Thursday, 21 August 2014

Failing ssh connections on Centos 7 docker host

When I tried to connect to a container running on Centos 7 host running ssh service I was getting:

Read from socket failed: Connection reset by peer

I was running a container with ssh service inside it on Ubuntu using Dockerfile from:

# sshd
# VERSION               0.0.1

FROM     ubuntu:12.04
MAINTAINER Thatcher R. Peskens ""

# make sure the package repository is up to date
RUN apt-get update

RUN apt-get install -y openssh-server
RUN mkdir /var/run/sshd
RUN echo 'root:screencast' |chpasswd

CMD    ["/usr/sbin/sshd", "-D"]

It worked perfectly on Ubuntu 14.04 as the docker host, but when I tried the same docker file build on Centos 7 host I was unable to connect to the ssh service running inside container. I've tried all the available solutions mentioned on the internet like disabling selinux, disabling firewalld , changing container ssh configuration from UsePAM yes to UsePAM no and generating ssh keys inside the container before running sshd daemon. Also used the docker file from here:

Running netcat and using telnet to connect works.
But the ssh problem still persisted and after searching further found this discussion:
which helped me resolve the problem. So basically to summarize the solution
set UsePrivilegeSeparation no in the sshd_config of the container and you should be able to login 
Dockerfile for the same adapted from ( :

One nice tip learned from this troubleshooting is that you can enter a container using tool called nsenter as follows:

PID=$(docker inspect --format '{{.State.Pid}}' my_container_id)

nsenter --target $PID --mount --uts --ipc --net --pid

But got another problem, the session hangs right after logging in. working on finding a fix for that issue.

Wednesday, 30 May 2012

Merging Branch with Trunk

SVN: Merge a branch with your trunk

When created a branch a few days back to try some fancy new technology in application. Now I want to merge the code in the branch with my trunk.

I have a checked-out working copy of the branch available.

First, make sure you have a working copy of your trunk. I choose to switch my working copy back: (oh, make sure you have all your changes checked in in your branch before you switch!)

$ svn switch
This removes, adds and updates all files you have worked on in your branch and creates a working copy of the code in the trunk.

Now, with my trunk in place, I can call 'merge' and apply the changes.

$ svn merge
Since the files from the trunk and the beginning of the TRY-branch are still exact copies, I won't get in any trouble. If you do (and you did change your code in your trunk), make sure to resolve merging problems before checking in. When ready, check in your new code!

$ svn ci -m "Merge TRY-AJAX branch with trunk"
That's it. You have now merged the branch with your trunk. Enjoy!