[libvirt-users] Problems with user namespaces

[Gao feng]

On 09/06/2013 03:15 AM, Jaka Hudoklin wrote:
> Hello!
> 
> I'm testing user namespaces and I have quite some problem getting them to work.
> 
> First of all, I have user namespaces support enabled in kernel:
> 
> offlinehacker:~/ $ uname -r
> 3.10.10
> offlinehacker:~/ $ ls /proc/self/ns/
> ipc@  mnt@  net@  pid@  user@  uts@
> 
> I created simple ubuntu rootfs and when I start container without idmap, so without user namespace mappings, it works just fine:
> 
> Libivrt config:
> 
> <domain type='lxc'>
>   <name>helloworld</name>
>   <memory>102400</memory>
>   <os>
>     <type>exe</type>
>     <init>/bin/dash</init>
>   </os>
>   <!--<idmap>
>     <uid start='0' target='499' count='10'/>
>     <gid start='0' target='100' count='10'/>
>   </idmap>-->
>   <devices>
>     <console type='pty'/>
>     <filesystem type='mount'>
>       <source dir='/home/offlinehacker/rootfs'/>
>       <target dir='/'/>
>     </filesystem>
>   </devices>
> </domain>
> 

Your configuration looks good.

> This is how my rootfs looks like:
> 
> offlinehacker:~/ $ ls -la rootfs
> drwxr-xr-x 23 offlinehacker users          4096 sep  5 19:06 ./
> drwxr-xr-x 59 offlinehacker users          4096 sep  5 19:06 ../
> drwxr-xr-x  2 offlinehacker users          4096 avg 27 14:11 bin/
> drwxr-xr-x  3 offlinehacker users          4096 avg 27 14:11 boot/
> drwxr-xr-x  4 offlinehacker users          4096 avg 27 14:11 dev/
> drwxr-xr-x 86 offlinehacker users          4096 sep  5 18:20 etc/
> drwxr-xr-x  3 offlinehacker users          4096 avg 27 14:11 home/
> lrwxrwxrwx  1 offlinehacker users            33 avg 27 14:10 initrd.img -> /boot/initrd.img-3.2.0-52-virtual
> drwxr-xr-x 18 offlinehacker users          4096 avg 27 14:10 lib/
> drwxr-xr-x  2 offlinehacker users          4096 avg 27 14:10 lib64/
> drwx------  2 offlinehacker users          4096 avg 27 14:11 lost+found/
> drwxr-xr-x  2 offlinehacker users          4096 avg 27 14:09 media/
> drwxr-xr-x  2 offlinehacker users          4096 apr 19  2012 mnt/
> drwxr-xr-x  2 offlinehacker users          4096 avg 27 14:09 opt/
> -rw-r--r--  1 offlinehacker vboxusers 231671365 avg 27 14:12 precise-server-cloudimg-amd64-root.tar.gz
> drwxr-xr-x  2 offlinehacker users          4096 apr 19  2012 proc/
> drwx------  2 offlinehacker users          4096 sep  3 23:47 root/
> drwxr-xr-x  2 offlinehacker users          4096 avg 27 14:11 run/
> drwxr-xr-x  2 offlinehacker users          4096 avg 27 14:11 sbin/
> drwxr-xr-x  2 offlinehacker users          4096 mar  5  2012 selinux/
> drwxr-xr-x  2 offlinehacker users          4096 avg 27 14:09 srv/
> drwxr-xr-x  2 offlinehacker users          4096 apr 14  2012 sys/
> drwxrwxrwt  2 offlinehacker users          4096 sep  4 01:39 tmp/
> drwxr-xr-x 10 offlinehacker users          4096 avg 27 14:09 usr/
> drwxr-xr-x 12 offlinehacker users          4096 sep  5 18:10 var/
> lrwxrwxrwx  1 offlinehacker users            29 avg 27 14:10 vmlinuz -> boot/vmlinuz-3.2.0-52-virtual
> 
> And this is who I am:
> offlinehacker:~/ $ id
> uid=499(offlinehacker) gid=67(libvirtd) groups=100(users),1(wheel),57(networkmanager),67(libvirtd)

Can this user exec //home/offlinehacker/rootfs/bin/dash successfully ?

> 
> When I create the container with idmap uncommented I get the following error:
> 
> offlinehacker:~/ $ virsh -c lxc:/// create helloworld.xml
> error: Failed to create domain from helloworld.xml
> error: internal error: guest failed to start: 2013-09-05 19:08:57.781+0000: 19036: debug
> 
> And these are the logs:
> sep 05 19:08:52 laptop libvirtd[1542]: server=0x7fc8a60ddd60 client=0x7fc8a60e68d0 msg=0x7fc8a60e9380 rerr=0x7fc89a32cd40 args=0x7fc88800b4a0 ret=0x7fc88800a1c0
> sep 05 19:08:52 laptop libvirtd[1542]: priv=0x7fc8a60e91f0 conn=(nil)
> sep 05 19:08:52 laptop libvirtd[1542]: name=lxc:///
> sep 05 19:08:57 laptop libvirtd[1542]: Cannot recv data: Connection reset by peer
> sep 05 19:08:58 laptop libvirtd[1542]: internal error: guest failed to start: 2013-09-05 19:08:57.781+0000: 19036: debug
> 
> Looks like .oldroot, dev, proc and sys gets created with mapped permissions(499:100), but container fails to start.
> 

Please enable debug mode, I need more information.

http://libvirt.org/logging.html

Thansk