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
(“f78375b1c487e03c9438c729345e54db9d20cfa2ac1fc3494b6eb60872e74778”)
UUID short identifier (“f78375b1c487”) Name
(“jonah”)
podman generates a UUID for each pod, and if a name is not assigned to the
container with
--name then a random string name will be generated for
it. The name is useful any place you need to identify a pod.
Note: resource limit related flags work by setting the limits explicitly in the
pod's cgroup which by default, is the cgroup parent for all containers joining
the pod. Containers are still delegated the ability to set their own resource
limits when joining a pod meaning that if you run
podman pod create
--cpus=5 you can also run
podman container create
--pod=<pod_id|pod_name> --cpus=4 and the container will only
see the smaller limit. containers do NOT get the pod level cgroup resources if
they specify their own cgroup when joining a pod such as
--cgroupns=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. 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 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.
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 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 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:
|
PID |
container |
CPU |
CPU share |
| 100 |
C0 |
0 |
100% of CPU0 |
| 101 |
C1 |
1 |
100% of CPU1 |
| 102 |
C1 |
2 |
100% 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.
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 will only use 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 will be resolved first.
The pod will only store the major and minor numbers of the host device.
Podman may load kernel modules required for using the specified device. The
devices that Podman will load 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 will be shared between
all containers in the pod. A special option, "none" is allowed which
disables creation of /etc/resolv.conf for the pod.
Set custom DNS options in the /etc/resolv.conf file that will be shared between
all containers in the pod.
Set custom DNS search domains in the /etc/resolv.conf file that will be shared
between all containers in the pod.
Set the exit policy of the pod when the last container exits. Supported policies
are:
|
Exit Policy |
Description |
| continue |
The pod continues running, by keeping its infra container alive, when
the last container exits. Used by default. |
| stop |
The pod (including its infra container) is stopped when the last
container exits. Used in kube play. |
GID map for the user namespace. Using this flag will run 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 will be 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 will be used for the infra container. Unless specified,
Podman builds a custom local image which does not require pulling down an
image.
The name that will be 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 will be 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 would be 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
should always 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:
- •
-
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:
- •
-
alias=name: Add network-scoped alias for the
container.
- •
-
ip=IPv4: Specify a static ipv4 address for this
container.
- •
-
ip=IPv6: Specify a static ipv6 address for this
container.
- •
-
mac=MAC: Specify a static mac address for this
container.
- •
-
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. - <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. You can use
the
--network option multiple times to specify additional networks. -
none: Create a network namespace for the container but do not configure
network interfaces for it, thus the container has no network connectivity. -
container:id: Reuse another container's network stack. -
host: Do not create a network namespace, the container will use the
host's network. Note: The host mode gives the container full access to local
system services such as D-bus and is therefore considered insecure. -
ns: path: Path to a network namespace to join. -
private:
Create a new namespace for the container. This will use the
bridge mode
for rootful containers and
slirp4netns for rootless ones. -
slirp4netns[:OPTIONS,...]: use
slirp4netns(1) to create a user
network stack. This is the default for rootless containers. It is possible to
specify these additional options, they can also be set with
network_cmd_options in containers.conf:
-
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.
-
mtu=MTU: Specify the MTU to use for this network. (Default is
65520).
-
cidr=CIDR: Specify ip range to use for this network. (Default is
10.0.2.0/24).
-
enable_ipv6=true|false: Enable IPv6. Default is true. (Required for
outbound_addr6).
-
outbound_addr=INTERFACE: Specify the outbound interface slirp should
bind to (ipv4 traffic only).
-
outbound_addr=IPv4: Specify the outbound ipv4 address slirp should
bind to.
-
outbound_addr6=INTERFACE: Specify the outbound interface slirp should
bind to (ipv6 traffic only).
-
outbound_addr6=IPv6: Specify the outbound ipv6 address slirp should
bind to.
-
port_handler=rootlesskit: Use rootlesskit for port forwarding.
Default.
Note: Rootlesskit changes the source IP address of incoming packets to an IP
address in the container network namespace, usually
10.0.2.100. If your
application requires the real source IP address, e.g. web server logs, use the
slirp4netns port handler. The rootlesskit port handler is also used for
rootless containers when connected to user-defined networks.
-
port_handler=slirp4netns: Use the slirp4netns port forwarding, it is
slower than rootlesskit but preserves the correct source IP address. This port
handler cannot be used for user-defined networks.
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 will only
have 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 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/hosts will be 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 host’s 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 will be bound on all
IPs on the host.
By default, Podman will publish 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 will be randomly assigned a
port on the host.
Use
podman port to see the actual mapping:
podman port $CONTAINER
$CONTAINERPORT.
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.
Security Options
- •
-
apparmor=unconfined : Turn off apparmor confinement
for the pod
- •
-
apparmor=your-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.
- •
-
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 : Whitelisted syscalls seccomp
Json file to be used as a seccomp filter
- •
-
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 will unmask 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. 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 (
/etc/containers/containers.conf or
$HOME/.config/containers/containers.conf) file.
