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.
