Issue with docker-py in executing /bin/bash - docker

Question

I have a docker image built from ubuntu base image with few softwares installed.
i have a startup script, as below
#!/bin/bash
/usr/local/sbin/process1 -d
/usr/local/sbin/process2 -d
/bin/bash
Now I use docker-py python library to start multiple of these containers from a python file.
c = docker.Client(base_url='unix://var/run/docker.sock',
version='1.12',
timeout=10)
container = c.create_container("p12", command="/startup.sh", hostname=None, user=None,
detach=False, stdin_open=False, tty=False, mem_limit=0,
ports=None, environment=None, dns=None, volumes=None,
volumes_from=None, network_disabled=False, name=None,
entrypoint=None, cpu_shares=None, working_dir=None,
memswap_limit=0)
c.start(container, binds=None, port_bindings=None, lxc_conf=None,
publish_all_ports=False, links=None, privileged=False,
dns=None, dns_search=None, volumes_from=None, network_mode=None,
restart_policy=None, cap_add=None, cap_drop=None)
This worked fine and I can start multiple (say 3) when I tested this on a Ubuntu Desktop, Ubuntu 14.04.1 LTS and with docker-py version of 1.10. It will start the dockers and I can do a docker attach later and work on the terminal.
Now i moved my testing environment to a Ubuntu Server edition with Ubuntu 14.04.1 LTS and with docker-py version of 1.12.
The issue i see is that, when I use the same script and try to start 3 dockers, after starting process1 and process 2 as background processes, all the dockers simply exit. It appears as if /bin/bash doesnt execute at all.
If i execute the same docker image as "docker run -t -i p14 /startup.sh --> then everything is fine again. The docker is started appropriately and i get the terminal access.
The only issue is when i execute this python library.
anybody has any similar issues...any idea on how to debug this problem...or any pointers for the fix ?
Thanks,
Kiran

Answer 1

The difference is you're in tty (-t) mode with an open stdin (-i) when you run your docker image with docker run -t -i p14 /startup.sh, whereas you set both stdin_open=False and tty=False in your docker-py configuration.
Because your docker container has no tty and can't take any input from stdin, your call to /bin/bash has nothing to do so exits with code 0.
Try it yourself:
An open stdin with a tty
$ docker run -t -i ubuntu:14.04 /bin/bash
root#1e7eda2bba03:/# ls -la
total 7184
drwxr-xr-x 21 root root 4096 Sep 19 21:30 .
drwxr-xr-x 21 root root 4096 Sep 19 21:30 ..
-rwxr-xr-x 1 root root 0 Sep 19 21:30 .dockerenv
-rwx------ 1 root root 7279686 Jul 21 10:50 .dockerinit
drwxr-xr-x 2 root root 4096 Sep 3 03:33 bin
drwxr-xr-x 2 root root 4096 Apr 10 22:12 boot
drwxr-xr-x 4 root root 360 Sep 19 21:30 dev
drwxr-xr-x 61 root root 4096 Sep 19 21:30 etc
drwxr-xr-x 2 root root 4096 Apr 10 22:12 home
drwxr-xr-x 12 root root 4096 Sep 3 03:33 lib
drwxr-xr-x 2 root root 4096 Sep 3 03:33 lib64
drwxr-xr-x 2 root root 4096 Sep 3 03:33 media
drwxr-xr-x 2 root root 4096 Apr 10 22:12 mnt
drwxr-xr-x 2 root root 4096 Sep 3 03:33 opt
dr-xr-xr-x 240 root root 0 Sep 19 21:30 proc
drwx------ 2 root root 4096 Sep 3 03:33 root
drwxr-xr-x 7 root root 4096 Sep 3 03:33 run
drwxr-xr-x 2 root root 4096 Sep 4 18:41 sbin
drwxr-xr-x 2 root root 4096 Sep 3 03:33 srv
dr-xr-xr-x 13 root root 0 Sep 19 18:44 sys
drwxrwxrwt 2 root root 4096 Sep 4 18:41 tmp
drwxr-xr-x 10 root root 4096 Sep 3 03:33 usr
drwxr-xr-x 11 root root 4096 Sep 3 03:33 var
root#1e7eda2bba03:/#
An open stdin with no tty (i.e., no prompt, but you can still send commands via stdin)
$ docker run -i ubuntu:14.04 /bin/bash
ls -la
total 7184
drwxr-xr-x 21 root root 4096 Sep 19 21:32 .
drwxr-xr-x 21 root root 4096 Sep 19 21:32 ..
-rwxr-xr-x 1 root root 0 Sep 19 21:32 .dockerenv
-rwx------ 1 root root 7279686 Jul 21 10:50 .dockerinit
drwxr-xr-x 2 root root 4096 Sep 3 03:33 bin
drwxr-xr-x 2 root root 4096 Apr 10 22:12 boot
drwxr-xr-x 4 root root 340 Sep 19 21:32 dev
drwxr-xr-x 61 root root 4096 Sep 19 21:32 etc
drwxr-xr-x 2 root root 4096 Apr 10 22:12 home
drwxr-xr-x 12 root root 4096 Sep 3 03:33 lib
drwxr-xr-x 2 root root 4096 Sep 3 03:33 lib64
drwxr-xr-x 2 root root 4096 Sep 3 03:33 media
drwxr-xr-x 2 root root 4096 Apr 10 22:12 mnt
drwxr-xr-x 2 root root 4096 Sep 3 03:33 opt
dr-xr-xr-x 243 root root 0 Sep 19 21:32 proc
drwx------ 2 root root 4096 Sep 3 03:33 root
drwxr-xr-x 7 root root 4096 Sep 3 03:33 run
drwxr-xr-x 2 root root 4096 Sep 4 18:41 sbin
drwxr-xr-x 2 root root 4096 Sep 3 03:33 srv
dr-xr-xr-x 13 root root 0 Sep 19 18:44 sys
drwxrwxrwt 2 root root 4096 Sep 4 18:41 tmp
drwxr-xr-x 10 root root 4096 Sep 3 03:33 usr
drwxr-xr-x 11 root root 4096 Sep 3 03:33 var
A closed stdin with a tty (you can see the prompt but you can't enter any commands)
$ docker run -t ubuntu:14.04 /bin/bash
root#95904c21e5a5:/# ls -la
hello
this does nothing :(
A closed stdin with no tty - /bin/bash has nothing to do
$ docker run ubuntu:14.04 /bin/bash
$