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README

Open Container Specifications

Open Container Initiative Specifications for standards on Operating System process and application containers.

Table of Contents

In the specifications in the above table of contents, the keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as described in RFC 2119 (Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997).

Use Cases

To provide context for users the following section gives example use cases for each part of the spec.

Application Bundle Builders

Application bundle builders can create a bundle directory that includes all of the files required for launching an application as a container. The bundle contains OCI configuration files where the builder can specify host-independent details such as which executable to launch and host-specific settings such as mount locations, hook paths, Linux namespaces and cgroups. Because the configuration includes host-specific settings, application bundle directories copied between two hosts may require configuration adjustments.

Hook Developers

Hook developers can extend the functionality of an OCI-compliant runtime by hooking into a container's lifecycle with an external application. Example use cases include sophisticated network configuration, volume garbage collection, etc.

Runtime Developers

Runtime developers can build runtime implementations that run OCI-compliant bundles and container configuration, containing low-level OS and host specific details, on a particular platform.

Releases

There is a loose Road Map. During the 0.x series of OCI releases we make no backwards compatibility guarantees and intend to break the schema during this series.

Contributing

Development happens on GitHub for the spec. Issues are used for bugs and actionable items and longer discussions can happen on the mailing list.

The specification and code is licensed under the Apache 2.0 license found in the LICENSE file of this repository.

Code of Conduct

Participation in the OpenContainers community is governed by OpenContainer's Code of Conduct.

Discuss your design

The project welcomes submissions, but please let everyone know what you are working on.

Before undertaking a nontrivial change to this specification, send mail to the mailing list to discuss what you plan to do. This gives everyone a chance to validate the design, helps prevent duplication of effort, and ensures that the idea fits. It also guarantees that the design is sound before code is written; a GitHub pull-request is not the place for high-level discussions.

Typos and grammatical errors can go straight to a pull-request. When in doubt, start on the mailing-list.

Weekly Call

The contributors and maintainers of the project have a weekly meeting Wednesdays at 10:00 AM PST. Everyone is welcome to participate in the BlueJeans call. An initial agenda will be posted to the mailing list earlier in the week, and everyone is welcome to propose additional topics or suggest other agenda alterations there. Minutes are posted to the mailing list and minutes from past calls are archived to the wiki for those who are unable to join the call.

Mailing List

You can subscribe and join the mailing list on Google Groups.

IRC

OCI discussion happens on #opencontainers on Freenode.

Markdown style

To keep consistency throughout the Markdown files in the Open Container spec all files should be formatted one sentence per line. This fixes two things: it makes diffing easier with git and it resolves fights about line wrapping length. For example, this paragraph will span three lines in the Markdown source.

Git commit

Sign your work

The sign-off is a simple line at the end of the explanation for the patch, which certifies that you wrote it or otherwise have the right to pass it on as an open-source patch. The rules are pretty simple: if you can certify the below (from developercertificate.org):

Developer Certificate of Origin
Version 1.1

Copyright (C) 2004, 2006 The Linux Foundation and its contributors.
660 York Street, Suite 102,
San Francisco, CA 94110 USA

Everyone is permitted to copy and distribute verbatim copies of this
license document, but changing it is not allowed.


Developer's Certificate of Origin 1.1

By making a contribution to this project, I certify that:

(a) The contribution was created in whole or in part by me and I
    have the right to submit it under the open source license
    indicated in the file; or

(b) The contribution is based upon previous work that, to the best
    of my knowledge, is covered under an appropriate open source
    license and I have the right under that license to submit that
    work with modifications, whether created in whole or in part
    by me, under the same open source license (unless I am
    permitted to submit under a different license), as indicated
    in the file; or

(c) The contribution was provided directly to me by some other
    person who certified (a), (b) or (c) and I have not modified
    it.

(d) I understand and agree that this project and the contribution
    are public and that a record of the contribution (including all
    personal information I submit with it, including my sign-off) is
    maintained indefinitely and may be redistributed consistent with
    this project or the open source license(s) involved.

then you just add a line to every git commit message:

Signed-off-by: Joe Smith <joe@gmail.com>

using your real name (sorry, no pseudonyms or anonymous contributions.)

