LWN: Comments on "Mount point removal and renaming"

Greenspun's tenth law

cesarb — Thu, 17 Oct 2013 21:32:05 +0000

Is it just me, or the more Linux namespaces develop, the more they look like an application of Greenspun's tenth law, only with microkernels instead of Lisp?

Mount point removal and renaming

ebiederm — Thu, 17 Oct 2013 18:44:39 +0000

I do not know how you are hitting this problem but it sounds like even with my changes you will have a problem. Aka one build environment killing a file or directory the other build environment is using for a mount point.

That said I agree, that this can be a problem already.

One of the points of user namespaces is to take a bunch of kernel functionality we have been allowing non-root users to use for a long time and remove the need for the suid root helpers. Much like what happened with ptys with the introduction of /dev/ptmx.

Mount point removal and renaming

fishface60 — Thu, 17 Oct 2013 12:56:06 +0000

> But, if distributions are to ever enable user namespaces, these kinds
> of problems need to be found and fixed.

This is a problem independent of user namespaces.

linux-user-chroot[1] allows you to run commands in a separate mount
namespace, since it's a privileged suid helper.

I have a build tool that prevents builds from messing with my system,
by making most of my rootfs read-only.

Currently I hit this mount point removal problem if I try to build two
different things at once.

1: http://git.gnome.org/browse/linux-user-chroot/