Building containers from scratch using Go Lang
This demo was made as a prove of concept and to easily show that containers is nothing more than Linux processes running with some isolation from the processes running on the host.
Inspiration
I started to study Go Lang couple weeks ago and I am a huge fan of Docker. Watching some videos from Golang UK Conf. 2016 I saw a talk from @lizrice: What is a container, really
Thanks
Need to thank Liz Rice (@lizrice) and as she mention at the talk, Julian Friedman (@julz), that with some lines of code could show details from it.
Links
- Gist from Liz Rice: https://gist.github.com/lizrice/a5ef4d175fd0cd3491c7e8d716826d27
- Gist from Julian Friedman: https://gist.github.com/julz/c0017fa7a40de0543001
- Julian post at InfoQ: https://www.infoq.com/articles/build-a-container-golang
- Liz Rice talk at Golang UK Conference 2016: https://www.youtube.com/watch?v=HPuvDm8IC-4
- Liz Rice talk at Container Camp UK 2016: https://www.youtube.com/watch?v=Utf-A4rODH8
How to run
1. Bring the VM up
$ vagrant upThis first step will take a while at the first time. The clean Ubuntu trusty VM will:
- Install and configure Go
- Untar the root file systems of each image
If it fails due to internet conection we can re-run with
$ vagrant up --provisionIf the box become outdated we can just run
$ vagrant box update2. Access the Ubuntu VM
Accessing it.
$ vagrant sshGoing to /container-demo and run stuff as superuser.
vagrant@vagrant-ubuntu-trusty-64:~$ sudo -i
root@vagrant-ubuntu-trusty-64:~# cd /container-demo/
root@vagrant-ubuntu-trusty-64:/container-demo#3. First example
run an echo command from inside a container
root@vagrant-ubuntu-trusty-64:/container-demo# go run demo.go run echo ola
Rodando [echo ola]
ola
Saindo do Container
root@vagrant-ubuntu-trusty-64:/container-demo#Run a bash with no isolation from inside a container
root@vagrant-ubuntu-trusty-64:/container-demo# go run demo.go run /bin/bash
Rodando [/bin/bash]
root@vagrant-ubuntu-trusty-64:/container-demo# hostname
vagrant-ubuntu-trusty-64
root@vagrant-ubuntu-trusty-64:/container-demo# hostname demo
root@vagrant-ubuntu-trusty-64:/container-demo# hostname
demo
root@vagrant-ubuntu-trusty-64:/container-demo# exit
exit
Saindo do Container
root@vagrant-ubuntu-trusty-64:/container-demo# hostname
demo
root@vagrant-ubuntu-trusty-64:/container-demo#We can also compile then use our binary
root@vagrant-ubuntu-trusty-64:/container-demo# go build demo.go
root@vagrant-ubuntu-trusty-64:/container-demo# demo run /bin/bash
Rodando [/bin/bash]
root@vagrant-ubuntu-trusty-64:/container-demo# exit
exit
Saindo do Container
root@vagrant-ubuntu-trusty-64:/container-demo# We can notice that hostname was changed also in the host
4. Second example
Runnig a bash with UTS namespace isolation
root@vagrant-ubuntu-trusty-64:/container-demo#
root@vagrant-ubuntu-trusty-64:/container-demo# go run demo-uts.go run /bin/bash
Rodando [/bin/bash]
root@demo:/container-demo# hostname
demo
root@demo:/container-demo# hostname yada
root@demo:/container-demo# hostname
yada
root@demo:/container-demo# exit
exit
Saindo do Container
root@vagrant-ubuntu-trusty-64:/container-demo# hostname
demo
root@vagrant-ubuntu-trusty-64:/container-demo#We can notice some isolation since hostname was changed inside the container but not in the host.
5. Third example
Running a bash with UTS and PID namespaces isolated
root@demo:/container-demo# go run demo-pid.go run debian ps aux
Rodando [ps aux] as PID 1 usando imagem debian
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
0 1 0.0 0.1 3240 956 ? Sl+ 19:23 0:00 /proc/self/exe
0 4 0.0 0.2 15568 1160 ? R+ 19:23 0:00 ps aux
Saindo do Container
root@demo:/container-demo# go run demo-pid.go run ubuntu cat /etc/issue
Rodando [cat /etc/issue] as PID 1 usando imagem ubuntu
Ubuntu 14.04 LTS \n \l
Saindo do Container
root@demo:/container-demo#
root@demo:/container-demo# go run demo-pid.go run ubuntu ls -al
Rodando [ls -al] as PID 1 usando imagem ubuntu
total 72
drwxr-xr-x 19 0 0 4096 May 13 2013 .
drwxr-xr-x 19 0 0 4096 May 13 2013 ..
drwxr-xr-x 2 0 0 4096 Apr 16 2014 bin
drwxr-xr-x 2 0 0 4096 Apr 10 2014 boot
...
drwxr-xr-x 11 0 0 4096 Apr 11 2014 var
Saindo do Container
root@demo:/container-demo#
root@demo:/container-demo#
root@demo:/container-demo# go run demo-pid.go run debian ps aux
Rodando [ps aux] as PID 1 usando imagem debian
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
root 1 0.0 0.1 3240 952 ? Sl+ 19:25 0:00 /proc/self/exe
root 4 0.0 0.9 4137480 4712 ? R+ 18:55 0:00 /usr/bin/qemu-a
Saindo do Container
root@demo:/container-demo#
root@demo:/container-demo# go run demo-pid.go run debian cat /etc/issue
Rodando [cat /etc/issue] as PID 1 usando imagem debian
Debian GNU/Linux 8 \n \l
Saindo do Container
root@demo:/container-demo#
root@demo:/container-demo# go run demo-pid.go run debian ls -al
Rodando [ls -al] as PID 1 usando imagem debian
total 76
drwxr-xr-x 20 root root 4096 Oct 24 18:43 .
drwxr-xr-x 20 root root 4096 Oct 24 18:43 ..
drwxr-xr-x 2 root root 4096 Oct 24 18:40 bin
...
drwxr-xr-x 11 root root 4096 Oct 24 18:37 var
Saindo do Container
root@demo:/container-demo#We can notice that the first proccess running inside the container have PID=1 due to a new PID namespace
We can also show the rootfs from each image in the host (my VM in this case)
root@demo:/container-demo# ls / | grep rootfs
alpine-rootfs.tar
centos-rootfs.tar
debian-rootfs.tar
fedora-rootfs.tar
ubuntu-rootfs.tar
root@demo:/container-demo#6. To shut down
To leave VM shell
root@demo:/container-demo# exit
logout
vagrant@vagrant-ubuntu-trusty-64:~$ exit
logout
Connection to 127.0.0.1 closed.Then shut the VM down
$ vagrant halt
==> containerdemo: Attempting graceful shutdown of VM...
React
Typescript
Django
Laravel
Facebook
Microsoft
Google
Alibaba
D3
Tencent