You can add the sign off when creating the git commit via git commit -s.

Commit Style

Simple house-keeping for clean git history. Read more on How to Write a Git Commit Message or the Discussion section of git-commit(1).

  1. Separate the subject from body with a blank line
  2. Limit the subject line to 50 characters
  3. Capitalize the subject line
  4. Do not end the subject line with a period
  5. Use the imperative mood in the subject line
  6. Wrap the body at 72 characters
  7. Use the body to explain what and why vs. how
  • If there was important/useful/essential conversation or information, copy or include a reference
  1. When possible, one keyword to scope the change in the subject (i.e. "README: ...", "runtime: ...")

Documentation

Index

Constants

View Source 
const (
	// PIDNamespace for isolating process IDs
	PIDNamespace NamespaceType = "pid"
	// NetworkNamespace for isolating network devices, stacks, ports, etc
	NetworkNamespace = "network"
	// MountNamespace for isolating mount points
	MountNamespace = "mount"
	// IPCNamespace for isolating System V IPC, POSIX message queues
	IPCNamespace = "ipc"
	// UTSNamespace for isolating hostname and NIS domain name
	UTSNamespace = "uts"
	// UserNamespace for isolating user and group IDs
	UserNamespace = "user"
)
View Source 
const (
	// VersionMajor is for an API incompatible changes
	VersionMajor = 0
	// VersionMinor is for functionality in a backwards-compatible manner
	VersionMinor = 3
	// VersionPatch is for backwards-compatible bug fixes
	VersionPatch = 0

	// VersionDev indicates development branch. Releases will be empty string.
	VersionDev = "-dev"
)
View Source 
const LinuxStateDirectory = "/run/opencontainer/containers"

LinuxStateDirectory holds the container's state information

Variables

View Source 
var Version = fmt.Sprintf("%d.%d.%d%s", VersionMajor, VersionMinor, VersionPatch, VersionDev)

Version is the specification version that the package types support.

Functions

This section is empty.

Types

type Action added in v0.0.4 

type Action string

Action taken upon Seccomp rule match 

const (
	ActKill  Action = "SCMP_ACT_KILL"
	ActTrap  Action = "SCMP_ACT_TRAP"
	ActErrno Action = "SCMP_ACT_ERRNO"
	ActTrace Action = "SCMP_ACT_TRACE"
	ActAllow Action = "SCMP_ACT_ALLOW"
)

Define actions for Seccomp rules

type Arch added in v0.0.5 

type Arch string

Arch used for additional architectures 

const (
	ArchX86         Arch = "SCMP_ARCH_X86"
	ArchX86_64      Arch = "SCMP_ARCH_X86_64"
	ArchX32         Arch = "SCMP_ARCH_X32"
	ArchARM         Arch = "SCMP_ARCH_ARM"
	ArchAARCH64     Arch = "SCMP_ARCH_AARCH64"
	ArchMIPS        Arch = "SCMP_ARCH_MIPS"
	ArchMIPS64      Arch = "SCMP_ARCH_MIPS64"
	ArchMIPS64N32   Arch = "SCMP_ARCH_MIPS64N32"
	ArchMIPSEL      Arch = "SCMP_ARCH_MIPSEL"
	ArchMIPSEL64    Arch = "SCMP_ARCH_MIPSEL64"
	ArchMIPSEL64N32 Arch = "SCMP_ARCH_MIPSEL64N32"
)

Additional architectures permitted to be used for system calls By default only the native architecture of the kernel is permitted

type Arg added in v0.0.4 

type Arg struct {
	Index    uint     `json:"index"`
	Value    uint64   `json:"value"`
	ValueTwo uint64   `json:"valueTwo"`
	Op       Operator `json:"op"`
}

