linux – “docker exec”命令的“-i”和“-t”选项的用途是什么？

说实话,我一直对docker exec -it …,docker exec -i …和docker exec -t …感到困惑,所以我决定做一个测试：

> docker exec -it …：

# docker exec -it 115c89122e72 bash
root@115c89122e72:/# ls
bin  boot  dev  etc  home  lib  lib64  media  mnt  opt  proc  root  run  sbin  srv  sys  tmp  usr  var

它正常工作.
> docker exec -i …：

# docker exec -i 115c89122e72 bash
^C

命令挂起,我必须使用Ctl c来中断它.
> docker exec -t …：

# docker exec -t 115c89122e72 bash
root@115c89122e72:/# ls
^C

它成功进入容器,但在执行第一个命令时挂起.

所以似乎没有必要使用docker exec -i …和docker exec -t …命令.任何人都可以详细说明为什么docker exec命令存在-i和-t选项？

解决方法:

-i, – interactive使STDIN保持打开即使没有附加,如果你想输入任何命令,你需要它.

-t,–tty分配一个伪TTY,一个连接用户的“终端”与stdin和stdout的pseudo terminal. (见container/container.go)

如果你做回声,只需要-t.
但是对于输入输入的交互式会话,您需要-i.

由于-i保持stdin打开,因此它也用于将输入管道输送到分离的docker容器.即使使用-d(分离)也可以.
见“When would I use --interactive without --tty in a Docker container?”：

$echo hello | docker run -i busyBox cat
  hello

-i keeps STDIN open even if not attached, what is the status of STDOUT in this case?

对于docker exec来说,它是由docker run设置的.

但是,关于docker exec,目前存在一个问题(issue 8755: Docker tty is not a tty with docker exec

unfortunately your discovery only amounts to a difference between the behavIoUr of tty in centos6 vs ubuntu:14.04. There is still not a functional tty inside the exec – just do ls -la /proc/self/fd/0 and see that it’s a broken link pointing to a pts which doesn’t exist.

the actual bug we’re dealing with is that certain standard libraries assume that the symlinks in /proc/self/fds/ must be valid symlinks

The problem is that the tty is created outside on the host and there is no reference to it in the container like how /dev/console is setup in the primary container.
One options to fix this would be allocate and bind mount the devpts from the host in to the containers.

注(2017年第4季度)：this should been fixed by now (docker 17.06-ce).
见PR 33007.

PR现在允许(从17.06开始)：

zacharys-pro:dev razic$docker run --rm -t -d ubuntu bash
83c292c8e2d13d1b1a8b34680f3fb95c2b2b3fef71d4ce2b6e12c954ae50965a

zacharys-pro:dev razic$docker ps
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
83c292c8e2d1        ubuntu              "bash"              2 seconds ago       Up 1 second                             xenodochial_bardeen

zacharys-pro:dev razic$docker exec -ti xenodochial_bardeen tty
/dev/pts/1

(在17.06之前,tty回来了“不是tty”)