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cloud engineer

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

Copy S3 to GCS

You can use gsutil to copy directly from a S3 bucket to a GCS bucket.

gsutil can read/write to a S3 bucket as long as it has access to your AWS credentials.

The -R option is recursive and -m is for multi-threaded or multi-processing.

gsutil -m cp -R s3://bucket/ gs://bucket

You can also use rsync instead of cp. Just be aware that rsync does not copy empty directory trees

gsutil -m rsync -r s3://bucket/ gs://bucket

If you plan to use -d, Use it with caution since it deletes content.

Git Reset

To undo a git add, run git reset file or get reset.

git reset filename
git reset

Run git status to check.

git status