Arg used for matching specific syscall arguments in Seccomp

type BlockIO 

type BlockIO struct {
	// Specifies per cgroup weight, range is from 10 to 1000
	Weight *uint16 `json:"blkioWeight,omitempty"`
	// Specifies tasks' weight in the given cgroup while competing with the cgroup's child cgroups, range is from 10 to 1000, CFQ scheduler only
	LeafWeight *uint16 `json:"blkioLeafWeight,omitempty"`
	// Weight per cgroup per device, can override BlkioWeight
	WeightDevice []*WeightDevice `json:"blkioWeightDevice,omitempty"`
	// IO read rate limit per cgroup per device, bytes per second
	ThrottleReadBpsDevice []*ThrottleDevice `json:"blkioThrottleReadBpsDevice,omitempty"`
	// IO write rate limit per cgroup per device, bytes per second
	ThrottleWriteBpsDevice []*ThrottleDevice `json:"blkioThrottleWriteBpsDevice,omitempty"`
	// IO read rate limit per cgroup per device, IO per second
	ThrottleReadIOPSDevice []*ThrottleDevice `json:"blkioThrottleReadIOPSDevice,omitempty"`
	// IO write rate limit per cgroup per device, IO per second
	ThrottleWriteIOPSDevice []*ThrottleDevice `json:"blkioThrottleWriteIOPSDevice,omitempty"`
}

BlockIO for Linux cgroup 'blkio' resource management

type CPU 

type CPU struct {
	// CPU shares (relative weight (ratio) vs. other cgroups with cpu shares).
	Shares *uint64 `json:"shares,omitempty"`
	// CPU hardcap limit (in usecs). Allowed cpu time in a given period.
	Quota *uint64 `json:"quota,omitempty"`
	// CPU period to be used for hardcapping (in usecs).
	Period *uint64 `json:"period,omitempty"`
	// How much time realtime scheduling may use (in usecs).
	RealtimeRuntime *uint64 `json:"realtimeRuntime,omitempty"`
	// CPU period to be used for realtime scheduling (in usecs).
	RealtimePeriod *uint64 `json:"realtimePeriod,omitempty"`
	// CPUs to use within the cpuset. Default is to use any CPU available.
	Cpus *string `json:"cpus,omitempty"`
	// List of memory nodes in the cpuset. Default is to use any available memory node.
	Mems *string `json:"mems,omitempty"`
}

CPU for Linux cgroup 'cpu' resource management

type Device added in v0.0.4 

type Device struct {
	// Path to the device.
	Path string `json:"path"`
	// Device type, block, char, etc.
	Type rune `json:"type"`
	// Major is the device's major number.
	Major int64 `json:"major"`
	// Minor is the device's minor number.
	Minor int64 `json:"minor"`
	// Cgroup permissions format, rwm.
	Permissions string `json:"permissions"`
	// FileMode permission bits for the device.
	FileMode os.FileMode `json:"fileMode"`
	// UID of the device.
	UID uint32 `json:"uid"`
	// Gid of the device.
	GID uint32 `json:"gid"`
}

Device represents the information on a Linux special device file

type Hook added in v0.0.3 

type Hook struct {
	Path string   `json:"path"`
	Args []string `json:"args,omitempty"`
	Env  []string `json:"env,omitempty"`
}

Hook specifies a command that is run at a particular event in the lifecycle of a container

type Hooks added in v0.0.3 

type Hooks struct {
	// Prestart is a list of hooks to be run before the container process is executed.
	// On Linux, they are run after the container namespaces are created.
	Prestart []Hook `json:"prestart,omitempty"`
	// Poststart is a list of hooks to be run after the container process is started.
	Poststart []Hook `json:"poststart,omitempty"`
	// Poststop is a list of hooks to be run after the container process exits.
	Poststop []Hook `json:"poststop,omitempty"`
}

Hooks for container setup and teardown

type HugepageLimit 

type HugepageLimit struct {
	// Pagesize is the hugepage size
	Pagesize *string `json:"pageSize,omitempty"`
	// Limit is the limit of "hugepagesize" hugetlb usage
	Limit *uint64 `json:"limit,omitempty"`
}

