日期：2015年5月20日

docker笔记（4）—— 如何进入一个正在运行的“docker container”？

“docker attach [container-id]”命令有时会hang住，执行Ctrl+C命令也不起作用：

[root@localhost ~]# docker attach a972e69ab444
^C^C^C^C^C^C^C^C^C^C

使用pstack命令查看函数调用栈：

[root@localhost ~]# pstack 29744
Thread 5 (Thread 0x7f9079bd8700 (LWP 29745)):
#0  runtime.futex () at /usr/lib/golang/src/pkg/runtime/sys_linux_amd64.s:269
#1  0x0000000000417717 in runtime.futexsleep () at /usr/lib/golang/src/pkg/runtime/os_linux.c:49
#2  0x0000000001161c58 in runtime.sched ()
#3  0x0000000000000000 in ?? ()
Thread 4 (Thread 0x7f90792d7700 (LWP 29746)):
#0  runtime.futex () at /usr/lib/golang/src/pkg/runtime/sys_linux_amd64.s:269
#1  0x0000000000417782 in runtime.futexsleep () at /usr/lib/golang/src/pkg/runtime/os_linux.c:55
#2  0x00007f907b830f60 in ?? ()
#3  0x0000000000000000 in ?? ()
Thread 3 (Thread 0x7f9078ad6700 (LWP 29747)):
#0  runtime.futex () at /usr/lib/golang/src/pkg/runtime/sys_linux_amd64.s:269
#1  0x0000000000417717 in runtime.futexsleep () at /usr/lib/golang/src/pkg/runtime/os_linux.c:49
#2  0x00000000011618a0 in text/template.zero ()
#3  0x0000000000000000 in ?? ()
Thread 2 (Thread 0x7f9073fff700 (LWP 29748)):
#0  runtime.futex () at /usr/lib/golang/src/pkg/runtime/sys_linux_amd64.s:269
#1  0x0000000000417717 in runtime.futexsleep () at /usr/lib/golang/src/pkg/runtime/os_linux.c:49
#2  0x000000c2080952f0 in ?? ()
#3  0x0000000000000000 in ?? ()
Thread 1 (Thread 0x7f907b9e1800 (LWP 29744)):
#0  runtime.epollwait () at /usr/lib/golang/src/pkg/runtime/sys_linux_amd64.s:385
#1  0x00000000004175dd in runtime.netpoll () at /usr/lib/golang/src/pkg/runtime/netpoll_epoll.c:78
#2  0x00007fff00000004 in ?? ()
#3  0x00007fff58720fd0 in ?? ()
#4  0xffffffff00000080 in ?? ()
#5  0x0000000000000000 in ?? ()

可以使用“docker exec -it [container-id] bash”命令进入正在运行的container：

[root@localhost ~]# docker exec -it a972e69ab444 bash
bash-4.1# ls
bin   dev  home  lib64  mnt  pam-1.1.1-17.el6.src.rpm  root      sbin     srv  tmp  var
boot  etc  lib   media  opt  proc                      rpmbuild  selinux  sys  usr
bash-4.1#

docker attach相当于复用了container当前使用的tty，因此在docker attach内执行exit，会导致正在运行的container退出。而docker exec会新建立一个tty，在docker exec中执行exit不会导致container退出。

 

参考资料：
（1）Docker – Enter Running Container with new TTY。

如何杀死一个已经detached的screen会话？

如果想杀死一个已经detached的screen会话，可以使用以下命令：

screen -X -S [session # you want to kill] quit

举例如下：

[root@localhost ~]# screen -ls
There are screens on:
        9975.pts-0.localhost    (Detached)
        4588.pts-3.localhost    (Detached)
2 Sockets in /var/run/screen/S-root.

[root@localhost ~]# screen -X -S 4588 quit
[root@localhost ~]# screen -ls
There is a screen on:
        9975.pts-0.localhost    (Detached)
1 Socket in /var/run/screen/S-root.

可以看到，4588会话已经没有了。

参考资料：
（1）Kill detached screen session。