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From:   Richard Weinberger <richard.weinberger@gmail.com>
Date:   Wed, 14 Feb 2018 12:30:18 +0100
Message-ID: <CAFLxGvzxLP_UTQbwEY99bQfyftWzZHwaOP+WrzJ8099EKtbVLg@mail.gmail.com>
Subject: Re: plan9 semantics on Linux - mount namespaces
To:     Enrico Weigelt <lkml@metux.net>
Cc:     Aleksa Sarai <asarai@suse.de>,
        Linux Containers <containers@lists.linux-foundation.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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On Wed, Feb 14, 2018 at 12:27 PM, Enrico Weigelt <lkml@metux.net> wrote:
> On 14.02.2018 11:24, Aleksa Sarai wrote:
>
>> What distribution are you using and which release?
>
>
> On a self-compiled system.
>
> Forgot to enable namespaces in the kernel. Now it seems to work
> as root, but not as an unprivileged user:
>
>
> daemon@alphabox:~ unshare -r -U
> unshare: can't open '/proc/self/setgroups': Permission denied
> daemon@alphabox:~ unshare -f -r -U
> unshare: can't open '/proc/self/setgroups': Permission denied
>

Please read http://man7.org/linux/man-pages/man7/user_namespaces.7.html
setgroups is a corner case and needs special care.

-- 
Thanks,
//richard