be6eb5d7ea1888f2f835fe0fff358f72572afeb4henning mueller

1d2a2bdc364ab8fecd3db98c17162ce9f03d4361Eugen Kuksa<!DOCTYPE refentry PUBLIC "-//Davenport//DTD DocBook V3.0//EN" [

7b025f9d9726413eb3f50ca2b39826e7eed816fbJulian Kornberger

7b025f9d9726413eb3f50ca2b39826e7eed816fbJulian Kornberger<!ENTITY seealso SYSTEM "@builddir@/see_also.sgml">

772a71bcc07f7001f5cd3cb4c3dc2cf393ffe9beJulian Kornberger]>

772a71bcc07f7001f5cd3cb4c3dc2cf393ffe9beJulian Kornberger

772a71bcc07f7001f5cd3cb4c3dc2cf393ffe9beJulian Kornberger<refentry>

772a71bcc07f7001f5cd3cb4c3dc2cf393ffe9beJulian Kornberger

772a71bcc07f7001f5cd3cb4c3dc2cf393ffe9beJulian Kornberger <docinfo>

7b025f9d9726413eb3f50ca2b39826e7eed816fbJulian Kornberger <date>@LXC_GENERATE_DATE@</date>

f9c64720306a03102ed06e2e497c8f7d5bd0910aChristian Clausen </docinfo>

1d2a2bdc364ab8fecd3db98c17162ce9f03d4361Eugen Kuksa

f9c64720306a03102ed06e2e497c8f7d5bd0910aChristian Clausen

f9c64720306a03102ed06e2e497c8f7d5bd0910aChristian Clausen <refmeta>

f9c64720306a03102ed06e2e497c8f7d5bd0910aChristian Clausen <refentrytitle>lxc</refentrytitle>

f9c64720306a03102ed06e2e497c8f7d5bd0910aChristian Clausen <manvolnum>7</manvolnum>

f9c64720306a03102ed06e2e497c8f7d5bd0910aChristian Clausen <refmiscinfo>

1d2a2bdc364ab8fecd3db98c17162ce9f03d4361Eugen Kuksa Version @LXC_MAJOR_VERSION@.@LXC_MINOR_VERSION@.@LXC_MICRO_VERSION@

f9c64720306a03102ed06e2e497c8f7d5bd0910aChristian Clausen </refmiscinfo>

0ae77dd0f6698fa1948d1c6c973cc64d6df9e8d6Christian Clausen </refmeta>

1d2a2bdc364ab8fecd3db98c17162ce9f03d4361Eugen Kuksa

0ae77dd0f6698fa1948d1c6c973cc64d6df9e8d6Christian Clausen <refnamediv>

0ae77dd0f6698fa1948d1c6c973cc64d6df9e8d6Christian Clausen <refname>lxc</refname>

0ae77dd0f6698fa1948d1c6c973cc64d6df9e8d6Christian Clausen

0ae77dd0f6698fa1948d1c6c973cc64d6df9e8d6Christian Clausen <refpurpose>

0ae77dd0f6698fa1948d1c6c973cc64d6df9e8d6Christian Clausen linux containers

1d2a2bdc364ab8fecd3db98c17162ce9f03d4361Eugen Kuksa </refpurpose>

0ae77dd0f6698fa1948d1c6c973cc64d6df9e8d6Christian Clausen </refnamediv>

ca68055161f6beb2ec248e789ab787e6de69bd18Christian Clausen

1d2a2bdc364ab8fecd3db98c17162ce9f03d4361Eugen Kuksa <refsect1>

0ae77dd0f6698fa1948d1c6c973cc64d6df9e8d6Christian Clausen <title>Quick start</title>

0ae77dd0f6698fa1948d1c6c973cc64d6df9e8d6Christian Clausen <para>

0ae77dd0f6698fa1948d1c6c973cc64d6df9e8d6Christian Clausen You are in a hurry, and you don't want to read this man page. Ok,

0ae77dd0f6698fa1948d1c6c973cc64d6df9e8d6Christian Clausen without warranty, here are the commands to launch a shell inside

0ae77dd0f6698fa1948d1c6c973cc64d6df9e8d6Christian Clausen a container with a predefined configuration template, it may

1d2a2bdc364ab8fecd3db98c17162ce9f03d4361Eugen Kuksa work.

ca68055161f6beb2ec248e789ab787e6de69bd18Christian Clausen <command>

ca68055161f6beb2ec248e789ab787e6de69bd18Christian Clausen @BINDIR@/lxc-execute -n foo -f @SYSCONFDIR@/lxc/lxc-macvlan.conf /bin/bash

