$cat run.sh
sleep 60&
ps
echo Goodbye!!!
$docker run --rm -v $(pwd)/run.sh:/run.sh ubuntu:16.04 bash /run.sh
PID TTY TIME CMD
1 ? 00:00:00 bash
5 ? 00:00:00 sleep
6 ? 00:00:00 ps
Goodbye!!!
这将启动一个Docker容器,其中bash为PID1.然后fork /执行一个睡眠进程,然后bash退出.当Docker容器死亡时,睡眠过程也会死亡.
我的问题是：睡眠过程被杀死的机制是什么？我尝试在一个子进程中捕获SIGTERM,似乎没有被绊倒.我的推测是,当关闭集群正在使用的cgroup时,Docker或者Linux内核会发送SIGKILL,但是我没有找到任何文档来澄清这一点.
编辑最接近我的解释是从baseimage-docker的以下引用：
If your init process is your app,then it’ll probably only shut down itself,not all the other processes in the container. The kernel will then forcefully kill those other processes,not giving them a chance to gracefully shut down,potentially resulting in file corruption,stale temporary files,etc. You really want to shut down all your processes gracefully.
因此,至少根据这一点,这意味着当容器退出时,内核将向所有剩余的进程发送一个SIGKILL.但是我仍然希望清楚它如何决定这样做(即,它是cgroups的一个特征？),理想的是一个更权威的来源将是不错的.
解决方法
CLONE_NEWPID (since Linux 2.6.24)
The first process created in a new namespace (i.e.,the process
created using the CLONE_NEWPID flag) has the PID 1,and is the
“init” process for the namespace. Children that are orphaned
within the namespace will be reparented to this process rather than
init(8). Unlike the traditional init process,the “init” process of a
PID namespace can terminate,and if it does,all of the processes in
the namespace are terminated.
不幸的是,命名空间中的进程究竟如何终止,但也许是因为与正常进程退出不同,进程表中没有任何条目.无论如何,似乎很清楚：
内核本身正在杀死其他进程>他们没有以一种允许他们有机会进行清理的方式被杀死,使它(几乎)与SIGKILL相同
