Linux Containers and Docker SHARE.ORG Seattle 2015

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Filipe Miranda <fmiranda@redhat.com>
Global Lead for Red Hat Products on IBM z Systems and Power Systems
Red Hat Inc.
Red Hat Enterprise Linux for IBM z Systems
Linux Containers and Docker
Session# 16443

Red Hat, Inc. in a Nutshell
- Red Hat and the Open Source Community
Linux Containers
- Introduction to Linux Containers
Docker (Image Container)
- Demo of Docker on RHEL for z Systems
Openshift (PaaS Cloud)
- A glimpse of what LCX/Docker technologies can do
- What if we had OpenShift for z Systems?
Session Topics
© Copyright Red Hat, Inc. 2015

Red Hat in a Nutshell

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Linux Containers
Application Containers
(same kernel and /usr as the host system)
What is Linux Containers?
LinuX Containers (LXC) is an operating system-level virtualization method for running multiple isolated Linux
systems (containers) on a single control host (LXC host). LXC does not provide a virtual machine, but rather
provides a virtual environment that has its own CPU, memory, block I/O, network etc.
Linux container feature allows you to carve out containers as lightweight application sandboxes.
All host containers launched are identical – each runs the same user space as the host system, so all applications
running in host containers are based on the host user space and run time.

Linux Containers
http://www.linuxjournal.com/content/containers—not-virtual-machines—are-future-cloud
The advantage of using Linux Containers:
Enables multiple running instances of an operating system or application on a single host, without inducing
overhead on CPU and memory.
Safely and securely run multiple applications on a single system without the risk of them interfering with each
other. If security of one container has been compromised, the other containers are unaffected.
Containers can be useful to quickly set up a “sandbox” environment, e.g. to test a new version of a Linux
distribution or to simulate a “clean” environment for testing/QA purposes.

Linux Containers building blocks
Linux Containers are built using the following RHEL technologies:
•Resource Management - Control groups (CGroups)
•Filesystem Separation – Device mapperThin Provisioning
•Isolation - Namespaces
•Security - SELinux
•Tooling – Libvirt-lxc and virt-sandbox-service
Linux Containers

Red Hat Enterprise Linux - Container Architecture
Linux Containers

Resource Management with Cgroups
Linux Containers

Red Hat Enterprise Linux - Container Architecture
Linux Containers
The kernel provides process isolation by creating separate namespaces for containers. Namespaces enable
creating an abstraction of a particular global system resource and make it appear as a separated instance to
processes within a namespace. Consequently, several containers can use the same resource simultaneously
without creating a conﬂict.

• Mount : mounting/unmounting filesystems
Isolates the set of file system mount points seen by a group of processes so that processes in different mount
namespaces can have different views of the file system hierarchy.
• UTS : hostname, domainname
Isolates two system identifiers – nodename and domainname.This allows each container to have its own hostname
and NIS domain name, which is useful for initialization and configuration scripts based on these names
• IPC : SysV message queues, shared memory segments
Isolates certain interprocess communication (IPC) resources, such as System V IPC objects and POSIX message
queues.This means that two containers can create shared memory segments and semaphores with the same name,
but are not able to interact with other containers memory segments or shared memory.
• Network: IPv4/IPv6 stacks, routing, firewall
Provides isolation of network controllers, system resources associated with networking, firewall and routing tables.
• PID: Private /proc, multiple pid 1’s
Allows processes in different containers to have the same PID, so each container can have its own init (PID1) process
that manages various system initialization tasks as well as containers life cycle
Mount, UTS, IPC, Network, PID are fully supported in RHEL 7.0
Namespaces
Linux Containers

Host based Application Container
Shared RHEL host based application container
•Generic application containers
•Run any command / package supported on the host system
•Systemd application containers
•Scale – launch 100s of containers using systemd
•/usr in container same as the host OS
Linux Containers
https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/Resource_Management_and_Linux_Containers_Guide/chap-Using_virsh.html

Docker is a technology behind image-based containers
It is a tool and a format designed for shipping applications as self-contained units
Docker builds on the core capabilities of Linux containers, such as cgroups, namespaces and SELinux and also
depends to certain extent on the underlying operating system, namely on device mapper thin provisioning
and on systemd for resource management.
Docker : Image Based Containers
Image Containers
(same kernel different /usr and package set)
Application Containers
(same kernel and /usr as the host system)

•Red Hat doing heavy lifting in Fedora to ensure Docker runs on a Red Hat based container stack
•Device mapper thin provisioning
•Replaces AUFS dependency in Docker
•Libvirt-lxc sandbox
•Replaces lxc-tools dependency in Docker
•SELinux
•Links: partnership and ongoing work
•http://tinyurl.com/RedHatDockerPR
•http://blog.docker.io/2013/09/red-hat-and-docker-collaborate/
Docker and Red Hat