HugepageLimit structure corresponds to limiting kernel hugepages

type IDMapping 

type IDMapping struct {
	// HostID is the UID/GID of the host user or group
	HostID uint32 `json:"hostID"`
	// ContainerID is the UID/GID of the container's user or group
	ContainerID uint32 `json:"containerID"`
	// Size is the length of the range of IDs mapped between the two namespaces
	Size uint32 `json:"size"`
}

IDMapping specifies UID/GID mappings

type InterfacePriority 

type InterfacePriority struct {
	// Name is the name of the network interface
	Name string `json:"name"`
	// Priority for the interface
	Priority uint32 `json:"priority"`
}

InterfacePriority for network interfaces

type Linux 

type Linux struct {
	// Capabilities are linux capabilities that are kept for the container.
	Capabilities []string `json:"capabilities"`
}

Linux contains platform specific configuration for linux based containers.

type LinuxRuntime added in v0.0.5 

type LinuxRuntime struct {
	// UIDMapping specifies user mappings for supporting user namespaces on linux.
	UIDMappings []IDMapping `json:"uidMappings,omitempty"`
	// GIDMapping specifies group mappings for supporting user namespaces on linux.
	GIDMappings []IDMapping `json:"gidMappings,omitempty"`
	// Rlimits specifies rlimit options to apply to the container's process.
	Rlimits []Rlimit `json:"rlimits,omitempty"`
	// Sysctl are a set of key value pairs that are set for the container on start
	Sysctl map[string]string `json:"sysctl,omitempty"`
	// Resources contain cgroup information for handling resource constraints
	// for the container
	Resources *Resources `json:"resources,omitempty"`
	// CgroupsPath specifies the path to cgroups that are created and/or joined by the container.
	// The path is expected to be relative to the cgroups mountpoint.
	// If resources are specified, the cgroups at CgroupsPath will be updated based on resources.
	CgroupsPath *string `json:"cgroupsPath,omitempty"`
	// Namespaces contains the namespaces that are created and/or joined by the container
	Namespaces []Namespace `json:"namespaces"`
	// Devices are a list of device nodes that are created and enabled for the container
	Devices []Device `json:"devices"`
	// ApparmorProfile specified the apparmor profile for the container.
	ApparmorProfile string `json:"apparmorProfile"`
	// SelinuxProcessLabel specifies the selinux context that the container process is run as.
	SelinuxProcessLabel string `json:"selinuxProcessLabel"`
	// Seccomp specifies the seccomp security settings for the container.
	Seccomp Seccomp `json:"seccomp"`
	// RootfsPropagation is the rootfs mount propagation mode for the container.
	RootfsPropagation string `json:"rootfsPropagation,omitempty"`
	// NoNewPrivileges controls whether additional privileges could be gained by processes in the container.
	NoNewPrivileges bool `json:"noNewPrivileges,omitempty"`
}

LinuxRuntime hosts the Linux-only runtime information

type LinuxRuntimeSpec added in v0.0.5 

type LinuxRuntimeSpec struct {
	RuntimeSpec
	// LinuxRuntime is platform specific configuration for linux based containers.
	Linux LinuxRuntime `json:"linux"`
}

LinuxRuntimeSpec is the full specification for linux containers.

type LinuxSpec 

type LinuxSpec struct {
	Spec
	// Linux is platform specific configuration for linux based containers.
	Linux Linux `json:"linux"`
}

LinuxSpec is the full specification for linux containers.

type Memory 

type Memory struct {
	// Memory limit (in bytes).
	Limit *uint64 `json:"limit,omitempty"`
	// Memory reservation or soft_limit (in bytes).
	Reservation *uint64 `json:"reservation,omitempty"`
	// Total memory limit (memory + swap).
	Swap *uint64 `json:"swap,omitempty"`
	// Kernel memory limit (in bytes).
	Kernel *uint64 `json:"kernel,omitempty"`
	// Kernel memory limit for tcp (in bytes)
	KernelTCP *uint64 `json:"kernelTCP"`
	// How aggressive the kernel will swap memory pages. Range from 0 to 100.
	Swappiness *uint64 `json:"swappiness,omitempty"`
}

