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December 6, 2024

Linux Commands & Snippets

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 * 
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