[CRIU] Problem in Seizing Open File Descriptors?

[Pavel Emelyanov]

On 07/15/2014 06:49 PM, Pavel Emelyanov wrote:
> On 07/15/2014 06:34 PM, Saied Kazemi wrote:
>> Thanks for the quick feedback.  I am using CRIU 1.3-rc2 (at commit e1b56c8fa) with Docker version
>> 1.1.0 on Ubuntu 14.04 which does not provide mnt_id in /proc/pid/fdinfo/fd files.
> 
> That can be a problem.
> 
>> I will look into Docker source today.  Assuming that it does open /dev/null before moving into the 
>> namespaces, can CRIU handle it?
> 
> It should, but without this field this would fail just the
> way you observe with Docker :) 

After refreshing my memory and talking to Andrey (who wrote this code) the
answer is -- no. When we have multiple mount namespaces files opened from
outside are not dumped.

For /dev/null you could consider using the --evasive-devices option. It will
ask criu to dump the device's path in whichever location it's found. Not
sure how would this affect Docker though.

> If you could confirm that on
> the kernel with mnt_id in fdinfo it works, that would be
> great. Meanwhile, I will try to make a test for this.
> 
> Thanks,
> Pavel
>