Uly.me

cloud engineer

AWS CloudWatch Alarms

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

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 Process in Auto Scaling Group

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.

Check Certificate Expiration

Here’s the openssl command to find out if a cert is expired.

$ openssl s_client -connect yourdomain.com:443 -servername yourdomain.com 2> /dev/null | openssl x509 -noout -dates

Result

notBefore=Apr  9 00:00:00 2020 GMT
notAfter=Apr  9 23:59:59 2022 GMT