[Lxc-users] How to start the network services so as to get the IP address using lxc-execute???

Brian K. White brian at aljex.com
Thu Dec 8 21:32:52 UTC 2011


This isn't meant as an insult but you seem to be trying to do things 
backwards and expecting, worse, demanding, a low level tool to contain 
high level features that really should be provided by your own 
scripting, or by other tools that already exist for that purpose.

If you want to assign container ip addresses in some particular order, 
then simply do so. You can ensure container IP's get set whatever way 
you want by any number of means. You can write a start script that 
writes IP's into the container config files and/or rewrites them 
dynamically every time it's started up, you can tell the containers to 
use dhcp and you can control the dhcp server. If you want to read the 
containers IP, you can get it from the hosts dhcp server state/log file 
or possibly from the arp table on the host or by directly reading files 
from the containers "filesystem".

Someone already gave you a good example of a simple bit of shell 
scripting that takes the container name and uses that to produce the ip 
address as long as the container names adhered to a consistent pattern.

If that's not what you wanted then what? Chronological order? That's 
sort of meaningless since containers can be stopped and restarted.

If you want the ip's to be assigned chronologically, ie, the first 
container to be started gets ip #1, that's trivial too, just write the 
start script to keep count in a temp file every time it is started, or 
have it parse the list of all running containers and add one to whatever 
is the current highest number running before starting a new container. 
But then this points out how meaningless this request is from the 
beginning. What happens after containers have been stopped and 
restarted? Do you want a restarted container to get a new next-highest 
number? or remember it's original number? If you want it to get a new 
number, then what happens when the always incrementing number gets to 
the end of the netmask? If you want it to remember the number that it 
got originally then what why not just write that number in it's config 
file from the beginning? If you want it to reuse IP's dynamically from a 
pool then that is already what a dhcp server does.

I really don't understand what you are trying to do or trying to avoid 
doing or why, that isn't easily answered by a little shell scripting 
and/or a dhcp server.

-- 
bkw

On 12/8/2011 7:59 AM, nishant mungse wrote:
>
> Hi Greg,
>
> Thanks 4 reply.
>
> I just want the IP addresses of the containers. And one more thing can I
> get the IP address of containers in sequence for eg. container1 ::
> 198.208.168.1 container 2 :: 198.208.168.2 and like this.
>
> Please help me ASAP.
>
> Regards,
> Nishant
>
> On Thu, Dec 8, 2011 at 5:09 PM, Greg Kurz <gkurz at fr.ibm.com
> <mailto:gkurz at fr.ibm.com>> wrote:
>
>     On Thu, 2011-12-08 at 16:03 +0530, nishant mungse wrote:
>      > Hi,
>      >
>      > I want to manually invoke a networking setup to start the network
>      > service to get the IP address of container , But the problem is i
>      > don't want to start the container and want to use lxc-execute.
>      >
>      > When I tried these things happened::
>      >
>      > command :: lxc-execute -n base
>      > -f /home/nishant/ubuntu.conf
>     /var/lib/lxc/base1/rootfs/etc/init.d/networking start
>
>     Ok... this can't work. lxc-execute is for application containers only:
>     it runs lxc-init instead of standard /sbin/init. The networking script
>     you invoke needs upstart to be already running in the container... You
>     seem to have a system container here, it _MUST_ be started with
>     lxc-start.
>
>      >
>      > O/P
>      >
>      > Rather than invoking init scripts through /etc/init.d, use the
>      > service(8)
>      > utility, e.g. service networking start
>      >
>      > Since the script you are attempting to invoke has been converted
>     to an
>      > Upstart job, you may also use the start(8) utility, e.g. start
>      > networking
>      > start: Unable to connect to Upstart: Failed to connect to
>      > socket /com/ubuntu/upstart: Connection refused
>      >
>      >
>      > How to start the network services so as to get the IP addresses of
>      > containers?
>      >
>
>     What's your true need here ? Controlling the containers network services
>     from the host or just knowing the addresses used by the containers ? I
>     guess both are doable in a variety of ways.
>
>     Cheers.
>
>      >
>      > Regards,
>      > Nishant
>      >
>      >
>      >
>      >
>     ------------------------------------------------------------------------------
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> discussion for anyone considering optimizing the pricing and packaging model
> of a cloud services business. Read Now!
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