[lxc-devel] [PATCH v2 1/2] Add option to lxc-attach to select specific namespaces

[Christian Seiler]

Hi Serge,

>> What about if we update the command interface to add an additional
>> command along the lines of LXC_COMMAND_GET_NSFLAGS or similar, which
>> returns the bitmask of CLONE_* used for starting the container? Then
>> we would have the logic:
>
> That works fine for persistent containers which were started without
> any command line changes.  But even with a persistent container with
> no network section, I could add a network section on the lxc-start
> command line with '-s' arguments, making the set of cloned namespaces
> different from what you'd expect from the config file.  So there is
> no good way I can think of, generally, to get that bitmask of CLONE_*
> flags used for starting the container.

You misunderstood me: I don't want to read the configuration file - I
want to ask the still-running lxc-start process (that listens on the
abstract socket for the container) to give me the flags it used when
it was run. Just as it may be asked to return a file descriptor for
the console or the PID of the init process. We don't have to generate
any file or store anything, we can just keep the information in a
simple variable that we return via the command interface in case
lxc-attach (or somebody else) asks.

Regards,
Christian