[lxc-users] busybox template in ubuntu 14.04 fails to install /usr/sbin/init.lxc?

[Fajar A. Nugraha]

On Mon, May 12, 2014 at 10:25 AM, Serge Hallyn <serge.hallyn at ubuntu.com> wrote:
> Quoting Fajar A. Nugraha (list at fajar.net):

>> It is also not a straightforward matter to copy init.lxc. In ubuntu
>> trusty at least, I had to copy to other libraries manually to a ubuntu
>> container to make it work: liblxc.so.1 and libseccomp.so.2. For a
>
> this difficulty is really bothering me so i'm thinking of teaching
> lxc-execute to look for /usr/sbin/init.lxc.static on the host, and
> binding that into the container automatically at start.  (Then probably
> publishing init.lxc.static in a new package).


In the mean time, I found something odd on a system: having init.lxc
as sylmink to /bin/bash doesn't work. Not sure why, as the same thing
works on another system (both trusty). Copying the real init.lxc (plus
dependencies) from the host works, as expected.

I was able to test that you CAN use busybox (I tested the
busybox-static) as init.lxc. Not with symlink, but with a script.

# cat usr/sbin/init.lxc
#!/bin/busybox ash
shift
"$@"

chmod 755, and it works ("trusty" is the host, "template" is the container)

trusty ~ # lxc-execute -n template -- sudo -i
template ~ # ps -efa
UID        PID  PPID  C STIME TTY          TIME CMD
root         1     0  0 12:11 ?        00:00:00 /bin/busybox ash
/usr/sbin/init.lxc -- sudo -i
root         4     1  0 12:11 ?        00:00:00 sudo -i
root         5     4  0 12:11 ?        00:00:00 -bash
root        23     5  0 12:11 ?        00:00:00 ps -efa
template ~ # logout
trusty ~ #


Note that when you do it this way, the output of some commands can be
different than what you'd expect due to busybox prioritizing it's
internal module. For example, If I pass "ps -efa" directly instead of
in the interactive shell after sudo:

trusty ~ # lxc-execute -n template -- ps -efa
PID   USER     COMMAND
    1 root     {init.lxc} /bin/busybox ash /usr/sbin/init.lxc -- ps -efa
    4 root     {busybox} ps -efa

-- 
Fajar