Memory for Linux cgroup 'memory' resource management

type Mount 

type Mount struct {
	// Type specifies the mount kind.
	Type string `json:"type"`
	// Source specifies the source path of the mount.  In the case of bind mounts on
	// linux based systems this would be the file on the host.
	Source string `json:"source"`
	// Options are fstab style mount options.
	Options []string `json:"options,omitempty"`
}

Mount specifies a mount for a container

type MountPoint added in v0.0.5 

type MountPoint struct {
	// Name is a unique descriptive identifier for this mount point.
	Name string `json:"name"`
	// Path specifies the path of the mount. The path and child directories MUST exist, a runtime MUST NOT create directories automatically to a mount point.
	Path string `json:"path"`
}

MountPoint describes a directory that may be fullfilled by a mount in the runtime.json.

type Namespace 

type Namespace struct {
	// Type is the type of Linux namespace
	Type NamespaceType `json:"type"`
	// Path is a path to an existing namespace persisted on disk that can be joined
	// and is of the same type
	Path string `json:"path,omitempty"`
}

Namespace is the configuration for a linux namespace

type NamespaceType added in v0.0.5 

type NamespaceType string

NamespaceType is one of the linux namespaces

type Network 

type Network struct {
	// Set class identifier for container's network packets
	ClassID *uint32 `json:"classID"`
	// Set priority of network traffic for container
	Priorities []InterfacePriority `json:"priorities"`
}

Network identification and priority configuration

type Operator added in v0.0.4 

type Operator string

Operator used to match syscall arguments in Seccomp 

const (
	OpNotEqual     Operator = "SCMP_CMP_NE"
	OpLessThan     Operator = "SCMP_CMP_LT"
	OpLessEqual    Operator = "SCMP_CMP_LE"
	OpEqualTo      Operator = "SCMP_CMP_EQ"
	OpGreaterEqual Operator = "SCMP_CMP_GE"
	OpGreaterThan  Operator = "SCMP_CMP_GT"
	OpMaskedEqual  Operator = "SCMP_CMP_MASKED_EQ"
)

Define operators for syscall arguments in Seccomp

type Pids added in v0.0.5 

type Pids struct {
	// Maximum number of PIDs. Default is "no limit".
	Limit *int64 `json:"limit,omitempty"`
}

Pids for Linux cgroup 'pids' resource management (Linux 4.3)

type Platform 

type Platform struct {
	// OS is the operating system.
	OS string `json:"os"`
	// Arch is the architecture
	Arch string `json:"arch"`
}

Platform specifies OS and arch information for the host system that the container is created for.

type Process 

type Process struct {
	// Terminal creates an interactive terminal for the container.
	Terminal bool `json:"terminal"`
	// User specifies user information for the process.
	User User `json:"user"`
	// Args specifies the binary and arguments for the application to execute.
	Args []string `json:"args"`
	// Env populates the process environment for the process.
	Env []string `json:"env,omitempty"`
	// Cwd is the current working directory for the process and must be
	// relative to the container's root.
	Cwd string `json:"cwd"`
}

Process contains information to start a specific application inside the container.

type Resources 

type Resources struct {
	// DisableOOMKiller disables the OOM killer for out of memory conditions
	DisableOOMKiller *bool `json:"disableOOMKiller,omitempty"`
	// Specify an oom_score_adj for the container.
	OOMScoreAdj *int `json:"oomScoreAdj,omitempty"`
	// Memory restriction configuration
	Memory *Memory `json:"memory,omitempty"`
	// CPU resource restriction configuration
	CPU *CPU `json:"cpu,omitempty"`
	// Task resource restriction configuration.
	Pids *Pids `json:"pids,omitempty"`
	// BlockIO restriction configuration
	BlockIO *BlockIO `json:"blockIO,omitempty"`
	// Hugetlb limit (in bytes)
	HugepageLimits []HugepageLimit `json:"hugepageLimits,omitempty"`
	// Network restriction configuration
	Network *Network `json:"network,omitempty"`
}

