[CRIU] LXC checkpoint/restore HOWTO using upstream tools

[Tycho Andersen]

Hi Krystof,

On Tue, Sep 23, 2014 at 08:29:30PM +0000, Zmudzinski, Krystof C wrote:
> In fact, the last time everything seems to be working is just before ldconfig -v.  I can start, attach and stop.  But as soon as I execute ldconfig, lxc-start says that lxc-start: Executing '/sbin/init' with no configuration file may crash the host and lxc-info says that the container doesn't exist.  Reverting ldconfig doesn't change anything.

Yes, that's (presumably) because it is looking at a new lxcpath
(/usr/local/var/lib/lxc vs. /var/lib/lxc) when you're using the right
liblxc.so. You have a few options here:

1. just re-create your container under /usr/local (or just copy it)
2. change your lxcpath to point to the old container
3. re-compile with --prefix /usr so that it installs over the packaged
   lxc (I don't recommend this :)

You can verify which lxcpath things are pointed to via:

sudo lxc-config lxc.lxcpath

Tycho

> 
> Krystof
> 
> -----Original Message-----
> From: Tycho Andersen [mailto:tycho.andersen at canonical.com] 
> Sent: Monday, September 22, 2014 4:32 PM
> To: Zmudzinski, Krystof C
> Cc: CRIU
> Subject: Re: [CRIU] LXC checkpoint/restore HOWTO using upstream tools
> 
> Hi Krystof,
> 
> On Mon, Sep 22, 2014 at 09:44:24PM +0000, Zmudzinski, Krystof C wrote:
> > Tycho,
> > 
> > After following the instructions on http://criu.org/LXC, I wanted to install the latest source for LXC and make some changes.  How can I build and install the new lxc-* so I overwrite what sudo apt-get install lxc did?  Right now, following the instructions on http://bazaar.launchpad.net/~tycho-s/+junk/snapshot-instructions/view/head:/README everything gets installed in different directories and things stop working completely.  
> 
> What's the output of ldd `which lxc-checkpoint`? Did you do the bit in there about modifying the ld.so.conf?
> 
> Tycho
> 
> > I always get this error when I try to start a container:
> >  >       lxc-start 1410804731.572 ERROR    lxc_cgfs - Could not find writable mount point for cgroup hierarchy 3 while trying to create cgroup.
> > >       lxc-start 1410804731.572 ERROR    lxc_start - failed creating cgroups
> > >       lxc-start 1410804731.599 ERROR    lxc_start - failed to spawn 'u1'
> > >       lxc-start 1410804736.604 ERROR    lxc_start_ui - The container failed to start.
> > 
> > Krystof
> > 
> > -----Original Message-----
> > From: Tycho Andersen [mailto:tycho.andersen at canonical.com]
> > Sent: Friday, September 19, 2014 10:53 AM
> > To: Zmudzinski, Krystof C
> > Cc: CRIU
> > Subject: Re: [CRIU] LXC checkpoint/restore HOWTO using upstream tools
> > 
> > Hi Krystof,
> > 
> > On Fri, Sep 19, 2014 at 05:18:32PM +0000, Zmudzinski, Krystof C wrote:
> > > lxc-checkpoint fails.  I did a fresh install of ubuntu 14.04 and followed your instructions.  I also installed criu-1.3.1.  
> > > 
> > > From dump.log:
> > > (00.377632) Error (mount.c:805): fusectl isn't empty: 8388625
> > 
> > Ah, that is a good point. Right now CRIU doesn't support dumping any fuse filesystems (i.e., /sys/fs/fuse/connections needs to be empty). I guess stock desktop ubuntu might have some of these enabled. You can either uninstall any fuse modules or try ubuntu-server (or better yet, the cloud images) as a host.
> > 
> > I guess maybe we should have lxc-checkpoint look for some of this stuff too, vs. just config.
> > 
> > > The container does contain ttys and console:
> > > 5784 ?        Ss     0:00              \_ lxc-start -n cn_01
> > >  5804 ?        Ss     0:01                  \_ /sbin/init
> > >  5998 ?        S      0:00                      \_ upstart-udev-bridge --daemon
> > >  6009 ?        Ss     0:00                      \_ /lib/systemd/systemd-udevd --daemon
> > >  6077 ?        S      0:00                      \_ upstart-socket-bridge --daemon
> > >  6079 ?        Ssl    0:00                      \_ rsyslogd
> > >  6085 ?        S      0:00                      \_ upstart-file-bridge --daemon
> > >  6117 ?        Ss     0:00                      \_ dhclient -1 -v -pf /run/dhclient.eth0.pid -lf /var/lib/dhcp/dhclient.eth0.leases eth0
> > >  6202 ?        Ss     0:00                      \_ cron
> > >  6207 ?        Ss     0:00                      \_ /usr/sbin/sshd -D
> > >  7083 ?        Ss     0:00                      \_ /sbin/getty -8 38400 tty2
> > >  7084 ?        Ss     0:00                      \_ /sbin/getty -8 38400 tty4
> > >  7085 ?        Ss     0:00                      \_ /sbin/getty -8 38400 tty3
> > >  7086 ?        Ss     0:00                      \_ /sbin/getty -8 38400 console
> > >  7087 ?        Ss     0:00                      \_ /sbin/getty -8 38400 tty1
> > > 
> > > I don't think it's enough to just add this to the config file:
> > > # hax for criu
> > > lxc.console = none
> > > lxc.tty = 0
> > > lxc.cgroup.devices.deny = c 5:1 rwm
> > > 
> > > because there is this at the very beginning:
> > > # Common configuration
> > > lxc.include = /usr/share/lxc/config/ubuntu.common.conf
> > 
> > Why is that a problem? The later values in the config override any earlier ones. lxc-checkpoint will also complain and refuse to dump a container that doesn't have the right configuration bits set, so if it tried to dump, that means it thinks the config is valid.
> > 
> > Tycho