Uly.me

cloud engineer

Linux

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

Running Top by Process

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

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

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

Jekyll on Docker Container

Here’s how to run Jekyll in a Docker container.

mkdir blog
cd blog
docker run -v $(pwd):/site bretfisher/jekyll new .
docker run -p 4000:4000 -v $(pwd):/site bretfisher/jekyll-serve

Another option is to use docker compose. Create a docker-compose.yml file.

version: 3.5
services:
  jekyll:
    image: bretfisher/jekyll-serve
    volumes:
      - .:/site
    ports:
      - '4000:4000'

Run Jekyll.

cd blog
docker-compose up -d

Stop Jekyll.

cd blog
docker-compose down

Cleanup Stale CVS Snapshots

Here’s the script that looks mounts with stale file handles and removes them.

#!/bin/bash
file='/tmp/stale.txt'
df -h | grep Stale > $file
sed -i -e 's/df: ‘/'""'/g' $file
sed -i -e 's/’: Stale file handle/'""'/g' $file
while IFS= read -r line; do
  echo 'unmounting '$line
  umount $line
done < $file