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From: Tijl Coosemans <tijl@FreeBSD.org>
To: Andriy Gapon <avg@FreeBSD.org>
Cc: freebsd-emulation@FreeBSD.org
Subject: Re: /compat/linux/dev and an odd program
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On Tue, 6 Dec 2016 18:49:06 +0200 Andriy Gapon <avg@FreeBSD.org> wrote:
> I have an old binary-only Linux program that, for whatever reason, opens
> /dev/null with O_CREAT flag (O_WRONLY | O_CREAT | O_TRUNC).  That works fine
> when there is no /compat/linux/dev: the code in kern_alternate_path() sees that
> the directory does not exist, strips /compat/linux prefix and, so, the real
> /dev/null is found.  But typically, if linux_base is installed, there is
> /compat/linux/dev directory, because of /compat/linux/dev/shm/.  The code will
> see the directory and, thus, it will try to open /compat/linux/dev/null.  But
> there is no such file, so it will try to create it.  And fail with EPERM for a
> non-privileged user.
> 
> I wonder if anyone has thoughts or suggestions on this situation.
> Either an administrative solution or a code change would be fine for me.
> Thanks!

Try creating this symlink:

ln -s /dev/null /compat/linux/dev/null