我在其中一台服务器上使用 Docker 和 docker-mailserver。将一些服务从旧版 Debian Jessie 服务器迁移到 Ubuntu 16.04 LTS 服务器后出现了非常奇怪的问题。服务器参数：
遗产：
someuser@legacyserver:~$ uname -r
3.16.0-4-amd64
someuser@legacyserver:~$ dpkg -l | grep systemd
...215-17+deb8u7...
someuser@legacyserver:~$ cat /proc/cmdline
root=ZFS=rpool/ROOT/debian-1 ro boot=zfs quiet
新服务器：
someuser@newserver:~$ uname -r
4.4.0-21-generic
someuser@newserver:~$ dpkg -l | grep systemd
...229-4ubuntu4...
someuser@newserver:~$ cat /proc/cmdline
root=ZFS=rpool/ROOT/debian-1 apparmor=0 ro
我在 systemd-nspawn Debian Jessie 容器中的 docker 上运行 docker-mailserver。我遇到的第一个问题是新 systemd 上的只读 cgroups，这解决了该问题：
mount | grep cgroup | tail -n +2 | while read line
do
umount -l $(echo $line | cut -f3 -d" ")
mount -t $(echo $line | cut -f5 -d" ") -o $(echo $line | cut -f6 - d" " | rev | cut -c2- | rev | cut -c2- | sed -e 's/ro,/rw,/g') $(echo $line | cut -f1 -d" ") $(echo $line | cut -f3 -d" ")
done
它只是以读写方式重新挂载所有 cgroup（不能使用 -o remount）。
但是，首先我要 rsh 到 systemd-nspawn 容器，然后从容器到 docker 容器。例如，当我重新加载 Postfix（或执行其他任何操作）时... 两个容器（嵌套的 docker 和 systemd-nspawn）都安静地退出... 就像这样：
someuser@newserver:~# rsh somesystemdcontainer
Last login: Sun Jun 25 15:27:24 CEST 2017 from host0 on pts/0
Linux somesystemdcontainer 4.4.0-21-generic #37-Ubuntu SMP Mon Apr 18 18:33:37 UTC 2016 x86_64
The programs included with the Debian GNU/Linux system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.
Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.
root@somesystemdcontainer:~# rsh mail #this is the docker container
Last login: Sun Jun 25 13:28:18 UTC 2017 from 172.18.0.1 on pts/0
Welcome to Ubuntu 14.04.5 LTS (GNU/Linux 4.4.0-21-generic x86_64)
* Documentation: https://help.ubuntu.com/
root@mail:~# service postfix reload
* Reloading Postfix configuration...
...done.
root@mail:~# rlogin: connection closed.
root@newserver:~#
DMESG 中没有任何内容，内核日志中没有任何内容，任何地方都没有任何内容。正如您在 cmdline 中看到的那样，在内核和用户空间端禁用 apparmor 都无济于事……尝试停止 systemd-nspawn 容器后：
jun 25 15:32:26 newserver kernel: INFO: task sh:10962 blocked for more than 120 seconds.
jun 25 15:32:26 newserver kernel: Tainted: P O 4.4.0-21-generic #37-Ubuntu
jun 25 15:32:26 newserver kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
jun 25 15:32:26 newserver kernel: sh D ffff88009ebb3c88 0 10962 9487 0x00000102
jun 25 15:32:26 newserver kernel: ffff88009ebb3c88 0000000000000000 ffff88040dab3700 ffff8800c9450dc0
jun 25 15:32:26 newserver kernel: ffff88009ebb4000 ffff8800c08008b0 0000000000000001 ffff8800c9450dc0
jun 25 15:32:26 newserver kernel: ffff8800c2fe87e8 ffff88009ebb3ca0 ffffffff818203f5 ffff8800c9450dc0
jun 25 15:32:26 newserver kernel: Call Trace:
jun 25 15:32:26 newserver kernel: [<ffffffff818203f5>] schedule+0x35/0x80
jun 25 15:32:26 newserver kernel: [<ffffffff8111fd4f>] zap_pid_ns_processes+0x13f/0x1a0
jun 25 15:32:26 newserver kernel: [<ffffffff8108432b>] do_exit+0xa6b/0xae0
jun 25 15:32:26 newserver kernel: [<ffffffff8122383f>] ? dput+0x2f/0x220
jun 25 15:32:26 newserver kernel: [<ffffffff81084423>] do_group_exit+0x43/0xb0
jun 25 15:32:26 newserver kernel: [<ffffffff810904d2>] get_signal+0x292/0x600
jun 25 15:32:26 newserver kernel: [<ffffffff8102e517>] do_signal+0x37/0x6f0
jun 25 15:32:26 newserver kernel: [<ffffffff8181fd36>] ? __schedule+0x386/0xa10
jun 25 15:32:26 newserver kernel: [<ffffffff81083526>] ? do_wait+0x116/0x240
jun 25 15:32:26 newserver kernel: [<ffffffff8100320c>] exit_to_usermode_loop+0x8c/0xd0
jun 25 15:32:26 newserver kernel: [<ffffffff81003c5e>] syscall_return_slowpath+0x4e/0x60
jun 25 15:32:26 newserver kernel: [<ffffffff81824650>] int_ret_from_sys_call+0x25/0x8f
jun 25 15:32:53 newserver systemd[1]: [email protected]: State 'stop-sigterm' timed out. Killing.
jun 25 15:32:53 newserver systemd-nspawn[9483]: somesystemdcontainer login:
jun 25 15:32:53 newserver systemd[1]: [email protected]: Main process exited, code=killed, status=9/KILL
jun 25 15:32:53 newserver systemd[1]: Stopped Container somesystemdcontainer.
jun 25 15:32:53 newserver systemd[1]: [email protected]: Unit entered failed state.
jun 25 15:32:53 newserver systemd[1]: [email protected]: Failed with result 'signal'.
jun 25 15:32:53 newserver systemd[1]: Stopped Container somesystemdcontainer.
jun 25 15:32:53 newserver systemd-machined[2890]: Machine somesystemdcontainer terminated.
10962 是... DOCKER 容器内的 bash，它在 pstree 上“跳出命名空间”...
我现在应该怎么做？