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Commonly used commands

  • date -d @1626647940
  • sudo systemctl restart network-manager
  • sudo gparted
  • nmap -sP scan ports
  • nmap -A detect OS and services
  • ls -l /dev/ttyS0
  • groups <username>
  • sudo gpasswd -a <username> <groupname>
  • sudo gpasswd -d <username> <groupname>
  • sudo groupadd <newgroupname>
  • sudo usermod -a -G <groupname> <username>
  • which pip to see which pip command you are running - useful for checking environment!
  • lsusb to check USB devices
  • lspci to check PCI devices
  • lspci | grep VGA to check GPUs
  • sudo lshw -C video to check GPU display details
  • uncomment #force_color_prompt=yes in .bashrc for a colored prompt
  • sudo !! where !! is for the last command
  • python3 -m site show searching path for python3
  • sudo python -m pip install --force-reinstall pip==8.1.1 if you inadvertently upgraded your system pip. More info can be found at this link, and this link.
  • sudo ldconfig after sudo make install to refresh the cache
  • tar -cf filename.tar file1 folder2 packed without compression
  • tar -xf filename.tar
  • tar -cvzf filename.tar.gz file1 folder2 compress by -z; verbose by -v
  • tar -xvzf filename.tar.gz
  • tar -xvzf filename.tar.gz -C {path} decompress to a designated path

running in the background

  • Ctrl + Z to stop the process, followed by bg to run in the background or fg to run in the foreground.
  • Use command ./ 1>stdout.log 2>stderr.log & and it will return a process ID.
  • Processes running in the background can be monitored by top command.
  • apt-cache showpkg <pkgname> show package info, both depends and reverse depends
  • apt-cache depends ros-melodic-desktop show one-level dependencies
  • apt-cache rdepends --installed ros-melodic-desktop
  • sudo apt install apt-rdepends
  • apt-rdepends ros-melodic-desktop | pager recursively show all dependencies
  • apt-rdepends --reverse protobuf-compiler | grep ros-melodic-desktop

apt commands to locate packages

  • dpkg -L <package-name>
  • apt list <package-name>
  • apt-cache madison
  • locate <filename> find a file in database (globally)
  • find <filename> find a file in local directory

vim commands

  • vi -b <filename> open file in binary mode
  • :%!xxd switch to hex mode
  • :%!xxd -r switch back to binary mode
  • :wq save and exit


  • sudo update-alternatives --config x-terminal-emulator

SSH Commands

  • ssh to see if ssh is installed (openssh-client is installed by default)
  • ssh-keygen or ssh-keygen -t rsa generate ssh key by RSA algorithm
  • cat ~/.ssh/ print public key (for settings on Github)
  • ssh -T [email protected] testing
  • sudo apt-get install openssh-server install server for incoming ssh connections
  • ssh-copy-id username@hostname copy your ssh key to remote computer to avoid verifying password on every connection
  • ssh username@ip ssh login to a remote computer with this ip and username
  • ssh username@hostname if mapped this hostname to its ip in /etc/hosts file
  • ssh -X username@hostname login with GUI open
  • ssh -p 1234 username@hostname login via port 1234
  • sudo gedit /etc/hosts modify hosts file
  • sudo gedit /etc/ssh/sshd_config modify ssh server configuration
References: The Unix Shell;