge
               'none': no networking
               'container:': reuse another container's network stack
               'host': use the podman host network stack.  Note: the host mode gives the container full access to local system services such as D-bus and is therefore considered insecure.
               '|': connect to a user-defined network
               'ns:': path to a network namespace to join
               'slirp4netns': use slirp4netns to create a user network stack.  This is the default for rootless containers

--network-alias=alias
Not implemented
--no-hosts=true|false
Do not create /etc/hosts for the container. By default, Podman will manage /etc/hosts, adding the container's own IP address and any hosts from --add-host. --no-hosts disables this, and the image's /etc/host will be preserved unmodified. This option conflicts with --add-host.
--oom-kill-disable=true|false
Whether to disable OOM Killer for the container or not.
--oom-score-adj=num
Tune the host's OOM preferences for containers (accepts -1000 to 1000)
--pid=pid
Set the PID mode for the container Default is to create a private PID namespace for the container
               'container:': join another container's PID namespace
               'host': use the host's PID namespace for the container. Note: the host mode gives the container full access to local PID and is therefore considered insecure.
                'ns': join the specified PID namespace
--pids-limit=limit
Tune the container's pids limit. Set -1 to have unlimited pids for the container.
--pod=name
Run container in an existing pod. If you want podman to make the pod for you, preference the pod name with new:. To make a pod with more granular options, use the podman pod create command before creating a container.
--privileged=true|false
Give extended privileges to this container. The default is false.

By default, podman containers are “unprivileged” (=false) and cannot, for example, modify parts of the kernel. This is because by default a container is not allowed to access any devices. A “privileged” container is given access to all devices.

When the operator executes a privileged container, podman enables access to all devices on the host, turns off graphdriver mount options, as well as turning off most of the security measures protecting the host from the container.

--publish, -p=port
Publish a container's port, or range of ports, 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. (e.g., podman run -p 1234-1236:1222-1224 --name thisWorks -t busybox but not podman run -p 1230-1236:1230-1240 --name RangeContainerPortsBiggerThanRangeHostPorts -t busybox) With ip: podman run -p 127.0.0.1:$HOSTPORT:$CONTAINERPORT --name CONTAINER -t someimage Use podman port to see the actual mapping: podman port CONTAINER $CONTAINERPORT

--publish-all, -P=true|false
Publish all exposed ports to random ports on the host interfaces. The default is false.

When set to true publish all exposed ports to the host interfaces. The default is false. If the operator uses -P (or -p) then podman will make the exposed port accessible on the host and the ports will be available to any client that can reach the host. When using -P, podman will bind any exposed port to a random port on the host within an ephemeral port range defined by /proc/sys/net/ipv4/ip_local_port_range. To find the mapping between the host ports and the exposed ports, use podman port.

--pull=missing
Pull image before creating ("always"|"missing"|"never") (default "missing").
      'missing': default value, attempt to pull the latest image from the registries listed in registries.conf if a local image does not exist.Raise an error if the image is not in any listed registry and is not present locally.
      '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.
      'never': 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 missing.

--quiet, -q
Suppress output information when pulling images
--read-only=true|false
Mount the container's root filesystem as read only.

By default a container will have its root filesystem writable allowing processes to write files anywhere.  By specifying the --read-only flag the container will have its root filesystem mounted as read only prohibiting any writes.

--read-only-tmpfs=true|false
If container is running in --read-only mode, then mount a read-write tmpfs on /run, /tmp, and /var/tmp.  The default is true
--restart=policy
Restart policy to follow when containers exit. Restart policy will not take effect if a container is stopped via the podman kill or podman stop commands. Valid values are:

Please note that restart will not restart containers after a system reboot. If this functionality is required in your environment, you can invoke Podman from a systemd unit file, or create an init script for whichever init system is in use. To generate systemd unit files, please see podman generate systemd

--rm=true|false
Automatically remove the container when it exits. The default is false.

Note that the container will not be removed when it could not be created or started successfully. This allows the user to inspect the container after failure.

--rootfs
If specified, the first argument refers to an exploded container on the file system.

This is useful to run a container without requiring any image management, the rootfs of the container is assumed to be managed externally.

--security-opt=option
Security Options

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

--shm-size=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.
--stop-signal=SIGTERM
Signal to stop a container. Default is SIGTERM.
--stop-timeout=seconds
Timeout (in seconds) to stop a container. Default is 10.
--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.
--sysctl=SYSCTL
Configure namespaced kernel parameters at runtime

IPC Namespace - current sysctls 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 you use the --ipc=host option these sysctls will not be allowed.

Network Namespace - current sysctls allowed:
   Sysctls beginning with net.*

Note: if you use the --network=host option these sysctls will not be allowed.

--systemd=true|false
Run container in systemd mode. The default is true.

If the command you running inside of the container is systemd or init, podman will setup tmpfs mount points in the following directories:

/run, /run/lock, /tmp, /sys/fs/cgroup/systemd, /var/lib/journal

It will also set the default stop signal to SIGRTMIN+3.

This allow systemd to run in a confined container without any modifications.

Note: On SELinux systems, systemd attempts to write to the cgroup file system.  Containers writing to the cgroup file system are denied by default. The container_manage_cgroup boolean must be enabled for this to be allowed on an SELinux separated system.

setsebool -P container_manage_cgroup true

--tmpfs=fs
Create a tmpfs mount

Mount a temporary filesystem (tmpfs) mount into a container, for example:

$ podman run -d --tmpfs /tmp:rw,size=787448k,mode=1777 my_image

This command mounts a tmpfs at /tmp within the container.  The supported mount options are the same as the Linux default mount flags. If you do not specify any options, the systems uses the following options: rw,noexec,nosuid,nodev.

