Hello there I am trying to locate the namespaces in place for a given lxc container (specifically /proc/<pid>/ns/*) And to this end I was wondering what is the recommended way to probe for an lxc container's init pid (mostly I'm after the mnt and pid namespaces, and probably network ones, but the actual list probably should not matter) I've found about "virsh domid" but this gives me the pid for libvirt_lxc, which turns out to have unmodified namespaces (at least as far as the mnt ns) OTOH this process has exactly one child which is the container's init, which seems to have the right set of namespaces My angle right now is to look in /proc/<domid_pid>/task/children for a - hopefully single - pid and that seems to work for now, but I am concerned this code may be fragile so I would rather use a more robust approach; or maybe this is robust ?

Hi Well if I need to run anything in the container context, short of entering it through e.g. ssh - hoping this is properly set up - well, I can’t.. I am using libvirt / lxc to set up a build box; essentially every night I would spawn a set of fresh VMs of some flavours (fedora18, ubuntu, what not) and use this to rebuild my system from scratch In this context it’s a real hassle to have to even set up ssh, there is no good reason for the build VM to run an ssh service at all, and I am concerned it might pull dependencies that I do not need/want I’d much rather have a direct means to just run some command inside the container. Admittedly I’m brain-damaged after having used vservers for too long, and their ‘vserver <container> exec command to run’ feature is in my genes now ;) Now maybe I am the one who is missing something and there already is something to do that ? Using the trick below I essentially have what I need mind you, I’m just concerned that it kind of works by accident :-) Thanks for the feedback in any case — Thierry On 20 Jan 2014, at 12:49, Daniel P. Berrange <berrange(a)redhat.com&gt; wrote: > On Mon, Jan 20, 2014 at 11:38:08AM +0100, Thierry Parmentelat wrote: >> Hello there >> >> I am trying to locate the namespaces in place for a given lxc container (specifically /proc/<pid>/ns/*) >> >> And to this end I was wondering what is the recommended way to probe for an lxc container's init pid >> (mostly I'm after the mnt and pid namespaces, and probably network ones, but the actual list probably should not matter) >> >> I've found about "virsh domid" but this gives me the pid for libvirt_lxc, which turns out to have unmodified namespaces (at least as far as the mnt ns) >> OTOH this process has exactly one child which is the container's init, which seems to have the right set of namespaces >> >> My angle right now is to look in /proc/<domid_pid>/task/children for a - hopefully single - pid and >> that seems to work for now, but I am concerned this code may be fragile so I would rather use a more >> robust approach; or maybe this is robust ? > > We don't really wish to expose the container PIDs to the host or namespace > details to client apps. Can you give more info about what you're trying to > achieve overall. I'd like to understand if there's some higher level API > we're missing that would more directly address your needs. > > > Daniel > -- > |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| > |: http://libvirt.org -o- http://virt-manager.org :| > |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| > |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|

On Mon, Jan 20, 2014 at 06:53:28PM +0100, Thierry Parmentelat wrote: > Hi > > Well if I need to run anything in the container context, short of entering > it through e.g. ssh - hoping this is properly set up - well, I can’t.. > > I am using libvirt / lxc to set up a build box; essentially every night > I would spawn a set of fresh VMs of some flavours (fedora18, ubuntu, > what not) and use this to rebuild my system from scratch > In this context it’s a real hassle to have to even set up ssh, there is > no good reason for the build VM to run an ssh service at all, and I am > concerned it might pull dependencies that I do not need/want > I’d much rather have a direct means to just run some command inside the container. > > Admittedly I’m brain-damaged after having used vservers for too long, and their > ‘vserver <container> exec command to run’ feature is in my genes now ;) > > Now maybe I am the one who is missing something and there already is something to do that ? > Using the trick below I essentially have what I need mind you, I’m just concerned that it > kind of works by accident :-) Yes, it already exists, albeit as a lxc specific custom command/api: $ virsh lxc-enter-namespace $CONTAINER /path/to/command/to/run arg1 arg2... There's a corresponding API in the libvirt-lxc.so library virDomainLxcEnterNamspace Eventually we'll turn this into a proper libvirt API with a less sucky virsh command name. Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|

Hi again

So I did give this interesting lxc-enter-namespace feature a try

So my comments are, - first that defining some even minimal PATH would help;

- and second that in this first form, it would be great if virsh could write some error on stderr instead of being almost totally silent, it took me some time to figure that it kind of worked Does this mean we would lose any message sent on stderr ?

On Mon, Jan 20, 2014 at 06:53:28PM +0100, Thierry Parmentelat wrote: > Hi > > Well if I need to run anything in the container context, short of entering > it through e.g. ssh - hoping this is properly set up - well, I can’t.. > > I am using libvirt / lxc to set up a build box; essentially every night > I would spawn a set of fresh VMs of some flavours (fedora18, ubuntu, > what not) and use this to rebuild my system from scratch > In this context it’s a real hassle to have to even set up ssh, there is > no good reason for the build VM to run an ssh service at all, and I am > concerned it might pull dependencies that I do not need/want > I’d much rather have a direct means to just run some command inside the container. > > Admittedly I’m brain-damaged after having used vservers for too long, and their > ‘vserver <container> exec command to run’ feature is in my genes now ;) > > Now maybe I am the one who is missing something and there already is something to do that ? > Using the trick below I essentially have what I need mind you, I’m just concerned that it > kind of works by accident :-) Yes, it already exists, albeit as a lxc specific custom command/api: $ virsh lxc-enter-namespace $CONTAINER /path/to/command/to/run arg1 arg2... There's a corresponding API in the libvirt-lxc.so library virDomainLxcEnterNamspace Eventually we'll turn this into a proper libvirt API with a less sucky virsh command name.

Hi

Admittedly I’m brain-damaged after having used vservers for too long, and their ‘vserver <container> exec command to run’ feature is in my genes now ;) Now maybe I am the one who is missing something and there already is something to do that ?