docker - containerd-shim 如何创建无守护进程的容器？

Question

它has been stated那:

The shim allows for daemonless containers. It basically sits as the parent of the container's process to facilitate a few things.

It keeps the STDIO and other fds open for the container incase containerd and/or docker both die. If the shim was not running then the parent side of the pipes or the TTY master would be closed and the container would exit.

然而，从进程级别来看，containerd 似乎会产生 containerd-shim，所以如果 containerd 关闭，我希望 containerd-shim 也会关闭。

有人能解释一下如果 containerd/docker 停机，containerd-shim 是如何保持运行的吗？

$ ps fxa | grep dockerd -A 3

     PID TTY      STAT   TIME COMMAND
 43449 pts/2    S+     0:00              \_ grep dockerd -A 3
117536 ?        Ssl  163:36 /usr/bin/containerd
 93633 ?        Sl     1:01  \_ containerd-shim -namespace moby -workdir /var/lib/containerd/io.containerd.runtime.v1.linux/moby/8f75a1b32bb09611430ea55958b11a482b6c83ba2a75f7ca727301eb49a2770f -address /run/containerd/containerd.sock -containerd-binary /usr/bin/containerd -runtime-root /var/run/docker/runtime-runc

$ pstree -lpTs
systemd(1)─┬─VGAuthService(45146)
           ├─accounts-daemon(1053)
           ├─agetty(104696)
           ├─agetty(104707)
           ├─agetty(104716)
           ├─atd(993)
           ├─containerd(117536)─┬─containerd-shim(8394)─┬─bash(8969)
           │                    │                       └─sh(8420)─┬─sshd(8512)
           │                    │                                  └─tail(8514)
           │                    ├─containerd-shim(13170)───bash(13198)
           │                    ├─containerd-shim(13545)───portainer(13577)
           │                    ├─containerd-shim(14156)───mysqld(14184)

...
 ├─dockerd(42320)─┬─docker-proxy(42700)
           │                ├─docker-proxy(42713)
           │                ├─docker-proxy(42725)
           │                ├─docker-proxy(42736)
           │                └─docker-proxy(42749)

更新:根据接受的答案中提供的解释:

$ pstree -lpTs
systemd(1)─┬─VGAuthService(45146)
           ├─accounts-daemon(1053)
           ├─agetty(104696)
           ├─agetty(104707)
           ├─agetty(104716)
           ├─atd(993)
           ├─containerd(117536)─┬─containerd-shim(8394)─┬─bash(8969)
           │                    │                       └─sh(8420)─┬─sshd(8512)
           │                    │                                  └─tail(8514)
           │                    ├─containerd-shim(13170)───bash(13198)
           │                    ├─containerd-shim(13545)───portainer(13577)
           │                    ├─containerd-shim(14156)───mysqld(14184)

$ sudo kill -9 117536

$ pstree -lpTs
systemd(1)─┬─VGAuthService(45146)
           ├─accounts-daemon(1053)
           ├─agetty(104696)
           ├─agetty(104707)
           ├─agetty(104716)
           ├─atd(993)
           ├─containerd-shim(8394)─┬─bash(8969)
           │                       └─sh(8420)─┬─sshd(8512)
           │                                  └─tail(8514)
           ├─containerd-shim(13170)───bash(13198)
           ├─containerd-shim(13545)───portainer(13577)
           ├─containerd-shim(14156)───mysqld(14184)

Answer 1

However from a process level, it appears that containerd spawns containerd-shim, so if containerd is down I would expect containerd-shim to go down too.

子进程不会在其父进程死亡时自动死亡，它们只是重新父进程为 PID 1。 systemd接管作为父级和 containerd-shim继续运行。