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% kpod(1) kpod-run - Run a command in a container % Dan Walsh kpod-run - Run a command in a new container

SYNOPSIS

kpod run [options [...]] IMAGE [COMMAND] [ARG...]

DESCRIPTION

Run a process in a new container. kpod run starts a process with its own file system, its own networking, and its own isolated process tree. The IMAGE which starts the process may define defaults related to the process that will be run in the container, the networking to expose, and more, but kpod run gives final control to the operator or administrator who starts the container from the image. For that reason kpod run has more options than any other kpod command.

If the IMAGE is not already loaded then kpod run will pull the IMAGE, and all image dependencies, from the repository in the same way running kpod pull IMAGE, before it starts the container from that image.

OPTIONS

--add-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.

-a, --attach=[] Attach to STDIN, STDOUT or STDERR.

In foreground mode (the default when -d is not specified), kpod 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.

--blkio-weight=0 Block IO weight (relative weight) accepts a weight value between 10 and 1000.

--blkio-weight-device=[] Block IO weight (relative device weight, format: DEVICE_NAME:WEIGHT).

--cap-add=[] Add Linux capabilities

--cap-drop=[] Drop Linux capabilities

--cgroup-parent="" 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="" Write the container ID to the file

--cpu-count=0 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=0 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=0 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=0 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=0 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=0 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    container	CPU	CPU share
100    {C0}		0	100% of CPU0
101    {C1}		1	100% of CPU1
102    {C1}		2	100% of CPU2

--cpus=0.0 Number of CPUs. The default is 0.0 which means no limit.

--cpuset-cpus="" CPUs in which to allow execution (0-3, 0,1)

--cpuset-mems="" 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.

-d, --detach=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 kpod ps in the other shell to view a list of the running containers. You can reattach to a detached container with kpod attach. If you choose to run a container in the detached mode, then you cannot use the -rm option.

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. You configure the key sequence using the --detach-keys option or a configuration file. See config-json(5) for documentation on using a configuration file.

--detach-keys="" Override the key sequence for detaching a container. Format is a single character [a-Z] or ctrl-<value> where <value> is one of: a-z, @, ^, [, , or _.

--device=[] Add a host device to the container (e.g. --device=/dev/sdc:/dev/xvdc:rwm)

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

--device-read-iops=[] Limit read rate (IO per second) from a device (e.g. --device-read-iops=/dev/sda:1000)

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

--device-write-iops=[] Limit write rate (IO per second) to a device (e.g. --device-write-iops=/dev/sda:1000)

--dns=[] Set custom DNS servers

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.

--dns-option=[] Set custom DNS options

--dns-search=[] Set custom DNS search domains (Use --dns-search=. if you don't wish to set the search domain)

--entrypoint="" 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.

-e, --env=[] Set environment variables

This option allows you to specify arbitrary environment variables that are available for the process that will be launched inside of the container.

--env-file=[] Read in a line delimited file of environment variables

--expose=[] Expose a port, or a range of ports (e.g. --expose=3300-3310) to set up port redirection on the host system.

--group-add=[] Add additional groups to run as

--hostname="" Container host name

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

--help Print usage statement

-i, --interactive=true|false Keep STDIN open even if not attached. The default is false.

When set to true, keep stdin open even if not attached. The default is false.

--ip="" Sets the container's interface IPv4 address (e.g. 172.23.0.9)

It can only be used in conjunction with --network for user-defined networks

--ip6="" Sets the container's interface IPv6 address (e.g. 2001:db8::1b99)

It can only be used in conjunction with --network for user-defined networks

--ipc="" Default is to create a private IPC namespace (POSIX SysV IPC) for the container 'container:<name|id>': 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.

--kernel-memory="" 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.

-l, --label=[] Add metadata to a container (e.g., --label com.example.key=value)

--label-file=[] Read in a line delimited file of labels

--link-local-ip=[] Add one or more link-local IPv4/IPv6 addresses to the container's interface

--log-opt=[] Logging driver specific options.

--mac-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.

-m, --memory="" 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="" 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="" Tune a container's memory swappiness behavior. Accepts an integer between 0 and 100.

--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”)

kpod generates a UUID for each container, and if a name is not assigned to the container with --name then the daemon will also generate a random string name. The name is useful when defining links (see --link) (or any other place you need to identify a container). This works for both background and foreground containers.

