[lxc-users] Can we run a container from ramfs?

[Stéphane Graber]

Hi,

There are also two scripts I'm using for the Android port that can be useful:
http://bazaar.launchpad.net/~ubuntu-lxc/lxc/android-build-scripts/files

On Android (ramfs), I'd start a container by using that run-lxc wrapper
which will then source prepare.sh which will in turn prepare a "fake"
environment that we can pivot_root to.

The trick is basically to create a new directory on a non-ramfs mount
point, then bind-mount all the bits you need, then chroot to that
directory and run LXC from it.

On Sat, Dec 14, 2013 at 01:08:09PM +0000, Cal Leeming [Simplicity Media Ltd] wrote:
> Seems there's a few discussions about ramfs and pivot [1], and apparently
> it's unsupported [2].
> 
> As a workaround you could try to place overlayfs on top of your ramfs [3],
> you'd then place both your lower and upper dir on ramfs - YMMV.
> 
> Others may chime in with a different workaround, as I'm not sure if this
> would be the best way.
> 
> Hope this helps
> 
> Cal
> 
> [1] https://www.google.co.uk/search?q=pivot_root+tmpfs
> [2] http://www.slax.org/blog/18438-initramfs-pivot-root-solution.html
> [3] http://askubuntu.com/questions/109413/how-do-i-use-overlayfs
> 
> 
> 
> 
> 
> On Sat, Dec 14, 2013 at 7:18 AM, Qiang Huang <h.huangqiang at huawei.com>wrote:
> 
> > Hi guys,
> >
> > I was trying to run a container from ramfs, to root filesystem is
> > rootfs(ramfs), the template is put onto a mounted disk whose fs is
> > ext3, and I got this error(I'll skip my config and version and os
> > and so on, I think they are not keys):
> > ...
> > lxc-start 1386999058.944 DEBUG    lxc_conf - mountpoint for old rootfs is
> > '/usr/local/lib/lxc/rootfs/lxc_putold'
> > lxc-start 1386999058.944 ERROR    lxc_conf - Invalid argument - pivot_root
> > syscall failed
> > lxc-start 1386999058.944 ERROR    lxc_conf - failed to setup pivot root
> > lxc-start 1386999058.944 ERROR    lxc_conf - failed to set rootfs for
> > 'hq91'
> > lxc-start 1386999058.944 ERROR    lxc_start - failed to setup the container
> > lxc-start 1386999058.944 ERROR    lxc_sync - invalid sequence number 1.
> > expected 2
> > lxc-start 1386999058.952 ERROR    lxc_start - failed to spawn 'hq91'
> >
> > I dug and figured out that pivot_root has some limitations with ramfs,
> > So is it possible to run a container from ramfs? And how can we do that?
> >
> > Any comments are appreciated.
> >
> >
> >
> > _______________________________________________
> > lxc-users mailing list
> > lxc-users at lists.linuxcontainers.org
> > http://lists.linuxcontainers.org/listinfo/lxc-users
> >

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-- 
Stéphane Graber
Ubuntu developer
http://www.ubuntu.com
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