Interface Priority on Linux

sudo nmcli connection modify 'enter ssid here' ipv4.route-metric 50
sudo nmcli connection up 'enter ssid here'

Install sudo on Debian 12

su
apt install sudo

Add a user to sudo group:

su -l
adduser <your_username_here> sudo
logout

Change IP Addressing from DHCP to Static

sudo nano /etc/network/interfaces

auto <interface>
iface <interface> inet static
address x.x.x.x
netmask 255.255.255.0
gateway xx.xx.xx
dns-nameservers xx.xx.xx

sudo systemctl restart networking.service
sudo systemctl status networking.service

Change hostname (Debian 9/10/11/12)

hostnamectl set-hostname {name-here}
sudo hostnamectl set-hostname enkielhostsample

sudo nano /etc/hosts   # replace old hostname references

Check DNS (systemd-resolved)

resolvectl status
resolvectl dns <interface> <dns address>,<dns address>

Remove folder contents

sudo rm -rf foldername/*

Missing disk space on new installation

lvextend -l +100%FREE /dev/ubuntu-vg/ubuntu-lv
resize2fs /dev/ubuntu-vg/ubuntu-lv

Root file system requires manual fsck

fsck -yf /dev/sda1

“Reading package lists… Error!”

sudo apt clean
sudo rm -rf /var/lib/apt/lists/*
sudo apt update

Setup mobile Linux/Termux storage sharing

termux-setup-storage

Kill zombied application

ps -eo pid,ppid,state,cmd | awk '$3=="Z" { print "Zombie PID:", $1, "Parent PID:", $2 }'
kill -HUP <parentPID>

Allow password auth only for a single IP (sshd_config)

# Default: key-based only for everyone
PasswordAuthentication no
PubkeyAuthentication yes

# Exception: allow password login from specific IP
Match Address 203.0.113.25
    PasswordAuthentication yes

Steps: 1) Edit sshd_config and add the block above.
2) Test syntax: sudo sshd -t
3) Reload SSH: sudo systemctl reload sshd

Fix DNS configuration

sudo nano /etc/resolv.conf
# Example
nameserver 8.8.8.8
nameserver 1.1.1.1

# If systemd-resolved keeps overwriting:
sudo systemctl disable systemd-resolved
sudo systemctl stop systemd-resolved
sudo rm /etc/resolv.conf
echo -e "nameserver 8.8.8.8\nnameserver 1.1.1.1" | sudo tee /etc/resolv.conf

Codex clear session caches

cd ~/.codex/sessions
rm -rf *