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FreeBSD Container Configuration

This document describes the schema for the FreeBSD-specific section of the container configuration.

Devices

Devices in FreeBSD are accessed via the devfs filesystem. Each container SHOULD have a devfs filesystem mounted into its /dev directory. Often, a minimal set of devices is exposed to the container using ruleset 4 from /etc/defaults/devfs.rules - the ruleset is specified as a mount option.

Optionally, additional devices can be exposed to the container using an array of entries inside the devices root field:

  • path (string, REQUIRED) - the device path relative to /dev
  • mode (uint32, OPTIONAL) - file mode for the device.

Note that JSON numbers must be represented in decimal. The value 448 below is the decimal representation of octal 0700 and this is used to request file mode rwx------ for the device.

Example

"devices": [
	{
        "path": "pf",
        "mode": 448
    }
]

Jail

On FreeBSD, containers are implemented using the platform's jail subsystem. Each jail is configured using a set of name/value pairs passed to the kernel using the jail(2) system calls. The jail root field contains values which are passed to the kernel when the container is created.

  • parent (string, OPTIONAL) - parent jail. If set, the value is the name of a jail which should be this container's parent, otherwise the container's parent is the host. This can be used to share namespaces such as vnet with another container.
  • host (string, OPTIONAL) - allow overriding hostname, domainname, hostuuid and hostid. The value can be "new" which allows these values to be overridden in the container or "inherit" to use the host values (or parent container values). If set to "new", the values for hostname and domainname are taken from the base config, if present.
  • ip4 (string, OPTIONAL) - control the availability of IPv4 addresses. Set to "inherit" to allow access to host (or parent container) addresses or set to "disable" to stop use of IPv4 entirely. This is typically left unset when vnet is used (see below).
  • ip4Addr (array of strings, OPTIONAL) - restrict the set of IPv4 addresses which the container can use. These addresses should be in numeric form (e.g. "10.11.12.13"). This can be used to allow restricted use of the host network. A common pattern with FreeBSD jails is to add alias addresses to a loopback interface and restrict each jail to a subset of addresses.
  • ip6 (string, OPTIONAL) - control the availability of IPv6 addresses. Set to "inherit" to allow access to host (or parent container) addresses or set to "disable" to stop use of IPv6 entirely. This is typically left unset when vnet is used (see below).
  • ip6Addr (array of strings, OPTIONAL) - restrict the set of IPv6 addresses which the container can use. These addresses should be in numeric form (e.g. "fd10::11:12:13"). This can be used to allow restricted use of the host network. A common pattern with FreeBSD jails is to add alias addresses to a loopback interface and restrict each jail to a subset of addresses.
  • vnet (string, OPTIONAL) - control the vnet used for this container. The value can be "new" which causes a new vnet to be created for the container or "inherit" which shares the vnet for the parent container (or host if there is no parent).
  • interface (string, OPTIONAL) A network interface to add the container's IP addresses (ip4Addr and ip6Addr) to. An alias for each address will be added to the interface when the container is created, and will be removed from the interface after the container is stopped. This is typically used when vnet is not set.
  • vnetInterfaces (array of strings, OPTIONAL) - a set of network interfaces which are added to the container's vnet during its lifetime.
  • sysvmsg (string, OPTIONAL) - allow access to SYSV IPC message primitives. If set to "inherit", all IPC objects in the host (or parent container) are visible to this container, whether they were created by the container itself, the base system, or other containers. If set to "new", the container will have its own key namespace, and can only see the objects that it has created; the system (or parent container) has access to the container's objects, but not to its keys. If set to "disable", the container cannot perform any sysvmsg-related system calls. Defaults to "new".
  • sysvsem (string, OPTIONAL) - allow access to SYSV IPC semaphore primitives, in the same manner as sysvmsg. Defaults to "new".
  • sysvshm (string, OPTIONAL) - allow access to SYSV IPC shared memory primitives, in the same manner as sysvmsg. Defaults to "new".
  • enforceStatfs (integer, OPTIONAL) - control visibility of mounts in the container. A value of 0 allows visibility of all host mounts, 1 allows visibility of mounts nested under the container's root and 2 only allows the container root to be visible. If unset, the default value is 2.
  • allow (object, OPTIONAL) - Some restrictions of the container environment may be set on a per-container basis. With the exception of setHostname and reservedPorts, these boolean parameters are off by default.
    • setHostname (bool, OPTIONAL) - Allow the container's hostname to be changed. Defaults to false.
    • rawSockets (bool, OPTIONAL) - Allow the container to use raw sockets to support network utilities such as ping and traceroute. Defaults to false.
    • chflags (bool, OPTIONAL) - Allow the system file flags to be changed. Defaults to false.
    • mount (array of strings, OPTIONAL) - Allow the listed filesystem types to be mounted and unmounted in the container.
    • quotas (bool, OPTIONAL) - Allow the filesystem quotas to be changed in the container. Defaults to false.
    • socketAf (bool, OPTIONAL) - Allow socket types other than IPv4, IPv6 and unix. Defaults to false.
    • mlock (bool, OPTIONAL) - Allow the container to use mlock(2) and munlock(2) system calls. Defaults to false.
    • reservedPorts (bool, OPTIONAL) - Allow the jail to bind to ports lower than 1024. Defaults to false.
    • suser (bool, OPTIONAL) - The value of the jail's security.bsd.suser_enabled sysctl. The super-user will be disabled automatically if its parent system has it disabled. The super-user is enabled by default.

