Linux

• Larger font: Ctrl + Shift + "+"
• Smaller font: Ctrl + Shift + "-"

Remote command

ssh user@server 'command arguments'

Interactive remote command

ssh -t user@server 'command arguments'

ls -l | head -n 1 | xargs gwenview

Copy to /usr/share/fonts/ or ~/.local/share/fonts/ and then run:

fc-cache -fv #for ~/.local/share/fonts
sudo fc-cache -fv  #for /usr/share/fonts/

chmod 755 /usr/share/fonts/dir
chmod 644 /usr/share/fonts/dir/*.ttf

• Serif: Gentium https://software.sil.org/gentium/download/
• Sans-Serif: Andika, Overpass

Umax boot: Esc

pacman-key --populate archlinux

gpg --edit-key 3E80... trust 5 y save

gpg --verify archlinux-2025.11.01-x86_64.iso.sig archlinux-2025.11.01-x86_64.iso

dd bs=4M if=path/to/archlinux-version-x86_64.iso of=/dev/disk/by-id/usb-My_flash_drive conv=fsync oflag=direct status=progress

free -h

• fyzická linka: MAC
• síťová vrstva (směrování): IP, ICMP, ARP
• transportní vrstva (komunikace mezi body): TCP, UDP
• aplikační vrstva (data aplikací): SSH, HTTPS, DNS, DHCP
• netstat is old (ifconfig, route, netstat)
• https://nmcheck.gnome.org
• https://github.com/Cyclenerd/static_status
• síťové rozhraní:

  ip link
  ip -s link
  nmcli device status
  enthtool enp0s3
  

• ip

  ip addr show
  ip -brief addr show
  ip route get 192.168.1.9
  ip route
  
  arping 192.168.1.8
  ip neighbour show
  

• maximum transmission unit

  ping -M do server.example.com -s 1500
  tracepath server.example.com
  tcpdump -i enp0s3 'icmp6 or icmp'
  
  iptables -t mangle -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu
  nft add rule ip filter forward tcp flags syn tcp option maxseg size set rt mtu
  

• porty (aplikační vrstva)

  ss -tulpn
  bat /etc/resolve.conf
  

https://www.joindns4.eu/for-public#resolver-options DNS4EU:

86.54.11.11
86.54.11.211
2a13:1001::86:54:11:11
2a13:1001::86:54:11:211

ss -tulpn | grep 53
nslookup www.example.com

• pohled do DNS

  dig www.example.com @1.1.1.1
  dig +cd www.rhybar.cz
  

• DHCP

  tcpdump -i enp0s3 -vvv 'port 67 or port 68'
  dhclient -v -1
  

• další nástroje

  mtr server.example.com
  iperf3 -c ping.online.net -u -b 10M -t 20
  speedtest-cli
  

for file in *.pdf
    magick $file $(basename $file .pdf).png
end

fd pattern
fd pattern -t d #directories
fd pattern -t f #files
fd pattern -x command {} # execute command for each file
fd pattern -X command # execute command for all files

fd . /srv/filmy -t d
fd . /srv/filmy -t d -x chmod 755 {}
fd . /srv/filmy/ -t f -x chmod 644 {}

• tldr
• fd (fdfind)
• bat
• ripgrep: rp
• exa
• dust, dua

bluetoothctl

if bluetooth headphones disconnect, run pavucontrol

ls -l /dev/ttyUSB0 sudo usermod -aG uucp $USER reboot groups

• Ctrl+A: Jump to the beginning.
• Ctrl+E: Jump to the end.
• Ctrl+U: Delete from cursor to the beginning.
• Ctrl+K: Delete from cursor to the end.
• Ctrl+C: Kill a command.

gsettings set org.gnome.desktop.wm.keybindings switch-input-source "['<Alt>Shift_L', '<Super>space', 'XF86Keyboard']" gsettings set org.gnome.desktop.wm.keybindings close "['<Super><Shift>Q', '<Alt>F4']" gsettings set org.gnome.desktop.wm.keybindings toggle-maximized "['<Super>F', '<Alt>F10']"

seq -w

cat /etc/passwd | grep "/\*/\*sh" awk -F: '($3 == 0) {print}' /etc/passwd sudo cat /root/.bash_history

for user in \((cut -f1 -d: /etc/passwd); do crontab -u \)user -l 2>/dev/null; done sudo cat /etc/crontab sudo ls -al /etc/cron.\/\

systemctl list-units --type=service --state=running ps aux --sort=-%mem | head -n 10 grep -r LD_PRELOAD /etc/profile /etc/bash* ~/.bashrc ~/.profile

sudo ss -tuln sudo netstat -tulnp

List of ports: Wikipedia

ls -la /home/*/.ssh/authorized_keys grep -r "" /root/.ssh/authorized_keys /home/*/.ssh/authorized_keys 2>/dev/null cat /etc/ssh/sshd_config | grep -E 'PermitRootLogin|PasswordAuthentication'

vim /etc/login.defs UMASK 027

lsmod

• Syncing files between one server to another server

rsync -avzh /source/path/ /destination/path/

• excludes specific directories (like temp/) from being synchronized

rsync -avzh --exclude 'temp/' /source/ /destination/

Identifying which process is using a specific port 8080 lsof -i :8080

• find files that are still held by a process after being deleted

lsof | grep deleted

git-delta package delta file1 file2

find /var/www -type f -name "*.log" -mtime +30 -delete find /etc -type f -exec chmod 644 {} \;

dust ncdu

Add the shell to /etc/shells with: echo /usr/local/bin/fish | sudo tee -a /etc/shells Change your default shell with: chsh -s /usr/local/bin/fish Again, substitute the path to fish for /usr/local/bin/fish - see command -s fish inside fish. To change it back to another shell, just substitute /usr/local/bin/fish with /bin/bash, /bin/tcsh or /bin/zsh as appropriate in the steps above.

• file.timer

  # file.timer
  # Copy this file to ~/.config/systemd/user/
  [Unit]
  Description=Run my-service.py script
  
  [Timer]
  OnBootSec=15min
  OnCalendar=*-*-* 18:00:00
  
  [Install]
  WantedBy=timers.target
  

• file.service

  # Change the path for the script in ExecStart
  [Unit]
  Description=Run my-service.py script
  
  [Service]
  Type=simple
  Restart=always
  ExecStart=/usr/bin/env python3 /home/user/.local/bin/my-service.py
  

• Management:

  systemctl --user daemon-reload
  systemctl --user start my-service.timer
  systemctl --user --all list-timers
  

libdvdread libdvdcss libdvdnav sudo pacman -S libdvdread libdvdnav libdvdcss

• iwd
• systemd-resolved

sudo systemctl enable iwd sudo systemctl start iwd sudo systemctl enable systemd-resolved sudo systemctl start systemd-resolved

ln -sf /run/systemd/resolve/stub-resolv.conf /etc/resolv.conf

vim /etc/iwd/main.conf EnableNetworkConfiguration=true

resolvectl status

pacstrap -K /mnt base linux linux-firmware arch-chroot /mnt pacman -S grub efibootmgr intel-ucode iwd vim man-db man-pages texinfo

pdfimages -all input.pdf output