live migrate container restore failed

[changuoqiang]

try live migrate container between hosts, rise error as below:

"Error: Failed container creation: Error transferring container data: migration restore failed
(00.000083) Warn (criu/log.c:203): The early log isn't empty
(00.084564) Warn (criu/cr-restore.c:1265): Set CLONE_PARENT | CLONE_NEWPID but it might cause restore problem,because not all kernels support such clone flags combinations!
(00.661074) 1: Error (criu/fsnotify.c:524): fsnotify: Unable to open /sys/fs/cgroup/unified/system.slice/cgroup.events: No such file or directory
(00.661096) 1: Error (criu/files.c:1196): Unable to open fd=6 id=0x28
(00.797136) Error (criu/cr-restore.c:2293): Restoring FAILED."

lxc info:
...
driver: lxc
driver_version: 3.0.4
kernel: Linux
kernel_architecture: x86_64
kernel_features: {}
kernel_version: 4.19.0-5-amd64
lxc_features: {}
project: ""
server: lxd
server_clustered: false
server_name: vmin
server_pid: 1477
server_version: 3.0.4
storage: zfs
storage_version: 0.7.13-1~bpo10+1

uname -a:
Linux vmin 4.19.0-5-amd64 #1 SMP Debian 4.19.37-5+deb10u2 (2019-08-08) x86_64 GNU/Linux

migration_restore_2019-08-14T11:14:44+08:00.log

[adrianreber]

The unified directory in the path of the error message indicates that this seems to be a system with cgroupv2. Not sure if CRIU already supports cgroupv2, I am not aware of any development in that direction.

[rst0git]

@adrianreber It seems like cgroup v2 support might be required for CRIU to work on Fedora 31 opencontainers/runc#2113

[adrianreber]

@rst0git Thanks for pointing that out. There is also a question to add CRIU support to crun containers/crun#71 also related to cgroup v2 (as far as I understand it).