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Allow passing of command line args to LXC container

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When booting a virtual machine with a kernel/initrd it is possible
to pass command line arguments using the <cmdline>...args...</cmdline>
element in the guest XML. These appear to the kernel / init process
in /proc/cmdline.

When booting a container we do not have a custom /proc/cmdline,
but we can easily set an environment variable for it. Ideally
we could pass individual arguments to the init process as a
regular set of 'char *argv[]' parameters, but that would involve
libvirt parsing the <cmdline> XML text. This can easily be added
later, even if we add the env variable now

* docs/drvlxc.html.in: Document env variables passed to LXC
* src/conf/domain_conf.c: Add <cmdline> to be parsed for
  guests of type='exe'
* src/lxc/lxc_container.c: Set LIBVIRT_LXC_CMDLINE env var
This commit is contained in:
Daniel P. Berrange 2011-10-03 18:37:47 +01:00
parent 6cc9ee9b18
commit 652f887144
3 changed files with 20 additions and 0 deletions
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17
docs/drvlxc.html.in
View File

@ -39,6 +39,23 @@ driver. On such kernels, it may be neccessary to unmount the blkio controller.
</p>
<h2>Environment setup for the container init</h2>
<p>
When the container "init" process is started, it will be given several useful
environment variables.
</p>
<dl>
<dt>LIBVIRT_LXC_NAME</dt>
<dd>The name assigned to the container by libvirt</dd>
<dt>LIBVIRT_LXC_UUID</dt>
<dd>The UUID assigned to the container by libvirt</dd>
<dt>LIBVIRT_LXC_CMDLINE</dt>
<dd>The unparsed command line arguments specified in the container configuration</dd>
</dl>
<h3>Example config version 1</h3>
<p></p>
<pre>

1
src/conf/domain_conf.c
View File

@ -6834,6 +6834,7 @@ static virDomainDefPtr virDomainDefParseXML(virCapsPtr caps,
goto error;
}
}
def->os.cmdline = virXPathString("string(./os/cmdline[1])", ctxt);
}
if (STREQ(def->os.type, "xen") ||

2
src/lxc/lxc_container.c
View File

@ -116,6 +116,8 @@ static virCommandPtr lxcContainerBuildInitCmd(virDomainDefPtr vmDef)
virCommandAddEnvString(cmd, "TERM=linux");
virCommandAddEnvPair(cmd, "LIBVIRT_LXC_UUID", uuidstr);
virCommandAddEnvPair(cmd, "LIBVIRT_LXC_NAME", vmDef->name);
if (vmDef->os.cmdline)
virCommandAddEnvPair(cmd, "LIBVIRT_LXC_CMDLINE", vmDef->os.cmdline);
return cmd;
}