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crtools -> criu
=== Preparations ===
=== Preparations ===
You not only need to [[Installation | install]] the crtools, but also check that the iproute2 utility (<code>ip</code>) is v3.6.0 or higher.
You not only need to [[Installation | install]] the criu, but also check that the iproute2 utility (<code>ip</code>) is v3.6.0 or higher.
You can clone the [http://git.kernel.org/?p=linux/kernel/git/shemminger/iproute2.git;a=summary git repo] or download the [http://kernel.org/pub/linux/utils/net/iproute2/ tarball] to compile it manually. In order to tell to crtools where the proper ip tool is set the <code>CR_IP_TOOL</code> environment variable.
You can clone the [http://git.kernel.org/?p=linux/kernel/git/shemminger/iproute2.git;a=summary git repo] or download the [http://kernel.org/pub/linux/utils/net/iproute2/ tarball] to compile it manually. In order to tell to criu where the proper ip tool is set the <code>CR_IP_TOOL</code> environment variable.
=== Dump and restore ===
=== Dump and restore ===
Dumping and restoring an LXC contianer means -- dumping a subtree of processes starting from container init plus all kinds of namespaces.
Dumping and restoring an LXC contianer means -- dumping a subtree of processes starting from container init plus all kinds of namespaces.
Restoring is symmetrical. The way LXC container works imposes some more requirements on crtools usage.
Restoring is symmetrical. The way LXC container works imposes some more requirements on criu usage.
* In order to properly isolate container from unwanted networking communication during checkpoint/restore you should provide a script for locking/unlocking the container network (see below)
* In order to properly isolate container from unwanted networking communication during checkpoint/restore you should provide a script for locking/unlocking the container network (see below)
Typically a container dump command will look like
Typically a container dump command will look like
<pre>
<pre>
criu dump
--tcp-established # allow for TCP connections dump
--tcp-established # allow for TCP connections dump
-n net -n mnt -n ipc -n pid # dump all the namespaces container uses
-n net -n mnt -n ipc -n pid # dump all the namespaces container uses
and restore command like
and restore command like
<pre>
<pre>
criu restore
--tcp-established
--tcp-established
-n net -n mnt -n ipc -n pid
-n net -n mnt -n ipc -n pid
</pre>
</pre>
We also find it useful to use the <code>--restore-detached</code> option for restore to make contianer reparent to init rather than hanging on a crtools process launched from shell. Another useful option is the <code>--pidfile</code> one -- you will be able to find out the host-side pid of a container init after restore.
We also find it useful to use the <code>--restore-detached</code> option for restore to make contianer reparent to init rather than hanging on a criu process launched from shell. Another useful option is the <code>--pidfile</code> one -- you will be able to find out the host-side pid of a container init after restore.
Also note, that there's a BUG in how LXC prepares the /dev filesystem for a container which sometimes makes it impossible to dump and container. The <code>--evasive-devices</code> option can help.
Also note, that there's a BUG in how LXC prepares the /dev filesystem for a container which sometimes makes it impossible to dump and container. The <code>--evasive-devices</code> option can help.
=== Example ===
=== Example ===
We have [http://git.criu.org/?p=crtools.git;a=tree;f=test/app-emu/lxc;hb=HEAD an application test] for dumping/restoring an LXC Container. You may look at it for better understanding how to dump and restore your container with crtools.
We have [http://git.criu.org/?p=crtools.git;a=tree;f=test/app-emu/lxc;hb=HEAD an application test] for dumping/restoring an LXC Container. You may look at it for better understanding how to dump and restore your container with criu.
This test contains two scripts:
This test contains two scripts:
;[http://git.criu.org/?p=crtools.git;a=blob;f=test/app-emu/lxc/run.sh;hb=HEAD run.sh]
;[http://git.criu.org/?p=crtools.git;a=blob;f=test/app-emu/lxc/run.sh;hb=HEAD run.sh]
:This is the main script, which executes ''crtools'' two times for dumping and restoring CT. It contains a working commands for dumping and restoring a container.
:This is the main script, which executes ''criu'' two times for dumping and restoring CT. It contains a working commands for dumping and restoring a container.
;[http://git.criu.org/?p=crtools.git;a=blob;f=test/app-emu/lxc/network-script.sh;hb=HEAD network-script.sh]
;[http://git.criu.org/?p=crtools.git;a=blob;f=test/app-emu/lxc/network-script.sh;hb=HEAD network-script.sh]