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SAMO Ready Oracle Linux

This guide describes the preparation steps for operating system and programs that need to be completed before any SAMO installation.

info

This guide focuses on Oracle Linux version 7 which is based on the RHEL and CentOS Linux distributions. Other distributions may differ. For additional information, refer to the official Docker installation guides.

tip

Lines starting with $ are shell commands.

Prepare Operating System​

Some tips for tools and steps for OS.

The operating system should be up to date not because of bug fixes and improvements but also because of the security. This step is not necessary but highly recommended.

$ yum update

I also recommend to restart the system after update but it also should not be necessary step.

$ reboot

Install essential tools- Some tools are not part of OS by default but they are good for debugging and investigating problems.​

  • wget - HTTP requests
  • net-tools and bind-utils - networking tools
  • htop - resources management tool
  • zip and unzip - ZIP packages handling

Note: If anything is not working you should enable epel repository

Check ​proxy settings and connectivity​

In case the server is behind proxy server we need to ensure that it is correctly configured.

Check whether www.google.com is accessible with one of these commands:

If the command are not working there is probably http_proxy is not properly set. In order to set the proxy put the export commands to the /etc/environment file (for CentOS/Oracle/RHEL):

  • ​​export http_proxy=PROXY_URL_WITH_PORT
  • ​​export HTTP_PROXY=PROXY_URL_WITH_PORT
  • ​​export https_proxy=PROXY_URL_WITH_PORT
  • ​​export HTTPS_PROXY=PROXY_URL_WITH_PORT
  • export no_proxy=localhost,127.0.0.1,gitlab,company.local,company.com

Proxy address and port can usually be found like this:

  • ​grep -rnw '/etc' -e "proxy"​

Then you can test the connection again.

This is not enough to provide proxy setup upon startup. You have to add these properties to the server environment. Add them to the /etc/environment file and reboot. You can check the properties after system reboot.

Check ​IP forwarding​

The IPv4 forarwarding is needed for Docker to work correctly.

  1. Check if enabled:
  • sysctl net.ipv4.ip_forward
  1. If not
  • you should add:
    • net.ipv4.ip_forward = 1
  • into file:
    • ​/usr/lib/sysctl.d/50-default.conf
  • and reboot

Tip: shell aliases​

It is convenient to setup some shortcats for working with docker on command line.

We use these aliases:

alias dcu='docker-compose up -d'
alias dcd='docker-compose down'
alias dcp='docker-compose pull'
alias dcinstall='dcp && dcd && dcu'

alias dlog='docker logs -f'
alias dlogt='docker logs -f --tail 1000'

alias dstats='docker stats $(docker ps --format={{.Names}})'

alias dps='docker ps --format "table {{.Names}}\t{{.Status}}\t{{.Ports}}" | sed -r "s/0.0.0.0://g" | sed -r "s/\/tcp//g"'
alias dpsa='docker ps -a --format "table {{.Names}}\t{{.Status}}\t{{.Ports}}" | sed -r "s/0.0.0.0://g" | sed -r "s/\/tcp//g"'

They are stored in the /etc/bashrc file which is loaded upon user login.

Install Docker (Required)​

Docker is our choice for containers. So far the only supported option for SAMO. It is also possible to install without Docker but the process is cumbersome and not bulletproof with a lot of dirty hand work.

This section is highly inspired with the official guide from Docker Get Docker CE for CentOS and Official blog post from Oracle: Install Docker on Oracle Linux 7.

Setting up Docker yum repositories​

$ ​sudo yum install -y yum-utils
$ sudo yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo
$ sudo yum-config-manager --enable docker-ce-edge​

Oracle Linux public repositories (must for Oracle Linux)​

$ sudo yum-config-manager --add-repo http://yum.oracle.com/public-yum-ol7.repo
$ sudo yum-config-manager --enable ​ol7_latest
$ sudo yum-config-manager --enable ​ol7_UEKR4
$ sudo yum-config-manager --enable ​ol7_addons

Note: If the enable command is not successfully executed edit the file (vi /etc/yum.repos.d/public-yum-ol7.repo) manually. Enable the above mentioned repositories.

RHEL public repositories and installation (must for RHEL)​

$ sudo yum install -y yum-utils
$ sudo yum-config-manager --add-repo https://download.docker.com/linux/rhel/docker-ce.repo
$ sudo yum install docker-ce docker-ce-cli containerd.io docker-compose-plugin

Install the Docker itself​

​$ sudo yum install -y docker-ce

The docker uses IP address range (by default 172.17.0.1 with mask 255.255.0.0) which might collide with infrastructure making it impossible to connect to the host using SSH. After docker installation and before reboot it is important to check this possible collision. Run $ ifconfig and look if your eth0 collides with the docker0 interface. (Collide means that the IP are overlaping).

In case that the eth0 uses 176... IP addresses you should change docker base IP address. Create file (if not exist) /etc/docker/daemon.json and paste this snippet:

{
  "bip": "10.9.0.1/24",

  "log-driver": "json-file",
  "log-opts": {
    "max-size": "10m",
    "max-file": "10"
  }
}

This file contains all configuration for Docker daemon. We also added log settings which is helpful for long-running containers where log files can get huge.

warning

After making changes to /etc/docker/daemon.json, you must restart Docker service with systemctl restart docker and verify that the IP address changed using ifconfig.

Docker service​

$ sudo systemctl start docker
$ sudo systemctl enable docker

Verify Docker is running​

$ ​docker version

Docker and proxy settings​

The most robust proxy settings which survives docker updates is with systemd settings. It is about creating simple files wich add service Environment variables to the Docker service.

  1. Create systemd configuration folder if it does not exist:
sudo mkdir -p /etc/systemd/system/docker.service.d
  1. Create /etc/systemd/system/docker.service.d/http-proxy.conf file and paste (edit the NO_PROXY according to your infrastructure):
[Service]
Environment="HTTP_PROXY=http://proxy.example.com:80/"
Environment="NO_PROXY=localhost,127.0.0.1,gitlab,*.company.com,*.company.local,.company.com,.company.local"
  1. Create /etc/systemd/system/docker.service.d/https-proxy.conf file and paste:
[Service]
Environment="HTTPS_PROXY=https://proxy.example.com:80/"
  1. Reload service daemon and restart Docker service:
sudo systemctl daemon-reload
sudo systemctl restart docker

For more information see official guide: Control Docker with systemd.

Enable the Docker service (optional)​

In order to automatically start the Docker service upon server startup you have to enable the service.

$ ​systemctl enable docker

tip

Reboot the system after enabling Docker service and check the system upon startup.

Install Docker Compose (Required)​

Docker Compose provides service orchestration which we use in our SAMO distribution. Therefore it is important to install this utility as well as Docker itself.

The easiest way to install Docker Compose is to download the binary and create a link:

sudo curl -L https://github.com/docker/compose/releases/download/1.23.2/docker-compose-`uname -s`-`uname -m` -o /usr/local/bin/docker-compose
sudo chmod +x /usr/local/bin/docker-compose
info

Updating Docker Compose is done the same way as installation. Just use a higher version number in the command above. See the Docker Compose release page to find the latest version.

Troubleshooting​

Some tips we found useful when using Docker.

Trust self-signed certificates​

If you ever need to use self-signed certificate which is not considered trustworthy you can easily tell docker to trust a certain certificate for certain hostname like this:

  1. ​get certificate and name it: ca.crt
  2. copy it to:
/etc/docker/cert.d/HOSTNAME:PORT/ca.crt
​/etc/pki/ca-trust/source/anchors/ca.crt
  1. run: update-ca-trust
  2. restart docker: sudo systemctl restart docker