Resources has container runtime resource constraints

type Rlimit 

type Rlimit struct {
	// Type of the rlimit to set
	Type string `json:"type"`
	// Hard is the hard limit for the specified type
	Hard uint64 `json:"hard"`
	// Soft is the soft limit for the specified type
	Soft uint64 `json:"soft"`
}

Rlimit type and restrictions

type Root 

type Root struct {
	// Path is the absolute path to the container's root filesystem.
	Path string `json:"path"`
	// Readonly makes the root filesystem for the container readonly before the process is executed.
	Readonly bool `json:"readonly"`
}

Root contains information about the container's root filesystem on the host.

type RuntimeSpec added in v0.0.5 

type RuntimeSpec struct {
	// Mounts is a mapping of names to mount configurations.
	// Which mounts will be mounted and where should be chosen with MountPoints
	// in Spec.
	Mounts map[string]Mount `json:"mounts"`
	// Hooks are the commands run at various lifecycle events of the container.
	Hooks Hooks `json:"hooks"`
}

RuntimeSpec contains host-specific configuration information for a container. This information must not be included when the bundle is packaged for distribution.

type Seccomp added in v0.0.4 

type Seccomp struct {
	DefaultAction Action     `json:"defaultAction"`
	Architectures []Arch     `json:"architectures"`
	Syscalls      []*Syscall `json:"syscalls"`
}

Seccomp represents syscall restrictions

type Spec 

type Spec struct {
	// Version is the version of the specification that is supported.
	Version string `json:"ociVersion"`
	// Platform is the host information for OS and Arch.
	Platform Platform `json:"platform"`
	// Process is the container's main process.
	Process Process `json:"process"`
	// Root is the root information for the container's filesystem.
	Root Root `json:"root"`
	// Hostname is the container's host name.
	Hostname string `json:"hostname,omitempty"`
	// Mounts profile configuration for adding mounts to the container's filesystem.
	Mounts []MountPoint `json:"mounts"`
}

Spec is the base configuration for the container. It specifies platform independent configuration. This information must be included when the bundle is packaged for distribution.

type State added in v0.0.5 

type State struct {
	// Version is the version of the specification that is supported.
	Version string `json:"version"`
	// ID is the container ID
	ID string `json:"id"`
	// Pid is the process id for the container's main process.
	Pid int `json:"pid"`
	// BundlePath is the path to the container's bundle directory.
	BundlePath string `json:"bundlePath"`
}

State holds information about the runtime state of the container. This information will be stored in a file called `state.json`. The location of this file will be operating system specific. On Linux it will be in `/run/opencontainers/runc/<containerID>/state.json`

type Syscall added in v0.0.4 

type Syscall struct {
	Name   string `json:"name"`
	Action Action `json:"action"`
	Args   []*Arg `json:"args"`
}

Syscall is used to match a syscall in Seccomp

type ThrottleDevice added in v0.0.5 

type ThrottleDevice struct {

	// Rate is the IO rate limit per cgroup per device
	Rate *uint64 `json:"rate,omitempty"`
	// contains filtered or unexported fields
}

ThrottleDevice struct holds a `major:minor rate_per_second` pair

type User 

type User struct {
	// UID is the user id.
	UID uint32 `json:"uid"`
	// GID is the group id.
	GID uint32 `json:"gid"`
	// AdditionalGids are additional group ids set for the container's process.
	AdditionalGids []uint32 `json:"additionalGids,omitempty"`
}

User specifies linux specific user and group information for the container's main process.

type WeightDevice added in v0.0.5 

type WeightDevice struct {

	// Weight is the bandwidth rate for the device, range is from 10 to 1000
	Weight *uint16 `json:"weight,omitempty"`
	// LeafWeight is the bandwidth rate for the device while competing with the cgroup's child cgroups, range is from 10 to 1000, CFQ scheduler only
	LeafWeight *uint16 `json:"leafWeight,omitempty"`
	// contains filtered or unexported fields
}

WeightDevice struct holds a `major:minor weight` pair for blkioWeightDevice

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