These fields SHOULD be mapped to a corresponding set of jail(8) parameters which can be used to create the container jail. A typical jail-based OCI implementation on FreeBSD MAY use the following mapping:

Jail parameter JSON equivalent
jid -
name see below
path root.path
ip4.addr freebsd.jail.ip4Addr
ip4.saddrsel -
ip4 freebsd.jail.ip4
ip6.addr freebsd.jail.ip6Addr
ip6.saddrsel -
ip6 freebsd.jail.ip6
vnet freebsd.jail.vnet
interface freebsd.jail.interface
vnet.interface see below
host.hostname hostname
host freebsd.jail.host
sysvmsg freebsd.jail.sysvmsg
sysvsem freebsd.jail.sysvsem
sysvshm freebsd.jail.sysvshm
securelevel -
devfs_ruleset see below
children.max see below
enforce_statfs freebsd.jail.enforceStatfs
persist -
parent freebsd.jail.parent
osrelease -
osreldate -
allow.set_hostname freebsd.jail.allow.setHostname
allow.sysvipc freebsd.jail.allow.sysvipc
allow.raw_sockets freebsd.jail.allow.rawSockets
allow.chflags freebsd.jail.allow.chflags
allow.mount freebsd.jail.allow.mount
allow.quotas freebsd.jail.allow.quotas
allow.read_msgbuf -
allow.socket_af freebsd.jail.allow.socketAf
allow.mlock freebsd.jail.allow.mlock
allow.nfsd -
allow.reserved_ports freebsd.jail.allow.reservedPorts
allow.unprivileged_proc_debug -
allow.suser freebsd.jail.allow.suser
allow.mount.* see below

The jail name SHOULD be set to the create command's container-id argument.

The vnet.interface jail pseudo parameter is not handled in the kernel but rather is implemented in user space (e.g. in jail(8)). In traditional jail configs, this parameter can be repeated several times and each instance specifies a network interface which is moved into the jail's vnet during the lifetime of the jail using the ifconfig(8) utility on the host. For OCI containers, this is managed using the freebsd.jail.vnetInterfaces field which is an array of interface names.

A container which needs its own network namespace SHOULD set "vnet" to "new" and leave "ip4" and "ip6" unchanged. A container which shares the parent/host vnet SHOULD leave "vnet" unchanged and set "ip4" and "ip6" to "inherit".

The devfs_ruleset parameter is only required for jails which create new devfs mounts - typically OCI runtimes will mount devfs on the host. The value is a rule set number - these rule sets are defined on the host, typically via /etc/defaults/devfs.rules or using the devfs command line utility.

The children.max parameter SHOULD be managed by the OCI runtime e.g. when a new container shares namespaces with an existing container.

The allow.mount.* parameter set is extensible - allowed mount types are listed as an array. As with devfs, typically the OCI runtime will manage mounts for the container by performing mount operations on the host.

Jail parameters not supported by this runtime extension are marked with "-". These parameters will have their default values - see the jail(8) man page for details.

Example

"jail": {
    "host": "new",
    "vnet": "new",
    "enforceStatfs": 1,
	"allow": {
		"rawSockets": true,
		"chflags": true,
		"mount": [
			"tmpfs"
		]
	}
}