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Managing images

  1. Save current image to tar file
sudo podman save -o example.tar imagename:v1.0
sudo podman save -o mysql.tar registry.access.redhat.com/rhscl/mysql-57-rhel7:5.7
  1. Load an image from .tar file
sudo podman load -i example.tar
  1. Commit current container to an image
sudo podman commit --author="Hamidulla Ziyo" container-name/id registry.example.com:5000/mysql7:5.7
  1. Identify which files were changed, created, or deleted since the container was started
sudo podman diff container-name/id
sudo podman diff mysql-basic
  1. Tag image to distinguish from other releases
sudo podman tag [OPTIONS] IMAGE[:TAG] [REGISTRYHOST/][USERNAME/]NAME[:TAG] 

sudo podman tag mysql-custom devops/mysql:snapshot
  1. Remove tag from an image
sudo podman rmi devops/mysql:snapshot
  1. Push the local image to registry
sudo podman push [OPTIONS] IMAGE [DESTINATION]
sudo podman push quay.io/bitnami/nginx

Building images with Podman

sudo podman build -t NAME:TAG DIR

Creating application in different ways

  1. Creating an application based on an image, mysql, from Docker Hub, with the label set to db=mysql
oc new-app mysql --as-deployment-config \
> MYSQL_USER=user MYSQL_PASSWORD=pass MYSQL_DATABASE=testdb -l db=mysql
  1. Creating an application based on an image from a private Docker image registry:
oc new-app --docker-image=myregistry.com/mycompany/myapp --name=myapp --as-deployment-config
  1. Creating an application based on source code stored in a Git repository:
oc new-app https://github.com/openshift/ruby-hello-world --name=ruby-hello --as-deployment-config
  1. Desribe information about template
oc describe template postgresql-ephemeral -n openshift
  1. Create application from temmplate
oc new-app --template=postgresql-ephemeral -p POSTGRESQL_DATABASE=acmedb |
> -p POSTGRESQL_PASSWORD=redhat -p POSTGRESQL_USER=acmeadmin -p DATABASE_SERVICE_NAME=infodb -l app=info -l db=postgres

expose route to the service

oc expose svc/infodb
oc get route
  1. Create an application based on git repo. (Source to image)
oc new-app --as-deployment-config  php~https://github.com/openshift/sti-ruby.git#develop --context-dir=2.0 --name=php-helloworld
  1. Start a new build after changing source code
oc start-build php-helloworld
  1. List all local available templates/images
oc new-app --list
  1. List template parametres
oc process --parameters mysql-persistent -n openshift
  1. Process template and create multi-container application
oc process \
> -f todo-template.json -p RHT_OCP4_QUAY_USER=${RHT_OCP4_QUAY_USER} \
> | oc create -f -

same result can be achieved using oc new-app command without processing the template first. Just wait little bit after exposing the service

oc new-app -f todo-template.json -p RHT_OCP4_QUAY_USER=${RHT_OCP4_QUAY_USER}

Troubleshooting

  1. retrieve the logs from a build configuration
oc logs bc/<application-name>
  1. If a build fails, after finding and fixing the issues, run the following command to request a new build:
oc start-build <application-name>
  1. Deployment logs
oc logs dc/<application-name>
  1. relax the OpenShift project security with the command oc adm policy. This's used when container user has permission issues
oc adm policy add-scc-to-user anyuid -z default
  1. automated way to remove obsolete images and other resources.
oc adm prune
  1. Temporarily access some of these missing commands is mounting the host binaries folders, such as /bin, /sbin, and /lib, as volumes inside the container
sudo podman run -it -v /bin:/bin image /bin/bash