1d2a2bdc364ab8fecd3db98c17162ce9f03d4361Eugen Kuksa </command>

ca68055161f6beb2ec248e789ab787e6de69bd18Christian Clausen </para>

ca68055161f6beb2ec248e789ab787e6de69bd18Christian Clausen </refsect1>

ca68055161f6beb2ec248e789ab787e6de69bd18Christian Clausen

ca68055161f6beb2ec248e789ab787e6de69bd18Christian Clausen <refsect1>

ca68055161f6beb2ec248e789ab787e6de69bd18Christian Clausen <title>Overview</title>

1d2a2bdc364ab8fecd3db98c17162ce9f03d4361Eugen Kuksa <para>

ca68055161f6beb2ec248e789ab787e6de69bd18Christian Clausen The container technology is actively being pushed into the

ca68055161f6beb2ec248e789ab787e6de69bd18Christian Clausen mainstream linux kernel. It provides the resource management

1d2a2bdc364ab8fecd3db98c17162ce9f03d4361Eugen Kuksa through the control groups aka process containers and resource

ca68055161f6beb2ec248e789ab787e6de69bd18Christian Clausen isolation through the namespaces.

ca68055161f6beb2ec248e789ab787e6de69bd18Christian Clausen </para>

ca68055161f6beb2ec248e789ab787e6de69bd18Christian Clausen

ca68055161f6beb2ec248e789ab787e6de69bd18Christian Clausen <para>

ca68055161f6beb2ec248e789ab787e6de69bd18Christian Clausen The linux containers, <command>lxc</command>, aims to use these

1d2a2bdc364ab8fecd3db98c17162ce9f03d4361Eugen Kuksa new functionalities to provide an userspace container object

0ae77dd0f6698fa1948d1c6c973cc64d6df9e8d6Christian Clausen which provides full resource isolation and resource control for

813c1fb6ef7f1d386c65abf8d79389be3cb0f4e9Christian Clausen an applications or a system.

1d2a2bdc364ab8fecd3db98c17162ce9f03d4361Eugen Kuksa </para>

813c1fb6ef7f1d386c65abf8d79389be3cb0f4e9Christian Clausen

813c1fb6ef7f1d386c65abf8d79389be3cb0f4e9Christian Clausen <para>

813c1fb6ef7f1d386c65abf8d79389be3cb0f4e9Christian Clausen The first objective of this project is to make the life easier

813c1fb6ef7f1d386c65abf8d79389be3cb0f4e9Christian Clausen for the kernel developers involved in the containers project and

813c1fb6ef7f1d386c65abf8d79389be3cb0f4e9Christian Clausen especially to continue working on the Checkpoint/Restart new

1d2a2bdc364ab8fecd3db98c17162ce9f03d4361Eugen Kuksa features. The <command>lxc</command> is small enough to easily

7c5e9db9a07461d92c007563a2a27ca42ce93baeChristian Clausen manage a container with simple command lines and complete enough

7c5e9db9a07461d92c007563a2a27ca42ce93baeChristian Clausen to be used for other purposes.

1d2a2bdc364ab8fecd3db98c17162ce9f03d4361Eugen Kuksa </para>

813c1fb6ef7f1d386c65abf8d79389be3cb0f4e9Christian Clausen </refsect1>

7b025f9d9726413eb3f50ca2b39826e7eed816fbJulian Kornberger

1d2a2bdc364ab8fecd3db98c17162ce9f03d4361Eugen Kuksa <refsect1>

1d2a2bdc364ab8fecd3db98c17162ce9f03d4361Eugen Kuksa <title>Requirements</title>

7b025f9d9726413eb3f50ca2b39826e7eed816fbJulian Kornberger <para>

7b025f9d9726413eb3f50ca2b39826e7eed816fbJulian Kornberger The <command>lxc</command> relies on a set of functionalies

7b025f9d9726413eb3f50ca2b39826e7eed816fbJulian Kornberger provided by the kernel which needs to be active. Depending of

432ee743a5f1c5688c73446b5977b06ed97fb67cJulian Kornberger the missing functionalities the <command>lxc</command> will

432ee743a5f1c5688c73446b5977b06ed97fb67cJulian Kornberger work with a restricted number of functionalities or will simply

8566aec18eff0f0d248d73d2f44f9df16cc41456Julian Kornberger fails.

