Uly.me

cloud engineer

FFMPEG Resize

How to resize JPEG using FFMPEG.

ffmpeg -i TREE.JPG -y -vf scale=iw*.2:ih*.2 tree.jpg

Another option is to set resolution.

ffmpeg -i TREE.JPG -y -vf scale=-1:720 tree.jpg

How to resize video using FFMPEG.

ffmpeg -i TREE.MP4 -s 640x360 -pix_fmt yuv420p -crf 18 tree.mp4

How to create a thumbnail from a video.

ffmpeg -ss 00:00:00 -i tree.mp4 -vframes 1 tree.jpg

Vim Colors

I had trouble getting my vi editor to display all black background color. This includes the background color after the end of the file. I just wanted an all black background for better visibility. I did a little bit of googling and found this nice little gem. I happen to like the dessert theme and went with that instead of the recommended mustang theme which I don’t have installed. Hope you’ll find this helpful.

set t_Co=256
set background=dark
colorscheme dessert
highlight Normal ctermbg=NONE
highlight nonText ctermbg=NONE

Install Cockpit on Rocky 9

Cockpit is a web-based graphical interface for Linux users and admins.

Install

dnf install cockpit

Start and Enable

systemctl start cockpit
systemctl enable cockpit.socket

Status

systemctl status cockpit

Web access

http://192.168.0.20:9090

Saving and Restoring iptables

iptables can be saved or loaded from a file. Here’s a way to do it.

Saving to a file

# Debian/Ubuntu
iptables-save > /etc/iptables/rules.v4
# Redhat/Centos/Rocky
iptables-save > /etc/sysconfig/iptables

Loading from a file

# Debian/Ubuntu
iptables-restore > /etc/iptables/rules.v4
# Redhat/Centos/Rocky
iptables-restore > /etc/sysconfig/iptables

Listing rules

iptables -L

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