Re: [PATCH v2] sys-tools: Enhance unshare command to support the switching of namespaces

[Neil Horman <nhorman@tuxdriver.com>]

On Fri, Dec 28, 2012 at 01:54:45PM +0100, Ángel González wrote:
> On 20/12/12 19:22, Neil Horman wrote:
> >  		case 'm':
> > -			unshare_flags |= CLONE_NEWNS;
> > +			ns = "mount";
> > +			if (!optarg)
> > +				unshare_flags |= CLONE_NEWNS;
> >  			break;
> 
> Is this right? I don't have a /proc/<task>/ns/mount locally nor is it
> documented in
> http://git.kernel.org/?p=docs/man-pages/man-pages.git;a=blob;f=man5/proc.5
> 
> However looking at
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=blob;f=fs/proc/namespaces.c
> there is a reference to mntns_operations, which is defined in
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=blob;f=fs/proc/namespaces.c
> 
> but seems to be called "mnt", not "mount"
> 
Shoot, I thought Biederman was going to call it mount, not mnt, I'll fix that
shortly.

> There are also pid and user namespaces there, but support for those are
> better handled in a different patch IMHO.
> 
I'm not really sure what you mean by a different patch here.  Why would I add
support for setns for other pid/uts namespaces in a different patch?

> 
> > +				sprintf(path, "/proc/%d/ns/%s", (int)pid, ns); 
> > +				ns_pids[nscount] = open(path, O_RDONLY);
> > +				if (ns_pids[nscount] < 0)
> > +					err(EXIT_FAILURE, _("could not open %s"), path);
> > +				nscount++;
> 
> What about err(EXIT_FAILURE, _("The kernel doesn't seem to support %s
> migrations: could not open %s"), ns, path); ?
> 
Sure, I can do that.

> Mention in the man page the kernel version from which each namespace can
> be migrated.
> 
Yeah, ok
Neil

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