$ lxc-attach -l DEBUG -n openjdk-xenial-amd64
lxc-attach: cgmanager.c: lxc_cgmanager_enter: 698 call to cgmanager_move_pid_abs_sync failed: invalid request
lxc-attach: cgmanager.c: cgm_attach: 1460 Failed to enter group /user.slice/user-1000.slice/session-c2.scope/lxc/openjdk-xenial-amd64/init.scope
lxc-attach: attach.c: lxc_attach: 909 error communicating with child process
/mnt ⌚ 16:35:05
$ lxc-attach -l DEBUG -o /tmp/attach -n openjdk-xenial-amd64
lxc-attach: cgmanager.c: lxc_cgmanager_enter: 698 call to cgmanager_move_pid_abs_sync failed: invalid request
lxc-attach: cgmanager.c: cgm_attach: 1460 Failed to enter group /user.slice/user-1000.slice/session-c2.scope/lxc/openjdk-xenial-amd64/init.scope
lxc-attach: attach.c: lxc_attach: 909 error communicating with child process
/mnt ⌚ 16:35:19
$ cat /tmp/attach
lxc-attach 1447439719.583 WARN lxc_confile - confile.c:config_pivotdir:1801 - lxc.pivotdir is ignored. It will soon become an error.
lxc-attach 1447439719.583 INFO lxc_confile - confile.c:config_idmap:1437 - read uid map: type u nsid 0 hostid 100000 range 65536
lxc-attach 1447439719.584 INFO lxc_confile - confile.c:config_idmap:1437 - read uid map: type g nsid 0 hostid 100000 range 65536
lxc-attach 1447439719.584 INFO lxc_seccomp - seccomp.c:parse_config_v2:324 - processing: .reject_force_umount # comment this to allow umount -f; not recommended.
lxc-attach 1447439719.584 INFO lxc_seccomp - seccomp.c:parse_config_v2:426 - Adding native rule for reject_force_umount action 0
lxc-attach 1447439719.584 INFO lxc_seccomp - seccomp.c:do_resolve_add_rule:216 - Setting seccomp rule to reject force umounts
lxc-attach 1447439719.584 INFO lxc_seccomp - seccomp.c:parse_config_v2:429 - Adding compat rule for reject_force_umount action 0
lxc-attach 1447439719.584 INFO lxc_seccomp - seccomp.c:do_resolve_add_rule:216 - Setting seccomp rule to reject force umounts
lxc-attach 1447439719.584 INFO lxc_seccomp - seccomp.c:parse_config_v2:324 - processing: .[all].
lxc-attach 1447439719.584 INFO lxc_seccomp - seccomp.c:parse_config_v2:324 - processing: .kexec_load errno 1.
lxc-attach 1447439719.584 INFO lxc_seccomp - seccomp.c:parse_config_v2:426 - Adding native rule for kexec_load action 327681
lxc-attach 1447439719.584 INFO lxc_seccomp - seccomp.c:parse_config_v2:429 - Adding compat rule for kexec_load action 327681
lxc-attach 1447439719.584 INFO lxc_seccomp - seccomp.c:parse_config_v2:324 - processing: .open_by_handle_at errno 1.
lxc-attach 1447439719.584 INFO lxc_seccomp - seccomp.c:parse_config_v2:426 - Adding native rule for open_by_handle_at action 327681
lxc-attach 1447439719.584 INFO lxc_seccomp - seccomp.c:parse_config_v2:429 - Adding compat rule for open_by_handle_at action 327681
lxc-attach 1447439719.584 INFO lxc_seccomp - seccomp.c:parse_config_v2:324 - processing: .init_module errno 1.
lxc-attach 1447439719.584 INFO lxc_seccomp - seccomp.c:parse_config_v2:426 - Adding native rule for init_module action 327681
lxc-attach 1447439719.584 INFO lxc_seccomp - seccomp.c:parse_config_v2:429 - Adding compat rule for init_module action 327681
lxc-attach 1447439719.584 INFO lxc_seccomp - seccomp.c:parse_config_v2:324 - processing: .finit_module errno 1.
lxc-attach 1447439719.584 INFO lxc_seccomp - seccomp.c:parse_config_v2:426 - Adding native rule for finit_module action 327681
lxc-attach 1447439719.584 INFO lxc_seccomp - seccomp.c:parse_config_v2:429 - Adding compat rule for finit_module action 327681
lxc-attach 1447439719.584 INFO lxc_seccomp - seccomp.c:parse_config_v2:324 - processing: .delete_module errno 1.
lxc-attach 1447439719.584 INFO lxc_seccomp - seccomp.c:parse_config_v2:426 - Adding native rule for delete_module action 327681
lxc-attach 1447439719.584 INFO lxc_seccomp - seccomp.c:parse_config_v2:429 - Adding compat rule for delete_module action 327681
lxc-attach 1447439719.584 INFO lxc_seccomp - seccomp.c:parse_config_v2:436 - Merging in the compat seccomp ctx into the main one
lxc-attach 1447439719.588 ERROR lxc_cgmanager - cgmanager.c:lxc_cgmanager_enter:698 - call to cgmanager_move_pid_abs_sync failed: invalid request
lxc-attach 1447439719.588 ERROR lxc_cgmanager - cgmanager.c:cgm_attach:1460 - Failed to enter group /user.slice/user-1000.slice/session-c2.scope/lxc/openjdk-xenial-amd64/init.scope
lxc-attach 1447439719.588 ERROR lxc_attach - attach.c:lxc_attach:909 - error communicating with child process