Environment Setup

A single CentOS 6.5 virtual machine is required, along with febootstrap and docker intsalled.

Installing febootstrap

yum install -y yum-priorities && rpm -ivh http://dl.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm && rpm --import /etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-6 
yum -y install febootstrap

Installing Docker

yum -y install docker-io
service docker start

The image creation process must be performed under the root account; using a regular user may lead to various issues.

Creating the Base Image

febootstrap -i bash -i wget -i yum -i iputils -i iproute -i man -i vim -i openssh-server -i openssh-clients -i tar -i gzip centos6 centos6-image http://mirrors.aliyun.com/centos/6/os/x86_64/

Upon copmletion, a directory named centos6-image will be created.

cd centos6-image
cp etc/skel/.bash* root/
tar -c . | docker import - centos6-base

Verifying the Image

docker images
REPOSITORY           TAG                 IMAGE ID            CREATED             VIRTUAL SIZE
centos6-base         latest              8f94e0bebd19        6 hours ago         399.4 MB

Starting a Container

docker run -itd 8f94e0bebd19 bash
2e943abb130a32830dd8580ab9345dd514b7b39597559cd08a790a8754ef56f1
docker exec -it 84f48b314bfa bash
[root@2e943abb130a /]#

Once inside the container, applications such as PHP and Nginx can be installed. Init scripts for Nginx and PHP-FPM are added to /etc/init.d/ (optional).

Enabling Application Startup on Container Boot

Multiple methods exist to manage startup services with in containers, including Supervisord and shell scripts. Here we use a shell script approach:

mkdir /usr/local/scripts

Create /usr/local/scripts/init-bashrc.sh:

#!/bin/sh

function service_start()
{
    for SERVICE in nginx php-fpm sshd
    do
      if ! (ps ax | grep -v grep | grep $SERVICE > /dev/null)
      then
         /etc/init.d/$SERVICE start;
      fi
    done
}

service_start

Modify ~/.bashrc:

# .bashrc

# Source global definitions
if [ -f /etc/bashrc ]; then
        . /etc/bashrc
fi

alias rm='rm -i'
alias cp='cp -i'
alias mv='mv -i'
alias ll='ls -l'
alias vi='vim'

/usr/local/scripts/init-bashrc.sh
# User specific aliases and functions

Remember to source the file: source ~/.bashrc. Exit the container with Ctrl+D.

Committing the Container

docker commit 2e943abb130a centos6-nginx-php56:v1
d85f477d9e00d12c380ebc442d544e0d8c9dd8ee86441e0885bb54f636c18ec1

After committing, a new image appears in docker images.

Launching the New Image

docker run -it centos6-nginx-php56:v1
Starting nginx:                                            [  OK  ]
Starting php-fpm:                                          [  OK  ]
Starting sshd:                                             [  OK  ]
[root@36abc5805a89 /]#

Ports can also be exposed during launch, and the root password modified. This can be achieved via a Dockerfile.

Example Dockerfile:

FROM centos6-nginx-php56:v1
MAINTAINER Tempted
RUN sed -i 's/UsePAM yes/UsePAM no/g' /etc/ssh/sshd_config
RUN echo "root:123456" | chpasswd
EXPOSE 22 80
CMD ["bash"]

Building the Final Image

docker build -t centos6-lnp:v1 .
Sending build context to Docker daemon 15.87 kB
Step 0 : FROM centos6-nginx-php56:v1
 ---> d85f477d9e00
Step 1 : MAINTAINER Tempted
 ---> Running in 46ec3f0fab12
 ---> 4ed3d31476d0
Removing intermediate container 46ec3f0fab12
Step 2 : RUN sed -i 's/UsePAM yes/UsePAM no/g' /etc/ssh/sshd_config
 ---> Running in 48ece83ad435
 ---> c02f08cf9b19
Removing intermediate container 48ece83ad435
Step 3 : RUN echo "root:123456" | chpasswd
 ---> Running in 22d1086800ca
 ---> 18db13e52113
Removing intermediate container 22d1086800ca
Step 4 : EXPOSE 22 80
 ---> Running in 8a65e01a0e84
 ---> 63a5bd61ba88
Removing intermediate container 8a65e01a0e84
Step 5 : CMD bash
 ---> Running in 671572d70abf
 ---> d0c9c51584ee
Removing intermediate container 671572d70abf
Successfully built d0c9c51584ee

Three images should now appear when listing docker images.

Starting the New Image

docker run -itd d0c9c51584ee bash
bc10a9e77a8c8b9eb12a7da16d6513ffa11a686d29dc86e050e702fac96a6109
docker ps
CONTAINER ID        IMAGE               COMMAND                CREATED             STATUS              PORTS               NAMES
bc10a9e77a8c        d0c9c51584ee        "bash"                 20 seconds ago      Up 17 seconds       22/tcp, 80/tcp      cocky_morse

Check network interfaces:

docker exec -it bc10a9e77a8c ifconfig
eth0      Link encap:Ethernet  HWaddr 02:42:AC:11:00:51  
          inet addr:172.17.0.81  Bcast:0.0.0.0  Mask:255.255.0.0
          inet6 addr: fe80::42:acff:fe11:51/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:41 errors:0 dropped:0 overruns:0 frame:0
          TX packets:38 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:5060 (4.9 KiB)  TX bytes:5179 (5.0 KiB)
lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)

Connecting via SSH

ssh 172.17.0.81
root@172.17.0.81's password: 
Last login: Fri Nov  3 17:23:16 2017 from 172.17.42.1
[root@bc10a9e77a8c ~]#

Exporting the Image

docker save centos6-lnp:v1 > centos6-lnp.tar