8566aec18eff0f0d248d73d2f44f9df16cc41456Julian Kornberger </para>

8566aec18eff0f0d248d73d2f44f9df16cc41456Julian Kornberger

432ee743a5f1c5688c73446b5977b06ed97fb67cJulian Kornberger <para>

f4f335875509867dd238df7c92b0b8f4fe101705Julian Kornberger The following list gives the kernel features to be enabled in

f4f335875509867dd238df7c92b0b8f4fe101705Julian Kornberger the kernel to have the full features container:

f4f335875509867dd238df7c92b0b8f4fe101705Julian Kornberger </para>

f4f335875509867dd238df7c92b0b8f4fe101705Julian Kornberger <programlisting>

3c4b1bd39fa36d241f2ef0d6f7ebbf2a9a6f4d36henning mueller * General setup

3c4b1bd39fa36d241f2ef0d6f7ebbf2a9a6f4d36henning mueller * Control Group support

df8908f48450f65ca99c9b997ebd3711f49049e5Eugen Kuksa -> Namespace cgroup subsystem

df8908f48450f65ca99c9b997ebd3711f49049e5Eugen Kuksa -> Freezer cgroup subsystem

4755669b9d408e3240e1f005349399973923c095Eugen Kuksa -> Cpuset support

df8908f48450f65ca99c9b997ebd3711f49049e5Eugen Kuksa -> Simple CPU accounting cgroup subsystem

17e3eda463c5fe407b4498c996c7fd0474e34e41henning mueller -> Resource counters

17e3eda463c5fe407b4498c996c7fd0474e34e41henning mueller -> Memory resource controllers for Control Groups

7b025f9d9726413eb3f50ca2b39826e7eed816fbJulian Kornberger * Group CPU scheduler

7b025f9d9726413eb3f50ca2b39826e7eed816fbJulian Kornberger -> Basis for grouping tasks (Control Groups)

7b025f9d9726413eb3f50ca2b39826e7eed816fbJulian Kornberger * Namespaces support

7b025f9d9726413eb3f50ca2b39826e7eed816fbJulian Kornberger -> UTS namespace

7b025f9d9726413eb3f50ca2b39826e7eed816fbJulian Kornberger -> IPC namespace

-> User namespace

-> Pid namespace

-> Network namespace

* Security options

-> File POSIX Capabilities

</programlisting>

<para>

The kernel version >= 2.6.27 shipped with the distros, will

work with <command>lxc</command>, this one will have less

functionalities but enough to be interesting.

With the kernel 2.6.29, <command>lxc</command> is fully

functional.

</para>

<para>

Before using the <command>lxc</command>, your system should be

configured with the file capabilities, otherwise you will need

to run the <command>lxc</command> commands as root.

</para>

<para>

The control group can be mounted anywhere, eg:

<command>mount -t cgroup cgroup /cgroup</command>.

If you want to dedicate a specific cgroup mount point

for <command>lxc</command>, that is to have different cgroups

mounted at different places with different options but

let <command>lxc</command> to use one location, you can bind

the mount point with the <option>lxc</option> name, eg:

<command>mount -t cgroup lxc /cgroup4lxc</command> or

<command>mount -t cgroup -ons,cpuset,freezer,devices

lxc /cgroup4lxc</command>

</para>

</refsect1>

<refsect1>

<title>Functional specification</title>

<para>

A container is an object where the configuration is

persistent. The application will be launched inside this

container and it will use the configuration which was previously

created.

</para>

<para>How to run an application in a container ?</para>

<para>

Before running an application, you should know what are the

resources you want to isolate. The default configuration is to

isolate the pids, the sysv ipc and the mount points. If you want

to run a simple shell inside a container, a basic configuration

is needed, especially if you want to share the rootfs. If you

want to run an application like <command>sshd</command>, you

should provide a new network stack and a new hostname. If you

want to avoid conflicts with some files

eg. <filename>/var/run/httpd.pid</filename>, you should

remount <filename>/var/run</filename> with an empty

directory. If you want to avoid the conflicts in all the cases,

you can specify a rootfs for the container. The rootfs can be a

directory tree, previously bind mounted with the initial rootfs,

so you can still use your distro but with your

own <filename>/etc</filename> and <filename>/home</filename>

</para>

<para>

Here is an example of directory tree

for <command>sshd</command>:

<programlisting>

[root@lxc sshd]$ tree -d rootfs

rootfs

|-- bin

|-- dev

| |-- pts

| `-- shm

| `-- network

|-- etc

| `-- ssh

|-- lib

|-- proc

|-- root

|-- sbin

|-- sys

|-- usr

`-- var

|-- empty

| `-- sshd

|-- lib

| `-- empty

| `-- sshd

`-- run

`-- sshd

</programlisting>

and the mount points file associated with it:

