Useful Linux Commands

Zathura

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Get cpu temp:

cat /sys/class/thermal/thermal_zone*/temp

It looks like when date and time gets out of sync for too long, unbound's DNSSEC feature will fail and we wont be able to connect anything. To detect errors, follow these steps.

Use ping 8.8.8.8 or other dns server to check if we are be able to connect them using ips. If not, the issue is with the internet. Check wireguard health.
If it succeeds, use ping google.com. If it fails to resolve, the issue is with the DNS.
Then use this: dig @127.0.0.1 google.com. If it says status: SERVFAIL somewhere, the issue is indeed with the unbound.
Check unbound's logs using sudo systemctl status unbound.service. If it says failed to prime trust anchor -- DNSKEY rrset is not secure . DNSKEY IN. The DNSSEC is failing.
Check the system time via date. If it returns something else from the real time, you need to fix it.
Check current datetime status: timedatectl status
Enable auto setting time and date: sudo timedatectl set-ntp true
Check the time again. If it may be not fixed if the date was out of sync for too long.
Do these: sudo timedatectl set-ntp false && sudo timedatectl set-time "2026-02-21 13:25:00" && sudo timedatectl set-ntp true. It should be fixed now. In set-time, write the actual current date and time.
Then restart unbound: sudo systemctl unbound

Change HDMI screen's brightness

ddcutil detect Detect the displays
ddcutil getvcp 10 Most monitors use the standard VCP (Virtual Control Panel) code 10 for brightness, but it’s good to verify. Check if 10 is reserved for brightness.
ddcutil setvcp 10 70 Change brightness to 70%
ddcutil setvcp 10 + 5 increase brightness by 5%. Place "-" instead of "+" if you want to decrease it.

Neovim diff tool. Merge conflicts in two different files.

nvim -d file1.md file2.md

You can also use:

sdiff
meld
git merge-file

Get the lines of code without comments and empty lines in the directory

scc .

ventoy!!!

List storage devices

lsblk

Write an iso file to a device.

sudo dd if=/path/to/your.iso of=/dev/sdX bs=4M status=progress

Send notifications on ssh login using .profile

(&>/dev/null simplex -e "#status $(date) New SSH login is established in VPS" -t 10 --smp-web-port &)

NFTables see what ips are blocked in a set.

sudo nft list set inet filter mail_flood_v4
Available sets: ssh_flood_v4, ssh_flood_v6, mail_flood_v4, mail_flood_v6, web_flood_v4, web_flood_v6

Get the actively used public network interface name:

ip -4 route ls | grep default | awk '{print $5}'

https://docs.redhat.com/en/documentation/red_hat_enterprise_linux/8/html/configuring_and_managing_networking/manually-configuring-the-etc-resolv-conf-file_configuring-and-managing-networking

sudo setcap 'cap_net_bind_service=+ep' /usr/local/bin/maddy

cap_net_bind_service: Allows binding to privileged ports (below 1024).
+ep: Adds the capability (effective, permitted).

Maddy systemd service gives error and cant start because /usr/lib/maddy was not created in installation.

It also gives permission errors and we need to change the ownership of directories to maddy user we created.

run commands with user maddy: sudo -u maddy <cmd>

vnstat: monitor network interface traffic with historical data.

Crowdsec list decisions: sudo cscli decisions list

Crowdsec remove decision: sudo cscli decisions delete -i <IP_ADDRESS>

Show CrowdSec metrics: sudo cscli metrics

check used ports

sudo netstat -tunlp

Get the password of the entry named rp_server:

secret-tool lookup Title rp_server
Example application: SSH_PASS=$(secret-tool lookup Title rp_server) SSH_USER=tired ./scripts/update-index.sh

Continue to downloading a file in wget
wget -c -t 0 --waitretry=1 <url>

-c continues to the download.
-t 0 retries downloading infinitely if it fails at some point. (0 means infinite, 1 means try only for 1 more time.)
--waitretry=1 waits for 1 seconds before retrying.

