Docker: How To Commit Container changes
Docker provides us cool features to build applications in the complete isolated environment. we could manage and deploy our application with very minimal resources in Docker container.
So if we have a container that hosting a useful application and we like to setup same application on another machine, then we need to save the same state of the container into an image and move it to another Host machine to launch container from the same image.
So, In Docker, we have features to save container changes in another image to launch container from same. This container would have a same deployed application that was working on the first Host machine.
In this post, we would understand how we could save co
Container changes in an images.
For this post we have one Ubuntu 17.04 host with Docker 17.06
root@srvU:~# lsb_release -d Description: Ubuntu 17.04 root@srvU:~# docker -v Docker version 17.06.0-ce, build 02c1d87
Now we have one Ubuntu image which we run and perform some changes to commit into a new image.
root@srvU:~# docker images ubuntu REPOSITORY TAG IMAGE ID CREATED SIZE ubuntu latest 14f60031763d 3 days ago 120MB
Run Container over official Image
Let’s run it with bash to connect like below
root@srvU:~# docker run -it --name ubuntu-latest ubuntu /bin/bash root@0731a89a026e:/# cat /etc/issue Ubuntu 16.04.2 LTS \n \l root@srvU:~# docker ps -a CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 0731a89a026e ubuntu "/bin/bash" 2 minutes ago Up 2 minutes ubuntu-latest
Perform some changes
Now we would perform some changes on Ubuntu and commit it into a new image.
root@af1b3db2b163:/# apt-get update > /dev/null 2>&1 ; echo $? 0 root@af1b3db2b163:/# ps aux USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND root 1 0.1 0.1 18244 3288 pts/0 Ss 19:46 0:00 /bin/bash root 195 0.0 0.1 34428 2832 pts/0 R+ 19:47 0:00 ps aux root@af1b3db2b163:/# apt-get install openssh-server -y > /dev/null 2>&1 ; echo $? 0 root@af1b3db2b163:~# /etc/init.d/ssh start * Starting OpenBSD Secure Shell server sshd [ OK ] root@af1b3db2b163:~# ps aux USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND root 1 0.0 0.1 18248 3308 pts/0 Ss 19:46 0:00 /bin/bash root 3632 0.0 0.1 65524 3124 ? Ss 19:50 0:00 /usr/sbin/sshd root 3634 0.0 0.1 34428 2848 pts/0 R+ 19:50 0:00 ps aux
Now we SSH server installed on ubuntu Container, which is running and should connect from outside. Let’s check. for same we have to perform some changes in SSH configuration file and set root password.
root@af1b3db2b163:~# grep Permit /etc/ssh/sshd_config PermitRootLogin prohibit-password PermitEmptyPasswords no # the setting of "PermitRootLogin without-password". root@af1b3db2b163:~# sed -i 's/PermitRootLogin prohibit-password/PermitRootLogin yes/' /etc/ssh/sshd_config root@af1b3db2b163:~# passwd Enter new UNIX password: Retype new UNIX password: passwd: password updated successfully
Now we should connect Ubuntu container from outside (from Host Machine)
root@srvU:~# ssh "172.17.0.2" firstname.lastname@example.org's password: Welcome to Ubuntu 16.04.2 LTS (GNU/Linux 4.10.0-19-generic x86_64) * Documentation: https://help.ubuntu.com * Management: https://landscape.canonical.com * Support: https://ubuntu.com/advantage The programs included with the Ubuntu system are free software; the exact distribution terms for each program are described in the individual files in /usr/share/doc/*/copyright. Ubuntu comes with ABSOLUTELY NO WARRANTY, to the extent permitted by applicable law. root@af1b3db2b163:~# logout Connection to 172.17.0.2 closed.
Commit Container changes
I think, we have done plenty of changes on ubuntu container, we should commit changes and build new image.
root@srvU:~# docker commit -a Sang.Sirohi -m "This ubuntu has OpenSSH installd" ubuntu-latest ubuntu-with-ssh sha256:1d66b84132843f9d0db5d4d87693841db98d3dc82bf381e159e0cabf81069098 root@srvU:~# docker inspect ubuntu-with-ssh | egrep "Author|Comment" "Comment": "This Ubuntu has OpenSSH Installed", "Author": "Sang.Sirohi",
In above command, I tried to cover few more points -a, Author and -m, Message. Same could inspect with Container properties as well.
Let’s launch another Container and see those changes persistent or not.
root@srvU:~# docker images ubuntu-with-ssh REPOSITORY TAG IMAGE ID CREATED SIZE ubuntu-with-ssh latest 1d66b8413284 5 minutes ago 213MB root@srvU:~# docker run -it ubuntu-with-ssh root@975cdcd9a93c:/# ps aux USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND root 1 0.4 0.1 18244 3348 pts/0 Ss 20:17 0:00 /bin/bash root 9 0.0 0.1 34428 2872 pts/0 R+ 20:17 0:00 ps aux root@975cdcd9a93c:/# /etc/init.d/ssh status * sshd is not running root@975cdcd9a93c:/# /etc/init.d/ssh start * Starting OpenBSD Secure Shell server sshd [ OK ]
Let’s check SSH service from outside container
root@srvU:~# docker ps -a CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES a201ec37daec ubuntu-with-ssh "/bin/bash" 3 minutes ago Up 3 minutes friendly_montalcini 0731a89a026e ubuntu "/bin/bash" 15 minutes ago Up 15 minutes ubuntu-latest # docker inspect a201ec37daec | grep \"IPAdd "IPAddress": "172.17.0.3", root@srvU:~# ssh "172.17.0.3" The authenticity of host '172.17.0.3 (172.17.0.3)' can't be established. ECDSA key fingerprint is SHA256:+yEhwbi7iANhsJLPAQ//Px7JMTvi+vEA/7q7lk1qmQs. Are you sure you want to continue connecting (yes/no)? yes Warning: Permanently added '172.17.0.3' (ECDSA) to the list of known hosts. email@example.com's password: Welcome to Ubuntu 16.04.2 LTS (GNU/Linux 4.10.0-19-generic x86_64) * Documentation: https://help.ubuntu.com * Management: https://landscape.canonical.com * Support: https://ubuntu.com/advantage Last login: Sun Jul 23 20:57:14 2017 from 172.17.0.1 root@a201ec37daec:~# logout Connection to 172.17.0.3 closed.
You should always see command-line (docker commit –help) help and docker website help for the same topic