[systemd-devel] changing the "mount --make-shared /" default

[Tom Gundersen]

On Feb 4, 2013 10:31 AM, "Lennart Poettering" <lennart at poettering.net>
wrote:
>
> On Fri, 01.02.13 12:50, Jake Edge (jake at lwn.net) wrote:
>
> > [ OK, let's try this again ... since I'm impatient about it sitting in
> > the moderator queue, I went ahead and joined up ]
> >
> > Hi Lennart (and the rest of the systemd gang),
> >
> > I was quite surprised by some behavior that I found today in Fedora 18,
> > which I think comes from systemd.  I was trying to play with mount
> > namespaces and was rather surprised to find that they didn't work as
> > expected. After some googling, I realized that Fedora makes / a shared
> > mount by default.  That appears to come from:
> >
> >
http://cgit.freedesktop.org/systemd/systemd/commit/?id=b3ac5f8cb98757416d8660023d6564a7c411f0a0
> >
> > where you say:
> >
> > Setups which prefer the default of "private" should undo this change
> > via invoking "mount --make-private /" or a similar command after boot.
> >
> > I am not sure that I want the default to be "private", but if I did,
> > what is the proper, systemd-ish way to do so?
>
> Drop a unit file like this one to /etc/systemd/system/make-shared.service:
>
>     [Unit]
>     Description=I like my hierarchies private
>     DefaultDependencies=no
>     Conflicts=shutdown.target
>     Before=local-fs-pre.target shutdown.target
>
>     [Service]
>     Type=oneshot
>     RemainAfterExit=yes
>     ExecStart=/bin/mount --make-rprivate /
>
> And then pull this into the early boot:
>
>     # mkdir -p /etc/systemd/system/local-fs.target.wants/
>     # ln -s ../make-shared.service
/etc/systemd/system/local-fs.target.wants/
>
> I didn't test this, but it should do the job, nicely.
>
> Explanations:
>
> As this is an early boot process we need to disable the default
> ordering/requirement dependencies systemd adds to services via
> DefaultDependencies=no. Then, we order ourselves before
> "local-fs-pre.target", which has the benefit that we can be sure that
> further mounted fs will inherit the flag nicely and
> race-freely. local-fs-pre.target is ordered after all local mounts.

*before*?

> We also order ourselves relative to shutdown.target, which ensures this
> unit is stopped at shutdown. This is just to make things nice, and
> actually has very little effect, as the unit doesn't do anything anyway
> when stopped.
>
> We use Type=oneshot since the specified command should be executed at
> boot and be waited for before boot progresses (adhering to the ordering
> dependencies expressed in [Unit]).
>
> We use RemainAfterExit=yes so that the unit stays around after it is
> started, so that we can easily check after boot if it got properly
> started during boot.
>
> Finally, the ln -s line makes sure the unit is activated as part of
> local-fs.target, which is where all local file system units tend to be
> pulled in.
>
> Hope this makes sense!
>
> Lennart
>
> --
> Lennart Poettering - Red Hat, Inc.
> _______________________________________________
> systemd-devel mailing list
> systemd-devel at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/systemd-devel
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.freedesktop.org/archives/systemd-devel/attachments/20130204/becbcca4/attachment.html>