Category: Oracle Linux

I stupidly reinstalled Ubuntu on my desktop on which I had Linux Mint just because I wanted to try it but I ended up with going back to Linux Mint again. I’m writing this blog from my Linux Mint. I casually formatted the hard drive and did a little distro hopping. When I tried to SSH into my blog host on OCI, I realized that I lost the SSH key and no other host can access the blog host. Crap!

However, I was able to recover it relatively quickly. Here is the list of what I did.

1. Cloned the existing boot volume.
2. Created an instance out of the cloned boot volume. When I created the instance, I had a chance to enter public key.
3. Since it was a cloned volume, everything was already on it. Since it’s got a different public IP, I just changed the DNS A Record to point to the new instance.

It’s all back up and I am able to SSH into the host again.

I remember doing some experiment with Ansible on Azure sometime in January for about 2 weeks. I just got charged $12.16. Azure charges come to my as surprise… Hmm I didn’t think it was costing that much, kind of surprise. I should have monitored the cost as I was using it but I provisioned just one small VM, so I didn’t think it was going to be $12.

I went head and did some analysis. Here is the details of the cost.

• VM License: $7.43
• Storage: $2.50
• VM: $0.77

Oh, I was paying to a VM license… I wondered what I provisioned… If I remember correctly, it was Oracle Linux. When you use Oracle Linux on Azure, it costs about $0.019/h. I had it a little more than 2 weeks so it makes sense. However, as far as I know, Oracle does not charge anything for its license if you provision Oracle Linux on Oracle Cloud Infrastructure (OCI), so if you want to use Oracle Linux, OCI is a good choice.

I see people posting question like “Which distro is good other than CentOS?”. I’d say Oracle Linux is a very good choice. It is 100% compatible with RedHat Linux and it’s free. As far as I know, Oracle Linux is very well maintained by Oracle very often and as long as Oracle is in business, it will continue to be distributed for free. RedHat dropped the ball on CentOS because it didn’t make business sense to RedHat but Oracle uses Oracle Linux for their production a lot so I don’t see them dropping the ball anytime soon.

I just migrated my blog to Oracle Linux 8 on Oracle Cloud Infrastructure. Here is the spec.

• VM Shape: VM.Standard.A1.Flex
• OS: Oracle Linux 8
• CPU: AMPERE Arm64 1 CPU
• Memory: 6GB
• Boot Volume: 100GB
• Docker Containers: WordPress, MariaDB, NGINX and phpMyAdmin

I will probably keep this machine running for the foreseeable future. Configuring a new VM was a breeze because of the Ansible project I worked on.

Most of the articles I find on creating a permanent Jenkins slave on Linux requires the slave node to be exposed to public Internet. I want the Linux slave to be pinging Jenkins master just like Windows service. Here is the way I came up with.

Install Prerequisites

• Java (sudo dnf install java-11-openjdk.x86_64)
  • Check if the Java has been installed. (java -version)
    Result:

openjdk version "11.0.12" 2021-07-20 LTS
OpenJDK Runtime Environment 18.9 (build 11.0.12+7-LTS)
OpenJDK 64-Bit Server VM 18.9 (build 11.0.12+7-LTS, mixed mode, sharing)

Add a Permanent Node

Login to Jenkins master and click Manage Jenkins -> Manage Nodes and Clouds. Click New Node. And then give the node a name (like linux-node), select Permanent Agent and click OK.

And then, click Save button. If you navigate to the node that you just created, you should see something like…

We will take copy this line.

java -jar agent.jar -jnlpUrl https://jenkins.hayato-iriumi.net/computer/linux%2Dnode/jenkins-agent.jnlp -secret 136fa14dcc4013727e24c9f1a9b84127d7c7ca0cfa15e22c1e1d4e0140122529 -workDir ""

Now, we’ll have to download agent.jar from the Jenkins master and upload the file to the slave machine. Just click on the agent.jar link to download it.

I have the agent.jar file in Downloads directory, so here is the command to upload the agent.jar file to the slave machine.

scp ./Downloads/agent.jar hiriumi@192.168.1.29:~

Now, ssh into the slave machine.

ssh hiriumi@192.169.1.29

Trust SSL Certificate

If your Jenkins master has SSL implemented, it’s a good practice to trust the SSL certificate. Here is how you can download the certificate on your slave machine.

openssl s_client -showcerts -connect jenkins.hayato-iriumi.net:443 < /dev/null | openssl x509 -outform DER > jenkins.hayato-iriumi.net.cer

Now use keytool to trust it.

sudo keytool -trustcacerts \
-keystore "/etc/java/java-11-openjdk/java-11-openjdk-11.0.12.0.7-0.el8_4.x86_64/lib/security/cacerts" \
-storepass changeit -alias jenkins -import -file \
"/home/hiriumi/jenkins.hayato-iriumi.net.cer"

Create a Script File and Execute

Paste the Java command you get from the node page in to slave.sh

java -jar agent.jar \
-jnlpUrl https://jenkins.hayato-iriumi.net/computer/linux%2Dnode/jenkins-agent.jnlp \
-secret 136fa14dcc4013727e24c9f1a9b84127d7c7ca0cfa15e22c1e1d4e0140122529 -workDir "./slave"

Make sure slave.sh is executable by adding execute flag on the file.

chmod +x slave.sh

If you execute the slave.sh file, it starts to communicate with the Jenkins master and starts to serve as one of the Jenkins slave.

./slave.sh

Once the connection is successful, you will see something like the following.

Now, this method does not survive restarting the slave machine. Now that the communication is successful, I will look into making this script a daemon.