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<title>Functional specification</title>
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A container is an object where the configuration is
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persistent. The application will be launched inside this
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container and it will use the configuration which was previously
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created or specified in parameter of the command.
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A container is an object isolating some resources of the host,
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for the application or system running in it.
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The application / system will be launched inside a
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container specified by a configuration that is either
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initially created or passed as parameter of the starting commands.
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<para>How to run an application in a container ?</para>
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<title>Creating / Destroying the containers</title>
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<title>Creating / Destroying container
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(persistent container)</title>
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The container is created via the <command>lxc-create</command>
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command. It takes a container name as parameter and an
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optional configuration file. The name is used by the different
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A persistent container object can be
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created via the <command>lxc-create</command>
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command. It takes a container name as parameter and
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optional configuration file and template.
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The name is used by the different
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commands to refer to this
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container. The <command>lxc-destroy</command> command will
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destroy the container object.
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<title>Starting / Stopping a container</title>
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<title>Volatile container</title>
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<para>It is not mandatory to create a container object
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The container can be directly started with a
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configuration file as parameter.
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<title>Starting / Stopping container</title>
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<para>When the container has been created, it is ready to run an
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application / system. When the application has to be destroyed,
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the container can be stopped, that will kill all the processes
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of the container. If the container was not created before
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application / system.
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This is the purpose of the <command>lxc-execute</command> and
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<command>lxc-start</command> commands.
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If the container was not created before
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starting the application, the container will use the
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configuration file passed as parameter to the command, otherwise
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it will use the default isolation.</para>
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configuration file passed as parameter to the command,
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and if there is no such parameter either, then
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it will use a default isolation.
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If the application is ended, the container will be stopped also,
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but if needed the <command>lxc-stop</command> command can
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be used to kill the still running application.
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Running an application inside a container is not exactly the
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same thing as running a system. For this reason, there is two
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commands to run an application into a container:
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same thing as running a system. For this reason, there are two
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different commands to run an application into a container:
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lxc-execute -n foo [-f config] /bin/bash
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lxc-start -n foo [/bin/bash]
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lxc-start -n foo [-f config] [/bin/bash]
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</programlisting>
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<command>lxc-execute</command> command will run the
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specified command into a container but it will mount /proc
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and autocreate/autodestroy the container if it does not
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exist. It will furthermore create an intermediate
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process, <command>lxc-init</command>, which is in charge to
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launch the specified command, that allows to support daemons
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in the container. In other words, in the
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container <command>lxc-init</command> has the pid 1 and the
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specified command into the container via an intermediate
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process, <command>lxc-init</command>.
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This lxc-init after launching the specified command,
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will wait for its end and all other reparented processes.
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(that allows to support daemons in the container).
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In other words, in the
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container, <command>lxc-init</command> has the pid 1 and the
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first process of the application has the pid 2.
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<command>lxc-start</command> command will run the specified
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command into the container doing nothing else than using the
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configuration specified by <command>lxc-create</command>.
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<command>lxc-start</command> command will run directly the specified
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command into the container.
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The pid of the first process is 1. If no command is
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specified <command>lxc-start</command> will
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run <filename>/sbin/init</filename>.
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To summarize, <command>lxc-execute</command> is for running
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an application and <command>lxc-start</command> is for
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an application and <command>lxc-start</command> is better suited for
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running a system.
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If the application is no longer responding, inaccessible or is
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If the application is no longer responding, is inaccessible or is
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not able to finish by itself, a
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wild <command>lxc-stop</command> command will kill all the
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processes in the container without pity.
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doc/lxc.sgml.in
