With CentOS 6 and LXC, "ifconfig" is unable to see network interface (but busybox "ifconfig" works fine)
- by larsks
I've just started working with LXC under CentOS 6 (via the libvirt adapter). If I create an LXC container, I'm unable to see any network interfaces when using the native system tools:
# ifconfig -a
#
The behavior is very odd; specifying an interface by names yields neither the expected output nor an error message. This is true even for clearly invalid interface names, like this:
# ifconfig foo
#
The ip command exhibits the same behavior.
On the other hand, if I use "ifconfig" provided by busybox, everything works as expected:
# busybox ifconfig -a
eth0 Link encap:Ethernet HWaddr 52:54:00:E0:12:C8
inet6 addr: fe80::5054:ff:fee0:12c8/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:268 errors:0 dropped:0 overruns:0 frame:0
TX packets:6 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:17814 (17.3 KiB) TX bytes:552 (552.0 B)
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
So...what does busybox know that the native tools don't? The libvirt config for this environment is pretty standard; the network definition looks like this:
<interface type='network'>
<mac address='52:54:00:e0:12:c8'/>
<source network='default'/>
<target dev='veth0'/>
</interface>
The full configuration is here if you think it might help.
I'm running:
lxc-0.7.2-2.el6.x86_64
kernel-2.6.32-71.29.1.el6.x86_64
EDIT
Weirder and weirder...it's a display issue, not a functionality issue. I can see the output of ifconfig if I pipe it into anything, so for example:
# ifconfig eth0 | cat
eth0 Link encap:Ethernet HWaddr 52:54:00:E0:12:C8
inet addr:192.168.10.10 Bcast:192.168.10.255 Mask:255.255.255.0
inet6 addr: fe80::5054:ff:fee0:12c8/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:573 errors:0 dropped:0 overruns:0 frame:0
TX packets:6 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:37914 (37.0 KiB) TX bytes:552 (552.0 b)
And in fact even when not piping the output, strace shows that ifconfig is in fact writing the output to file descriptor 1 (aka stdout), so it's not clear why no output is actually showing up. This could be either an LXC or a virsh issue, I guess.
