[CRIU] [lxc-devel] LXC live migrate

[Serge Hallyn]

Yup, I won't have time to work on this until cgmanager is in better
shape at least, but I hope someone else has some time.  I'd love for
criu folks to get api feedback as early as possible.

Quoting Ranjib Dey (dey.ranjib at gmail.com):
> hi all,
> 
> now that criu supports plugin[1], has any one tried revisiting this? we
> should be able to address most of the issues encountered in this thread,
> 
> 
> [1] http://criu.org/Plugins
> 
> 
> On Wed, Nov 27, 2013 at 3:51 AM, Pavel Emelyanov <xemul at parallels.com>wrote:
> 
> > On 11/27/2013 01:58 PM, Daniel Lezcano wrote:
> > > On 11/27/2013 09:54 AM, Pavel Emelyanov wrote:
> > >> On 11/27/2013 06:19 AM, Qiang Huang wrote:
> > >>> On 2013/11/27 0:19, Marian Marinov wrote:
> > >>>> On my test setup it works for processes like apache, dovecot and
> > mysql.
> > >>>>
> > >>>> However it does not work with containers:
> > >>>>
> > >>>> root at s321:~# criu dump -D deb1 -t 19332 --file-locks
> > >>>> (00.004962) Error (namespaces.c:155): Can't dump nested pid namespace
> > for 28352
> > >>>> (00.004985) Error (namespaces.c:321): Can't make pidns id
> > >>>> (00.005327) Error (cr-dump.c:1811): Dumping FAILED.
> > >>>> root at s321:~#
> > >>>> When I try to dump the init process(which I believe I should not do),
> > here is what I see:
> > >>>>     http://pastebin.com/DFC0ADpp
> > >>>>
> > >>>> (00.291294) Error (tty.c:222): tty: Unexpected format on path
> > /dev/tty1
> > >>>> (00.291315) Error (cr-dump.c:1491): Dump files (pid: 29702) failed
> > with -1
> > >>>> (00.291892) Error (cr-dump.c:1811): Dumping FAILED.
> > >>>>
> > >>>> This is my setup:
> > >>>> 19332 ?        Ss     0:00 lxc-start -n deb1 -d
> > >>>> 28352 ?        Ss     0:00  \_ init [3]
> > >>>> 28393 ?        Ss     0:00      \_ /usr/sbin/apache2 -k start
> > >>>> 28419 ?        S      0:00      |   \_ /usr/sbin/apache2 -k start
> > >>>> 28422 ?        Sl     0:00      |   \_ /usr/sbin/apache2 -k start
> > >>>> 28423 ?        Sl     0:00      |   \_ /usr/sbin/apache2 -k start
> > >>>> 28489 ?        S      0:00      \_ /bin/sh /usr/bin/mysqld_safe
> > >>>> 28620 ?        Sl     0:00      |   \_ /usr/sbin/mysqld
> > --basedir=/usr --datadir=/var/lib/mysql --user=mysql
> > >>>> --pid-file=/var/run/mysqld/mysqld.pid
> > --socket=/var/run/mysqld/mysqld.sock --port
> > >>>> 28621 ?        S      0:00      |   \_ logger -t mysqld -p
> > daemon.error
> > >>>> 28598 ?        Ss     0:00      \_ /usr/sbin/sshd
> > >>>> 29702 pts/0    Ss+    0:00      \_ /sbin/getty 38400 tty1 linux
> > >>>>
> > >>>> I rebooted the container without getty on tty1 and then I got this:
> > >>>>
> > >>>> (00.260757) Error (mount.c:255): 86:/dev/tty4 doesn't have a proper
> > root mount
> > >> This is the reason. That's container's console which is a bind mounted
> > tty from
> > >> the host. And since this is an external connection, CRIU doesn't dump
> > one.
> > >>
> > >> There are two ways to resolve this. The first is disable container's
> > console. It's
> > >> fast, but ugly. The second way is supporting one, but it would require
> > criu hacking.
> > >> We should detect, that this is an external tty, decide, that we're OK
> > to disconnect
> > >> it after dump and on restore -- connect it back.
> > >
> > > The third one would be to implement lxc-checkpoint and lxc-restart
> > > (which are empty) to invoke CRUI. Then from there you can dump the
> > > container's configuration and restart with.
> >
> > Yes, it's also possible and probably easier. But as far as the console is
> > concerned,
> > some patching on the criu code will still be needed.
> >
> > Thanks,
> > Pavel
> >
> >
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