--network="bridge" Set the Network mode for the container 'bridge': create a network stack on the default bridge 'none': no networking 'container:<name|id>': reuse another container's network stack 'host': use the kpod 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

--network-alias=[] Add network-scoped alias for the container

--oom-kill-disable=true|false Whether to disable OOM Killer for the container or not.

--oom-score-adj="" Tune the host's OOM preferences for containers (accepts -1000 to 1000)

--pid="" Set the PID mode for the container Default is to create a private PID namespace for the container 'container:<name|id>': 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.

--pids-limit="" Tune the container's pids limit. Set -1 to have unlimited pids for the container.

--pod="" Run container in an existing pod

--privileged=true|false Give extended privileges to this container. The default is false.

By default, kpod 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 kpod run --privileged, kpod enables access to all devices on the host as well as set turn off most of the security messurs protecting the host from the container.

-p, --publish=[] 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., kpod run -p 1234-1236:1222-1224 --name thisWorks -t busybox but not kpod run -p 1230-1236:1230-1240 --name RangeContainerPortsBiggerThanRangeHostPorts -t busybox) With ip: kpod run -p 127.0.0.1:$HOSTPORT:$CONTAINERPORT --name CONTAINER -t someimage Use kpod port to see the actual mapping: kpod port CONTAINER $CONTAINERPORT

-P, --publish-all=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 kpod 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, kpod 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 kpod port.

--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.

--rm=true|false Automatically remove the container when it exits. The default is false. --rm flag can work together with -d, and auto-removal will be done on daemon side. Note that it's incompatible with any restart policy other than none.

--security-opt=[] Security Options

"label=user:USER"   : Set the label user for the container
"label=role:ROLE"   : Set the label role for the container
"label=type:TYPE"   : Set the label type for the container
"label=level:LEVEL" : Set the label level for the container
"label=disable"     : Turn off label confinement for the container
"no-new-privileges" : Disable container processes from gaining additional privileges

"seccomp=unconfined" : Turn off seccomp confinement for the container
"seccomp=profile.json :  White listed syscalls seccomp Json file to be used as a seccomp filter

"apparmor=unconfined" : Turn off apparmor confinement for the container
"apparmor=your-profile" : Set the apparmor confinement profile for the container

--shm-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.

--sig-proxy=true|false Proxy received signals to the process (non-TTY mode only). SIGCHLD, SIGSTOP, and SIGKILL are not proxied. The default is true.

--stop-signal=SIGTERM Signal to stop a container. Default is SIGTERM.

--stop-timeout=10 Timeout (in seconds) to stop a container. Default is 10.

--storage-opt=[] Storage driver options per container

$ kpod run -it --storage-opt size=120G fedora /bin/bash

This (size) will allow to set the container rootfs size to 120G at creation time. This option is only available for the devicemapper, btrfs, overlay2 and zfs graph drivers. For the devicemapper, btrfs and zfs storage drivers, user cannot pass a size less than the Default BaseFS Size. For the overlay2 storage driver, the size option is only available if the backing fs is xfs and mounted with the pquota mount option. Under these conditions, user can pass any size less then the backing fs size.

--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.

--tmpfs=[] Create a tmpfs mount

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

$ kpod 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,size=65536k.

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

When set to true kpod 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 kpod client standard input.

--ulimit=[] Ulimit options

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

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

--userns="" Set the usernamespace mode for the container when userns-remap option is enabled. host: use the host usernamespace and enable all privileged options (e.g., pid=host or --privileged).

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

-v|--volume[=HOST-DIR:]CONTAINER-DIR[:OPTIONS] Create a bind mount. If you specify, -v /HOST-DIR:/CONTAINER-DIR, kpod bind mounts /HOST-DIR in the host to /CONTAINER-DIR in the kpod container. If 'HOST-DIR' is omitted, kpod automatically creates the new volume on the host. The OPTIONS are a comma delimited list and can be:

[rw|ro]
[z|Z]
[[r]shared|[r]slave|[r]private]
[nocopy]

The CONTAINER-DIR must be an absolute path such as /src/docs. The HOST-DIR can be an absolute path or a name value. A name value must start with an alphanumeric character, followed by a-z0-9, _ (underscore), . (period) or - (hyphen). An absolute path starts with a / (forward slash).

If you supply a HOST-DIR that is an absolute path, kpod bind-mounts to the path you specify. If you supply a name, kpod creates a named volume by that name. For example, you can specify either /foo or foo for a HOST-DIR value. If you supply the /foo value, kpod creates a bind-mount. If you supply the foo specification, kpod creates a named volume.

