来自新贵的嵌套非特权 lxc 容器，其所有者可以停止

Question

在运行Ubuntu 14.04.5 LTS的主机中，我有一个名为ci的用户，该用户可以创建一个同样运行Ubuntu 14.04.5 LTS的启动非特权 lxc 容器。用户的 subid 范围为200000-231071。这样一个容器的配置文件是：

# Distribution configuration
lxc.include = /usr/share/lxc/config/ubuntu.common.conf
lxc.include = /usr/share/lxc/config/ubuntu.userns.conf
lxc.arch = x86_64

# Nested
lxc.mount.auto = cgroup
lxc.aa_profile = lxc-container-default-with-nesting

# Container specific configuration
lxc.id_map = u 0 200000 65536
lxc.id_map = u 100000 265536 65536
lxc.id_map = g 0 200000 65536
lxc.id_map = g 100000 265536 65536
lxc.rootfs = /home/ci/.local/share/lxc/ci/rootfs
lxc.utsname = ci

# Network configuration
lxc.network.type = veth
lxc.network.flags = up
lxc.network.link = lxcbr0
lxc.network.hwaddr = 00:16:3e:dd:f1:99

用户可以毫无问题地创建和启动非特权容器：

ci@host:~$ lxc-create -t download -n ci -- -d ubuntu -r trusty -a amd64
ci@host:~$ lxc-start -n ci -d
ci@host:~$ lxc-ls --fancy
    NAME  STATE    IPV4                 IPV6  AUTOSTART
    ---------------------------------------------------
    ci    RUNNING  10.0.3.75, 10.0.4.1  -     NO

在主机中，cgmanager正在运行：

root@host ~ # ps ax | grep cgmanager
    382 ?        Ss     0:01 /sbin/cgmanager --sigstop -m name=systemd

在非特权容器ci 中，cgproxy正在运行：

root@ci:~# ps ax | grep cgproxy
    288 ?        Ss     0:00 /sbin/cgproxy --sigstop

在unprivilaged容器CI，用户名为詹金斯与子编号范围100000-65535可以创建并启动里面unprivilaged容器，即unprivilaged嵌套容器，但并非没有一些技巧，它们是：

1. 在非特权容器ci 中以用户jenkins ssh 登录后，结果为：cat /proc/self/cgroup

   jenkins@ci:~$ cat /proc/self/cgroup
       12:hugetlb:/user/1012.user/11.session/lxc/ci
       11:net_prio:/user/1012.user/11.session/lxc/ci
       10:perf_event:/user/1012.user/11.session/lxc/ci
       9:net_cls:/user/1012.user/11.session/lxc/ci
       8:freezer:/user/1012.user/11.session/lxc/ci
       7:devices:/user/1012.user/11.session/lxc/ci
       6:memory:/user/1012.user/11.session/lxc/ci
       5:blkio:/user/1012.user/11.session/lxc/ci
       4:name=systemd:/user/1012.user/11.session/lxc/ci/user/1012.user/11.session/lxc/ci/user/107.user/c1.session
       3:cpuacct:/user/1012.user/11.session/lxc/ci
       2:cpu:/user/1012.user/11.session/lxc/ci
       1:cpuset:/user/1012.user/11.session/lxc/ci
   

2. 此时jenkins可以创建容器，但是不能启动：

   jenkins@ci:~$ lxc-create -t download -n test -- -d ubuntu -r trusty -a amd64
   jenkins@ci:~$ lxc-start -n test
       lxc_container: cgmanager.c: lxc_cgmanager_create: 301 call to cgmanager_create_sync failed: invalid request
       lxc_container: cgmanager.c: lxc_cgmanager_create: 303 Failed to create hugetlb:lxc/test
       lxc_container: cgmanager.c: cgm_create: 650 Error creating cgroup hugetlb:lxc/test
       lxc_container: start.c: lxc_spawn: 891 failed creating cgroups
       lxc_container: start.c: __lxc_start: 1121 failed to spawn 'test'
       lxc_container: lxc_start.c: main: 341 The container failed to start.
       lxc_container: lxc_start.c: main: 345 Additional information can be obtained by setting the --logfile and --logpriority options.
   

