Installing postgresql 9.6 on RHEL/CentOS 7 without repository

Postgres has released the final version of postgresql 9.6 on November 2021, and this version is no longer supported by postgresql.org. So installing out of support software in production server is not recommended.

But for anyone who still wanted postgresql 9.6 on CentOS 7, here is how you can install it (the official pgrepo do not allow any installation of postgresql version less than 10)

1. Using your browser, browse to the postgresql download page at https://download.postgresql.org/pub/repos/yum/

2. Search for your version and architecture, in my case I needed version 9.6 for a centos 7 x86_64 machine. So my url would be https://download.postgresql.org/pub/repos/yum/9.6/redhat/rhel-7-x86_64/

3. Download the necessary package, usually 1 package for the client, 1 package for the libs and one for the client (optional).

wget -c https://download.postgresql.org/pub/repos/yum/9.6/redhat/rhel-7-x86_64/

postgresql96-libs-9.6.22-1PGDG.rhel7.x86_64.rpm 

wget -c https://download.postgresql.org/pub/repos/yum/9.6/redhat/rhel-7-x86_64/postgresql96-libs-9.6.22-1PGDG.rhel7.x86_64.rpm 

wget -c https://download.postgresql.org/pub/repos/yum/9.6/redhat/rhel-7-x86_64/postgresql96-server-9.6.22-1PGDG.rhel7.x86_64.rpm

4. Install the packages. If any additional packages are needed, just download it from the repo url above.

sudo yum install ./postgresql96-libs-9.6.22-1PGDG.rhel7.x86_64.rpm ./postgresql96-libs-9.6.22-1PGDG.rhel7.x86_64.rpm ./postgresql96-server-9.6.22-1PGDG.rhel7.x86_64.rpm

5.  Initialize the database

sudo /usr/pgsql-9.6/bin/postgresql96-setup initdb

6. Enable the database startup on boot, and start the service

sudo systemctl enable --now postgresql-9.6 

Running singularity without installing using docker

Singularity is another container platform, similar to docker. It is widely used in high performance computing world, due to better security and portability.

But many of us are already familiar with docker, since that is the most widely used container technology. To try to learn singularity, the easiest way is to use docker that we already have inside our machine and launch singularity from there. 

We can run singularity image from quay.io by running below command

docker run --privileged --rm quay.io/singularity/singularity:v3.10.0 --version

singularity-ce version 3.10.0

In order to download image from docker and convert it into sif, we can use this

docker run --privileged --rm -v ${PWD}:/home/singularity quay.io/singularity/singularity:v3.10.0 pull /home/singularity/alpine_latest.sif docker://alpine

Once downloaded, we can run a command using the newly downloaded image

docker run --privileged --rm -v ${PWD}:/home/singularity quay.io/singularity/singularity:v3.10.0 exec /home/singularity/alpine_latest.sif cat /etc/os-release

NAME="Alpine Linux"

ID=alpine

VERSION_ID=3.15.4

PRETTY_NAME="Alpine Linux v3.15"

HOME_URL="https://alpinelinux.org/"

BUG_REPORT_URL="https://bugs.alpinelinux.org/"

Even though this is probably the easiest way to use singularity in a docker installed machine, but the command can get pretty confusing. It is highly advisable, that once you have tested enough and decided to use singularity, to actually install it in your system.

Run an apache webserver with php using docker

This is actually very easy, just run below command to start it

docker run -d -p 8000:80 --mount type=bind,source"$(pwd):/htdocs",target=/var/www/html php:apache

The options are:

-d : run this container in a detached mode (in the background)

--mount : mount a folder in current directory called htdocs (will be created by docker) into /var/www/html in the container

-p 8000:80 : will map port 8000 in localhost to port 80 in the container

Once started, create a simple php script inside the htdocs directory

cd htdocs

cat >> index.php<<EOF
<?php

echo "This is my php script";

?>

EOF

And browse using a normal web browser to http://localhost:8000. You should see "This is my php script" shown in your web browser 

Running a postgresql database using singularity

First, we need to pull the postgresql image from dockerhub

singularity pull docker://postgres:14.2-alpine3.15

The image will be saved as postgres_14.2-alpine3.15.sif. Now, create an environment file

cat >> pg.env <<EOF

export TZ=Asia/Kuala_Lumpurt

export POSTGRES_USER=pguser

export POSTGRES_PASSWORD=mypguser123

export POSTGRES_DB=mydb

export POSTGRES_INITDB_ARGS="--encoding=UTF-8"

EOF

Create 2 directories for data and run

mkdir pgdata

mkdir pgrun

Run the container. The options are -B to bind mount local directory to container, -e to clean environment before running the container, -C to start the container with PID, IPC and environment, and --env-file is to pass the environment variables in the file to the container

singularity run -B pgdata:/var/lib/postgresql/data -B pgrun:/var/run/postgresql -e -C --env-file pg.env postgres_14.2-alpine3.15.sif

The postgresql will be listening on localhost at port 5432. To test it out, just open another terminal, and use the same postgres_14.2-alpine3.15.sif to run psql

singularity exec postgres_14.2-alpine3.15.sif psql -h localhost -p 5432 -d mydb

mydb=#  

Running a simple nginx web server with custom index file using singularity

First, create a directory to house our index.html file

mkdir web

Create our custom index file

cat >> web/index.html<<EOF

<html>

<h1>This is my index<h1>

</html>

EOF 

Then, download the image from dockerhub. The image will be downloaded as nginx_latest.sif.

singularity pull docker://nginx

Run instance, and mount the web directory to /usr/share/nginx/html in the instance. The options are, -B to bind the web directory in the host machine to the /usr/share/nginx/html in the container, while the --writable-tmpfs is to allow the container to write temporary files during execution. The container will be running on localhost port 80.

sudo singularity run -B web/:/usr/share/nginx/html --writable-tmpfs nginx_latest.sif

Check if our webserver is running fine using a standard web browser:

Running a simple nginx web server using singularity

In this example, we will use the nginx web server image from docker hub.

1. Pull the nginx image from dockerhub. The image will be saved as nginx_latest.sif

singularity pull docker://nginx

2. Run an instance of nginx. We need to put --writable-tmpfs option so that the instance can write temporary files to disk.

sudo singularity run --writable-tmpfs docker://nginx web

3. To test, open a new terminal, and use curl to access http://localhost. We should be able to access the landing page of nginx running inside a singularity container 

curl localhost

<!DOCTYPE html>

10.22.0.1 - - [05/Mar/2022:15:45:10 +0800] "GET / HTTP/1.1" 200 615 "-" "curl/7.68.0" "-"

<html>

<head>

<title>Welcome to nginx!</title>

<style>

html { color-scheme: light dark; }

... 

 4. We can also use a web browser and browse to localhost

Running docker "hello-world" image using singularity

One of the advantage of singularity is, it does not require any service to run containers. And the images that you downloaded will be saved in normal files in your filesystem, rather than in some cache directory like docker.

To run dockerhub's hello-world image using singularity:

1. Pull the image from dockerhub

$ singularity pull docker://hello-world

2. The image will be saved as hello-world_latest.sif

$ ls 

hello-world_latest.sif

3.1 To run a container based on that image, just use "singularity run" against the sif file

$ singularity run  hello-world_latest.sif

...

Hello from Docker!      

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

...

3.2 Or you can just "./" the sif file

$ ./hello-world_latest.sif

...

Hello from Docker!      

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

...