SystemTap: Provisioning an AWS EC2-Based Docker Instance

In the first article in our SystemTap series, we learned how to install the powerful diagnostic tool, SystemTap, on an AWS EC2 instance and then wrote our very first “Hello World” script. We now need to explore some of the interesting (and more useful) scripts that come with SystemTap.

Building a SystemTap target environment

To make this article easier to read, we will split it into two parts. In this post, we will provide a Red Hat Enterprise Linux 7 platform container image with Docker on an AWS EC2 instance. After the SystemTap target environment is properly built, the final part will show how to run some serious scripts on a Docker container from its EC2 host to illustrate just how useful SystemTap can be.

Installing Docker on your AWS EC2 instance

To install Docker on an AWS EC2 instance, we’ll enable the “Red Hat Enterprise Linux Server 7 Extra(RPMs)” yum repository that, by default, is disabled.

$ sudo yum repolist disabled
Loaded plugins: amazon-id, rhui-lb
repo id                                                          repo name
rhui-REGION-rhel-server-debug-extras/7Server/x86_64              Red Hat Enterprise Linux Server 7 Extra Debug (Debug RPMs)
rhui-REGION-rhel-server-debug-optional/7Server/x86_64            Red Hat Enterprise Linux Server 7 Optional Debug (Debug RPMs)
rhui-REGION-rhel-server-debug-rh-common/7Server/x86_64           Red Hat Enterprise Linux Server 7 RH Common Debug (Debug RPMs)
rhui-REGION-rhel-server-debug-rhscl/7Server/x86_64               Red Hat Enterprise Linux Server 7 RHSCL Debug (Debug RPMs)
rhui-REGION-rhel-server-debug-supplementary/7Server/x86_64       Red Hat Enterprise Linux Server 7 Supplementary Debug (Debug RPMs)
rhui-REGION-rhel-server-extras/7Server/x86_64                    Red Hat Enterprise Linux Server 7 Extra(RPMs)
rhui-REGION-rhel-server-optional/7Server/x86_64                  Red Hat Enterprise Linux Server 7 Optional (RPMs)
rhui-REGION-rhel-server-releases-source/7Server/x86_64           Red Hat Enterprise Linux Server 7 (SRPMs)
rhui-REGION-rhel-server-rhscl/7Server/x86_64                     Red Hat Enterprise Linux Server 7 RHSCL (RPMs)
rhui-REGION-rhel-server-source-extras/7Server/x86_64             Red Hat Enterprise Linux Server 7 Extra (SRPMs)
rhui-REGION-rhel-server-source-optional/7Server/x86_64           Red Hat Enterprise Linux Server 7 Optional (SRPMs)
rhui-REGION-rhel-server-source-rh-common/7Server/x86_64          Red Hat Enterprise Linux Server 7 RH Common (SRPMs)
rhui-REGION-rhel-server-source-rhscl/7Server/x86_64              Red Hat Enterprise Linux Server 7 RHSCL (SRPMs)
rhui-REGION-rhel-server-source-supplementary/7Server/x86_64      Red Hat Enterprise Linux Server 7 Supplementary (SRPMs)
rhui-REGION-rhel-server-supplementary/7Server/x86_64             Red Hat Enterprise Linux Server 7 Supplementary (RPMs)
repolist: 0

We’ll use the yum-config-manager to enable the repo:

$ sudo yum-config-manager --enable "Red Hat Enterprise Linux Server 7 Extra(RPMs)"

Next, you should search for the Docker package and install it. Yum will take care of its dependencies.

$ sudo yum search docker
Loaded plugins: amazon-id, rhui-lb
rhui-REGION-rhel-server-extras                                                                                    | 2.9 kB  00:00:00
rhui-REGION-rhel-server-releases                                                                                  | 3.7 kB  00:00:00
rhui-REGION-rhel-server-releases-debug                                                                            | 2.9 kB  00:00:00
rhui-REGION-rhel-server-rh-common                                                                                 | 3.8 kB  00:00:00
rhui-REGION-rhel-server-extras/7Server/x86_64/primary_db                                                          |  56 kB  00:00:00
rhui-REGION-rhel-server-extras/7Server/x86_64/updateinfo                                                          |  27 kB  00:00:00
========================================================== N/S matched: docker ==========================================================
docker-logrotate.x86_64 : cron job to run logrotate on docker containers
docker-python.x86_64 : An API client for docker written in Python
docker-registry.noarch : Registry server for Docker
docker-registry.x86_64 : Registry server for Docker
docker-selinux.x86_64 : SELinux policies for Docker
docker.x86_64 : Automates deployment of containerized applications
  Name and summary matches only, use "search all" for everything.
$ sudo yum -y install docker

Once the Docker-related packages are installed, you should enable and start the docker service.

