From mboxrd@z Thu Jan  1 00:00:00 1970
From: ludo@gnu.org (Ludovic =?utf-8?Q?Court=C3=A8s?=)
Subject: Re: Problem installing Guix on OpenVZ host that uses zfs
Date: Thu, 13 Apr 2017 16:54:12 +0200
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References: <877f2q673x.fsf@xsteve.at> <20170412153319.GC5920@jasmine>
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In-Reply-To: <874lxtpdeb.fsf@xsteve.at> ("Stefan
	\=\?utf-8\?Q\?Reich\=C3\=B6r\=22\?\=
	\=\?utf-8\?Q\?'s\?\= message of "Wed, 12 Apr 2017 22:41:16 +0200")
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To: Stefan =?utf-8?Q?Reich=C3=B6r?= <stefan@xsteve.at>
Cc: guix-devel@gnu.org

Hello!

Stefan Reich=C3=B6r <stefan@xsteve.at> skribis:

> Here is the part that triggers the problem as I assume (I can send the
> full log as well when it is needed):
>
> [pid 31032] open("/proc/self/mountinfo", O_RDONLY) =3D 17
> [pid 31032] read(17, "2860 2854 0:102 / / rw,noatime m"..., 4096) =3D 4076
> [pid 31032] read(17, "", 4096)          =3D 0
> [pid 31032] close(17)                   =3D 0
> [pid 31032] mount(NULL, "/", NULL, MS_PRIVATE, NULL) =3D -1 EACCES (Permi=
ssion denied)
> [pid 31032] futex(0x7f827449c190, FUTEX_WAKE_PRIVATE, 2147483647) =3D 0
> [pid 31032] write(2, "while setting up the build envir"..., 97) =3D 97
> [pid 31032] exit_group(1)               =3D ?
> [pid 31028] close(16)                   =3D 0
>
> The entry for "/" in /proc/self/mountinfo is:
> 3966 3548 0:102 / / rw,noatime master:129 - zfs satazpool/data/subvol-618=
-disk-1 rw,xattr,posixacl

The corresponding code in nix/libstore/build.cc is this:

--8<---------------cut here---------------start------------->8---
            /* Make all filesystems private.  This is necessary
               because subtrees may have been mounted as "shared"
               (MS_SHARED).  (Systemd does this, for instance.)  Even
               though we have a private mount namespace, mounting
               filesystems on top of a shared subtree still propagates
               outside of the namespace.  Making a subtree private is
               local to the namespace, though, so setting MS_PRIVATE
               does not affect the outside world. */
            Strings mounts =3D tokenizeString<Strings>(readFile("/proc/self=
/mountinfo", true), "\n");
            foreach (Strings::iterator, i, mounts) {
                vector<string> fields =3D tokenizeString<vector<string> >(*=
i, " ");
                string fs =3D decodeOctalEscaped(fields.at(4));
                if (mount(0, fs.c_str(), 0, MS_PRIVATE, 0) =3D=3D -1)
                    throw SysError(format("unable to make filesystem `%1%' =
private") % fs);
            }
--8<---------------cut here---------------end--------------->8---

So =E2=80=9Cfs.c_str()=E2=80=9D evaluates to =E2=80=9C/=E2=80=9D, as expect=
ed.

Now maybe zfs-on-linux doesn=E2=80=99t implement MS_PRIVATE or has specific
constraints (is it on FUSE?).  Perhaps you should check with the
zfs-on-linux people what they think of it.

Thanks,
Ludo=E2=80=99.