--tty, -t=true|false
Allocate a pseudo-TTY. The default is false.

When set to true podman will allocate a pseudo-tty and attach to the standard input of the container. This can be used, for example, to run a throwaway interactive shell. The default is false.

Note: The -t option is incompatible with a redirection of the podman client standard input.

--uidmap=container_uid:host_uid:amount
UID map for the user namespace.  Using this flag will run the container with user namespace enabled.  It conflicts with the --userns and --subuidname flags.

The following example maps uids 0-2000 in the container to the uids 30000-31999 on the host and gids 0-2000 in the container to the gids 30000-31999 on the host. --uidmap=0:30000:2000

--ulimit=option
Ulimit options

You can pass host to copy the current configuration from the host.

--user, -u=user
Sets the username or UID used and optionally the groupname or GID for the specified command.

The followings examples are all valid: --user [user | user:group | uid | uid:gid | user:gid | uid:group ]

Without this argument the command will be run as root in the container.

--userns=host --userns=keep-id --userns=container:container --userns=ns:my_namespace
Set the user namespace mode for the container.  It defaults to the PODMAN_USERNS environment variable.  An empty value means user namespaces are disabled.

This option is incompatible with --gidmap, --uidmap, --subuid and --subgid

--uts=host
Set the UTS mode for the container
   host: use the host's UTS namespace inside the container.
   ns: specify the user namespace to use.
   Note: the host mode gives the container access to changing the host's hostname and is therefore considered insecure.
--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:

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 the /foo value, podman creates a bind-mount.

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

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.

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 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 container 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.

To control mount propagation property of volume one can use :[r]shared, :[r]slave or :[r]private 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 source mount point (mount point where source dir is mounted on) has to have right propagation properties. For shared volumes, source mount point has to be shared. And for slave volumes, source mount has to be either shared or slave.

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 mount entry for 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.

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.

--volumes-from[=CONTAINER[:OPTIONS]]
Mount volumes from the specified container(s). OPTIONS is a comma delimited list with the following available elements:

Mounts already mounted volumes from a source container onto another container. You must supply the source's container-id or container-name. To share a volume, use the --volumes-from option when running the target container. You can share volumes 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. Optionally, you can change this by suffixing the container-id with either the ro or rw keyword.

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 z to the volume mount. This suffix tells 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.

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

--workdir, -w=dir
Working directory inside the container

The default working directory for running binaries within a container is the root directory (/). The image developer can set a different default with the WORKDIR instruction. The operator can override the working directory by using the -w option.

Examples

Create a container using a local image

$ podman create alpine ls

Create a container using a local image and annotate it

$ podman create --annotation HELLO=WORLD alpine ls

Create a container using a local image, allocating a pseudo-TTY, keeping stdin open and name it myctr

  podman create -t -i --name myctr alpine ls

Set UID/GID mapping in a new user namespace

Running a container in a new user namespace requires a mapping of the uids and gids from the host.

$ podman create --uidmap 0:30000:7000 --gidmap 0:30000:7000 fedora echo hello

Rootless Containers

Podman runs as a non root user on most systems. This feature requires that a new enough version of shadow-utils be installed.  The shadow-utils package must include the newuidmap and newgidmap executables.

Note: RHEL7 and Centos 7 will not have this feature until RHEL7.7 is released.

In order for users to run rootless, there must be an entry for their username in /etc/subuid and /etc/subgid which lists the UIDs for their user namespace.

Rootless podman works better if the fuse-overlayfs and slirp4netns packages are installed. The fuse-overlay package provides a userspace overlay storage driver, otherwise users need to use the vfs storage driver, which is diskspace expensive and does not perform well. slirp4netns is required for VPN, without it containers need to be run with the --net=host flag.

Environment

Environment variables within containers can be set using multiple different options:  This section describes the precedence.

Precedence Order:   --env-host : Host environment of the process executing podman is added.

   Container image : Any environment variables specified in the container image.

   **--env-file** : Any environment variables specified via env-files.  If multiple files specified, then they override each other in order of entry.

   **--env** : Any environment variables specified will override previous settings.

Create containers and set the environment ending with a * and a *****

$ export ENV1=a
$ podman create --name ctr --env ENV* alpine printenv ENV1
$ podman start --attach ctr
a

$ podman create --name ctr --env ENV*****=b alpine printenv ENV*****
$ podman start --attach ctr
b

Files

/etc/subuid /etc/subgid

See Also

subgid(5), subuid(5), libpod.conf(5), systemd.unit(5), setsebool(8), slirp4netns(1), fuse-overlayfs(1)

History

October 2017, converted from Docker documentation to podman by Dan Walsh for podman dwalsh@redhat.com ⟨mailto:dwalsh@redhat.com⟩

November 2014, updated by Sven Dowideit SvenDowideit@home.org.au ⟨mailto:SvenDowideit@home.org.au⟩

September 2014, updated by Sven Dowideit SvenDowideit@home.org.au ⟨mailto:SvenDowideit@home.org.au⟩

August 2014, updated by Sven Dowideit SvenDowideit@home.org.au ⟨mailto:SvenDowideit@home.org.au⟩

Referenced By

podman(1), podman-commit(1), podman-container(1), podman-remote(1), podman-restart(1), podman-start(1), toolbox-init-container(1).

The man page podman-container-create(1) is an alias of podman-create(1).