A comma-separated list of kernel namespaces to share. If none or "" is
specified, no namespaces will be shared and the infra container will not be
created unless expiclity specified via
--infra=true. The namespaces to
choose from are cgroup, ipc, net, pid, uts. If the option is prefixed with a
"+" then the namespace is appended to the default list, otherwise it
replaces the default list. Defaults matches Kubernetes default (ipc, net, uts)
This boolean determines whether or not all containers entering the pod will use
the pod as their cgroup parent. The default value of this flag is true. If you
are looking to share the cgroup namespace rather than a cgroup parent in a
pod, use
--share
Note: This options conflict with
--share=cgroup since that would set the
pod as the cgroup parent but enter 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.
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:
- •
- 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.
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:
|
Key |
Host User |
Container User |
| "" |
$UID |
0 (Default User account mapped to root user in container.) |
| keep-id |
$UID |
$UID (Map user account to same UID within container.) |
| auto |
$UID |
nil (Host User UID is not mapped into container.) |
| nomap |
$UID |
nil (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:HOSTGID:SIZE to
force a GID mapping to be present in the user namespace.
- •
-
size=SIZE: to specify an explicit size for
the automatic user namespace. e.g. --userns=auto:size=8192. If
size is not specified, auto will estimate a size for the
user namespace.
- •
-
uidmapping=_CONTAINER_UID:HOSTUID:SIZE to
force a UID mapping to be present in the user namespace.
- •
-
host: run in the user namespace of the caller. The
processes running in the container will have the same privileges on the
host as any other process launched by the calling user (default).
- •
-
keep-id: creates a user namespace where the current
rootless user's UID:GID are mapped to the same values in the container.
This option is 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.
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.
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 will mount
the named volume from the host into the container. If no such named volume
exists, Podman will create one. If no source is given, the volume will be
created as an anonymously named volume with a randomly generated name, and
will be removed when the pod is removed via the
--rm flag or the
podman rm --volumes command.
(Note when using the remote client, including Mac and Windows (excluding WSL2)
machines, the volumes will be mounted from the remote server, not necessarily
the client machine.)
The
OPTIONS is a comma-separated list and can be: [1]
⟨#Footnote1⟩
- •
-
rw|ro
- •
-
z|Z
- •
- [O]
- •
- [U]
- •
- [no]copy
- •
- [no]dev
- •
- [no]exec
- •
- [no]suid
- •
- [r]bind
- •
- [r]shared|[r]slave|[r]private[r]unbindable
The
CONTAINER-DIR must be an absolute path such as
/src/docs. The
volume will be 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 will return an error. Users must pre-create the source
files or directories.
Any source that does not begin with a
. or
/ will be treated as
the name of a named volume. If a volume with that name does not exist, it will
be created. Volumes created with names are not anonymous, and they are not
removed by the
--rm option and the
podman rm --volumes command.
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.
Warning use with caution since this will modify the host filesystem.
Labeling Volume Mounts
Labeling systems like SELinux require that proper labels are placed on volume
content mounted into a pod. Without a label, the security system might prevent
the processes running inside the pod from using the content. By default,
Podman does not change the labels set by the OS.
To change a label in the pod context, add either of two suffixes
:z or
:Z to the volume mount. These suffixes tell Podman to relabel file
objects on the shared volumes. The
z option tells Podman that two pods
share the volume content. As a result, Podman labels the content with a shared
content label. Shared volume labels allow all containers to read/write
content. The
Z option tells Podman to label the content with a private
unshared label. Only the current pod can use a private volume.
Note: Do not relabel system files and directories. Relabeling system content
might cause other confined services on your 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 will be the
lower, and the container storage directory will be the upper. Modifications to
the mount point are destroyed when the pod finishes executing, similar to a
tmpfs mount point being unmounted.
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 will not remove it on lifecycle completion. Example
:O,upperdir=/some/upper,workdir=/some/work
Subsequent executions of the container will see the original source directory
content, any changes from previous pod executions no longer exist.
One use case of the overlay mount is sharing the package cache from the host
into the container to allow speeding up builds.
Note:
- The `O` flag conflicts with other options listed above.
Content mounted into the container is labeled with the private label.
On SELinux systems, labels in the source directory must be readable by the 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.
- The source directory mounted into the pod with an overlay mount should not be
modified, it can cause unexpected failures. It is recommended to not modify
the directory until the container finishes running.
Mounts propagation
By default bind mounted volumes are
private. That means any mounts done
inside the pod will not be visible on host and vice versa. One can change this
behavior by specifying a volume mount propagation property. Making a volume
shared mounts done under that volume inside the pod will be visible on host
and vice versa. Making a volume
slave enables only one way mount
propagation and that is mounts done on host under that volume will be visible
inside container but not the other way around. [1] ⟨#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 will not be mounted into the pod.
Mounting the volume with the
nosuid options means that SUID applications
on the volume will not be able to change their privilege. By default volumes
are mounted with
nosuid.
Mounting the volume with the
noexec option means that no executables on
the volume will be able to be executed within the pod.
Mounting the volume with the
nodev option means that no devices on the
volume will be able to be used by processes within the pod. By default volumes
are mounted with
nodev.
If the
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 will convert /foo into a shared mount point. Alternatively, one
can directly change propagation properties of source mount. Say
/ is
source mount for
/foo, then use
mount --make-shared / to convert
/ into a shared mount.
Note: if the user only has access rights via a group, accessing the volume from
inside a rootless pod will fail.
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:
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 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 should 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.