[Lxc-users] read only rootfs

[Michael H. Warfield]

On Tue, 2011-07-19 at 15:32 -0500, Serge E. Hallyn wrote: 
> Quoting Michael H. Warfield (mhw at WittsEnd.com):
> > On Tue, 2011-07-19 at 13:34 -0500, Serge E. Hallyn wrote: 
> > > Quoting C Anthony Risinger (anthony at xtfx.me):
> > > > there it would seem.  however, while i could *maybe* see the rootfs
> > > > being an unconditional slave, i would NOT want to see any lxc
> > > > default/enforcement preventing container -> host propagation on a
> > > > globally recursive scale.  im of the opinion that the implementor
> > > > should decide the best tactic ... especially in light of the fact the
> > > > one distro may not even have the same problems as say
> > > > ubutnu/fedora/etc because they keep mount points private by default.
> > 
> > > Good point.  (I don't see it on ubuntu either fwiw)  Perhaps there
> > > should be a toggle in the per-container config file?
> > 
> > Quick question.
> > 
> > Is there any way to test for these flags (SHARED, PRIVATE, SLAVE)?  I
> > don't see them showing up anywhere from mount, in proc mounts or
> > mountstats.  How do you check to see if they are set?

> /proc/self/mountinfo is supposed to tell that.  i.e. if you do
> a --make-shared on /mnt, it'll show 'shared' next to the /mnt entry.
> (I say 'is supposed to' bc --make-rslave just shows nothing, but
> maybe that's bc the way i did it it wasn't a slave to anything,
> so it was actually private)

Ok...  This may be telling us something.  What?

On the host Forest:

[root at forest ~]# cat /proc/self/mountinfo | grep export
50 22 8:18 / /export rw,relatime - ext4 /dev/sdb2 rw,barrier=1,data=ordered
[root at forest ~]# mount --make-shared /export
[root at forest ~]# cat /proc/self/mountinfo | grep export
50 22 8:18 / /export rw,relatime shared:1 - ext4 /dev/sdb2 rw,barrier=1,data=ordered
[root at forest ~]# mount --make-slave /export
[root at forest ~]# cat /proc/self/mountinfo | grep export
50 22 8:18 / /export rw,relatime - ext4 /dev/sdb2 rw,barrier=1,data=ordered
[root at forest ~]# mount --make-private /export
[root at forest ~]# cat /proc/self/mountinfo | grep export
50 22 8:18 / /export rw,relatime - ext4 /dev/sdb2 rw,barrier=1,data=ordered

So, shared looks like it worked and the other two didn't?  Does
something have to be done to enable them?

You say "maybe that's bc the way i did it it wasn't a slave to anything"
meaning we're missing a step.  What's the missing step.

On the guest Alcove (with your patch to add MS_REC | MS_SLAVE):

[root at alcove mhw]# cat /proc/self/mountinfo | grep devpts
107 105 0:10 /6 /dev/console rw,relatime - devpts devpts rw,mode=600,ptmxmode=666
108 105 0:10 /0 /dev/tty1 rw,relatime - devpts devpts rw,mode=600,ptmxmode=666
109 105 0:10 /1 /dev/tty2 rw,relatime - devpts devpts rw,mode=600,ptmxmode=666
110 105 0:10 /2 /dev/tty3 rw,relatime - devpts devpts rw,mode=600,ptmxmode=666
111 105 0:10 /3 /dev/tty4 rw,relatime - devpts devpts rw,mode=600,ptmxmode=666
112 105 0:10 /4 /dev/tty5 rw,relatime - devpts devpts rw,mode=600,ptmxmode=666
113 105 0:10 /5 /dev/tty6 rw,relatime - devpts devpts rw,mode=600,ptmxmode=666
56 105 0:44 / /dev/pts rw,relatime - devpts devpts rw,mode=600,ptmxmode=666
64 56 0:10 / /dev/pts rw,relatime - devpts devpts rw,mode=600,ptmxmode=666

I'd say that's not good.

Regards,
Mike
-- 
Michael H. Warfield (AI4NB) | (770) 985-6132 |  mhw at WittsEnd.com
   /\/\|=mhw=|\/\/          | (678) 463-0932 |  http://www.wittsend.com/mhw/
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