It looks like something being executed is expecting your rootfs to be writeable, this could be something in lxc-execute or it could be /bin/bash itself (I wouldn't know without strace'ing both or looking at the source).
You could try adding the necessary /dev, /proc and /sys mounts, which may be enough to get it to run without error (add the following into your lxc config); http://pastebin.com/ZAcXn926 However any applications expecting a write-able FS are going to fail hard - for example, anything relying on /tmp, or /var/log, and numerous other places. You could in theory bind mount a ramfs to those locations, but it would be easier, in my opinion, to use a stacked file system. Here is an example of using overlayfs; http://askubuntu.com/questions/109413/how-do-i-use-overlayfs In short, you'd build your container rootfs and make whatever changes you wanted to make, once you're happy with it you then do; $ mount -t overlayfs -o lowerdir=/your.rootfs.here,upperdir=/your.discarded.changes.here overlayfs /your.new.mount.here lxc.rootfs = /your.new.mount.here There is also a previous discussion on this; http://osdir.com/ml/lxc-chroot-linux-containers/2011-07/msg00019.html https://www.redhat.com/archives/libvirt-users/2011-December/msg00024.html http://s3hh.wordpress.com/2011/09/22/sharing-mounts-with-a-container/ https://www.mail-archive.com/[email protected]/msg02190.html Hope this helps Cal On Thu, Dec 19, 2013 at 1:51 AM, Antonin Bas <[email protected]> wrote: > Hi, > > I guess that could do it. But I don't understand while it would not be > possible to have a read-only rootfs (i.e. is what I am seeing the > expected behaviour?). > What would the configuration look like if I decided to use overlayfs? > Is it easy to use with lxc-execute? Because I just want to run an > application, and I don't want to pay the overhead of > lxc-start-ephemeral. > > Thanks, > > Antonin > > 2013/12/18 Cal Leeming [Simplicity Media Ltd] > <[email protected]>: > > Would it not be better to use a stacked file system, such as overlayfs or > > aufs, then discard the changes? > > > > Cal > > > > > > On Thu, Dec 19, 2013 at 12:49 AM, Antonin Bas <[email protected]> > wrote: > >> > >> Hi, > >> > >> I am trying to run an application container with lxc-execute. I am > >> going to run "untrusted" student codes in this container and I want > >> the root file system to be shared with the host but read-only. I > >> thought this would be as easy as using the following configuration > >> file: > >> > >> # Container with new network withtout network devices > >> lxc.utsname = omega > >> lxc.network.type = empty > >> lxc.network.flags = up > >> > >> lxc.rootfs = /tmp/guest/rootfs > >> lxc.mount.entry=/ /tmp/guest/rootfs/ none ro,bind 0 0 > >> > >> However, when I run `sudo lxc-execute -n test -f grader.conf > >> --logpriority=DEBUG -- /bin/bash`, I get the following message: > >> > >> lxc-execute: Read-only file system - error unlinking > >> /usr/lib/x86_64-linux-gnu/lxc/dev/kmsg > >> > >> lxc-execute: failed to setup kmsg for 'test' > >> lxc-execute: Read-only file system - failed to create directory > >> '/usr/lib/x86_64-linux-gnu/lxc/lxc_putold' > >> > >> lxc-execute: Read-only file system - failed to create pivotdir > >> '/usr/lib/x86_64-linux-gnu/lxc/lxc_putold' > >> lxc-execute: failed to setup pivot root > >> lxc-execute: failed to set rootfs for 'test' > >> lxc-execute: failed to setup the container > >> lxc-execute: invalid sequence number 1. expected 2 > >> lxc-execute: failed to spawn 'test' > >> > >> > >> Is it possible to have some insight on what the problem is here? > >> I am using Ubuntu 13.10, and my lxc is the one from the official repo > >> (1.0.0.alpha1). > >> > >> Thanks you in advance for your help, > >> > >> Antonin > >> _______________________________________________ > >> lxc-users mailing list > >> [email protected] > >> http://lists.linuxcontainers.org/listinfo/lxc-users > > > > > > > > _______________________________________________ > > lxc-users mailing list > > [email protected] > > http://lists.linuxcontainers.org/listinfo/lxc-users > _______________________________________________ > lxc-users mailing list > [email protected] > http://lists.linuxcontainers.org/listinfo/lxc-users >
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