• Jails

Jails

Introduction

Jails were introduced in FreeBSD 4.x by Poul-Henning Kamp

More information:

• Jails (FreeBSD Handbook)

• jail(8) Manual Page

• freebsd-jail mailing list

• FreeBSD jail (Wikipedia)

Patches

Future plans for FreeBSD jails / virtualization

If you have any idea or request, please address the freebsd-jail maililng list.

freebsd-arch mailing list discussions:

• kernel level virtualisation requirements (2007-10-11)

• kernel level virtualisation requirements / quota system changes (2007-10-14)

• kernel level virtualisation requirements / list of ideas (2007-10-18)

Well known or frequent requests, some of these will never be done with jails, some are (or will be) done with alternative technologies:

• be able to specify a different root for the virtual machine

• be able to specify a different output for "uname" jail(8) (r279361 )

• be able to specify a different network address

• be able to specify a different routing table setfib(1)

• be able to specify a completely different network universe
• be able to dedicate an interface to it
• be able to have a separate PID space for it
• be able to specify a separate UID space for it
• be able to specify a CPU maximum quota

• be able to confine it to some set of CPUs cpuset(1)

• be able to have different mount tables for it

• be able to specify a different security level for it [sysctl kern.securelevel is already per jail]

• be able to specify a disk IO limits for it

• SNMP monitoring of jail resources port by Stef Walter http://memberwebs.com/stef/software/bsnmp-jails/ (broken)

• exposure of certain sysctl values inside jails

• wildcard ip (INADDR_ANY) should not bind inside a jail PR 84215 this is known problem from beginning of the jails and is stated in manpage section bugs jail(8) [fixed by Multi-IPv4/v6/no-IP jails patch]

• Unprivileged jail_attach / a way to do jail_attach as non-root; Done as port sysutils/jailme by Bill Moran - jailme

• Hierarchical jails (Multilevel jails) mailing list discussion patches by Jamie Gritton: jh jhu

Netgraph-based networking for jails

Introduction

A few links to other resources:

• Using jails with if_bridge(4) and epair(4) (Mason Loring Bliss)

• Sample (and simple) VNET configurations in shell (Bjoern Zeeb)

There are three ways to do networking with jails: (i) using IP addresses (aliases) from the host, (ii) using if_bridge(4) and epair(4) interfaces, and (iii) using netgraph. I will start this how-to with the third method as the second method has already been explained by Mason Loring Bliss.

Before we kick off, we need to understand some new terms that netgraph introduces.

Node

Any object that can connect to another object. This can be a bridge, a virtual interface, but also a VLAN interface or a BPF object.

Edge

The connection between two nodes. You could consider it to be a virtual network cable.

Hook

In netgraph, edges do not really exist per se. Instead, an edge is simply an association of two hooks, one from each node. A node's hooks define how that node can be connected. For a bridge node, the hooks are the virtual interfaces, though for a virtual interface node, hooks can be each protocol supported by that interface.

Path

Every netgraph node is addressable via an ASCII string called a node address or path. Many nodes have names. When a node has a name, it can always be addressed usingthe absolute address consisting of the name followed by a colon. If a node does not have a name, you can construct one from the node's unique ID number by enclosing the number in square brackets. Relative addressing is also possible when two nodes are indirectly connected. A relative address uses the names of consecutive hooks on the path from the source node to the target node. Relative and absolute addressing can be combined.

This is quite confusing. See the example at https://people.freebsd.org/~julian/netgraph.html.

Let's start off with a small network consisting of two jails, called "test1" and "test2", which are bridged to an new, virtual interface on the host machine. We thus need three new virtual interfaces. We will use ngctl to manage all netgraph nodes, hooks, and edges. This tool can be used interactively or you can supply the command on the command line. Below we will use it interactively. Note that this command must be run as the root user.

# ngctl

mkpeer eiface ether ether
mkpeer eiface ether ether
mkpeer eiface ether ether
name ngeth0: ng_host
name ngeth1: ng_test1
name ngeth2: ng_test2

We create three interfaces of type eiface as we need Ethernet interfaces (as opposed to L3 interfaces when using type iface). The man page state they are named ngeth0, etc. We rename them to indicate their purpose.

Next we need to bridge these interfaces together. We can either create the bridge first and then connect it to the three interfaces, or while creating the bridge, we can already connect it to an interface.

/*
 * OPTION A:
 * To only create the bridge but not connect it to any existing nodes
 */
mkpeer bridge link0 link0

/*
 * OPTION B:
 * Create a new node of type bridge and connect it to the
 * path 'ng_host:'.  Use its hook called 'ether' to connect it to the
 * hook 'link0' of the new node (the bridge).
 */
mkpeer ng_host: bridge ether link0

/*
 * As opposed to the Ethernet interfaces, a bridge does not have a
 * name by default. So we name it here.
 */
name [1e]: br0

/*
 * Now connect the nodes together.  The first connection is only needed
 * when option A was used.
 */
connect br0: ng_host: link0 ether
connect br0: ng_test1: link1 ether
connect br0: ng_test2: link2 ether

The above configuration is pretty straightforward, the exception being the name command. Since the bridge does not have a name, we can't use it to construct a path. Instead we must use its unique ID (between brackets). To determine this ID, we need the list command which I ommitted from the configuration above. Let's show it here.

+ list
There are 6 total nodes:
  Name: ng_host         Type: eiface          ID: 00000007   Num hooks: 1
  Name: ng_test1        Type: eiface          ID: 00000009   Num hooks: 0
  Name: ngctl85802      Type: socket          ID: 0000002b   Num hooks: 0
  Name: <unnamed>       Type: bridge          ID: 0000001e   Num hooks: 1
  Name: ng_test2        Type: eiface          ID: 0000000e   Num hooks: 0
+

The above output shows the unique ID for the bridge (preceding zeros can be ommitted) as well as the number of hooks used, i.e. connections made. I thus created the bridge by directly connecting it to the ng_host interface.

