Following two sets of patches is an early attempt to integrate LXC and
USER-CR.
Overview:
Have USER-CR export the core checkpoint and restart functionality into a
library (/lib/libcheckpoint.a and <usercr.h>) and have LXC link with this
library.
TODO:
1. For now, libcheckpoint.a implements only the restart functionality
and so only lxc_restart command is implemented. Implementing the
checkpoint functionality and lxc_checkpoint command can be done
similarly and is hopefully easier than the restart functionality.
2. The restart() functionality in user-cr makes extensive use of global
variables and debug code. The API must be extended to properly
include these variables/debug code in the API.
Similarly, the 'struct restart_args' may need to be sanitized for
use in a formal API.
3. lxc_restart command restarts entire containers only (specifically
it simulates the --pidns --pids --mount-pty arguments to
/bin/restart).
4. Link lxc_restart and lxc_checkpoint with the shared library
liblxc.so (currently links statically)
5. ...
STATUS:
I was able to checkpoint/restart a simple '/bin/sleep 1000' LXC
container, except for a cgroup naming issue after restart (see below).
STEPS:
1. [USER-CR] Build/install /lib/libcheckpoint.a, /usr/include/usercr.h
1.1 Apply the attached [user-cr] patches to the user-cr git tree
(I tested with following commit as base)
commit 67cfee9329670ab28eb1a52e94745252b614718f
Author: Oren Laadan <or...@cs.columbia.edu>
Date: Mon Feb 22 18:00:06 2010 -0500
1.2 Build/install user-cr binaries/libraries/includes
$ make all
$ make install
This should install /lib/libcheckpoint.a and /usr/include/usercr.h
2. [LXC] Build lxc_restart using USER-CR API (usercr.h, libcheckpoint.a)
2.1 Apply attached [lxc] patches to Daniel Lezcano's lxc.git tree (0.6.5)
2.2 Build lxc_restart (this uses static linking for now)
$ make -f Makefile2 lxc_restart
3. Create and checkpoint a simple LXC container
$ lxc-execute --name foo --rcfile lxc-macvlan.conf -- /bin/sleep 1000
$ lxc-freeze --name foo
TODO:
lxc_checkpoint --name foo should checkpoint the container,
For now, use "lxc-ps --name foo" to find pid of lxc-init and
checkpoint using:
$ /bin/checkpoint --output=/tmp/sleep.ckpt <pid-of-lxc-init>
$ lxc-unfreeze --name foo
$ lxc-stop --name foo
4. Restart a checkpointed LXC container
$ ./lxc_restart --statefile /tmp/sleep.ckpt --name bar
# Test some common lxc commands after restart
$ lxc-ps --name "bar/1"
CONTAINER PID TTY TIME CMD
bar/1 8511 ? 00:00:00 lxc-init
bar/1 8512 ? 00:00:00 sleep
$ lxc-freeze --name "bar/1"
$ grep State /proc/8511/status
State: D (disk sleep)
$ grep State /proc/8512/status
State: D (disk sleep)
NOTE: For some reason, the container name after restart is "bar/1"
instead of "bar". Due to this, when the lxc_restart is
exiting, I get a "-EBUSY - failed to remove "/cgroup/bar"
error. I need to fix this still.
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