You can specify multiple -v options to mount one or more mounts to a container. To use these same mounts in other containers, specify the --volumes-from option also.

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, kpod 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 kpod to relabel file objects on the shared volumes. The z option tells kpod that two containers share the volume content. As a result, kpod labels the content with a shared content label. Shared volume labels allow all containers to read/write content. The Z option tells kpod 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-a-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-a-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 propagaion 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.

To disable automatic copying of data from the container path to the volume, use the nocopy flag. The nocopy flag can be set on bind mounts and named volumes.

--volumes-from=[] Mount volumes from the specified container(s)

Mounts already mounted volumes from a source container onto another container. You must supply the source's container-id. 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, kpod 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.

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.

-w, --workdir="" 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.

Exit Status

The exit code from kpod run gives information about why the container failed to run or why it exited. When kpod run exits with a non-zero code, the exit codes follow the chroot standard, see below:

125 if the error is with kpod itself

$ kpod run --foo busybox; echo $?
# flag provided but not defined: --foo
  See 'kpod run --help'.
  125

126 if the contained command cannot be invoked

$ kpod run busybox /etc; echo $?
# exec: "/etc": permission denied
  kpod: Error response from daemon: Contained command could not be invoked
  126

127 if the contained command cannot be found

$ kpod run busybox foo; echo $?
# exec: "foo": executable file not found in $PATH
  kpod: Error response from daemon: Contained command not found or does not exist
  127

Exit code of contained command otherwise

$ kpod run busybox /bin/sh -c 'exit 3'
# 3

EXAMPLES

Running container in read-only mode

During container image development, containers often need to write to the image content. Installing packages into /usr, for example. In production, applications seldom need to write to the image. Container applications write to volumes if they need to write to file systems at all. Applications can be made more secure by running them in read-only mode using the - -read-only switch. This protects the containers image from modification. Read only containers may still need to write temporary data. The best way to handle this is to mount tmpfs directories on /run and /tmp.

# kpod run --read-only --tmpfs /run --tmpfs /tmp -i -t fedora /bin/bash

Exposing log messages from the container to the host's log

If you want messages that are logged in your container to show up in the host's syslog/journal then you should bind mount the /dev/log directory as follows.

# kpod run -v /dev/log:/dev/log -i -t fedora /bin/bash

From inside the container you can test this by sending a message to the log.

(bash)# logger "Hello from my container"

Then exit and check the journal.

# exit

# journalctl -b | grep Hello

This should list the message sent to logger.

Attaching to one or more from STDIN, STDOUT, STDERR

If you do not specify -a then kpod will attach everything (stdin,stdout,stderr) . You can specify to which of the three standard streams (stdin, stdout, stderr) you'd like to connect instead, as in:

# kpod run -a stdin -a stdout -i -t fedora /bin/bash

Using shm_server.c available here: https://www.cs.cf.ac.uk/Dave/C/node27.html

Testing --ipc=host mode:

Host shows a shared memory segment with 7 pids attached, happens to be from httpd:

 $ sudo ipcs -m

 ------ Shared Memory Segments --------
 key        shmid      owner      perms      bytes      nattch     status
 0x01128e25 0          root       600        1000       7

Now run a regular container, and it correctly does NOT see the shared memory segment from the host:

 $ kpod run -it shm ipcs -m

 ------ Shared Memory Segments --------
 key        shmid      owner      perms      bytes      nattch     status

Run a container with the new --ipc=host option, and it now sees the shared memory segment from the host httpd:

$ kpod run -it --ipc=host shm ipcs -m

------ Shared Memory Segments --------
key        shmid      owner      perms      bytes      nattch     status
0x01128e25 0          root       600        1000       7

Testing --ipc=container:CONTAINERID mode:

Start a container with a program to create a shared memory segment:

 $ kpod run -it shm bash
 $ sudo shm/shm_server &
 $ sudo ipcs -m

 ------ Shared Memory Segments --------
 key        shmid      owner      perms      bytes      nattch     status
 0x0000162e 0          root       666        27         1

Create a 2nd container correctly shows no shared memory segment from 1st container:

 $ kpod run shm ipcs -m

 ------ Shared Memory Segments --------
 key        shmid      owner      perms      bytes      nattch     status

Create a 3rd container using the new --ipc=container:CONTAINERID option, now it shows the shared memory segment from the first:

 $ kpod run -it --ipc=container:ed735b2264ac shm ipcs -m
 $ sudo ipcs -m

 ------ Shared Memory Segments --------
 key        shmid      owner      perms      bytes      nattch     status
 0x0000162e 0          root       666        27         1

