Archives for October 2021

Install AdoptOpenJDK

October 28, 2021

OpenJDK is an open-source implementation of the Java.

How to install AdoptOpenJDK.

TAR

cd /usr/java
wget --no-check-certificate https://bit.ly/3jKm3KZ
tar xzf OpenJDK8U-jdk_x64_linux_hotspot_8u312b07.tar.gz
export PATH=$PWD/jdk8u312-b07/bin:$PATH
java -version

RPM

cat <<'EOF' > /etc/yum.repos.d/adoptopenjdk.repo
[AdoptOpenJDK]
name=AdoptOpenJDK
baseurl=http://adoptopenjdk.jfrog.io/adoptopenjdk/rpm/centos/$releasever/$basearch
enabled=1
gpgcheck=1
gpgkey=https://adoptopenjdk.jfrog.io/adoptopenjdk/api/gpg/key/public
EOF

yum install adoptopenjdk-8-openj9

Terraform User Data

October 26, 2021

Here’s how to add userdata in Terraform.

user_data = filebase64("${path.module}/example.sh")

AWS CloudWatch Alarms

October 25, 2021

How to enable and disable CloudWatch alarms

$ aws cloudwatch disable-alarm-actions --alarm-names myalarm --region us-east-1
$ aws cloudwatch enable-alarm-actions --alarm-names myalarm --region us-east-1

Run Telnet on Git Bash

October 20, 2021

Although telnet is not used regularly since insecure, it’s a handy tool for testing ports.

For example, to check if a port 80 is open, you run this command.

$ telnet servername 80

Git Bash does not come with telnet, but you can use the Windows version by using winpty.

$ winpty telnet servername 457
Connecting To servername...Could not open connection to the host, on port 457: Connect failed

If port is open, you get an empty reply, just like in Windows.

AWS Suspend Auto Scaling Group

October 20, 2021

You can administratively suspend a process in AWS Auto Scaling group for troubleshooting purposes.

Here are the available processes.

Terminate
Launch
AddToLoadBalancer
AlarmNotification
AZRebalance
HealthCheck
ReplaceUnhealthy
ScheduledActions

If you have difficulty launching a VM, check if any of these processes are suspended.

Removed them if applicable.