• 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 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 support

  • 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

Devices and Filesystem

  • sudo gparted

  • 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>

  • lscpu , lsmem , lshw list CPU, memory, hardware info

  • lsusb list USB devices

  • lsblk list block devices, often used to check external ssd

  • lspci list PCI devices

  • lspci | grep VGA check GPUs

  • sudo lshw -C video check GPU display details

  • du -h -d 1 check file size/usage in current directory

  • df -h check hard disk usage

Environment Variables

  • which pip to see which pip command you are running - useful for checking environment!

  • 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

Date and Time

  • date

  • sudo systemctl stop systemd-timesyncd

  • sudo systemctl start systemd-timesyncd

  • timedatectl

  • sudo timedatectl set-ntp false

  • sudo timedatectl set-time 'YYYY-MM-DD'

  • sudo timedatectl set-time 'YYYY-MM-DD HH:MM:SS'


  • sudo systemctl restart network-manager

  • nmap -sP scan ports

  • nmap -A detect OS and services


  • tar -cf filename.tar file1 folder2 packed without compression

  • tar -xf filename.tar create an archive by -c, extract an archive by -x

  • tar -cvzf filename.tar.gz file1 folder2 compress by -z; verbose by -v

  • tar -xvzf filename.tar.gz decompress

  • tar -xvzf filename.tar.gz -C {path} decompress to a designated path

  • sudo apt-get install zip unzip

  • zip -r myfolder

  • unzip

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


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