[libvirt] Environmental Variables inside a container

[Eric Blake]

On 07/27/2011 12:44 PM, Devendra K. Modium wrote:
> Hi All
>
> I am trying to pass an environmental flag to the
> LXC container when it is started.I found libvirt_lxc is
> already doing it  in lxc_container.c as shown below
>
>
> static virCommandPtr lxcContainerBuildInitCmd(virDomainDefPtr vmDef)
> {
>      char uuidstr[VIR_UUID_STRING_BUFLEN];
>      virCommandPtr cmd;
>
>      virUUIDFormat(vmDef->uuid, uuidstr);
>
>      cmd = virCommandNew(vmDef->os.init);
>
>      virCommandAddEnvString(cmd, "PATH=/bin:/sbin");
>      virCommandAddEnvString(cmd, "TERM=linux-deva");
>      virCommandAddEnvPair(cmd, "LIBVIRT_LXC_UUID", uuidstr);
>      virCommandAddEnvPair(cmd, "LIBVIRT_LXC_NAME", vmDef->name);

Yes, this list is hard-coded, and only guarantees to affect the 
environment of the process at the root of the lxc process tree.

> But only
> TERM flag is getting visible inside the container not remaining.
>
> Does it depends on how /sbin/init is receiving them? Is /sbin/init
> only recognizing TERM flag.

Probably something in your lxc process hierarchy is scrubbing 
environment variables prior to starting additional processes, but that's 
out of libvirt's control - libvirt can only affect the environment of 
the parent process.

> If so what is intention of sending remaining flags in current libvirt.
>
> Please let me know if there is any elegant way to send environmental
> variable to container.

Sounds like it might be an interesting feature to enhance the xml for 
lxc domains to allow the specification of additional environment 
variables that should be inherited into the lxc process tree, beyond the 
few variables already hard-coded by libvirt.

-- 
Eric Blake   eblake at redhat.com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org