•Recently as a result of the collaboration between IBM and the open source community, Docker is finally
running on s390x systems (as well as PPC64)
•Docker was originally developed in Golang (only available to x86 systems)
•IBM and the open source community developed go-gcc (Docker have been ported to go-gcc)
•Docker can now run on Linux on IBM z Systems (and IBM Power Systems)
Docker on Linux for IBM z Systems

Steps by Step:
Testing environment, Red Hat Enterprise Linux 7 running as a z/VM guest OS
1) Copy the Docker binary (IBM) to /usr/local/bin
2) Start Docker deamon:
[root@rhel7 ~]# docker -d
INFO[0000] +job serveapi(unix:///var/run/docker.sock)
INFO[0000] Listening for HTTP on unix (/var/run/docker.sock)
INFO[0006] +job init_networkdriver()
INFO[0008] -job init_networkdriver() = OK (0)
INFO[0009] Loading containers: start.
Demo of Docker running on RHEL for z Systems

4)To use as a test subject, I created a standard RHEL on z z/VM guest and I created an image out of it in a tarball
ﬁle.
# tar -cvf rhel6-s390.tar --exclude=/root/rhel6-s390.tar --exclude=/proc
--exclude=/sys --one-file-system /
5 )from the test subject system, I copied it to the Docker system, using a simple scope command and then I
started the process to import that system image into Docker.
cat rhel6-s390.tar | docker import - rhel6-s390
8223b049356123458040c6167b5421c975054f31d4e72c3d8d7eadd8e439b9a1

4) Check if the Docker image was imported correctly:
[root@rhel7 ~]# docker images
REPOSITORY TAG IMAGE ID CREATED VIRTUAL SIZE
rhel6-s390 latest 8223b0493561 44 seconds ago 1.437 GB
5) Let’s now run a shell environment within the container we just imported into Docker:
[root@rhel7 ~]# docker run -i -t rhel6-s390 bash
[root@722f09e42426 /]#
6) Once you have access to the shell within the container, check the process isolation:
[root@722f09e42426 /]# ps aux
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
root 1 0.0 0.1 100500 1844 ? Ss 07:13 0:00 bash
root 24 0.0 0.1 100204 1120 ? R+ 07:15 0:00 ps aux

7) From another terminal, if you issue the command docker ps, it will tell you what containers are running:
[root@rhel7 ~]# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS
NAMES
0863965787ea rhel6-s390:latest "bash" 2 minutes ago Up 2 minutes
goofy_feynman

[root@08dfb98ac145 /]# rhn_register
8) Back to the original terminal, lets start a different application, for example

[root@08dfb98ac145 /]# yum update
Loaded plugins: product-id, rhnplugin, security, subscription-manager
This system is not registered to Red Hat Subscription Management. You can
use subscription-manager to register.
This system is receiving updates from RHN Classic or RHN Satellite.
Setting up Update Process
Resolving Dependencies
Dependencies Resolved
. . .
Transaction Summary
============================================================================
Install 14 Package(s)
Upgrade 322 Package(s)
Total download size: 249 M
Is this ok [y/N]: n
9) Let’s try yum update to check if the registration worked

[root@rhel7 ~]# docker commit 722f09e42426
07d308404e3edb04a580f0fce6d89887b717fd9e70ef1424a4be01412b5994fb
11)To identify the new image create a dog tag for that:
[root@rhel7 ~]# docker tag
07d308404e3edb04a580f0fce6d89887b717fd9e70ef1424a4be01412b5994fb
rhel6-s390-repo
12) Check the Docker images
[root@rhel7 ~]# docker images
REPOSITORY TAG IMAGE ID CREATED VIRTUAL SIZE
rhel6-s390 latest 8223b0493561 2 hours ago 1.437 GB
rhel6-s390-repo latest 17ec773d1bcd 1 hours ago 1.437 GB
10)To keep the modified container, we can issue a commit command thus creating another container image that will
only have the modified files (in our case virtually no extra space):

Openshift - PaaS (private/public cloud)
OpenShift is Red Hat's Platform-as-a-Service (PaaS) that allows developers to quickly develop, host, and scale
applications in a cloud environment.With OpenShift you have choice of offerings, including online, on premise,
and open source project options.
Red Hat Openshift is currently only available to x86 systems

Get StartedToday for Free
• Deploy Apps to the OpenShift OnLine Developer Preview
• Request an Evaluation of OpenShift Enterprise
• Join the OpenShift Origin Open Source Project community
http://openshift.redhat.com

Filipe Miranda <fmiranda@redhat.com>
Global Lead for Red Hat Products on IBM z Systems and Power Systems
Red Hat Inc.

Linux Containers and Docker SHARE.ORG Seattle 2015

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