Uly.me

cloud engineer

Bash Menu and Functions

How to integrate menus and functions in your Bash script.

#!/bin/bash
function show_logs {
ls -l /var/log/
}
function show_users {
cat /etc/passwd
}
echo '--------'
echo 'My Menu'
echo '--------'
PS3='Choose an option: '
commands=("Show logs" "Show users" "Quit")
COLUMNS=0
select cmd in "${commands[@]}"; do
    case $cmd in
        "Show logs")
            echo "Showing logs ... "
            show_logs
            ;;
        "Show users")
            echo "Showing users ... "
            show_users
            ;;
	"Quit")
	    echo "Exiting ... "
	    exit
	    ;;
        *) echo "invalid option $REPLY";;
    esac
done

Result

--------
My Menu
--------
1) Show logs
2) Show users
3) Quit

GCP List of BMS Servers

Here’s how to list Bare Metal Servers in Google Cloud Platform via gcloud.

gcloud bms instances list --region REGION --project PROJECT

Result

NAME            ID                 PROJECT         REGION       MACHINE_TYPE           CLIENT_IPS    PRIVATE_IPS                    STATE
server-001      at-xxxxxxx-svr001  project-01      us-central1  o2-ultramem-896-metal  10.0.0.1      192.168.253.1,192.168.252.1    RUNNING
server-002      at-xxxxxxx-svr002  project-02      us-central1  o2-ultramem-896-metal  10.0.0.2      192.168.253.2,192.168.252.2    RUNNING

Obviously you can see the same from GCP’s Console.

Running Top by Process

Here’s how to isolate a process via the top command.

top -c -p $(pgrep -f process_name | head -20 | tr "\\n" "," | sed 's/,$//')

Hide All Windows Except Current

Less clutter is good. There are times when there’s too many windows in our desktop. Having less clutter leads to better focus. Here’s how to hide all Windows on a Mac OS except for the current or active one.

Command + Option + h

I wished there was a command to bring them all back, but I have not found one yet.

History Without Line Numbers

Here’s how to display history without the line numbers.

history -w /dev/stdout

Result

cd /etc/httpd/conf
view httpd.conf 
vim wiki.conf 
vim ssl.conf

CloudWatch Notifications

How to give someone access to enable/disable CloudWatch notifications.

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Action": [
                "cloudwatch:DescribeAlarms",
                "cloudwatch:EnableAlarmActions",
                "cloudwatch:DisableAlarmActions"
            ],
            "Effect": "Allow",
            "Resource": "*"
        }
    ]
}

GCP Role Policy Binding

How to display the policy binding.

gcloud compute instances get-iam-policy SERVER --project=PROJECT_ID --zone=ZONE

Result

# There is no binding policy
etag: ACAB
 
# There is a binding policy
bindings:
- members:
  - serviceAccount:SERVICEACCOUNT
  role: organizations/xxxxxxxxxxxx/roles/ROLE
etag: xxxxxxxxxxx=
version: 1

Add a role binding policy

gcloud compute instances add-iam-policy-binding SERVER \
--project=PROJECT_ID \
--zone=ZONE \
--member=serviceAccount:SERVICEACCOUNT \
--role="organizations/xxxxxxxxxxxx/roles/ROLE"

Remove a role binding policy

gcloud compute instances remove-iam-policy-binding SERVER \
--project=PROJECT_ID \
--zone=ZONE \
--member=serviceAccount:SERVICEACCOUNT \
--role="organizations/xxxxxxxxxxxx/roles/ROLE"