Configuring the jails

I assume you know how to setup a jail, i.e. create a base jail, clone it, etc. If not, please read the Jails chapter of the FreeBSD Handbook.

The below configuration only includes the networking-specific configuration for the two jails. Although shown per jail, you can easily move these two lines to the default configuration using the variable $name to customize the interface name.

test1 {
   vnet;
   vnet.interface = ng_test1;
}
test2 {
   vnet;
   vnet.interface = ng_test2;
}

Once the jails have been started, you can manually configure IP addresses on their interfaces, as well as on the host interface ng_host.

Known issues

• impossible to kill a jail / zombie jail PR 89528 Fixing old TTY bugs
  This will (hopefully) be fixed by new TTY layer

• multiple postgresql servers in multiple jails (SysV IPC problem) initial question continuation
  In a short answer - use different UIDs for PostgreSQL in each jail
  You can also use some loader.conf tunables for IPC kern.ipc.shmmni=2048 kern.ipc.shmseg=2048 kern.ipc.semmni=128 kern.ipc.semmns=512
  And of course allow IPC in jails by jail_sysvipc_allow="YES" in hosts rc.conf (or security.jail.sysvipc_allowed=1 in hosts sysctl.conf)

• bug in cpuset(1) - At the moment it is possible for a superuser inside a jail to modify the root cpuset of that jail. PR 134050

Tips

leak of system message buffer from host system to jails

By default jails can read the system message buffer (ie: the console buffer). In many cases this isn't desired. Add the following line to /etc/sysctl.conf to turn it off: security.bsd.unprivileged_read_msgbuf=0

allow ping inside jail

If you need to use ping inside jail, you must set sysctl security.jail.allow_raw_sockets=1 (add security.jail.allow_raw_sockets=1 in hosts sysctl.conf).

installing 32-bit jail in to 64-bit host

Cross compiling FreeBSD and 32-bit jails on a 64-bit system

Running CentOS 5.5 in a jail

FreeBSD Wiki Centos 5.5 jail running on a host running FreeBSD 8-STABLE

Running Debian 6.0 (Squeeze) in a FreeBSD jail

Tutorial: Debian GNU/kFreeBSD in a FreeBSD jail
Can I run Debian GNU/kFreeBSD in a chroot under FreeBSD?

Jail management

Some of these utilities are usable only with ancient versions of FreeBSD (4.x / 5.x).

bastille

Pure shell system for automating deployment and management of containerized applications in jails

sysutils/bastille

BSDploy

Container management and orchestration for FreeBSD jails using ansible

sysutils/bsdploy

cbsd

FreeBSD jail and bhyve management utility

sysutils/cbsd

crate

An application containerizer utilizing jails

sysutils/crate

ezjail

A framework to easily create, manipulate and run FreeBSD jails

sysutils/ezjail

focker

A jail-based image orchestration tool in the vein of Docker

sysutils/py-focker

iocage

Utility for managing jails

sysutils/iocage

iocell

iocage fork focused on supporting classic iocage experience and adding fixes and features requested by the iocage users

sysutils/iocell

jadm

FreeBSD jail framework with zfs, vnet and jail.conf support

sysutils/jadm

jailadmin

A system for managing a set of named jails

sysutils/jailadmin

jailaudit

Script for generating portaudit reports for jails

ports-mgmt/jailaudit

jailctl

Jail management tool

sysutils/jailctl

jailer

Manage FreeBSD jail startup, shutdown and console

sysutils/jailer (This port expired on: 2014-03-10)

jailme

A setuid version of jexec to allow normal users access to jails

sysutils/jailme

jailrc

Improved jail startup/shutdown script

sysutils/jailrc

jailutils

Several utilities for managing jails

sysutils/jailutils

jest

REST API for creating and managing jails

sysutils/jest

jkill

Shutdowns a running jail and all its processes

sysutils/jkill

jps

Wrapper to ps(1) that maps pids to jails

sysutils/jps

jruls

A top-alike utility to display and update FreeBSD jails resource usage

sysutils/jruls

jtop

Wrapper to top(1) that maps pids to jails

sysutils/jtop

mkjail

Easy jail creation, updates and upgrades

sysutils/mkjail

mod_jail

Apache 1.3.x/2.0.xx module to enable an easy alternative to mod_chroot

www/mod_jail (This port expired on: 2017-04-30)

p5-BSD-Jail-Object

An object oriented perl interface to jail(2)

sysutils/p5-BSD-Jail-Object

ploy

Command-line tool to provision, manage, and control servers, including jails

sysutils/py-ploy

pot

Container framework for FreeBSD, based on jails, ZFS and pf

sysutils/pot

qjail

Utility to deploy large number of jails quickly

sysutils/qjail

quickjail

utility to create transient single-command jails

sysutils/quickjail

runj

Proof-of-concept OCI-compatible runtime for FreeBSD jails

sysutils/runj

Other resources

• Eclipse/BSD - based on FreeBSD 3.4 (QoS - hierarchical proportional-share cpu, disk and link schedulers) (Wayback Machine, 2013-10-23)

• freebsd-virtualization mailing list (jail, VIMAGE, Xen Project …)

• The FreeBSD Network Stack Virtualization Project

• SysJail for NetBSD / OpenBSD (Wayback Machine, 2014-04-08)

• Debian GNU/kFreeBSD inside native FreeBSD jail

• An Introduction to Jails and Jail Networking (SKYFORGE, 2018-03-14)

• FreeVPS - jail2 implementation for FreeBSD kernels

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