3. 我以 root 身份在容器中发出：

   restart systemd-logind
   

4. 现在作为容器中的jenkins用户，我注销并使用ssh再次登录。cgroup 已更改，现在我可以创建和运行容器：

   jenkins@ci:~$ cat /proc/self/cgroup
       12:hugetlb:/user/1012.user/11.session/lxc/ci/user/1012.user/11.session/lxc/ci/user/107.user/c1.session
       11:net_prio:/user/1012.user/11.session/lxc/ci/user/1012.user/11.session/lxc/ci/user/107.user/c1.session
       10:perf_event:/user/1012.user/11.session/lxc/ci/user/1012.user/11.session/lxc/ci/user/107.user/c1.session
       9:net_cls:/user/1012.user/11.session/lxc/ci/user/1012.user/11.session/lxc/ci/user/107.user/c1.session
       8:freezer:/user/1012.user/11.session/lxc/ci/user/1012.user/11.session/lxc/ci/user/107.user/c1.session
       7:devices:/user/1012.user/11.session/lxc/ci/user/1012.user/11.session/lxc/ci/user/107.user/c1.session
       6:memory:/user/1012.user/11.session/lxc/ci/user/1012.user/11.session/lxc/ci/user/107.user/c1.session
       5:blkio:/user/1012.user/11.session/lxc/ci/user/1012.user/11.session/lxc/ci/user/107.user/c1.session
       4:name=systemd:/user/1012.user/11.session/lxc/ci/user/1012.user/11.session/lxc/ci/user/107.user/c1.session
       3:cpuacct:/user/1012.user/11.session/lxc/ci/user/1012.user/11.session/lxc/ci/user/107.user/c1.session
       2:cpu:/user/1012.user/11.session/lxc/ci/user/1012.user/11.session/lxc/ci/user/107.user/c1.session
       1:cpuset:/user/1012.user/11.session/lxc/ci/user/1012.user/11.session/lxc/ci/user/107.user/c1.session
   jenkins@ci:~$ lxc-create -t download -n test -- -d ubuntu -r trusty -a amd64
   jenkins@ci:~$ lxc-start -n test -d
   jenkins@ci:~$ lxc-ls --fancy
       NAME     STATE    IPV4       IPV6  AUTOSTART
       --------------------------------------------
       test     RUNNING  10.0.4.64  -     NO
   

第一个问题：为什么我需要restart systemd-logind以及如何避免在能够创建嵌套的非特权容器之前以 root 用户身份输入它？

在容器ci 中，我创建了一个 init 配置文件（一个位于/etc/init/jenkins.conf的 upstart conf 文件）来以jenkins用户身份运行软件Jenkins：

description "jenkins"

start on filesystem and static-network-up
stop on runlevel [016]

env USER="jenkins"
env GROUP="jenkins"
env HOME="/var/lib/jenkins"
env JENKINS_LOG="/var/log/jenkins"
env JENKINS_ROOT="/usr/share/jenkins"
env JENKINS_RUN="/var/run/jenkins"
env JENKINS_PIDFILE="jenkins.pid"

pre-start script
    test -f $JENKINS_ROOT/jenkins.war || { stop ; exit 0; }
    mkdir $JENKINS_RUN > /dev/null 2>&1  || true
    chown -R $USER:$GROUP $JENKINS_RUN || true
    mkdir $JENKINS_LOG > /dev/null 2>&1  || true
    chown -R $USER:$GROUP $JENKINS_LOG || true
end script

script
    . /etc/default/jenkins
    # export XDG_SESSION_ID="/run/user/`id -u $USER`"
    export HOME
    export USER
    export GROUP
    exec daemon --name=jenkins --foreground --inherit --user=$USER:$GROUP --pidfile=$JENKINS_RUN/$JENKINS_PIDFILE --output=$JENKINS_LOG -- $JAVA $JAVA_ARGS -jar $JENKINS_WAR $JENKINS_ARGS
end script

post-start script
    while [ ! -f $JENKINS_RUN/$JENKINS_PIDFILE ]; do sleep 1; done
    PID=$(cat $JENKINS_RUN/$JENKINS_PIDFILE)
    cgm create all $USER
    cgm chown all $USER $(id -u $USER) $(id -g $USER)
    # this need to be run in the jenkins job script:
    # cgm movepid all $USER $$
end script

# vim: ft=upstart

在Jenkins进程为启动所谓的Jenkins' build发出的脚本中，如果我添加以下行：

cgm movepid all $USER $$

该脚本可以创建和启动非特权嵌套容器，即它的 cgroup：

+ cat /proc/self/cgroup
12:hugetlb:/user/1012.user/11.session/lxc/ci/jenkins
11:net_prio:/user/1012.user/11.session/lxc/ci/jenkins
10:perf_event:/user/1012.user/11.session/lxc/ci/jenkins
9:net_cls:/user/1012.user/11.session/lxc/ci/jenkins
8:freezer:/user/1012.user/11.session/lxc/ci/jenkins
7:devices:/user/1012.user/11.session/lxc/ci/jenkins
6:memory:/user/1012.user/11.session/lxc/ci/jenkins
5:blkio:/user/1012.user/11.session/lxc/ci/jenkins
4:name=systemd:/user/1012.user/11.session/lxc/ci/jenkins
3:cpuacct:/user/1012.user/11.session/lxc/ci/jenkins
2:cpu:/user/1012.user/11.session/lxc/ci/jenkins
1:cpuset:/user/1012.user/11.session/lxc/ci/jenkins

但是使用 ssh 登录的用户jenkins无法停止脚本创建的容器。以下永远不会完成：

jenkins@ci:~$ lxc-stop -n test

第二个问题：我怎样才能实现用户jenkins可以停止用户jenkins从上面的初始化脚本创建的任何容器？