README ¶
libcontainer - reference implementation for containers
background
libcontainer specifies configuration options for what a container is. It provides a native Go implementation for using Linux namespaces with no external dependencies. libcontainer provides many convenience functions for working with namespaces, networking, and management.
container
A container is a self contained directory that is able to run one or more processes without
affecting the host system. The directory is usually a full system tree. Inside the directory
a container.json
file is placed with the runtime configuration for how the processes
should be contained and ran. Environment, networking, and different capabilities for the
process are specified in this file. The configuration is used for each process executed inside the container.
See the container.json
file for what the configuration should look like.
Using this configuration and the current directory holding the rootfs for a process, one can use libcontainer to exec the container. Running the life of the namespace, a pid
file
is written to the current directory with the pid of the namespaced process to the external world. A client can use this pid to wait, kill, or perform other operation with the container. If a user tries to run a new process inside an existing container with a live namespace, the namespace will be joined by the new process.
You may also specify an alternate root place where the container.json
file is read and where the pid
file will be saved.
nsinit
nsinit
is a cli application used as the reference implementation of libcontainer. It is able to
spawn or join new containers giving the current directory. To use nsinit
cd into a Linux
rootfs and copy a container.json
file into the directory with your specified configuration.
To execute /bin/bash
in the current directory as a container just run:
nsinit exec /bin/bash
If you wish to spawn another process inside the container while your current bash session is running just run the exact same command again to get another bash shell or change the command. If the original process dies, PID 1, all other processes spawned inside the container will also be killed and the namespace will be removed.
You can identify if a process is running in a container by looking to see if pid
is in the root of the directory.
Documentation ¶
Index ¶
Constants ¶
This section is empty.
Variables ¶
Functions ¶
func GetAllCapabilities ¶ added in v0.12.0
func GetAllCapabilities() []string
Types ¶
type Capabilities ¶
type Capabilities []*Capability
func (Capabilities) Contains ¶
func (c Capabilities) Contains(capp string) bool
Contains returns true if the specified Capability is in the slice
func (Capabilities) Get ¶ added in v0.10.0
func (c Capabilities) Get(capp string) *Capability
type Capability ¶
type Capability struct { Key string `json:"key,omitempty"` Value capability.Cap `json:"value,omitempty"` }
func GetCapability ¶
func GetCapability(key string) *Capability
func (*Capability) String ¶
func (c *Capability) String() string
type Container ¶
type Container struct { // Hostname optionally sets the container's hostname if provided Hostname string `json:"hostname,omitempty"` // ReadonlyFs will remount the container's rootfs as readonly where only externally mounted // bind mounts are writtable ReadonlyFs bool `json:"readonly_fs,omitempty"` // NoPivotRoot will use MS_MOVE and a chroot to jail the process into the container's rootfs // This is a common option when the container is running in ramdisk NoPivotRoot bool `json:"no_pivot_root,omitempty"` // User will set the uid and gid of the executing process running inside the container User string `json:"user,omitempty"` // WorkingDir will change the processes current working directory inside the container's rootfs WorkingDir string `json:"working_dir,omitempty"` // Env will populate the processes environment with the provided values // Any values from the parent processes will be cleared before the values // provided in Env are provided to the process Env []string `json:"environment,omitempty"` // Tty when true will allocate a pty slave on the host for access by the container's process // and ensure that it is mounted inside the container's rootfs Tty bool `json:"tty,omitempty"` // Namespaces specifies the container's namespaces that it should setup when cloning the init process // If a namespace is not provided that namespace is shared from the container's parent process Namespaces map[string]bool `json:"namespaces,omitempty"` // Capabilities specify the capabilities to keep when executing the process inside the container // All capbilities not specified will be dropped from the processes capability mask Capabilities []string `json:"capabilities,omitempty"` // Networks specifies the container's network setup to be created Networks []*Network `json:"networks,omitempty"` // Routes can be specified to create entries in the route table as the container is started Routes []*Route `json:"routes,omitempty"` // Cgroups specifies specific cgroup settings for the various subsystems that the container is // placed into to limit the resources the container has available Cgroups *cgroups.Cgroup `json:"cgroups,omitempty"` // Context is a generic key value format that allows for additional settings to be passed // on the container's creation // This is commonly used to specify apparmor profiles, selinux labels, and different restrictions // placed on the container's processes Context Context `json:"context,omitempty"` // Mounts specify additional source and destination paths that will be mounted inside the container's // rootfs and mount namespace if specified Mounts Mounts `json:"mounts,omitempty"` // The device nodes that should be automatically created within the container upon container start. Note, make sure that the node is marked as allowed in the cgroup as well! DeviceNodes []*devices.Device `json:"device_nodes,omitempty"` }
Container defines configuration options for executing a process inside a contained environment
type Mount ¶ added in v0.10.0
type Mount struct { Type string `json:"type,omitempty"` Source string `json:"source,omitempty"` // Source path, in the host namespace Destination string `json:"destination,omitempty"` // Destination path, in the container Writable bool `json:"writable,omitempty"` Private bool `json:"private,omitempty"` }
type Namespace ¶
type Namespace struct { Key string `json:"key,omitempty"` Value int `json:"value,omitempty"` File string `json:"file,omitempty"` }
func GetNamespace ¶
type Namespaces ¶
type Namespaces []*Namespace
func (Namespaces) Contains ¶
func (n Namespaces) Contains(ns string) bool
Contains returns true if the specified Namespace is in the slice
func (Namespaces) Get ¶ added in v0.10.0
func (n Namespaces) Get(ns string) *Namespace
type Network ¶
type Network struct { // Type sets the networks type, commonly veth and loopback Type string `json:"type,omitempty"` // Context is a generic key value format for setting additional options that are specific to // the network type Context Context `json:"context,omitempty"` // Address contains the IP and mask to set on the network interface Address string `json:"address,omitempty"` // Gateway sets the gateway address that is used as the default for the interface Gateway string `json:"gateway,omitempty"` // Mtu sets the mtu value for the interface and will be mirrored on both the host and // container's interfaces if a pair is created, specifically in the case of type veth Mtu int `json:"mtu,omitempty"` }
Network defines configuration for a container's networking stack
The network configuration can be omited from a container causing the container to be setup with the host's networking stack
type Route ¶ added in v0.12.0
type Route struct { // Sets the destination and mask, should be a CIDR. Accepts IPv4 and IPv6 Destination string `json:"destination,omitempty"` // Sets the source and mask, should be a CIDR. Accepts IPv4 and IPv6 Source string `json:"source,omitempty"` // Sets the gateway. Accepts IPv4 and IPv6 Gateway string `json:"gateway,omitempty"` // The device to set this route up for, for example: eth0 InterfaceName string `json:"interface_name,omitempty"` }
Routes can be specified to create entries in the route table as the container is started
All of destination, source, and gateway should be either IPv4 or IPv6. One of the three options must be present, and ommitted entries will use their IP family default for the route table. For IPv4 for example, setting the gateway to 1.2.3.4 and the interface to eth0 will set up a standard destination of 0.0.0.0(or *) when viewed in the route table.