Mapping Ports for External Usage

The exposed port of an application can be mapped to a host port using the -p flag. For example, an httpd port 80 can be mapped to the host port 8080 using the following:

# kpod run -p 8080:80 -d -i -t fedora/httpd

Creating and Mounting a Data Volume Container

Many applications require the sharing of persistent data across several containers. kpod allows you to create a Data Volume Container that other containers can mount from. For example, create a named container that contains directories /var/volume1 and /tmp/volume2. The image will need to contain these directories so a couple of RUN mkdir instructions might be required for you fedora-data image:

# kpod run --name=data -v /var/volume1 -v /tmp/volume2 -i -t fedora-data true
# kpod run --volumes-from=data --name=fedora-container1 -i -t fedora bash

Multiple --volumes-from parameters will bring together multiple data volumes from multiple containers. And it's possible to mount the volumes that came from the DATA container in yet another container via the fedora-container1 intermediary container, allowing to abstract the actual data source from users of that data:

# kpod run --volumes-from=fedora-container1 --name=fedora-container2 -i -t fedora bash

Mounting External Volumes

To mount a host directory as a container volume, specify the absolute path to the directory and the absolute path for the container directory separated by a colon:

# kpod run -v /var/db:/data1 -i -t fedora bash

When using SELinux, be aware that the host has no knowledge of container SELinux policy. Therefore, in the above example, if SELinux policy is enforced, the /var/db directory is not writable to the container. A "Permission Denied" message will occur and an avc: message in the host's syslog.

To work around this, at time of writing this man page, the following command needs to be run in order for the proper SELinux policy type label to be attached to the host directory:

# chcon -Rt svirt_sandbox_file_t /var/db

Now, writing to the /data1 volume in the container will be allowed and the changes will also be reflected on the host in /var/db.

Using alternative security labeling

You can override the default labeling scheme for each container by specifying the --security-opt flag. For example, you can specify the MCS/MLS level, a requirement for MLS systems. Specifying the level in the following command allows you to share the same content between containers.

# kpod run --security-opt label=level:s0:c100,c200 -i -t fedora bash

An MLS example might be:

# kpod run --security-opt label=level:TopSecret -i -t rhel7 bash

To disable the security labeling for this container versus running with the --permissive flag, use the following command:

# kpod run --security-opt label=disable -i -t fedora bash

If you want a tighter security policy on the processes within a container, you can specify an alternate type for the container. You could run a container that is only allowed to listen on Apache ports by executing the following command:

# kpod run --security-opt label=type:svirt_apache_t -i -t centos bash

Note:

You would have to write policy defining a svirt_apache_t type.

Setting device weight

If you want to set /dev/sda device weight to 200, you can specify the device weight by --blkio-weight-device flag. Use the following command:

kpod run -it --blkio-weight-device "/dev/sda:200" ubuntu

$ kpod run -d busybox top

Setting Namespaced Kernel Parameters (Sysctls)

The --sysctl sets namespaced kernel parameters (sysctls) in the container. For example, to turn on IP forwarding in the containers network namespace, run this command:

$ kpod run --sysctl net.ipv4.ip_forward=1 someimage

Note:

Not all sysctls are namespaced. kpod does not support changing sysctls inside of a container that also modify the host system. As the kernel evolves we expect to see more sysctls become namespaced.

See the definition of the --sysctl option above for the current list of supported sysctls.

HISTORY

April 2014, Originally compiled by William Henry (whenry at redhat dot com) based on docker.com source material and internal work. June 2014, updated by Sven Dowideit SvenDowideit@home.org.au July 2014, updated by Sven Dowideit SvenDowideit@home.org.au November 2015, updated by Sally O'Malley somalley@redhat.com October 2017, converted from Docker documentation to kpod by Dan Walsh for kpod dwalsh@redhat.com

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SYNOPSIS

DESCRIPTION

OPTIONS

Exit Status

EXAMPLES

Running container in read-only mode

Exposing log messages from the container to the host's log

Attaching to one or more from STDIN, STDOUT, STDERR

Sharing IPC between containers

Mapping Ports for External Usage

Creating and Mounting a Data Volume Container

Mounting External Volumes

Using alternative security labeling

Setting device weight

kpod run -it --blkio-weight-device "/dev/sda:200" ubuntu

Setting Namespaced Kernel Parameters (Sysctls)

HISTORY

35 KiB

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