<programlisting>

[root@lxc sshd]$ cat fstab

/lib /home/root/sshd/rootfs/lib none ro,bind 0 0

/bin /home/root/sshd/rootfs/bin none ro,bind 0 0

/usr /home/root/sshd/rootfs/usr none ro,bind 0 0

/sbin /home/root/sshd/rootfs/sbin none ro,bind 0 0

</programlisting>

</para>

<para>How to run a system in a container ?</para>

<para>Running a system inside a container is paradoxically easier

than running an application. Why ? Because you don't have to care

about the resources to be isolated, everything need to be isolated

except <filename>/dev</filename> which needs to be remounted in

the container rootfs, the other resources are specified as being

isolated but without configuration because the container will set

them up. eg. the ipv4 address will be setup by the system

container init scripts. Here is an example of the mount points

file:

<programlisting>

[root@lxc debian]$ cat fstab

/dev /home/root/debian/rootfs/dev none bind 0 0

/dev/pts /home/root/debian/rootfs/dev/pts none bind 0 0

</programlisting>

More information can be added to the container to facilitate the

configuration. For example, make accessible from the container

the resolv.conf file belonging to the host.

<programlisting>

/etc/resolv.conf /home/root/debian/rootfs/etc/resolv.conf none bind 0 0

</programlisting>

</para>

<refsect2>

<title>Container life cycle</title>

<para>

When the container is created, it contains the configuration

information. When a process is launched, the container will be

starting and running. When the last process running inside the

container exits, the container is stopped.

</para>

<para>

In case of failure when the container is initialized, it will

pass through the aborting state.

</para>

<programlisting>

---------

| STOPPED |<---------------

--------- |

| |

start |

| |

V |

---------- |

| STARTING |--error- |

---------- | |

| | |

V V |

--------- ---------- |

| RUNNING | | ABORTING | |

--------- ---------- |

| | |

no process | |

| | |

V | |

---------- | |

| STOPPING |<------- |

---------- |

| |

---------------------

</programlisting>

</refsect2>

<refsect2>

<title>Configuration</title>

<para>The container is configured through a configuration

file, the format of the configuration file is described in

<citerefentry>

<refentrytitle><filename>lxc.conf</filename></refentrytitle>

<manvolnum>5</manvolnum>

</citerefentry>

</para>

</refsect2>

<refsect2>

<title>Creating / Destroying the containers</title>

<para>

The container is created via the <command>lxc-create</command>

command. It takes a container name as parameter and an

optional configuration file. The name is used by the different

commands to refer to this

container. The <command>lxc-destroy</command> command will

destroy the container object.

<programlisting>

lxc-create -n foo

lxc-destroy -n foo

</programlisting>

</para>

</refsect2>

<refsect2>

<title>Starting / Stopping a container</title>

<para>When the container has been created, it is ready to run an

application / system. When the application has to be destroyed

the container can be stopped, that will kill all the processes

of the container.</para>

<para>

Running an application inside a container is not exactly the

same thing as running a system. For this reason, there is two

commands to run an application into a container:

<programlisting>

lxc-execute -n foo [-f config] /bin/bash

lxc-start -n foo [/bin/bash]

</programlisting>

</para>

<para>

<command>lxc-execute</command> command will run the

specified command into a container but it will mount /proc

and autocreate/autodestroy the container if it does not

exist. It will furthermore create an intermediate

process, <command>lxc-init</command>, which is in charge to

launch the specified command, that allows to support daemons

in the container. In other words, in the

container <command>lxc-init</command> has the pid 1 and the

first process of the application has the pid 2.

</para>

<para>

<command>lxc-start</command> command will run the specified

command into the container doing nothing else than using the

configuration specified by <command>lxc-create</command>.

The pid of the first process is 1. If no command is

specified <command>lxc-start</command> will

run <filename>/sbin/init</filename>.

</para>

<para>

To summarize, <command>lxc-execute</command> is for running

an application and <command>lxc-start</command> is for

running a system.

</para>

<para>

If the application is no longer responding, inaccessible or is

not able to finish by itself, a

wild <command>lxc-stop</command> command will kill all the

processes in the container without pity.

<programlisting>

lxc-stop -n foo

</programlisting>

</para>

</refsect2>

<refsect2>

<title>Connect to an available tty</title>

<para>

If the container is configured with the ttys, it is possible

to access it through them. It is up to the container to

provide a set of available tty to be used by the following

command. When the tty is lost, it is possible to reconnect it

without login again.

<programlisting>

lxc-console -n foo -t 3

</programlisting>

</para>

</refsect2>

<refsect2>

<title>Freeze / Unfreeze a container</title>

<para>

Sometime, it is useful to stop all the processes belonging to

a container, eg. for job scheduling. The commands:

<programlisting>

lxc-freeze -n foo

</programlisting>

will put all the processes in an uninteruptible state and

<programlisting>

lxc-unfreeze -n foo

</programlisting>

will resume all the tasks.

