Get insight into a Linux machine using Cockpit

Cockpit is an interactive Linux server admin interface. You can use it to monitor/ manage a Linux node through a web browser.

Install Cockpit on the Linux machine

yum install cockpit -y

systemctl start cockpit

systemctl enable --now cockpit.socket

Docker 101 Blog Series

Consolidating my Docker 101 blog series.

Docker 101 - Part1 - Installation

Docker 101 - Part2 - Basic operations

Docker 101 - Part3 - Persisting data using volumes

Docker 101 - Part4 - Creating images using dockerfile

Docker 101 - Part3 - Persisting data using volumes

In this article, I will explain how to use Docker volumes for persisting data generated by and used by containers with --mount flag. Volumes use the Docker area and it can be found under /var/lib/docker/volumes/ directory of the Docker host.

Example:

docker run -dit --name centos_volume_test --mount source=data_volume01,target=/datavol01 centos sleep 1800

The above command will run a CentOS container and mounts a volume at /datavol01 inside the container. It uses source /var/lib/docker/volumes/data_volume01. The below screenshot shows the necessary steps to verify it.

Hope it was useful. Cheers!

Related posts

Docker 101 - Part2 - Basic operations

Docker 101 - Part1 - Installation

References

https://docs.docker.com/storage/volumes/

https://docs.docker.com/storage/bind-mounts/

Docker 101 - Part1 - Installation

Enter cloud native! In this article, I will briefly explain how to build a virtual Docker host. Here I am installing Docker on a CentOS 7.4 virtual machine running on ESXi 6.5 which is part of a VMware vSAN cluster.

Prerequisites:

• Deploy a basic CentOS 7.4 VM
• Assign IP address and ensure the VM has internet connectivity
• You should have root creds

Installation:

• SSH to the CentOS VM as root
• yum check-update
• yum install -y yum-utils device-mapper-persistent-data lvm2
• yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo
• yum install docker-ce
• systemctl start docker
• systemctl enable docker
• systemctl status docker

Verify version:

• docker version

Run your first container:

• docker run hello-world

Hope it was useful. Cheers! In the next part, I will explain basic Docker commands and operations.

Related posts

Docker 101 - Part2 - Basic operations

References

https://docs.docker.com/install/linux/docker-ce/centos/
https://phoenixnap.com/kb/how-to-install-docker-centos-7
https://linuxize.com/post/how-to-install-and-use-docker-on-centos-7/
https://www.digitalocean.com/community/tutorials/how-to-install-and-use-docker-on-centos-7

How to restore services if your Hyper-V host is not booting up : Incident management

How to restore services if your Hyper-V host goes down all of a sudden. It can be something like, the server is not booting up after a reboot, showing that operating system not found. This can be due to many reasons. But, you have to find a work around to fix this and to restore the services which were running before. There may be a few VMs running on that host and you have to find a solution to bring those VMs up and running.

 

If you don't have much time to troubleshoot and fix this, the best possible option is to copy those VM files to another Hyper-V host (if you have another Hyper-V hosts running with enough resources). In this case, you can try using a Linux live CD/ DVD (say CentOS or Ubuntu), to boot from the CD/ DVD. Once it boots up, you can see your drives and VM files, copy it to another Hyper-V host. Once copying is done, you can import the VMs using Hyper-V manager and power it on.