Linux

• https://www.youtube.com/watch?v=X8h304Jp9N8 Fedora Silverblue’s move to bootable OCI images: Linux will never be the same
• io_uring #async
  • https://en.wikipedia.org/wiki/Io_uring
  • https://unixism.net/loti/what_is_io_uring.html
  • https://kernel.dk/io_uring.pdf
• Alternatives to Apache Benchmark
• listening for codes sent by the keyboard: sudo showkey
• listening for codes sent by the mouse: sudo apt install evtest && sudo evtest
• How to transform curl to ab
  • <curl> = <ab>
  • -H = -H: headers
  • --data-raw <json> = -p <file>.json: request body
  • --data @file = -p <file>.json: request body
• How to print and redirect the stdout

  <command> | tee <filename>
  

• Converting images from webp (or jpg, png, etc.) to jpg (or webp, png, etc) (Tweet)

  sudo apt install imagemagick
  convert <file>.webp <file>.jpg
  

• How to resize images

  sudo apt install imagemagick
  

  # Reducing quality
  convert <input> -quality <n>% <output>
  

  # Keeping aspect ratio
  convert <input> -resize <w>x<h> <output>
  

  # Ignoring aspect ratio
  convert <input> -resize <w>x<h>! <output>
  

• List and sort directories by size

  du -sh * | sort -hr
  

• Open a terminal logged in as another user

  su $OTHER_USER
  

• Lorem Ipsum

  sudo apt update && sudo apt install libtext-lorem-perl
  lorem -w 96  # 96 words
  lorem -s 8   # 8 sentences
  lorem -p 12  # 12 paragraphs
  

• Captive Portals - Accessing WiFi that requires a browser authentication

  ip --oneline route get 1.1.1.1 | awk '{print $3}' | xargs google-chrome
  

• Format pendrive

  df -h
  # find the pendrive to be formatted
  sudo umount /dev/sdXX
  sudo mkfs.vfat /dev/sdXX
  

• Bootable pendrive

  df -h
  # find the pendrive
  sudo umount /dev/sdXX
  cp image.iso /dev/sdXX
  sync
  

• Reading the output of a process

  less /proc/$PID/fd/1  #stdout
  less /proc/$PID/fd/2  #stderr
  

• How to use SSH as SOCKS5 proxy

  ssh -vCND localhost:9999 -i <path_to_id_rsa> <username>@<remote_server>
  

• How to learn what type (DDR?) memory my computer uses?

  sudo dmidecode -t 17
  

• Profiling zsh startup

  # .zshrc
  zmodload zsh/zprof
  ...
  zprof
  

• Run command skipping alias

  \<command>
  

  
• Comando time (POSIX)
  • real é o tempo total do processo, do início ao fim;
  • user é o tempo de CPU gasto em user-mode (fora do Kernel);
  • sys é o tempo de CPU gasto no Kernel (ex.: syscalls, alocação de memória, I/O, etc.);
  • user + sys é o tempo total de CPU do processo;
• Inverter o teclado - Símbolos serem primários e os números secundários (créditos ao Vítor)

  xmodmap -pke | sed -nre 's/keycode  (1[0-9]) = ([^ ]*) ([^ ]*)/keycode \1 = \3 \2/p' | xmodmap -
  

• Ignoring lines in sed

  # Ignore lines containing '# noqa'
  sed -i '/# noqa/! s|@pytest.mark.django_db(transaction=True)|@pytest.mark.django_db|'
  

Debian Link to heading

• How to validate a .desktop file

  desktop-file-validate ~/.local/share/applications/<file>.desktop
  

• How to load .desktop files

  update-desktop-database ~/.local/share/applications/
  

• How to install Apache Benchmark Package

  sudo apt install apache2-utils
  

• Empty trash using terminal

  sudo apt install trash-cli
  trash-empty
  

• Headset Bluetooth failing to connect as A2DP profile - “Failed to change profile to a2dp_sink”

  sudo apt remove bluez-alsa-utils
  

CPU Link to heading

• How to discover CPU model and version

  lscpu | rg 'Model name'
  

GPU Link to heading

• How to discover GPU. Options:

  lspci | grep VGA
  

  sudo lshw -C display
  

  sudo apt install mesa-utils
  glxinfo | grep "OpenGL vendor\|OpenGL renderer"
  

  sudo apt install inxi
  inxi -G
  

• How to show Intel GPU usage

  sudo apt install intel-gpu-tools
  sudo intel_gpu_top
  

Network Link to heading

• List used ports

  nmap -p- --open localhost
  # or
    sudo netstat -tulpn | grep LISTEN
  

• Lists all processes listening a specific port

  sudo lsof -nP -iTCP:<port> -sTCP:LISTEN
  

• How to see the WiFi network name (SSID): iwgetid
• How to test speed between two devices in a private network
  1. Install iperf on both devices: sudo apt install iperf3
  2. Run the server in one device: iperf -s
  3. Run the test in the other device: iperf -c <server-ip>
• How to discover devices in the same network

  sudo apt update && sudo apt install nmap
  sudo nmap -sn 192.168.0.0/24
  

• How to discover the open ports of a specific device:

  sudo nmap -p 1-65535 <ip>
  

Terminal Emulators Link to heading

• Alacritty - #OpenSource
  • No tabs or splits
• kitty
• rio
• Warp - closed source
• WezTerm
  • vs Alacritty

ThinkPad Link to heading

• Fix keyboard to work / (slash) key #troubleshooting - Source

  sudo dpkg-reconfigure keyboard-configuration
  

XFCE4 Link to heading

• Window top part (minimize, maximize, close, etc.) disappeared #troubleshooting : xfwm4
• Desktop icons disappeared #troubleshooting: xfdesktop
• Dead keys stopped working #troubleshooting: setxkbmap -option
• Sending notification

  notify-send "<title>" "<message>"
  

• Customizing Keyboard shortcuts

  xfconf-query --channel xfce4-keyboard-shortcuts --property <property> --set <command> --create --type 'string'
  

  • Examples of <property>: '/commands/custom/<Super>d', '/commands/custom/Print', '/xfwm4/custom/<Primary><Shift><Alt>Left'
  • Example of <command>: 'thunar', 'xfce4-screenshooter --fullscreen', 'move_window_left_workspace_key'
  • More examples on https://github.com/lucasrcezimbra/dotfiles/blob/master/install.sh
• Reload panel configs without logging out

  vim ~/.config/xfce4/xfconf/xfce-perchannel-xml/xfce4-panel.xml  # edit configs and save
  pkill xfconfd
  xfce4-panel -r