https://www.cyberciti.biz/tips/wget-resume-broken-download.html

Pass environment variables to a command:

(export $(grep -v '^#' .env | xargs) && env)
The parantheses makes it run in a sub-shell, protecting the environment variables from fetting exposed to the whole shell session.
env -S $(grep -v '^#' .env) env
env command sets temporary environment variables just for the command we run. (in this case, env)

Grep command will ignore the lines starting with #

Show how many files contains a string in a directory:

rg --glob '*.md' --line-number --no-heading "/1tvynN.md" .

just list the files, to use with sed:

rg --glob '*.md' -l --color never "/1tvynN.md" .

replace the strings with sed:
rg --glob '*.md' -l --color never "/1tvynN.md" . | xargs -r sed -i 's//1tvynN.md//index.md/g'

ffmpeg -ss 00:00:30 -i orginalfile -t 00:00:05 -vcodec copy -acodec copy newfile

-t parametresi -ss ile belirtilen dakikadan itibaren kaç dakikanın kesilen videoya dahil edileceğini ifade eder. Kaçıncı dakikaya kadar kesileceğini değil!

Install excalidraw using podman

podman pull docker.io/excalidraw/excalidraw:latest
podman run -p 8080:80 -d docker.io/excalidraw/excalidraw:latest
rename it to excalidraw
run podman start excalidraw next time

start an interactive bash shell inside a container
docker exec -it <container> bash

going to 10.1.0.1 address in web browser redirects to the captive portal. A web based authentication method usually for free wifi networks.

Load neovim session

source desuna-session.nvim

save neovim session

mksession desuna-session.vim

v4l2-ctl --list-devices

sudo modprobe v4l2loopback video_nr=0,8

scrcpy --v4l2-sink=/dev/video8

sudo rmmod -f v4l2loopback

Print page

lpr -o ColorModel=Gray -o orientation-requested=4 -o fit-to-page -o media=A4 photo-name.jpg

Make some app default for xdg-open

xdg-mime default org.pwmt.zathura.desktop application/pdf

desktop names are in /usr/share/applications

Write ISO to the usb from cmd line

sudo dd if=~/downloads/debian-12.11.0-amd64-netinst.iso of=/dev/sda bs=4M status=progress

Mount Disk Without Root

udisksctl mount -b /dev/sda1

To unmount: udisksctl unmount -b /dev/sda1

lua vim.diagnostic.open_float(nil, {focus=false})

LINUX ONE LINER TERMINAL COMMANDS

Get all files in a directory that contains a string

rg -l "string" ./

DROIDCAMX PORT FORWARD

adb forward tcp:4747 tcp:4747

KILL ALL MANDOS PROCESSES & START ONE

ps aux | grep 'md-folder' | grep -v 'grep' | awk '{print $2}' | xargs kill -9

SIMPLEX

podman run -d \
    -e "ADDR=smp.zynexis.com" \
    -e "PASS=pass" \
    -p 9384:5223 \
    -v $HOME/drive2/simplex/smp/config:/etc/opt/simplex:z \
    -v $HOME/drive2/simplex/smp/logs:/var/opt/simplex:z \
    docker.io/simplexchat/smp-server:latest

podman run -d \
    -e "ADDR=xftp.zynexis.com" \
    -e "QUOTA=40gb" \
    -p 9357:443 \
    -v $HOME/drive2/simplex/xftp/config:/etc/opt/simplex-xftp:z \
    -v $HOME/drive2/simplex/xftp/logs:/var/opt/simplex-xftp:z \
    -v $HOME/drive2/simplex/xftp/files:/srv/xftp:z \
    docker.io/simplexchat/xftp-server:latest

Clamav

Scan home folder with clamav:
sudo nice -n 15 clamscan && sudo clamscan -r -i -o -l /home/user/clamav.log –move=/home/user/infected /home/

Neovim

7,$!sort –> sort lines from 7 (included) to end of the file
lua vim.diagnostic.open_float()) –> show diagnostic in float