[lxc-users] Packet flow from application running in container to physical NIC transmission

[Guido Jäkel]

Dear Mohit,

you're welcome. The LXC project is a "meta project" which has bundled and is based on a couple of other work, e.g. from the teams of the kernel or the cgroup developers. From that, no all userland stuff is LXC-aware yet. The LXC team know about, point this out to other package maintainers and try to offer workarounds.


The manpage of dmesg states the purpose "print or control the kernel ring buffer". As this is a low level tool interfacing the kernel and LXC does all on the same kernel and the kernel message buffer offers no namespace feature (yet), the output of dmesg will be the same on the host and on the containers (if a container is allowed to use dmesg). 

But the "console" output of each container bootstrapping might be recorded into a unique file because the console device is virtualized. And if something like a syslog daemon is running in a Container, the kernel feed should be disabled here. In the other hand, log entries from applications inside the container will be catched and (normaly) filed by the containers syslog daemon.


Other prominent tools that are not LXC-aware are e.g. 'free' or 'top', because (historical driven) they use no real propper userland API but access low level kernel information in a direct way. There are some contributes to offer a workaround (lxc-...) and an ongoing work to "overlay" the /proc and /sys pseudo filesystems.


greetings

Guido

On 2014-06-27 15:31, Mohit Saxena wrote:
> Thanks a Lot Jäkel, it clarifies a lot of doubts for me.
> 
> What will be output of dmesg from the container? Is it same as host output
> or it will show the container bootup sequence.