UPDATE: Docker 0.9.0 use libcontainer now, diverting from LXC see: Attaching process to Docker libcontainer container
I'm running an istance of elasticsearch:
docker run -d -p 9200:9200 -p 9300:9300 dockerfile/elasticsearch
Checking the process it show like the following:
$ docker ps --no-trunc
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
49fdccefe4c8c72750d8155bbddad3acd8f573bf13926dcaab53c38672a62f22 dockerfile/elasticsearch:latest /usr/share/elasticsearch/bin/elasticsearch java About an hour ago Up 8 minutes 0.0.0.0:9200->9200/tcp, 0.0.0.0:9300->9300/tcp pensive_morse
Now, when I try to attach the running container, I get stacked:
$ sudo docker attach 49fdccefe4c8c72750d8155bbddad3acd8f573bf13926dcaab53c38672a62f22
[sudo] password for lsoave:
the tty doesn't connect and the prompt is not back. Doing the same with lxc-attach works fine:
$ sudo lxc-attach -n 49fdccefe4c8c72750d8155bbddad3acd8f573bf13926dcaab53c38672a62f22
root@49fdccefe4c8:/# ps -ef
UID PID PPID C STIME TTY TIME CMD
root 1 0 49 20:37 ? 00:00:20 /usr/bin/java -Xms256m -Xmx1g -Xss256k -Djava.awt.headless=true -XX:+UseParNewGC -XX:+UseConcMa
root 88 0 0 20:38 ? 00:00:00 /bin/bash
root 92 88 0 20:38 ? 00:00:00 ps -ef
root@49fdccefe4c8:/#
Does anybody know what's wrong with docker attach ?
NB. dockerfile/elasticsearch ends with:
ENTRYPOINT ["/usr/share/elasticsearch/bin/elasticsearch"]
You're attaching to a container that is running elasticsearch which isn't an interactive command. You don't get a shell to type in because the container is not running a shell. The reason lxc-attach works is because it's giving you a default shell. Per man lxc-attach:
If no command is specified, the current default shell of the user running lxc-attach will be looked up inside the container and executed. This will fail if no such user exists inside the container or the container does not have a working nsswitch mechanism.
docker attach is behaving as expected.