[lxc-devel] [RFC] rootfs pinning

Serge Hallyn serge.hallyn at ubuntu.com
Wed Sep 25 13:46:12 UTC 2013


Quoting Michael H. Warfield (mhw at WittsEnd.com):
> On Tue, 2013-09-24 at 17:19 -0500, Serge Hallyn wrote: 
> > Quoting Michael H. Warfield (mhw at WittsEnd.com):
> > > No.  There's a change there, all right, and thank you for reminding me
> > > of that, but (afaik) it's NOT in the kernel itself.  It's a mount
> > > option.  It's that bloody MS_SHARED option and, to a lessor extent,
> > 
> > There *is* a kernel change which dhansen was telling me about last
> > week - I believe it's commit 4ed5e82fe77f4147cf386327c9a63a2dd7eff518.
> > It allows you to now do
> 
> > 	sudo mount -t tmpfs tmpfs /tmp/a
> > 	sudo mount -o bind,remount,ro /tmp/a /tmp/b
> 
> > In the past you had to first create a bind mount before you could
> > mark it readonly, i.e.
> 
> > 	sudo mount -t tmpfs tmpfs /tmp/a
> > 	sudo mount --bind /tmp/a /tmp/b
> > 	sudo mount -o remount,ro /tmp/b /tmp/b
> 
> Interesting point.  Very interesting.  I guess I can dig into it an look
> it up but, what rev did that commit show up in and does it impact the
> way we handle things dependent on kernel version?

Oh, it's older than I thought.  Came between 3.2 and 3.3.  But no, it
makes some things easier but shouldn't affect anything we do negatively.

-serge




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