$ sudo systemctl enable docker
ln -s '/usr/lib/systemd/system/docker.service' '/etc/systemd/system/multi-user.target.wants/docker.service'
$ sudo systemctl start docker
$ sudo systemctl status docker
docker.service - Docker Application Container Engine
   Loaded: loaded (/usr/lib/systemd/system/docker.service; enabled)
   Active: active (running) since Wed 2015-09-16 02:02:26 EDT; 20ms ago
     Docs: http://docs.docker.com
 Main PID: 10738 (docker)
   CGroup: /system.slice/docker.service
           └─10738 /usr/bin/docker -d --selinux-enabled --add-registry registry.access.redhat.com
Sep 16 02:02:00 ip-172-30-0-123.ap-southeast-1.compute.internal systemd[1]: Starting Docker Application Container Engine...
Sep 16 02:02:00 ip-172-30-0-123.ap-southeast-1.compute.internal docker[10738]: time="2015-09-16T02:02:00.179717121-04:00" level=inf...k)"
Sep 16 02:02:00 ip-172-30-0-123.ap-southeast-1.compute.internal docker[10738]: time="2015-09-16T02:02:00.447391712-04:00" level=err...se"
Sep 16 02:02:26 ip-172-30-0-123.ap-southeast-1.compute.internal docker[10738]: time="2015-09-16T02:02:26.342873074-04:00" level=war....10
Sep 16 02:02:26 ip-172-30-0-123.ap-southeast-1.compute.internal docker[10738]: time="2015-09-16T02:02:26.360314551-04:00" level=inf...se"
Sep 16 02:02:26 ip-172-30-0-123.ap-southeast-1.compute.internal docker[10738]: time="2015-09-16T02:02:26.798683604-04:00" level=inf...t."
Sep 16 02:02:26 ip-172-30-0-123.ap-southeast-1.compute.internal docker[10738]: time="2015-09-16T02:02:26.798853557-04:00" level=inf...e."
Sep 16 02:02:26 ip-172-30-0-123.ap-southeast-1.compute.internal docker[10738]: time="2015-09-16T02:02:26.798869375-04:00" level=inf...on"
Sep 16 02:02:26 ip-172-30-0-123.ap-southeast-1.compute.internal docker[10738]: time="2015-09-16T02:02:26.798882151-04:00" level=inf...7.1
Sep 16 02:02:26 ip-172-30-0-123.ap-southeast-1.compute.internal systemd[1]: Started Docker Application Container Engine.
Hint: Some lines were ellipsized, use -l to show in full.

In order to use Docker with the ec2-user normal user, we need to create a docker group and add ourselves in it.

$ sudo groupadd docker
$ sudo usermod -aG docker ec2-user
$ grep ^docker /etc/group
dockerroot:x:995:
docker:x:1001:ec2-user

Provisioning Red Hat Enterprise Linux 7 container with Docker

To provision our container with Docker, pull down the Red Hat Enterprise Linux 7 platform container image from Red Hat.

$ docker pull rhel7
Trying to pull repository registry.access.redhat.com/rhel7 ...
82ad5fa11820: Download complete
Status: Downloaded newer image for registry.access.redhat.com/rhel7:latest

Run docker images to list the container we have downloaded.

$ docker images
REPOSITORY                           TAG                 IMAGE ID            CREATED             VIRTUAL SIZE
registry.access.redhat.com/rhel7     latest              82ad5fa11820        6 days ago          158.3 MB

Let’s do a quick test to see if everything is working.

$ docker run -ti rhel7 /bin/bash
Usage of loopback devices is strongly discouraged for production use. Either use `--storage-opt dm.thinpooldev` or use `--storage-opt dm.no_warn_on_loop_devices=true` to suppress this warning.
[root@35f99cabc19a /]# cat /etc/redhat-release
Red Hat Enterprise Linux Server release 7.1 (Maipo)
[root@c8a8740808c0 bin]# df -h
Filesystem                                                                                          Size  Used Avail Use% Mounted on
/dev/mapper/docker-202:2-51421425-c8a8740808c0d41b7294f6f2906543740b7a9b54791b6f5bed6a150616b18dd5  9.8G  213M  9.0G   3% /
tmpfs                                                                                               497M     0  497M   0% /dev
shm                                                                                                  64M     0   64M   0% /dev/shm
tmpfs                                                                                               497M   20K  497M   1% /run/secrets
/dev/xvda2                                                                                           10G  3.6G  6.5G  36% /etc/hosts
[root@c8a8740808c0 bin]#

So far so good! We are now ready to run some real troubleshooting scripts against our VMs…which we’ll describe in the final installment of this series.

If you want to learn more on Docker, this is your go-to course Introduction to Docker.

Introduction to Docker

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