</para>

<para>

This feature is enabled if the cgroup freezer is enabled in the

kernel.

</para>

</refsect2>

<refsect2>

<title>Getting information about the container</title>

<para>When there are a lot of containers, it is hard to follow

what has been created or destroyed, what is running or what are

the pids running into a specific container. For this reason, the

following commands give this information:

<programlisting>

lxc-ls

lxc-ps -n foo

lxc-info -n foo

</programlisting>

</para>

<para>

<command>lxc-ls</command> lists the containers of the

system. The command is a script built on top

of <command>ls</command>, so it accepts the options of the ls

commands, eg:

<programlisting>

lxc-ls -C1

</programlisting>

will display the containers list in one column or:

<programlisting>

lxc-ls -l

</programlisting>

will display the containers list and their permissions.

</para>

<para>

<command>lxc-ps</command> will display the pids for a specific

container. Like <command>lxc-ls</command>, <command>lxc-ps</command>

is built on top of <command>ps</command> and accepts the same

options, eg:

<programlisting>

lxc-ps -n foo --forest

</programlisting>

will display the process hierarchy for the container 'foo'.

</para>

<para>

<command>lxc-info</command> gives informations for a specific

container, at present time, only the state of the container is

displayed.

</para>

<para>

Here is an example on how the combination of these commands

allow to list all the containers and retrieve their state.

<programlisting>

for i in $(lxc-ls -1); do

lxc-info -n $i

done

</programlisting>

And displaying all the pids of all the containers:

<programlisting>

for i in $(lxc-ls -1); do

lxc-ps -n $i --forest

done

</programlisting>

</para>

<para>

<command>lxc-netstat</command> display network information for

a specific container. This command is built on top of

the <command>netstat</command> command and will accept its

options

</para>

<para>

The following command will display the socket informations for

the container 'foo'.

<programlisting>

lxc-netstat -n foo -tano

</programlisting>

</para>

</refsect2>

<refsect2>

<title>Monitoring the containers</title>

<para>It is sometime useful to track the states of a container,

for example to monitor it or just to wait for a specific

state in a script.

</para>

<para>

<command>lxc-monitor</command> command will monitor one or

several containers. The parameter of this command accept a

regular expression for example:

<programlisting>

lxc-monitor -n "foo|bar"

</programlisting>

will monitor the states of containers named 'foo' and 'bar', and:

<programlisting>

lxc-monitor -n ".*"

</programlisting>

will monitor all the containers.

</para>

<para>

For a container 'foo' starting, doing some work and exiting,

the output will be in the form:

<programlisting>

'foo' changed state to [STARTING]

'foo' changed state to [RUNNING]

'foo' changed state to [STOPPING]

'foo' changed state to [STOPPED]

</programlisting>

</para>

<para>

<command>lxc-wait</command> command will wait for a specific

state change and exit. This is useful for scripting to

synchronize the launch of a container or the end. The

parameter is an ORed combination of different states. The

following example shows how to wait for a container if he went

to the background.

<programlisting>

# launch lxc-wait in background

lxc-wait -n foo -s STOPPED &

LXC_WAIT_PID=$!

# this command goes in background

lxc-execute -n foo mydaemon &

# block until the lxc-wait exits

# and lxc-wait exits when the container

# is STOPPED

wait $LXC_WAIT_PID

echo "'foo' is finished"

</programlisting>

</para>

</refsect2>

<refsect2>

<title>Setting the control group for a container</title>

<para>The container is tied with the control groups, when a

container is started a control group is created and associated

with it. The control group properties can be read and modified

when the container is running by using the lxc-cgroup command.

</para>

<para>

<command>lxc-cgroup</command> command is used to set or get a

control group subsystem which is associated with a

container. The subsystem name is handled by the user, the

command won't do any syntax checking on the subsystem name, if

the subsystem name does not exists, the command will fail.

</para>

<para>

<programlisting>

lxc-cgroup -n foo cpuset.cpus

</programlisting>

will display the content of this subsystem.

<programlisting>

lxc-cgroup -n foo cpu.shares 512

</programlisting>

will set the subsystem to the specified value.

</para>

</refsect2>

</refsect1>

<refsect1>

<title>Bugs</title>

<para>The <command>lxc</command> is still in development, so the

command syntax and the API can change. The version 1.0.0 will be

the frozen version.</para>

</refsect1>

&seealso;

<refsect1>

<title>Author</title>

<para>Daniel Lezcano <email>daniel.lezcano@free.fr</email></para>

</refsect1>

</refentry>