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A system software / performance engineer's home

Tag: RedHat (Page 1 of 3)

Deploy Docker Swarm cluster on one host

Sometimes, you just want to learn the internal mechanics of Docker Swarm, but unfortunately there is only one Linux box at hand, and you don’t want to bother to install Virtual Machines on it. In this scenario, you certainly can build a Docker Swarm cluster on one host, and this tutorial will provide a detailed guide:

(1) Make sure the Go environment has been ready on your system, if not, please follow this document to setup it. Also remember add$GOPATH/bin into $PATH environment variable.

(2) Install Docker Swarm:

# go get -u

Execute swarm command to check whether Docker Swarm is well equipped:

# swarm
Usage: swarm [OPTIONS] COMMAND [arg...]

A Docker-native clustering system

Version: 1.2.3 (HEAD)

  --debug                       debug mode [$DEBUG]
  --log-level, -l "info"        Log level (options: debug, info, warn, error, fatal, panic)
  --experimental                enable experimental features
  --help, -h                    show help
  --version, -v                 print the version

(3) Modify the Docker configuration file. E.g., on my RHEL 7, the file is /etc/sysconfig/docker:

# systemctl show docker
EnvironmentFile=/etc/sysconfig/docker (ignore_errors=yes)

Add “-H tcp://” in OPTIONS field:

# cat /etc/sysconfig/docker
# /etc/sysconfig/docker

# Modify these options if you want to change the way the docker daemon runs
OPTIONS='--selinux-enabled -H tcp:// -H unix:///var/run/docker.sock'

Restart Docker, and check whether the new OPTIONS takes effect:

# systemctl restart docker
# systemctl status docker
● docker.service - Docker Application Container Engine
   Loaded: loaded (/usr/lib/systemd/system/docker.service; disabled; vendor preset: disabled)
   Active: active (running) since Wed 2016-06-08 12:32:19 CST; 10s ago
 Main PID: 14429 (sh)
   CGroup: /system.slice/docker.service
           ├─14429 /bin/sh -c /usr/bin/docker-current daemon $OPTIONS            $DOCKER_STORAGE_OPTIONS            $DOCKER_NETWORK_OPTI...
           ├─14430 /usr/bin/docker-current daemon --selinux-enabled -H tcp:// -H unix:///var/run/docker.sock --add-registr...
           └─14431 /usr/bin/forward-journald -tag docker

(4) Run “swarm create” command to create token for the cluster:

# swarm create

(5) Execute swarm join to create a Docker Swarm node:

# swarm join --addr token://d10eacbda9763b0740548a2a4c2f1a59
INFO[0000] Registering on the discovery service every 1m0s...  addr= discovery=token://d10eacbda9763b0740548a2a4c2f1a59

You should notice that the argument of --addr option is the IP and port of the Docker engine on this host. Since we have set theOPTIONS in Docker configuration file in step 3, the IP should be whilst port is 2375.

(6) Open a new terminal, and create the manager of the cluster. Because port 2375 is occupied by Docker engine, we use another available port:

# swarm manage -H token://d10eacbda9763b0740548a2a4c2f1a59
INFO[0000] Listening for HTTP                            addr= proto=tcp
INFO[0001] Registered Engine localhost.localdomain at

Through the log, you can see the node and manager have communicated successfully.

Now, you can think a Docker engine is listening on tcp://, but actually, there is one Docker cluster behindtcp://, even though the cluster has only one node. You can play docker client commands now, such as get the cluster info:

# docker -H tcp:// info
Containers: 0
Images: 5
Server Version: swarm/1.2.3
Role: primary
Strategy: spread
Filters: health, port, containerslots, dependency, affinity, constraint
Nodes: 1
  └ Status: Healthy
  └ Containers: 0 (0 Running, 0 Paused, 0 Stopped)
  └ Reserved CPUs: 0 / 8
  └ Reserved Memory: 0 B / 12.1 GiB
  └ Labels: executiondriver=native-0.2, kernelversion=3.10.0-327.el7.x86_64, operatingsystem=Red Hat Network, storagedriver=devicemapper
  └ UpdatedAt: 2016-06-08T04:58:05Z
  └ ServerVersion: 1.9.1
Kernel Version: 3.10.0-327.el7.x86_64

Or run a container:

# docker -H tcp:// run hello-world

Hello from Docker.
This message shows that your installation appears to be working correctly.

To generate this message, Docker took the following steps:
 1. The Docker client contacted the Docker daemon.

Enjoy Docker Swarm now!

Swarm docs;
Docker Swarm Tutorial and Examples.


Upgrade Linux kernel on RHEL 7

My OS is RHEL 7.2 (minimal installation version). To use some new kernel features (such as BPF), I need to upgrade kernel to 4.x.

(1) Register the system and apply a subscription:

# subscription-manager register --username <username> --password <password> --auto-attach

(2) Use yum install to install the following software packages:


BTW, when executing yum install perl, it prompts errors, so I download the source code from perl official website, and build it form scratch:

make test
make install

(3) Download the stable kernel from and extract it, then build it:

make menuconfig
make modules_install install

According to your requirement, maybe installing the header files is also need:

make INSTALL_HDR_PATH=/usr/local headers_install

(4) Reboot system, and select right kernel on boot time, enjoy it:

# uname -a
Linux localhost.localdomain 4.5.0 #1 SMP Mon Apr 11 09:56:46 EDT 2016 x86_64 x86_64 x86_64 GNU/Linux


Install ncurses-devel package when building htop

I download htop 2.0.0 and want to build it from source code on RHEL 7.1, but “./configure” outputs the following errors:

checking for addnwstr in -lncursesw6... no
checking for addnwstr in -lncursesw... no
checking for addnwstr in -lncurses... no
configure: error: You may want to use --disable-unicode or install libncursesw.

The solution is to install ncurses-devel package:

yum install ncurses-devel

Then the configuration & build processes are smooth.


How to pull docker image behind proxy on RHEL7?

My host OS is RHEL7, and running behind proxy. The output of executing docker run hello-world is like this:

# docker run hello-world
Unable to find image 'hello-world:latest' locally
Trying to pull repository ... failed
Trying to pull repository ... failed
Error while pulling image: Get x509: certificate is valid for FG3K6C3A15800021, not

It prompts pull image failed, so I need to configure proxy to make docker work correctly:

(1) Add proxy info in /etc/sysconfig/docker file:


(2) Restart docker service:

# service docker restart

Then docker works OK now:

# docker run hello-world
Unable to find image 'hello-world:latest' locally
Trying to pull repository ... not found
Trying to pull repository ... latest: Pulling from library/hello-world
3f12c794407e: Pull complete
975b84d108f1: Pull complete

Cannot download Docker images behind a proxy

Install sysdig on RHEL7

The manual of advanced installing sysdig focus on RHEL6 only. To install sysdig on RHEL7, just need to modify this step:

2) Install the EPEL repository
rpm -i

We should install EPEL7 for RHEL7:

yum install -y

Other steps are same! The you can play sysdig now!


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