[CRIU] Can't launch unshare with -U or -r as unprivileged user

[Christopher Covington]

On 06/04/2014 11:51 AM, Allan Cecil wrote:
> Bottom-posted for clarity, please see below.
> 
> On 2014-06-04 07:38, Christopher Covington wrote:
>> Hi Allan,
>>
>> On 06/04/2014 01:46 AM, Allan Cecil wrote:
> ~snip~
>>> Unfortunately, this fails on unshare from util-linux 2.24.903-56ce because
>>> virtually all of the flags require root privileges.  The manpage talks about
>>> using -U and -r instead to allow unshare to run without resorting to sudo
>>> (which is not available to the unprivileged user account in use).  The issue
>>> is unshare -U or unshare -r always fails with the following error message:
>>> unshare: unshare failed: Invalid argument

> Hi Christopher, thanks for your response.  This should help:
> 
> $ uname -a
> Linux silvermine 3.11.0-19-generic #33-Ubuntu SMP Tue Mar 11 18:48:34 UTC 2014
> x86_64 x86_64 x86_64 GNU/Linux
> $ sudo unshare -fp -- echo hello
> [sudo] password for ac:
> hello
> $ unshare -fp -- echo hello
> unshare: unshare failed: Operation not permitted
> $
> 
> So, with that kernel it's not possible to pass -fp as a normal user.  I'll be
> upgrading to Linux Mint 17 as soon as the Xfce edition becomes available but
> until then I assume I am at the mercy of my existing kernel.  Any
> suggestions?  Thanks for your time,

So after my digression it comes back to the question of how to get `unshare
-r` to work. I noticed that in a kernel where CONFIG_USER_NS is not set, I was
getting the "Invalid argument" error there when trying stuff like `unshare -r
-- echo hello` or the example given in the patch introducing the -r option [1].

1. http://thread.gmane.org/gmane.linux.utilities.util-linux-ng/8317

Is there a /boot/config or /proc/config.gz that you can use to confirm
CONFIG_USER_NS=y?

Being entirely new to the subject, I found the following thread interesting
background information.

https://lists.linux-foundation.org/pipermail/containers/2013-June/032727.html

Regards,
Christopher

-- 
Employee of Qualcomm Innovation Center, Inc.
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